Gastrointestinal surgery
John Berg, DVM, DACVS
Atlantic Provinces Veterinary Conference, February 2015
Choice of needles and suture materials for gastrointestinal surgery
The cross section of the point of taper needles is circular. These needles are designed to pass through
non-resistant soft tissues with minimal trauma, leaving a very small needle track. Small taper needles are
ideal for gastrointestinal surgery. The cross section of the point of cutting needles is triangular, with sharp
edges at the corners. These needles are designed to pass through more resistant soft tissues, such as
skin. Because the cutting edge is on the concave surface of the needle, the needles are prone to cutting
through tissue, leaving a large needle track, when suturing fragile soft tissues. Reverse cutting needles, in
which the cutting edge is on the convex surface, are less prone to this problem. In large dogs, the
mucosa of the stomach and the submucosa of the small intestine can be dense and difficult to pass a
taper needle through, and some surgeons prefer cutting needles in these situations.
While virtually any type of monofilament synthetic suture material may be used for stomach or small
intestine, I prefer the slowly absorbed materials such as PDS and Maxon, which provide approximately 6
weeks of effective strength (the rapidly absorbed materials such as Biosyn and Monocryl are ideal for
urinary tract and subcutaneous tissues, where rapid absorption is advantageous).
I prefer 4-0 suture for intestine in cats and small dogs, and 3-0 in medium and large dogs.
Perioperative antibiotics in gastrointestinal surgery
There is a great deal of variability among surgeons in their use of perioperative antibiotics for intestinal
surgery. I believe the following approach to be rational; however, there are a variety of other approaches
with similar effectiveness:
A small amount of spillage of intestinal contents occurs during any intestinal surgery. If the patient is
reasonably healthy and not geriatric, if spillage is properly controlled, and if the abdomen is thoroughly
lavaged prior to closure, the risk of bacterial peritionitis is very low, and perioperative antibiotics are not
necessarily indicated. However, if a complex (therefore long) procedure is anticipated, or if there are
patient factors present that increase the risk of infection (eg., old age, severe
dehydration,immunosuppression, concurrent disease), prophylactic antibiotics are indicated. Common SI
bacteria include Bacteroides, clostridium, enterococcus, E coli, staphylococcus,and anaerobes. Good
coverage for these bacteria can be provided by first generation cepahlosporins such as Cefazolin. For
cecal or large intestinal lesions, additional gram negative coverage (eg., second generation rather than
first generation cephalosporins,or the addition of an aminoglycoside) should be considered. Prophylactic
antibiotics should be given immediately preoperatively IV, then every 2 hours during surgery, then
discontinued.
Gastrotomy
Types and clinical signs of gastric foreign bodies - Gastrotomy is most commonly performed for
gastric foreign bodies. Most gastric foreign bodies in dogs and cats are the “usual suspects:” fabric,
plastic, balls, etc., causing nausea, vomiting, and occasionally weight loss and inappetance. Balls will
occasionally move in and out of the pyloric antrum, causing a history of intermittent vomiting.
Unusual gastric foreign bodies - Veterinarians should be aware of 4 types of foreign bodies that are
somewhat unusual, but important because they are particularly dangerous to the patient – each of these
are worth warning owners about:
1. Expansile materials – These include wood glue (if swallowed in large quantity) and grains such as
cous cous, or, theoretically rice (also if swallowed in large quantity). These materials have the potential to
expand rapidly in the stomach, causing acute severe gastric dilatation that requires emergency surgery.
2. Post-1982 pennies – Pennies minted after 1982 have a ring of zinc surrounding a copper core – a
step that was taken by the US government to reduce the cost of penny production. The zinc can corrode
in gastric acid, causing hemolytic anemia, acute renal failure, and gastric mucosal ulceration. It is
important to recognize that corrosion of the zinc ring will dramatically distort the appearance of these
pennies on radiographs – they may resemble misshapen pieces of metal, and not be recognizable as
coins. The most important therapeutic measure is to remove the pennies, either endoscopically or
surgically, as soon as possible.
3. Multiple magnets – Classic offenders here are “Bucky Balls:” small, spherical magnets that, once
swallowed, can attract each other across gastrointestinal walls, causing pressure necrosis, perforation,
and bacterial peritonitis. This is a well-recognized problem in children, and it can occur in dogs and cats
as well. Whenever 2 of these magnets are seen in apposition on radiographs, surgical exploration should
be considered.
4. Teriyaki sticks – These have a tendency to migrate out through the gastric wall and into a variety of
locations in the chest and abdomen, causing organ perforation and localized abscessation. Large dogs
are usually affected.
Endoscopy - Many gastric foreign bodies can be removed endoscopically, and this technique, if
available, should always be attempted prior to gastrotomy (with the exception of items 1, 3 and 4 above).
Technique for gastrotomy - Gastrotomy is typically performed in on the ventral surface of the body of
the stomach. An avascular area is chosen and isolated with stay sutures, and an adequate longitudinal
incision is made to permit removal of the foreign body and inspection of the interior of the stomach. The
stomach should be closed in 2 layers, although there are major inconsistencies between the major
veterinary surgery textbooks regarding exactly what those layers should be. I prefer a simple continuous
pattern in the mucosa, followed by a second simple continuous pattern in the outer 3 layers. Neither layer
is inverting, allowing the cut surfaces to be in apposition. In cats and small dogs, if the separation
between the mucosa and the outer layers is not obvious, a single simple continuous suture line may be
used. I typically use PDS on a taper needle – 4-0 material in cats and small dogs, 3-0 in medium and
larger dogs and 2-0 in very large dogs. Unless the stomach has suffered vascular compromise, as in
GDV, dehiscence of gastric incisions is very unusual.
What’s new regarding GDV?
Causes - Possible causes of GDV can be subdivided into dog-specific risk factors, environmental risk
factors, and management-related risk factors. Specific risk factors that are known to be contributory with
some degree of certainty, and risk factors of uncertain significance, are listed below:
Dog-specific risk factors: Known risk factors are breed (Great Dane, German shepherd, St. Bernard, etc.),
deep chested dogs, dogs with a first degree relative (parent or sibling) that had GDV, middle aged and
older dogs, and dogs whose owners characterize them as aggressive or fearful. Factors of uncertain
significance are gender, being underweight, having IBD, presence of a gastric foreign body, and previous
splenectomy.
Environmental risk factors: Stressful events such as kenneling, hospitalization and car rides are known
risk factors. The influence of weather extremes such as cold or hot weather, or thunderstorms, is
uncertain.
Management risk factors: It is reasonably well-documented that feeding large volumes of food per meal
and single daily feedings predispose to GDV. Uncertain risk factors include moistening the food, feeding
small kibble, allowing dogs to eat rapidly, elevating the food bowl, allowing exercise after eating ( a recent
large internet-based study suggested that moderate exercise after eating may be protective against
GDV), and water restriction after eating.
Lifetime risk of GDV and indications for prophylactic gastropexy - The lifetime risk of GDV in large
breed dogs, overall, has been estimated at 24%; in Great Danes, it is about 42%. These figures suggest
that prophylactic gastropexy in GDV-prone breeds makes sense, even if the dog is not undergoing a
concurrent elective procedure such as a spay or castration – particularly if more than one risk factor other
than breed is present. The decision how to perform the pexy (laparoscopic or open) is far less important
than the decision whether to perform the pexy.
Recognizing the direction of GDV - GDV is almost invariably a surgical emergency. It is very
worthwhile to understand how the stomach typically rotates in GDV, because it can be difficult to simply
“figure it out” during surgery when the stomach is extremely dilated. I prefer not to remember the typical
direction of volvulus as being “clockwise” or “counterclockwise,” because this requires also remembering
whether I am viewing the dog from the front or the back, and whether the dog is lying on his back or
standing. Instead, I prefer to remember this: the pylorus and pyloric antrum are normally on the right and
ventral, and in a GDV dog, they are typically on the left and dorsal. They get there by traveling from right
to left along the ventral abdominal wall. If this is the direction of volvulus (and it is, 99% of the time), the
omentum will be found to be overlying the ventral surface of the stomach when the abdomen is entered.
The GDV can be corrected by reaching dorsally along the left abdominal wall, grasping the stomach in
that region, and drawing it ventrally and to the right. Following this, the greater curvature is inspected for
vascular compromise, the splenic vasculature is inspected for thrombosis, and a gastropexy is performed.
Gastropexy technique - Many gastropexy techniques are available, and all of them work well, but some
(belt-loop, circumcostal) are unnecessarily complicated. I prefer the incisional gastropexy, in which a 45cm incision is made in the ventral pyloric antrum, down to but not through the mucosa. This incision
may be oriented either parallel to or perpendicular to the long axis of the stomach – I prefer a
perpendicular incision because I find it easier to suture. A matching incision is made in the innermost
muscular layer of the body wall, caudal to the last rib and about 10cm from the midline. The 2 incisions
are then apposed with 2 simple continuous suture lines of 2-0 or 0-0 PDS or polypropylene
Intestinal foreign bodies
Types of foreign bodies – As a general rule, discrete foreign bodies (balls, peach pits, corn cobs, etc.)
are most common in dogs, and linear foreign bodies (string, fishing line, dental floss, etc.) are more
common in cats.
Pathophysiology of intestinal obstruction – After about 2 hours of intestinal obstruction, there is a net
loss of water, Na, K and Cl into the intestinal lumen, and loss of these major electrolytes is often reflected
in lab work. Most of us were taught that distal small intestinal obstructions cause metabolic acidosis (due
to fluid loss), and that proximal (duodenal or gastric outflow) obstructions cause hypochloremic metabolic
alkalosis (due to loss of HCl). However, a recent study (Boag et al, JVIM 2005) showed that patients with
jejunal obstruction often have metabolic alkalosis, possibly related to loss of Cl. Therefore, in very sick
ptients, selection of correct fluids requires measurement of acid-base and electrolyte status.
Choice of IV fluids – For relatively stable patients with an unknown acid-base status, and for patients
with known metabolic acidosis, LRS + K is an appropriate fluid choice. For patients with a known
metabolic alkalosis, NaCl + K is ideal. Colloids should be considered for critically ill patients.
Imaging – Diagnosis of intestinal obstruction on radiographs can be difficult if the foreign material is
radio-opaque. Identification of a gas pattern that is stationary on radiographs taken an hour or so apart is
highly suggestive of obstruction. The diameter of the gas-filled area can also be helpful: one publication
demonstrated that the upper limit of normal for small intestinal diameter in dogs is 1.6x the height of the
vertebral body of L5 on a lateral view, and that a diameter > 2x the L5 height indicated likely obstruction.
Ultrasound is the ideal imaging modality, as it will allow identification of radiolucent foreign material.
Timing of surgery - Monitoring for foreign body passage using serial radiographs is an option for stable
patients. Correcting dehydration using IV fluids can often promote foreign body passage. Monitoring with
ultrasound or radiographs can assist in determining whether the foreign body is moving. There is no such
thing as a large intestinal foreign body obstruction – any foreign body that reaches the LI should pass on
its own. In our practice, we are occasionally fooled by foreign bodies that we think are lodged in position,
but are not. For these reasons, I am reluctant to take patients to surgery based on images that are more
than about 2 hours old, because new images may show that the foreign body is passing or has reached
the LI. Once the decision has been made that enterotomy is necessary, the procedure is always
considered a surgical emergency because of the potential for a delay to allow progressive intestinal
compromise.
Technique for enterotomy - Once the foreign body has been identified, a longitudinal antimesenteric
incision should be made just distal (aboral) to the foreign body. The intestine overlying the foreign body,
and the intestine proximal to it, may have been compromised by the presence of the foreign body. The
incision should be just long enough to allow the foreign body to be milked through it without splitting the
ends of the incision. The incision may be closed with either a simple interrupted or simple continuous
pattern. It is not necessary to close the incision transversely: the risk of stricture of longitudinal
enterotomy incision (or an anastomosis) is negligible.
Linear foreign bodies
Pathophysiology - Linear foreign bodies are particularly common in cats, but also occur in dogs. One
end of the foreign body becomes lodged beneath the tongue or at the pylorus, and the SI attempts to
advance the other end. The intestine gathers proximally along the foreign body, producing obstruction.
The foreign body may become taut and lacerate the mucosa or completely perforate the intestine at the
mesenteric surface. The condition is diagnosed by radiography and/or ultrasonography, both of which
demonstrate characteristic gathering of the intestine toward the pylorus and tear drop-shaped gas
bubbles within the intestinal lumen. Linear foreign bodies are always surgical emergencies.
Treatment with multiple enterotomies - Once anesthesia is induced, if the foreign body is lodged
beneath the tongue, it is released by transecting it and removing as much of the oral portion as possible.
A cranial midline laparotomy is then performed. If the foreign body is lodged at the pylorus, a gastrotomy
is performed as described above, the foreign body is released from the stomach by transecting it where it
emerges from the pylorus, and the gastric portion is removed. The gastrotomy is then closed. Multiple
enterotmies are usually needed to remove linear foreign bodies that involve a significant length of the
small intestine. Enterotomies are made with a 15 blade, and are oriented parallel to the long axis of the
bowel, on its antimesenteric surface. Each enterotomy is approximately 2 cm in length. The most
proximal enterotomy is made first, several centimeters distal to the proximal end of the foreign body. The
proximal end of the foreign body is drawn through the enterotomy and transected. Enterotomies are
closed with simple interrupted appositional sutures, placed as described above. The procedure is then
repeated, working from proximal to distal. To limit the number of enterotomies, they are spaced as far
apart as possible to permit withdrawal of the foreign body with minimal resistance. In cases in which the
foreign body is deeply embedded in mucosa, enterotomies at close intervals – eg 10 cm or less – may be
needed. Following foreign body removal, the bowel should be thoroughly inspected for perforations at the
mesenteric border; perforated areas should be treated by R and A.
Red rubber catheter technique - The catheter technique allows linear foreign bodies to be removed with
fewer enterotomies. Following gastrotomy or the first enterotomy and transection of the foreign body, the
new proximal end of the foreign body is sutured to one end of a large red rubber catheter, eg., for a cat,
an 8 or 10 French red rubber catheter. The catheter is completely passed through the enterotomy and
into the distal intestine. The catheter is then milked down the intestine, pulling the foreign body with it –
the foreign body is peeled out of the intestinal mucosa as the catheter progresses down the lumen. If
possible, the catheter can be milked all the way through the intestinal tract and out the anus, allowing the
foreign body to be removed with a gastrotomy or single enterotomy. If this is not possible, the catheter
can be milked as far as possible, and an additional enterotomy can be performed.
Intestinal resection and anastomosis
The most common indications for intestinal R&A in dogs and cats are bowel compromise or perforation
due to an intestinal foreign body or trauma, and intestinal tumors.
Assessment of intestinal viability – Bowel viability can be difficult to assess during surgery. Useful
parameters include bowel color and thickness. Red bowel is inflamed, but likely viable. Black or deep
purple bowel is nonviable. Lighter purple bowel is questionable. Palably thin bowel is potentially necrotic,
particularly in combination with deep purple discoloration. There should be very fine jejunal artery
pulsations visible in the mesentery adjacent to viable intestine. If the bowel is malpositioned or contains a
foreign body, the primary problem can be corrected before making a final assessment – the bowel may
“pink up” within 5-10 minutes once the underlying problem is addressed. Whenever bowel integrity is
uncertain, resection and anastomosis (R & A) should be performed.
Intestinal tumors in dogs - Our concept of the spectrum of surgically-managed tumors effecting the
small intestine in dogs has changed. Formally, we considered about half of these tumors to be
leiomyosarcomas, and the remainder to be adenocarcinomas. We now know that a significant proportion
of SI tumors formerly classified as leiomyosarcomas are actually Gastrointestinal Stromal Tumors, or
GISTs. GISTs likely arise from the interstitial cells of Cajal, which control peristalsis. By definition, GISTs
express KIT, a gene that codes for tyrosine kinas receptors, which, when activated by growth factors,
initiate cell division. The GIST concept is relevant to clinicians for 2 reasons: 1. GISTs may be
responsive to therapy with tyrosine kinase inhibitors such as Palladia, and 2. There is some evidence
that GISTs may be associated with significantly better survival than leiomyosarcomas. GISTs are
diagnosed by immunohistochemistry for KIT. Small intestinal tumors other than GISTs, leiomyosarcomas
and adenocarcinomas occur infrequently.
Unfortunately, metastatic rates for canine SI tumors are rarely reported in the literature, but are likely
about 50%. The metastatic rate for carcinomas appears to be somewhat higher than for GISTs or
leiomyosarcomas. Important metastatic sites are regional lymph nodes (these should always be biopsied
at surgery), liver and lungs.
Intestinal tumors in cats - The majority of surgically managed intestinal tumors in cats are
adenocarcinomas. These tumors have a metastatic rate of approximately 75%, and carcinomatosis is
fairly common. Typical clinical signs are cachexia, vomiting and diarrhea. Siamese cats appear to be
predisposed.
Intestinal lymphoma in cats is increasing in incidence, and surgery occasionally has a role in the
diagnosis or treatment of the disease. Partial thickness biopsy often does not reliably distinguish small
cell lymphoma from inflammatory bowel disease, and full thickness biopsies obtained at surgery are more
accurate. Cats with lymphoma in the form of an intestinal mass lesion can experience intestinal
perforation when chemotherapy is given, and mass excision prior to chemotherapy should always be a
consideration in these cats. Many cats with mass lesions have large cell lymphoma, which has a worse
prognosis than small cell lymphoma. Surgery is also indicated in the treatment of cats that present with
intestinal perforation, ultrasound evidence of imminent perforation, or obstruction. Although intestinal
lymphoma is almost invariably diffusely present throughout the bowel, cats undergoing full thickness
intestinal surgery for the disease do not appear to be at greater risk of intestinal dehiscence than cats
undergoing intestinal surgery for other conditions (Smith, J Vet Surg, 2011).
Clinical signs - The clinical signs of intestinal tumors depend upon the level of intestine effected. All
intestinal tumors may cause inappetance, lethargy and weight loss. Other signs may include the
following:
Site
Signs
Upper SI
Vomiting, dehydration
Lower SI*
Diarrhea
Cecum*
Abdominal distension (R/O spleen!), acute perforation/septic abdomen
LI*
Hematochezia, tenesmus
*Often palpable
Hypoglycemia is a paraneoplastic syndrome that may be associated with leiomyosarcomas.
Hypoglycemia typically resolves following tumor excision.
Imaging - The overwhelming majority of intestinal mass lesions can be diagnosed with ultrasound, which
should be a routine test for older,vomiting dogs. Ultrasound has largely supplanted gastrointestinal
contrast studies, although contrast studies are quite accurate, particularly for SI lesions.
Surgical technique - When intestinal R&A is being performed for intestinal cancer, lymph node biopsy
should be performed first to avoid contamination of the lymph node with intestinal contents. A small
wedge of mesenteric lymph node adjacent to the tumor is obtained with a 15 blade, taking care to avoid
hitting nearby jejunal vessels.
Wide margins of normal bowel should always be taken when R&A is performed for intestinal neoplasia.
At least 5 cm of grossly healthy bowel can be removed on either side of the lesion without difficulty in
most cases. The mesenteric arcadial vessels feeding the segment of bowel to be excised are double
ligated. Atraumatic forceps (Doyen forceps or bobby pins) are placed transversely across the intestine to
occlude the cut ends of the segments to be preserved. Traumatic forceps such as Carmalts may be used
to occlude the segment to be removed. The intestine is transected at either end, using scissors or a
blade. To assure that blood supply to the cut ends is preserved, the transection may be performed at a
slightly oblique angle. The intestine is sutured with a simple interrupted appositional pattern using a small
(4-0) synthetic slowly-absorbable monofilament material such as PDS or Maxon, on a small taper needle.
To the degree possible, eversion of mucosal edges through the anastomosis should be avoided. Excess
mucosa should be trimmed prior to suturing. Mucosa can be inverted by placing the initial surgeon’s
throw of each knot immediately adjacent to the previous knot, tightening it somewhat, then sliding it into
position. The integrity of the anastomosis may be checked by gently injecting saline into the lumen of the
bowel using a syringe and needle. The completed anastomosis should be wrapped in omentum, which
encourages the early phases of healing.
Stapled anastomosis - R&A can also be performed with stapling equipment. Stapling is particularly
helpful when there are disparate lumen sizes, because the anastomosis created is side-to-side. A GIA
stapler is used to create the side-to-side anastomosis, and a TA stapler is used to close the resultant
open lumens.
Prognosis – The overall median survival times for dogs with intestinal tumors is approximately 10
months. One of the most important prognostic factors is mesenteric lymph node status – in one
publication, dogs without nodal metastases had a MST of approximately 15 mos, whereas dogs with
nodal metastases had a MST of about 3 months.
Unfortunately, little information is available concerning the prognosis for cats with intestinal
adenocarcinoma. In one study of 23 cats undergoing surgery (Kosovsky, JAVMA, 1988), the MST for
cats that survived to discharge was 15 months, and cats with nodal metastases often survived well over 1
year.
Urogenital Surgery
John Berg, DVM, DACVS
Atlantic Provinces Veterinary Conference, 2015
Cystotomy
Indications - Cystotomy for removal cystic calculi is the most commonly performed surgery of the urinary
tract. Cystotomy is also occasionally performed also used to explore the bladder and to address
problems such as ectopic ureters and benign and malignant bladder masses.
Types and causes of cystic calculi in dogs and cats – In both dogs and cats, the most common types
of calculi are struvite and calcium oxalate. In dogs, struvite calculi are commonly caused by UTI with
urease-producing bacteria, and are most likely to form in alkaline urine. In cats, alkaline urine and
concentrated urine are predisposing factors, but UTI is not a common underlying cause. In both dogs
and cats, predisposing factors for calcium oxalate calculi are chronic hypercalcemia (eg., due to primary
hyperparathyroidism or hypercalcemia of malignancy; or in cats, idiopathic hypercalcemia) and acidic
urine. Widespread use of acidifying diets to prevent struvite calculi during the past ~20 years has caused
a decrease in the frequency of struvite calculi and an increase in the frequency of calcium oxalate calculi.
While struvite calculi most commonly form in the lower urinary tract, calcium oxalate calculi appear to
form in the kidneys, and the use of acidifying diets has resulted in an unfortunate increase in the
frequency of obstructive ureteral calculi in both dogs and cats.
Choice of suture material - The correct selection of suture material is a critical success factor in urinary
tract surgery. It is well known that long lasting absorbable sutures and nonabsorbable sutures can act as
a nidus for stone formation. Approximately 9.4% of recurrent canine uroliths, and 4% of recurrent feline
uroliths, are suture-related. Because the urinary tract regains 100% of its original strength within 2-3
weeks, long lasting absorbable sutures or nonabsorbable sutures are not necessary. Rapidly absorbable
monofilament sutures such as Monocryl or Biosyn, both of which maintain effective wound support for
approximately 3 weeks, are preferable. 4-0 material can be used for cats and small dogs, and 3-0
material for larger dogs.
Use of prophylactic antibiotics - In most dogs and cats undergoing cystotomy, it is desirable to obtain
a urine culture intraoperatively to aid selection of therapeutic antibiotics postoperatively. A common
question is whether the use of preoperatively-administered prophylactic antibiotics to prevent surgical
infection will alter intraoperative culture results.
Although prophylactic antibiotics are typically
unnecessary with cystotomies, a recent study (Buote et al, JAVMA 2012) showed that preoperative
administration of Cefazolin had no effect on bladder culture results.
Surgical technique - Cystotomy incisions are most often made in the ventral surface of the bladder in a
relatively avascular area. Calculi are removed with a bladder spoon, and the bladder and urethra are
checked for additional calculi by passing a catheter normograde and retrograde and flushing with saline.
A sample of bladder mucosa is submitted for culture.
During bladder closure, an effort should be made to avoid placing suture material in the lumen by
excluding the mucosa from the suture line and including only the submucosa, muscularis and serosa.
This is easy to accomplish if the bladder wall is thick, but somewhat more difficult when the bladder wall is
thin. Although the time-honored technique for bladder closure involves placement of 2 inverting suture
lines, many surgeons now use a single simple continuous layer. A recent retrospective study (ThiemanMankin, JAVMA 2012) of dogs and cats undergoing routine cystotomy showed no difference in
complication rates between double and single layer closure, and all complications that did occur were
minor.
Postoperative imaging – In a recent study in which radiographs or abdominal ultrasound were
performed in a series of dogs undergoing cystotomy, 20% of dogs were found to have residual stones in
the bladder or urethra following surgery. The authors recommended that radiography to check for residual
radio-opaque calculi (struvite and calcium oxalate) and ultrasound to check for radiolucent calculi (urate
and cystine) be performed prior to recovery from anesthesia in all patients, so that residual calculi can be
removed. In my opinion, with appropriate normograde and antegrade flushing of the bladder, the
incidence of residual calculi should be much lower than 20%, and those calculi that are left behind are
most likely to be small ones that can pass during urination. However, veterinarians should be aware that
obtaining postoperative images may now be considered the standard of care, and it is occasionally useful
to be able to prove to a client that new calculi that formed following an initial surgery are not calculi that
were left behind at surgery.
Feline Perineal Urethrostomy
Technical errors to avoid - While nutritional and other forms of management have decreased the
frequency with which PU’s are performed, the procedure remains a mainstay of the overall management
of cats with FLUTD and urethral obstruction. PU is a surgery that can punish poor technique. There are
several technical errors that must be avoided to reduce the risk of stricture, the most frequent and serious
complication of PU. A detailed description of the surgical technique for PU will not be provided here;
however, the critical errors to avoid are:

Failure to accurately suture urethral mucosa to skin. Prior to each suture bite, the cut edge of the
urethral mucosa should be identified. Urethral mucosa is white in color and can be readily
identified in a blood-free field. The 3 dorsal sutures in a P.U. are most critical in maintaining a
good urethral opening, although the urethral edges are difficult to visualize dorsally. Care should
be taken to pass the needle down the urethral lumen as these sutures are placed, and preplacement can aid in accurate placement. Subcutaneous fat should be trimmed away prior to
placement of these sutures to assure that fat is not interposed between the skin and mucosa.

Making the stoma in the penile urethra . The stoma should be located in the distal pelvic urethra,
not the proximal penile urethra. The penile urethra is very narrow and therefore prone to
stricture. The urethral incision should extend to or just beyond the bulbourethral glands. These
glands are occasionally difficult to identify in castrated cats; if the glands cannot be identified, the
urethral incision should be extended carefully until it enters a region of the pelvic urethra that is
about 5mm in diameter. At this level, the opening should easily accept the widest dimension of a
tomcat catheter.

Excessive tension at the stoma site. Tension can cause small dehiscences in the P.U. site,
allowing urine to leak into surrounding tissues, leading to inflammation, scaring and stricture.
Excessive tension often results from:
o
Incising the urethra too far proximally – the landmarks described above should be used.
o
Incising the skin dorsal to the prepuce too close to the anus – the skin incision should be
halfway between the ventral aspect of the anus and the dorsal aspect of the scrotum.
o
Failure to transect the ischiocavernosus muscles and incise the fibrous tissue directly
below the penis that attaches the penis to the pubis. These errors cause the penis to be
tethered ventrally, creating tension on the stoma site.
Treatment of PU strictures - PU stricture, when it does occur, typically occurs 2-6months after surgery.
Cats present for a recurrence of straining to urinate, and on examination have an extremely small – or
absent – urehtrostomy opening. The solution is creation of a new PU proximal to the initial PU site. On
rare occasions, antepubic urethrostomy is necessary.
Scrotal urethrostomy in dogs
Options for managing urethral obstruction by calculi – Treatment options for dogs with obstructive
calculi lodged at the tip of the os penis include urohydropulsion followed by cystotomy; permanent scrotal
urethrostomy; prescrotal urethrotomy and calculus removal; and laser lithotripsy followed by
urohydropulsion into the bladder and cystotomy. Laser lithotripsy, while an excellent option, is not yet
widely available and will not be discussed here. My preference for calculi that cannot be removed by
urohydropulsion and cystotomy is scrotal urethrostomy. I prefer scrotal urethrostomy to prescrotal
urethrotomy because it allows the urethral incision to be made through nontraumatized urethral mucosa
(the scrotal urethrostomy site is caudal to the site of obstruction), and because it prevents future episodes
of urethral obstruction.
Technique for scrotal urethrostomy - There are several advantages to performing urethrostomies in
the scrotal location: the urethra is wide and superficial at this location, there is less cavernous tissue
(less bleeding), and it allows the dog to urinate in a way that prevents scalding of the inner thighs. The
scrotum is excised by making a circumferential skin incision around its base, and a routine castration is
performed if necessary through the scrotal incision. A catheter is passed and a 2-3 cm longitudinal
incision is made into the urethral lumen. The urethral mucosa is sutured to the skin – with no interposed
fat – using a simple continuous pattern of a rapidly absorbed monofilament such as Monocryl or Biosyn.
4-0 material is appropriate for small dogs, and 3-0 for larger dogs. Suture removal is unnecessary. An e
collar should be placed postoperatively.
Postoperative hemorrhage - Owners should be made aware before surgery that because the urethral
incision passes through cavernous tissue, dogs often have episodes of hemorrhage when urinating or
when they become excited during the first few days postoperatively. While this bleeding is not life
threatening, it can be a significant nuisance. Sedation (acepromazine) and ice packing may be helpful in
diminishing bleeding.
Cesarean section
Normal gestation periods - The total gestation times measured from the time of mating are 56-59 days
in cats and 57-72 days in dogs. Measured from the time of the progesterone surge, gestation times are
63-66 days in cats and 62-68 days in dogs. However, mating and progesterone surge dates are often
unknown, and in determining when and whether a c-section may be necessary, it is useful to know how
far into gestation a pregnant female is: Fetal mineralization becomes appreciable on radiographs on
about day 25-29 in cats, and on about day 42 in dogs. On ultrasound, the fetus and fetal heartbeat
becomes detectable around day 23-25.
Normal parturition - In dogs, the mother’s temperature reliably drops to 99-100 8-24 hours before
parturition. In cats, this drop is far less reliable. The stages of parturition in cats are the same as in dogs:
Stage 1- nonvisible uterine contractions, mother is restless, anxious and seeks seclusion. This
stage lasts up to 24 hours.
Stage 2 – Delivery of puppies or kittens, visible abdominal contractions
Stage 3 – Delivery of placentas, alternating with puppies or kittens
In cats, stages 2 and 3 last a total of < 6 hours. In dogs, these stages may last up to 36 hours.
Fetuses should be delivered within 30 minutes of the onset of visible contractions. Delays between
puppies should be no longer than 4 hours. A very small proportion of cats – 1% - will have an interrupted
parturition in which parturition stops for up to 48 hours, the mother acts like it is complete, and then she
delivers more kittens.
Recognizing dystocia - Dystocia is estimated to occur in about 6% of cats, and is most likely in
purebreeds. It occurs in about 16% of non-brachycephalic dogs. The #1 cause in both species is
primary uterine inertia. Other causes observed less frequently include a small pelvic canal (or oversized
fetuses), malpositioned fetuses, and old pelvic fractures. Signs of uterine inertia many include absence of
stage 1 of parturition, failure to progress to stage 2 within 12-24 hours, failure to deliver a puppy every 4
hours in dogs, and stages 2 and 3 extending beyond their usual limits. In obstructive dystocia, there are
vigorous uterine contractions, but no delivery of a puppy or kitten within about 30 minutes. Radiographs
may demonstrate fetal malpositioning (eg., transverse presentation). When there is significant fetal
distress, skull collapse due to intracranial gas is a common early sign. Ultrasound may demonstrate a
lack of fetal motion and slow fetal heart rates.
Medical management – Medical management of dystocia is only indicated for uterine inertia – never for
obstructive dystocia, which is always treated by c-section. Oxytocin (0.2 U/dog or cat SQ or IM) may be
repeated once if it is not effective within 30 minutes. Any abnormalities in electrolytes, glucose or
hydration should be corrected. C-section is indicated if medical management is unsuccessful, if dystocia
is obstructive, if there is fetal distress on ultrasound, or if the mother is septic (sepsis is often hard to
recognize in cats). The overall success rate of medical management of dystocia is about 30-40%.
Technique for C-section - The incision is made in the caudal abdominal midline, which may be quite thin
in the presence of a very gravid uterus. The uterus is carefully exteriorized (by lifting it out, rather than
pinching it and pulling it out, which may tear the uterine wall), and a longitudinal incision is made in the
ventral uterine body. Fetuses are simultaneously milked and pulled through the uterine incision. Dogs
and cats have a zonary placenta that must be gently separated from the endometrium. If the placenta
does not separate, the fetus may be removed by opening the placenta, and the placenta can be left in
place to pass later. Once all fetuses are removed, the uterus is lavaged and the uterine incision is closed
in a simple continuous pattern with an absorbable monofilament material.
Puppy/kitten care - The puppies or kittens are cared for by first opening and removing the amniotic sacs,
and ligating the umbilical cord .5-1 cm from the body. The mouth and nostrils are gently suctioned of
mucus, and VERY GENTLY slinging to remove additional mucus. Puppies or kittens are rubbed to
encourage breathing. Doxapram (1 drop in the mouth) may be used to stimulate breathing, and naloxone
(same dose) may be used if the mother received an opioid. The puppies or kittens are dried and slowly
warmed, and discharged with the mother as soon as she is awake.
Ear Surgery
John Berg, DVM, DACVS
Atlantic Provinces Veterinary Conference, 2015
Total ear canal ablation (TECA)
End stage otitis externa - TECA is indicated for end stage otitis externa, and is most commonly
performed in Cocker spaniels. In end stage otitis externa, the ear canal is severely thickened and often
calcified, and the ear canal lumen is significantly narrowed. By definition, end stage otitis externa is
unlikely to respond meaningfully to further medical management. All dogs with end stage otitis externa
are assumed to have erosion of the tympanic membrane, and to have advanced otitis media as well as
otitis externa – if the history and physical examination findings suggest that a dog is a TECA candidate,
imaging tests to prove that otitis media is present are unnecessary.
Surgical technique - The majority of dogs requiring TECA’s have bilateral end stage otitis externa; in
these cases, the surgery may be performed on both sides during a single anesthetic procedure. TECA’s
are always accompanied by significant diffuse bleeding, and electrocautery is essential. The procedure is
initiated by making a T-shaped incision that incorporates the ear canal opening and extends along the
vertical ear canal. As the external ear canal is dissected out, care must be taken to identify and preserve
the facial nerve, which courses ventral to the horizontal canal near its junction with the middle ear. The
nerve often must often be dissected free from surrounding scar tissue. The external canal is then excised
from the bulla and removed. Care should be taken to assure that no remnants of the canal are left
behind. A lateral bulla osteotomy is then performed by enlarging the external acoustic meatus ventrally
with a drill or rongeurs. A large enough opening is made to allow curettage and visual inspection of the
middle ear. The middle ear is cleaned as thoroughly as possible of infected debris. Care should be taken
not to aggressively curette dorsally, where the facial and sympathetic nerves are located; or medially,
where the round window is located. The middle ear is flushed and cultured, and the skin incision is
closed. It is not necessary to place a drain in the middle ear. Because the entire infected bulla wall
cannot be removed, appropriate antibiotic therapy must be continued for 4 weeks to eliminate residual
infection within the bone.
Prognosis – Although TECA is a tedious and potentially complication-prone surgery to perform, the
overwhelming majority of dogs that undergo the surgery are dramatically and permanently helped: the
chronic pain disappears, and there is no longer a need for daily efforts at medical management.
Complications – Prior to surgery, owners must be made aware of several potential complications:
Hearing loss – Most dogs with end stage otitis externa have significantly decreased hearing
before surgery, and studies using brain stem auditory evoked responses have shown that hearing is
usually minimally affected by the surgery. The improvement in quality of life resulting from pain relief far
outweighs the significance of any marginal loss of hearing.
Facial nerve paralysis – Clinically apparent damage to the facial nerve occurs in under 5% of
cases. Nerve damage is almost always transient, and usually resolves within 3-4 weeks. Because the
facial nerve is responsible for lacrimation, artificial tears should be used during this period.
Persistent infection – Persistent infection may result from failure to remove remnants of the
horizontal canal at its junction with the bulla, or from resistant bacterial infection within the bulla.
Pseudomonas spp. are often responsible for resistant infections. Clinical signs usually become apparent
several months to years after surgery. These may include a recurrence of any of the common signs of
otitis externa, or development of swelling or drainage near the ventral portion of the skin incision. If the
surgeon is confident that the canal was completely removed, therapy consists of long term (occasionally
lifetime) use of the most effective antibiotic, as indicated by culture and sensitivity results. For
pseudomonas infections, ciprofloxacin is often a good choice. If the surgeon is not confident that the
original surgery was performed correctly, or if antibiotics fail to produce improvement, surgical exploration
in an effort to identify and remove residual ear canal tissue may be indicated. Persistent infection is a
rare complication of total ear canal ablation and lateral bulla osteotomy, but it can be extremely frustrating
to manage.
Inflammatory nasopharyngeal polyps in cats
Nasopharyngeal polyps are inflammatory masses that usually occur in 1-5 year old cats. The
etiology is unknown, although viral upper respiratory infections earlier in life, and hereditary causes, are
suspected. The polyps appear to arise from in the middle ear epithelium, and usually grow into the
nasopharyngeal area, or, more rarely, the external ear canal. Nasopharyngeal polyps may produce
upper respiratory stridor or dysphagia; external canal polyps produce chronic otitis externa.
Nasopharyngeal polyps are observed by retracting the soft palate forward under general anesthesia.
They may occasionally be bilateral. The polyps are removed by gentle traction with a forceps (in some
cases, fairly forcible traction must be applied). Recurrence rates are reported to be lower when traction is
combined with a ventral bulla osteotomy to allow removal of the source of the polyp within the middle ear.
My approach is to remove NP polyps with traction once and consider VBO if they recur.
Ventral bulla osteotomy involves making a skin incision just medial to the angle of the mandible,
and approaching the bulla by dissecting medial to the digastricus muscle. The bulla of the cat is very
prominent and easy to identify. The bulla is entered with a Steinmann pin or air drill, and is then very
gently curetted, lavaged, and cultured. The bulla of the cat is separated into dorsomedial and
ventrolateral compartments by a septum; both compartments should be opened and inspected at surgery.
A temporary Horner’s syndrome is almost inevitable after VBO in the cat, and the occasional cat with an
inflammatory polyp will present with a mild Horner’s. Following surgery, the Horner’s syndrome typically
resolves within a few weeks, although I have seen cats with a permanent mild Horner’s. Cats with
Horner’s syndrome have decreased lacrimation and require artificial tears.
Antibiotics should be continued for 2-4 weeks if the culture is positive. Reported recurrence rates
for cats with NP polyps treated by VBO are very low. There is evidence that a 3-4 week course of
prednisolone may reduce recurrence rates after either traction removal of VBO.
Surgery in Sick Cats
John Berg, DVM, DACVS
Atlantic Provinces Veterinary Conference, 2015
Cats differ from dogs in some key ways: they mask illnesses and are often debilitated by the time surgery
is elected; they are often stressed by hospitalization; they are reclusive and can be difficult to assess
postoperatively; and they often remain anorectic postop and are prone to hepatic lipidosis. Cats heal
better than dogs, with the exception of axillary and inguinal wounds, which can be problematic. In
general they don’t bleed as much as dogs, with the exceptions of liver, biliary and GI surgery. It is very
easy to underestimate their blood loss: a blood soaked 4x4 sponge contains 10 ml of blood, and a typical
cat’s blood volume is about 300 ml.
Under anesthesia, cats are prone to hypothermia (because of their small body size),
hypotension, and fluid overload (many cats have occult HCM, and are predisposed to pulmonary edema).
The risk of hypothermia can be minimized by insulating cats well (Bair Huggers – Arizant Helathcare – are
great), avoiding inadvertent soaking of the skin during prepping or surgical flushing, placing a warm fluid
bag on the anesthesia machine’s Y piece, warming IV fluids, and not wasting time while the cat is under
anesthesia. Safe fluid rates are 10ml/kg/h in healthy cats and 5ml/kg/h in cats with heart disease. Prior to
surgery, it is helpful to prehydrate old, stressed or anorectic cats for 12-24 hours at 10ml/kg/h.
The gold standard for blood pressure measurement is direct measurement via an arterial line,
but this is difficult in cats and rarely done. Indirect methods are much more practical, but unfortunately
are relatively insensitive in cold or vasoconstricted cats. Doppler is more sensitive than oscillometric
measurement, but only provides a systolic reading. Oscillometric measurement provides systolic,
diastolic and mean arterial pressure readings. There is wide variability in normal cat BP readings, but a
systolic pressure of 125-160 and a mean of 100 are good approximations of normal. Elevated readings
are common in struggling or stressed cats but are believable in the face of renal disease, hyperthyroidism
or retinal changes. If a cat has good urine output, he is probably not hypotensive, regardless of the BP
reading. BP’s below 80 systolic or 60 mean are suggestive of hypotension – but during anesthesia, the
trend is more important than the number. Hypotension is likely in any sick cat, and especially in cats
undergoing biliary surgery.
A reasonable stepwise protocol for the cat who is becoming hypotensive during anesthesia
is: 1. Turn down the gas (Be careful – cats wake up easily). Consider a fentanyl or ketamine CRI, which
will provide analgesia, let you turn down the gas, and support BP. If that fails, 2. Fluid bolus, 3-10
ml/kg. Repeat once if needed. If that fails, 3. Colloids, eg. VetStarch, 1-5 ml/kg, titrate slowly, watching
BP. Colloids are particularly indicated if albumin is < 1.5 or TP is <3.5. If that fails, 4. Dopamine 8ug/kg/min up to 20 ug/kg/min. It’s best to figure out the dosing in advance so you don’t have to do it
under pressure.
Cats have a poor tolerance for blood loss, and it is best to consider a transfusion early (eg.,
PCV<20). Blood types in cats are A (most cats), B (rare but especially purebreds) and AB (even more
rare). Unlike dogs, cats have pre-formed antibodies to foreign blood types so must always be typed or
crossmatched. Fresh whole blood is fine for most situations and can be purchased (Animal Blood
Resources). In a pinch, canine blood can be given to cats, but the RBC’s don’t survive long (a few days),
and the transfusion cannot be repeated after 4 days. A good starting amount of blood in most situations
is 1 cat unit (~55 ml), which is an amount that can be safely taken from a donor cat. An alternative is ½
unit of packed cells. A good target PCV is 20%. If the cat is markedly hypotensive, correcting the BP
should be prioritized over correcting the PCV.
A good checklist for sick cats going to surgery is:
 Is blood available?
 Will a feeding tube be needed?
 Is a pressor (dopamine or dobutamine) available and the dose calculated?
 Any need for a lumen catheter?
 Liver disease? (Vitamin K 1 day prep if elevated PT)
 Antibiotics needed? (Septic cats may not seem septic)
Wound soaker catheters for cats
Wound soaker catheters are small catheters that are implanted in surgical wounds prior
to closure for delivery of local anesthetics during the postoperative period. They provide
outstanding analgesia and can reduce the need for (or reduce the doses of) opioids, NSAIDs
and other analgesics. The catheters are typically removed 2-3 days after surgery, near the end
of the inflammatory phase of wound healing, which is the most painful phase.
Good catheters are made by MILA (Medical Instrumentation for Animals) and Recathco.
The catheters have multiple side ports through which the local anesthetic passes, so they work
much like a “soaker” garden hose. The Recathco catheters are quite narrow-bore, so deliver
limited amounts of anesthetic to their distal end, and we prefer MILA catheters for that reason.
The MILA catheters come in a variety of lengths, but all have the same loading volume.
Wound soakers can be used in almost any large wound or incision on the surface of the
body – amputations, major traumatic wounds, thoracotomy incisions, etc. We generally do not
implant them in total ear canal ablation incisions because of concerns about neurologic effects
of delivering anesthetics to the middle/inner ear. The catheters are introduced through a small
skin incision adjacent to the main incision, should extend throughout the length of the wound,
and should be implanted in the deepest part of the wound. Be careful not to include the catheter
in a wound closure suture! The entrance point should be relatively dorsal so that the catheter
can easily be accessed for drug administration. A flange is provided for securing the catheter to
the skin with 2 sutures.
Because lidocaine delivery requires an infusion pump, bupivacaine, which is long-acting
and can be administered intermittently, is more practical. To increase dispersion of the drug,
dilute the initial 0.5% solution in which it comes to 0.25% (=2.5 mg/ml). Load the catheter
(regardless of catheter size) with 0.8ml. The drug is given every 4-6 hours at 1mg/kg (~1-2 ml
for a typical cat).
Principles of Surgical Oncology
John Berg, DVM, DACVS
Atlantic Provinces Veterinary Conference, 2015
Roles of surgery in the treatment of cancer
Surgery continues to play a key role in the management of many cancers in dogs and cats. The majority of malignant
tumors of companion animals that are cured are non-metastatic tumors that are completely excised. On the other
hand, because local tumor recurrences are often difficult or impossible to manage and are therefore life-threatening,
failure to adhere to basic principles of tumor excision can mean that cancers that should have been cured by surgery
instead result in the death of the patient.
Surgery can have the following roles in the management of patients with cancer:

Providing a diagnosis (biopsy)

Palliation of symptoms

Reduction of tumor volume (in conjunction with radiation therapy)

Complete tumor excision
Biopsy
While an experienced veterinarian can make an accurate educated guess regarding the histologic type of a given
mass as often as 75% of the time, no one can be right 100% of the time. For this reason, it is never wrong, and it is
very often correct, to obtain a biopsy prior to treatment.
Fine needle aspirate (FNA) cytology can give a quick, accurate and inexpensive indication of tumor type prior to or in
lieu of biopsy. However, because FNA’s do not preserve cellular relationships, they are less accurate than biopsies,
and do not permit tumor grading. In addition, FNA’s are only useful for tumors that readily exfoliate cells. They are
most useful for diagnosing lipomas, mast cell tumors and other round cell tumors; are often useful for carcinomas;
and are occasionally useful for sarcomas, including bone sarcomas.
Biopsies require sedation or general anesthesia. They can be obtained with a needle such as a Tru-cut needle, a
punch, or by making a small skin incision. These methods are often interchangeable, and the choice depends on the
size and depth of the tumor and the preferences of the veterinarian. Excisional biopsy refers to complete removal of
a mass (see below) and submission for histopathology without a separate preoperative biopsy. In general, if a mass
is nearly as easy to completely excise as it is to biopsy, it should be excised. For example, masses on the distal limb
are often biopsied prior to treatment because of the relative lack of available skin for closure after excision, whereas
proximally-located masses, which tend to be easy to remove, are often treated by excisional biopsy.
Biopsy principles include the following: Tissues should be handled gently, as crushed tissue is often impossible to
interpret accurately. Multiple samples should be obtained from multiple sites to improve the odds of obtaining truly
representative tissue. Biopsies should be obtained from both deep and superficial regions of the tumor. Because
biopsy can cause seeding of tumor cells in overlying normal tissues, the biopsy site should be chosen to allow easy
resection of the incision at the time of definitive surgery. Tissue should be placed in a large volume of formalin - 10
parts formalin to 1 part tissue.
Pathology is not an exact science, and biopsy results may not fit your clinical impression. The most likely cause of
disagreement between your impression and the actual biopsy result is that you missed the tumor. However, technical
errors in specimen collection, and pathologist error, are other possible explanations. Veterinarians should feel free to
request second opinions when biopsy results seem questionable; in one large retrospective study, 17% of second
opinions resulted in a change in the treatment plan or the prognosis given the owner.
Palliation
The term palliative refers to treatments that relieve symptoms without necessarily addressing the underlying disease.
Because cancer often causes pain, there is a palliative element to many cancer surgeries. Removal of highly
metastatic tumors that cause severe pain (eg., osteosarcoma) or hemorrhage (eg., hemangiosarcoma) are examples
of purely palliative surgeries.
Reduction of tumor volume
In general, “cytoreduction” or “debulking” are surgical procedures that should be avoided if possible: the first question
in examining a patient with a tumor should always be “can this tumor be completely removed?” Incompletely excised
malignancies will usually recur within a period of months. However, reduction of tumor volume can be a legitimate
goal when postoperative radiation therapy is planned. In general, radiation is most effective when tumors volume is
reduced to a microscopic level.
Complete tumor excision
Planning for surgery
The single most important principle of tumor excisions is to do what is necessary to obtain a complete excision on the
first attempt. Subsequent surgeries are always more difficult, and are statistically less likely to result in complete
excision, than is the first attempt. There are several reasons for this. If a first excision is incomplete, or results in a
local recurrence, it should be assumed that the entire original surgical field is contaminated with tumor cells, and must
be widely removed. Therefore, subsequent surgeries are always “larger” than initial surgeries. If critical anatomic
structures limited the aggressiveness of the first attempt, those structures will be even more limiting on subsequent
attempts. The presence of scar tissue in the area often makes subsequent surgeries more difficult. Finally,
incomplete excisions leave the most aggressive component of a tumor behind (ie., the outermost and newest cells).
Good planning is critical to the success of any tumor excision. Many tumor excisions are limited not by the size or
location of the tumor, but by the limited options for closing the wound once the tumor is removed. Veterinarians
performing cancer surgeries should have a good understanding of basic reconstructive surgical procedures such as
tension-relieving techniques, advancement flaps, rotation flaps, and transposition flaps; the latter flap is simple and
highly versatile, and can permit wound closure in many challenging areas of the body. Many axial pattern flaps are
also simple to perform and are easily applicable to primary care practice. Open wound management is often an
option for wounds that cannot be closed primarily, and is particularly useful in the distal limbs, where there are often
no applicable flaps. Combinations of the above techniques may be needed to achieve closure of some wounds.
Advanced cross sectional imaging (CT or MRI) is occasionally essential in planning cancer surgeries. In general,
these techniques are used to answer specific questions regarding the involvement of deep anatomic structures
adjacent to the tumor. Even with these modalities, it is often difficult to determine whether a tumor comes close to a
structure, abuts it, or actually invades it. The relative strengths and weaknesses of CT and MRI are summarized in
the following chart:
CT
MRI
Relatively inexpensive
Expensive
Fast
Relatively slow
Poor soft tissue detail
Good soft tissue detail
Good for assessing bone
Good for assessing bone
Key principles of tumor excision include the following:

Think about when to do the hardest part – in some cases it makes sense to do the hardest part early (eg.
isolation and ligation of major vessels during amputation), and in other cases, it easiest to do the hardest
part last (eg., isolation and ligation of major vessels during nephrectomy)

Control diffuse, minor bleeding as you go

Don’t dissect where you can’t see

Handle tumors gently

Ligate venous return early, if possible (eg., spleen, lung)

Don’t become impatient

Change gloves and instruments before closing body cavities to limit the risk of seeding the body wall
Margins
The conventional margin recommendations (1cm for most malignancies, 2cm for mast cell tumors) are simply
guidelines. An adequate margin depends in part on the tissue in question: eg., fat provides a very poor barrier to
tumor growth, and a 1 cm margin may be inadequate; whereas flat bones such as the maxillary bones provide a very
good barrier, and bone removal may provide an adequate margin even if the margin measures less than 1 cm.
Whenever possible, dissections should be made in normal tissue planes, and a fascial plane should be removed with
the tumor. A key point is to recognize that the apparent pseudocapsule that surrounds many tumors is not composed
of fibrous tissue – it is composed of compressed tumor cells. Marginal excisions – those just outside the
pseudocapsule – risk local tumor recurrence. With regard to margins, tumor excisions are classified as follows:
Type of excision
Definition
Risk of local recurrence
Intracapsular
Dissection inside pseudocapsule
100%
Marginal
Dissection just outside
pseudocapsule
Variable
Wide
Dissection completely within normal
tissue
Zero
Radical
Entire anatomic structure removed
(eg amputation)
Zero
Before submission of excised tumors for histopathology, steps should be taken to guide the pathologist interpreting
the margins. Most labs will only examine 3-4 sections per tumor – not the entire tumor. Therefore, if there are
margins you are particularly concerned about, those should be tagged with a suture and examination of the tagged
areas should be requested. The exterior of all excised tumors should be inked prior to submission to aid in
distinguishing true surgical margins from artifactual “margins” created during pathology processing – during histologic
examination, cancer cells adjacent to inked surfaces are of concern, whereas cells adjacent to non-inked cut surfaces
are not.
Margin reports should be interpreted as follows. A report of a “clean” or “complete” excision means that the limited
number of areas that were examined were free of tumor cells at the margin. There is a low likelihood, but not a zero
likelihood, of tumor recurrence. A report of “dirty” or “incomplete” margins means that in at least one location, the
excision was incomplete. There is a higher likelihood of local recurrence; however, local recurrence is not assured.
Recent data pertaining to soft tissue sarcomas and mast cell tumors excised with reports of incomplete margins
suggest that recurrence rates are typically 20-30% - lower than was once thought.
Therapeutic options when margins are interpreted as incomplete include:

Re-excision with wider margins. When feasible, this is often the least expensive and most effective option.

Close monitoring for recurrence. This is often elected when there are significant financial limitations.
Monitoring is often appropriate in anatomic locations where a recurrence could be easily managed with
additional surgery, but less appropriate where a recurrence would be unmanageable.

Radiation therapy. If radiation therapy is a consideration, the wound margins should be marked with metallic
clips during surgery to aid the radiation oncologist in planning the radiation field.
Regional lymph nodes
Lymph nodes that are known to contain metastatic cancer should be resected if possible to lower the risk of local
tumor recurrence. Unfortunately, in many locations, lymph nodes are surprisingly difficult to completely resect;
however, in others, nodes can easily be resected en bloc with the primary tumor (eg., mammary tumors). Lymph
node removal is often further complicated by the fact that in companion animals, the relevant draining lymph nodes in
many areas of the body are not well defined. While physical examination is not an accurate tool for preoperative
assessment of lymph nodes, FNA is an excellent tool, and lymph node FNA should be routine part of the preoperative
assessment of most patients for which a tumor excision is planned.
While it makes intuitive sense that removal of cancerous lymph nodes might improve a patient’s prognosis, to date,
there are no studies assessing the therapeutic value of lymph node excision for any canine or feline tumor type.
However, intraoperative removal or biopsy of regional lymph nodes provides valuable prognostic information for many
tumor types, because nodal metastasis is often an indicator of distant metastases. Canine tumors for which lymph
node status is known to be correlated with survival include mammary carcinoma, small intestinal tumors, anal sac
carcinoma, mast cell tumors, primary lung tumors, oral malignant melanoma, and osteosarcoma. For each of these
tumor types, a positive lymph node should prompt consideration of chemotherapy or other adjuvant therapy.
Ethical considerations in surgical oncology

The fact that a patient is old is not a contraindication to surgery or other forms of cancer therapy. Owners of
older animals with cancer are often the best possible clients, and older animals are often ideal patients.

On the other hand, the fact that a tumor can be removed with aggressive surgery does not mean that it
should be removed. Common sense should always prevail.

Lack of data regarding the efficacy of chemotherapy or radiation therapy for a given tumor does not mean
they’re contraindicated.
Upper Airway Surgery
John Berg, DVM, DACVS
Atlantic Provinces Veterinary Conference, 2015
Laryngeal paralysis
Laryngeal paralysis is caused by bilateral loss of function of the recurrent laryngeal nerves, resulting in
paralysis of the intrinsic muscles of the larynx. Two forms of this disease exist: congenital and acquired
(or idiopathic) forms. The congenital form occurs in dogs less than one year of age. Breeds affected
include Bouvier des Flanders, Siberian huskies, Malamutes, and English bull terriers. Acquired idiopathic
laryngeal paralysis is by far the most common form of the disease. Old and geriatric large and giant
breeds are most often effected.
Clinical signs of acquired laryngeal paralysis
The cardinal sign of acquired laryngeal paralysis is progressive inspiratory dyspnea and stridor. A
weakening bark, coughing and gagging may also be present. Signs are often more pronounced during
hot weather. Dogs may present for an acute episode of respiratory distress and require immediate
emergency treatment and stabilization. Radiographs of the thorax are indicated to evaluate the chest for
evidence of aspiration pneumonia, which is occasionally present on admission. It is now recognized that
acquired laryngeal paralysis is an early sign of a systemic polyneuropathy that may also involve the
innervation of the esophagus, and, eventually, the skeletal musculature. Dogs with esophageal
dysfunction often have radiographic evidence of aspiration prior to surgery.
A presumptive diagnosis is made based on signalment, history and presenting signs. The diagnosis is
confirmed by direct visualization of the larynx while the animal is under light sedation (thiopental 515mg/kg or propofol 2-6mg/kg IV). It is important to understand the normal anatomy and to note the
pattern of respiratory cycle compared to the movement of the arytenoids. A dog with laryngeal paralysis is
unable to abduct the arytenoids and vocal folds during inspiration. If there is movement, it is out of phase
with respiration.
Medical Treatment
Animals that present during a cyanotic episode need immediate treatment. Oxygen supplementation (O 2
mask or cage) as well as symptomatic treatment of shock and hyperthermia are indicated. If the patient is
stable but anxious a small dose of acepromazine (0.025-0.05mg/kg IV or SQ) is indicated. Steroids can
also be used to treat secondary inflammatory changes and edema caused by excessive panting and
coughing, as this swelling can further occlude the airway.
Surgery
A number of procedures have been described for surgical treatment of laryngeal paralysis. Of these, the
most commonly performed procedure is unilateral arytenoid lateralization.
Arytenoid lateralization
A lateral approach to the larynx is made. For right handed surgeons, the procedure is most easily
performed on the dog’s left. The thyropharygeus muscle is transected, the thyroid lamina is separated
from the underlying cricoid cartilage with a blade or scissors, and the thyroid cartilage lamina retracted
laterally to expose the muscular process of the arytenoid cartilage, to which the cricoarytenoideus muscle
attaches. The caudal border of the cricoid cartilage is identified, and 2 nonabsorbable sutures are placed
between the caudodorsal border of the cricoid cartilage and the muscular process, holding the left
arytenoid cartilage in the abducted position created by the presence of the endotracheal tube. In essence
this permanently opens the larynx on one side.
Postoperative care
Particularly during the first several days postoperatively, but also the balance of the dog’s life, there is
increased susceptibility to aspiration pneumonia. The overall incidence of postoperative aspiration
pneumonia is about 20-25%. Avoiding the use of opioid analgesics, and maintaining the head in an
elevated position, can reduce the risk of aspiration during the early post-op period. Feeding of meatballs
during the first 2-3 weeks after surgery may also reduce the risk of aspiration.
Brachycephalic airway syndrome
Brachycephalic airway syndrome primarily affects French and English bulldogs, Boston terriers and Pugs.
Primary components of the syndrome are elongated soft palate, stenotic nares, and hypoplastic trachea.
Eversion of the laryngeal saccules and eventual laryngeal collapse may develop secondarily. Of the
primary components, only elongation of the soft palate and stenotic nares can be treated surgically; the
elongated soft palate is usually the most important component, and the one that is most effectively
addresses with surgery.
Clinical Signs
Inspiratory dyspnea and stridor, typically developing at a few months of age, is the main clinical sign. It is
partially relieved by open-mouth breathing. Coughing, gagging and exercise intolerance may also be
present. Signs are typically more pronounced in hot weather. Effected dogs often have difficulty
sleeping, and some learn to sleep on their backs with the neck extended to maintain an open airway.
Surgery
Surgery for brachycephalic airway syndrome can be considered if the patient is compromised in any way
by the condition – noisy breathing alone is generally not an indication for surgery.
Elongated soft palate resection is performed with the dog in sternal recumbency and the head and
neck extended and elevated. The landmark for the resection is the cranial tip of the epiglottis or the
caudal 1/3 of the tonsils. The resection is most easily performed with a surgical laser, which limits
hemorrhage from the cut edge of the palate. Suturing is not necessary if a laser is used. The resection
may also be performed using a “cut and sew” method, in which scissors are used to transect the palate
and hemorrhage is controlled by concurrent placement of a continuous suture line apposing the dorsal
and ventral mucosal surfaces.
The decision whether or not to address stenotic nares is based largely on a subjective judgment as to
whether the nares are narrow or not. In larger dogs such as English bulldogs, the procedure is performed
by resecting a wedge of tissue from the dorsolateral nasal cartilage, then suturing with 1 or 2 fine
absorbable sutures (which do not require removal. In smaller dogs (and brachycephalic cats), Trader’s
technique may be used: a portion of the dorsolateral nasal cartilage is simply excised, and the cut surface
is allowed to heal by second intention.
Everted laryngeal saccules (ventricles) are often encountered along with stenotic nares and elongated
soft palate. The saccules evert in response to the abnormal negative pressure created in the larynx
during inspiration. On laryngeal exam, the saccules can be visualized as small, pinkish masses
immediately cranial to the vocal folds. While everted saccules can easily be treated by resection with a
blade or scissors, they will usually (but not always!) resolve on their own if the primary components of
brachycephalic airway syndrome are addressed as described above.
The Spay-Neuter Controversy
John Berg, DVM, DACVS
Atlantic Providences Veterinary Conference, 2015
In this lecture, I will summarize some of the major literature pertaining to the disease-related risks and
benefits of spaying and neutering dogs and cats, and will summarize my own recommendations on the
subject based on my interpretation of the literature. I will also briefly discuss the pros and cons of
laparoscopic spaying, and the pros and cons of ovariohysterectomy vs. ovariectomy.
Risks and benefits of spaying and neutering
This discussion will focus only on diseases whose frequency may be increased or decreased by spaying
or neutering – the value of gonadectomy in population control will not be considered.
When I graduated from veterinary school in 1981, and up until about 10 years ago, veterinarians routinely
recommended gonadectomy of all immature dogs and cats. However, during the past several years,
research has emerged that suggests that gonadectomy may predispose both dogs and cats to certain
diseases, including some very serious diseases, such as cancer. Some of the major research will be
summarized here.
Prevention of mammary cancer – Other than population control, the most important reason to
recommend spaying of female dogs is prevention of mammary cancer. In dogs, based on research
conducted in California in the early 1960’s, there is a correlation between the number of estrus cycles
prior to spaying and the risk of mammary cancer:
Time of OHE
Relative risk of mammary cancer (compared to intact dogs)
Before 1st estrus*
0.05%
Before 2nd estrus
8%
Before 3rd estrus
26%
After 3rd estrus
100%
* As early as 5 mos in cats and small breed dogs; 6 mos in larger dogs
In cats, a recent study (Overly, JVIM 2006) demonstrated a 91% reduction in mammary cancer risk in
cats spayed prior to 6 months, and an 86% reduction in risk in cats spayed prior to 1 year.
The above data suggest that the greatest benefit of spaying occurs if it is performed very early in life, so
that ovarian hormones are not present during puberty, when the majority of mammary development
occurs.
Although recent publications have called the methodology of the 1960’s research into question (Beuavais,
JSAP 2012), the incidence of mammary cancer appears to be dramatically higher in European countries
in which dog populations are predominantly sexually intact (Norway, Denmark, Italy). In these countries,
mammary tumors account for 50-70% of all tumors; meanwhile, mammary cancer is relatively uncommon
in the U.S., where the majority of female dogs and cats are spayed. While the early studies need to be
repeated, my personal bias is that the preponderance of the evidence suggests that an intact neuter
status is a strong risk factor for mammary cancer.
Increased risks of other cancers – Evidence has emerged that gonadectomy may predispose dogs to
certain very common, very serious cancers. Some of this evidence is quite strong, some of it is less
strong. It may be summarized as follows:
Type of cancer
Relative risk, castrated males
Relative risk, spayed females
OSA
3.8
3.1
Prostate*
2.4-4.3
Bladder TCC
2-4
2-4
Splenic HSA
2.2
MCT
4.11
* Prostate cancer is so rare that it really shouldn’t be part of the conversation.
Three of the recent, large studies in this area are summarized below.
Rottweilers (OSA) – In a very good study (Cooley, J Cancer Epid, 2002), 683 Rottweillers owned
by breed club members were followed for a total 71,000 dog-months. The relative risks among males
and females gonadectomized prior to a year of age are shown in the chart above; there was no increased
risk among dogs gonadectomized at later ages. The risk of OSA was inversely proportional to the age at
gonadectomy – the ealier the gonadecomy, the greater the risk. This may have been a highly OSA-prone
population of dogs: among dogs gonadectomized prior to a year of age, the lifetime risk of OSA was 1 in
4!
Golden retrievers (MCT, LSA, HSA) – This internet-based U.C. Davis study of 759 Golden
retrievers, published in an open-access journal (Torres de la Riva et al, Plos One 2013), showed that
among male dogs, early neutering (prior to 1 year) appeared to predispose to lymphoma, and among
female dogs, late-neutered females were predisposed to HSA and MCT.
Vizslas (MCT, LSA, HSA, other cancers) – This internet-based study (Zink et al, JAVMA 2014)
of 2,505 Vizslas showed that gonadectomized dogs, regardless of age at gonadectomy, were
predisposed to MCT, lymphoma and all types of cancer combined. Females spayed before 12 mos of
age and males neutered after 12 mos of age were at increased risk for HSA.
Effects of gonadectomy on non-cancerous diseases – The effects of gonadectomy on various noncancerous diseases are summarized in the charts below. (? = conflicting data)
Castrated male dogs
Decreased risk
Increased risk
Perineal hernia
Obesity
Benign prostatic diseases
CCL rupture
Perianal adenoma
Diabetes (?)
Male-on-male aggression
Hip dysplasia (?)
Castrated male cats
Decreased risk
Increased risk
Roaming, fighting, etc
Obesity
FLUTD (?)
Diabetes
Spayed female dogs
Decreased risk
Increased risk
Pyometra
Obesity
Urinary incontinence (5%)
CCL rupture
Hip dysplasia (?)
Spayed female cats
Decreased risk
Increased risk
Pyometra
Obesity
FLUTD (?)
Diabetes
Key open questions
1.
Does the information we have apply to all breeds of dogs and cats?
2.
other,
How do the incidences of the various diseases (cancerous and non-cancerous) compare to each
with and without gonadectomy?
3.
How should we weigh the fact that some diseases affected by gonadectomy are relatively rare,
but fatal, and others are relatively common, but treatable?
4.
What level of confidence should we have in the various studies?
Summary – recommendations
Below are my recommendations to owners, based on my biases and my interpretations of the literature
as it stands today. There are a few caveats:
1.
This is an extremely complex area, and there are far more questions than answers. New data
that will replace current data will likely emerge over the next 20 years.
2.
I have a bias toward preventing diseases that are likely to be fatal over preventing treatable
diseases, even though the treatable diseases in some instances may be more common.
3.
Spay-neuter decisions should be made in conjunction with owners, who need to be as fully
informed as possible. Veterinarians do not have all the answers.
4.
For dogs and cats of both sexes, gonadectomy increases the risk of obesity, but obesity is
preventable, so is only a minor consideration.
Male cats
This is the easiest one. Neutering prevents behavioral issues, making neutered male cats better
pets.
There are no major health downsides to neutering male cats.
Female cats
Until data emerges that supplants our current data, I believe that female cats should be spayed
prior to 5 mos of age to prevent mammary cancer, which is almost uniformly fatal in cats. Spaying will
also eliminate the risk of pyometra.
There are no major health downsides to spaying cats.
Small- and medium-sized male dogs (No OSA predilection)
The value of neutering is least clear for male dogs, and the issue should always be discussed
with the owner. My current bias is that male dogs should not be neutered unless they have clear maleon-male behavioral issues that cannot be resolved in other ways. Remember that vasectomy is a birth
control option.
Neutering will decrease the risk of perineal hernia and non-cancerous prostatic diseases, but both
of these are treatable.
Neutering may increase the risk of bladder TCC and possibly other cancers; and CCL rupture.
Small- and medium-sized female dogs (No OSA predilection)
Neuter prior to 5 mos of age to prevent mammary cancer (this will be my recommendation until
someone demonstrates definitively that the sparing effect is less powerful than we currently think it is).
Neutering will also decrease the risk of pyometra.
But it may increase the risk of bladder TCC and possibly other cancers; CCL rupture; and urinary
incontinence.
Large breed male dogs (OSA predilection)
Discuss neutering with the owner. My bias is that male dogs should not be neutered unless they
have male-on-male aggression issues that cannot be addressed in other ways. If the owner wants
neutering, recommend delaying it to beyond a year
of age to decrease the OSA risk (based on the
Rottweiler study described above). Remember that vasectomy is a birth control option.
Neutering will decrease the risk of perineal hernia and non-cancerous prostatic diseases, but
these are treatable and the reduction in risk will likely still be present even if neutering is delayed well into
young adult life.
Neutering may increase the risk of OSA, lymphoma, MCT, splenic HSA and possibly other
cancers; and CCL rupture.
Large breed female dogs (OSA predilection)
Neuter prior to 6 mos of age to prevent mammary cancer (until someone definitively
demonstrates that the sparing effect is less powerful than we currently think it is).
Neutering will eliminate the risk of pyometra.
But it may increase the risk of OSA, lymphoma, MCT, splenic HSA and possible other cancers;
CCL rupture; and urinary incontinence.
Issues related to spay technique
Laparoscopic spay - The main advantage of the laparoscopic spay is that it is probably less painful
than a traditional open spay during the first 1-3 days after surgery. However, the average dog tolerates a
routine spay incision extremely well, so the gain in pain relief through laparoscopy is somewhat marginal.
Lap spay requires a large equipment investment, and is more expensive for owners than open spay.
However, it is actually easier to spay a large, fat dog laparoscopically than with open surgery. Many
owners learn about laparoscopic surgery in animals via the internet, and develop a preference for it based
largely on the perceived pain-sparing benefit, and owner demand may continue to increase.
Nevertheless, open spaying is a quick, reliable, proven, safe and effective procedure, and practitioners
who do not offer laparoscopic spaying should not feel that they have “fallen behind.”
Ovariectomy (OVE) vs. ovariohysterectomy (OVH) - For many years, European veterinarians have
performed OVE’s rather than OVH’s. All of the advantages of spaying pertain equally with either
technique. The main reason that OVH has been favored in the US is that it has been thought to reduce
the risk of stump pyometra. However, the most common cause of stump pyometra is leaving an ovarian
remnant, not leaving a uterine remnant. Once the ovaries are completely removed, the uterus markedly
atrophies and in the absence of ovarian hormones is very unlikely to become infected. A laparoscopic
spay in the US is most commonly an OVE. To perform and OVE with open surgery, the uterus can be
single- or double-ligated about 1-2 cm from the ovary, and transected at that level.