ISRAEL JOURNAL OF
VETERINARY MEDICINE
APPLICATIONS OF ENDOSCOPY FOR AVIAN MEDICINE
Gancz A. Y,1 and Taylor W.M.2
1 The Center for Avian and Exotic Pet Medicine, Koret School of Veterinary Medicine, The
Hebrew University of Jerusalem, POB 12, 76100 Rehovot, Israel.
2 Veterinary Teaching Hospital, The Ontario Veterinary College, University of Guelph,
Guelph, Ontario N1G 2W1, Canada.
Summary
Endoscopy is an integral part of the diagnostic means available
to the avian veterinarian. Through a variety of minimally
invasive approaches and techniques it is possible to visualize
and sample almost every organ and tissue type in the bird’s
body. This paper describes the most common approaches and
their application.
Introduction
Endoscopic techniques and equipment have been in use in human medicine since
the 1950s and 1960s, and have become integral diagnostic tools in many medical
fields. In the 1970’s these techniques were adapted for use in veterinary medicine,
particularly in avian medicine. Initially, human endoscopy equipment was used,
and it was only in the 1990s that a dedicated system was developed for avian
endoscopy (1-5). Today endoscopy is recognized by most avian clinicians as an
important diagnostic tool, and is currently also being used to perform minimallyinvasive surgeries (6-9).
Indications
The indications for endoscopy can be divided into two groups: diagnostic
endoscopy, and therapeutic endoscopy. Diagnostic endoscopy is indicated when:
1. there is evidence (e.g. clinical, hematological, radiological) of a pathological
process that affects a specific organ or system and further information is needed
on the nature of the lesions
2. biopsies or fine needle aspirates are required from organs that are approachable
by endoscopy
3. a diagnosis can not be reached by other means, as an alternative for exploratory
surgery
Therapeutic indications include:
1. removal of foreign bodies from the upper digestive tract (to the level of the
ventriculus)
2. removal of foreign bodies, parasites, or inflammatory debris from the upper
respiratory system and/or air-sacs.
3. treatment of fungal granulomas (debulking, direct injection of antifungal
agents, fulguration).
4. Removal of eggs or egg fragments from the oviduct
5. Performance of certain minimally invasive surgeries (e.g. orchidectomy,
salpingohysterectomy, pericardial window)
Contraindications for endoscopy include:
1.a bird that Is not stable enough to be anesthetized
2. ascites
3. obese patient
4. distension of the digestive system (e.g. in raptors after a large meal)
5. space occupying lesions that reduce air sac size or severe air saculitis
Equipment
Endoscopes can be divided into two main categories, flexible and rigid. Although
both groups are useful for avian medicine, the use of rigid endoscopes is much
more common due to the fact that they are easier to position, have higher optical
quality for a given diameter, and their rigidity enables puncturing air-sac
membranes. A rigid endoscope of 2.7mm in diameter and with an insertion length
of 18 to 19cm is accepted as the most versatile tool for avian endoscopy. A 30
degree offset front lens is desirable as it increases the visible field and enables the
examination of objects from various angles. Other endoscope sizes may be
needed for examination of birds of unusual size while flexible endoscopes may be
useful for examination and removal of foreign bodies from the upper digestive
tract of large and/or long-necked birds.
The use of some form of examination sheath protects the endoscope and enables
the use of suction, insufflation, or irrigation at the tip of the endoscope. These
functions are particularly useful for the upper digestive tract and for cloacoscopy.
The operating sheath enables in addition the use of miniature flexible instruments
that can be passed through the instrument channel (3). The most useful
instruments are: 5 French (F) elliptical biopsy forceps, 3.5 F sharp scissors, 5F
and 3F grasping forceps, 20G injection needle with a silicon sheath, and a snare
that can be attached to a radiosurgical unit. Certain fiberoptic guides of surgical
lasers may also be passed through the instrument channel. Minimally invasive
multiple-entry surgery is generally performed using pediatric laparoscopy
instruments (9). The endoscope and instruments should be sterilized following the
manufacturer’s instructions.
Endoscopy requires the use of a light source. Several types of light sources exist
and are most commonly based on halogen or Xenon bulbs. These are connected to
the endoscope by a flexible fiberoptic cable. Although it is possible to perform
endoscopy by looking directly through the rigid endoscope’s eyepiece, this is
ergonomically undesirable when performing accurate procedures with surgical
instruments. For this reason the authors recommend the use of an endovideo
camera and a high definition video monitor. In addition, it is highly advisable to
use a documentation device (e.g. a VCR or a digital storage device). Documenting
the procedures enables the clinician to review the findings and present them to the
owner.
Anesthesia and Preparation
All of the procedures described bellow are performed under general anesthesia.
The authors prefer for most cases inhalant anesthesia (isoflurane or sevoflurane)
delivered through an endotracheal tube. This facilitates good control of the
anesthetic plane as well as momentary inflation of air-sacs when needed. Use of a
vascular Doppler device is recommended for monitoring heart rate and blood
pressure during anesthesia; however there is no substitute to the assistance of an
experienced assistant. Butorphanol (1-4 mg/kg) may be used as premedication as
well as to manage postoperative analgesia. Meloxicam (0.5 mg/kg q12-24h) may
be added; however, recovery from routine endoscopic procedures is usually rapid
and the patients rarely show signs of severe pain. The authors do not routinely
administer antibiotics to patients undergoing endoscopy.
In preparation for air-sac and peritoneal endoscopy the patient is placed in the
appropriate position and the entry point is prepared aseptically. In most cases only
a small number of feathers around the entry point need to be plucked. Adhesive
tape may be used to hold the surrounding feathers away from the surgical field.
The size of the area prepared will depend on the bird’s size (a minimal diameter
of 4cm is desired). The prepared area is isolated by the use a drape. Fenestrated
paper drapes or adhesive transparent drapes work well and are lightweight.
Approaches
Air-sac Endoscopy
Knowledge of the unique avian anatomy is essential for performing successful
air-sac endoscopy. The avian air-sac system includes nine sacs (four pairs and one
unpaired sac) that are associated with gas exchange. The paired sacs are (cranial
to caudal): cervical air-sac (CAS), cranial thoracic air-sac (CRTAS), caudal
thoracic air-sac (CTAS), and abdominal air-sac (AAS). The single clavicular airsac (CLAS) is located in the cranial thorax, cranial to and encompassing the heart
base. It has several extrathoracic extensions that communicate with the humeri
and the axillary regions. The shape and the relative size of the various air-sacs
differ between species. For example, in some species the CTAS is larger than the
AAS while in others it is vice versa. The air-sacs are separated from each other
and from other anatomical parts by thin, normally transparent, mesothelial
membranes. Each sac is connected to the bronchial tree by primary or secondary
bronchi. The openings (ostea) of these bronchi can be visualized and examined
from inside the air-sacs. In addition, birds possess paired cervicocephalic air-sacs
that are not connected to the bronchial tree but instead communicate with the
upper respiratory system. The latter are highly developed in psittacines, extending
from the mid skull to the thoracic inlet.
The most commonly used endoscopic approach to the visceral organs makes use
of the CTAS and the adjacent CRTAS and AAS. The entry point preferred by the
authors is just caudal to the last rib and immediately ventral to the flexor cruris
medialis muscle when the leg is pulled cranially (Image 2). After making a small
skin incision the flexor cruris medialis is bluntly separated from the underlying
abdominal muscles. The abdominal wall and CTAS membrane are punctured (e.g.
with a curved hemostat) at a point just caudal to the last rib near where the flexor
cruris medialis passes over. Care must be taken to prevent iatrogenic injury to
underlying internal organs by controlling the depth of penetration of the hemostat
by using both hands (with one near the tip) and aiming the tip slightly
dorsocranially. The puncture is expanded by opening the hemostat and the
instrument is removed. Accurate performance of this procedure will result in
entry directly to the CTAS in most species.
The endoscope should be introduced slowly with the non-dominant hand
controlling the distal tip. The opening made by the hemostat in the abdominal
wall should be identified and the tip of the endoscope guided into it. The CTAS is
easily identified by its unique landmarks and shape. The lung and ostium are
visible cranially and the liver and proventriculus/ventriculus ventrally. Cranially
and laterally, the CTAS is separated from the CRTAS a by thin membrane that
can be punctured by the endoscope tip. Passing into the CRTAS enables the
examiner to visualize the dorsocranial aspect of the liver, the heart, the lung, and
the pulmonary artery of the respective side.
Puncturing the caudomedial membrane of the CTAS enables entry into the AAS
of the respective side, from which the adrenal gland, urogenital system, lower
digestive tract, major nerves and blood vessels can be examined (Table 1). The
punctures made in air-sac membranes should be of the minimal size necessary.
Small tears heal well while large ones may not close. At the completion of the
procedure a single simple interrupted suture is passed between the abdominal
muscles and the flexor cruris medialis, while a second suture is used to close the
skin. Synthetic monofilament absorbable suture material is preferred.
The decision as to which side to examine depends on the organs or lesions
targeted. While most organs (e.g. lungs, liver, kidneys) may be visualized from
both sides, examination of the pancreas requires a right sided approach whereas
the spleen and female reproductive tract are best visualized from the left AAS.
The list of anatomical structures visible from each air-sac is presented in Table 1.
Endoscopy of the CLAS is indicated when examination of one or more of the
anatomical structures visible from this air-sac (Table 1) is required. The CLAS is
a narrow space packed with vital anatomical structures including the beating heart
base. Approach to this sac is done at the ventral midline, just cranial to the
furcula. A small skin incision is made and the crop is bluntly dissected and moved
cranially and dorsally to expose the thin membrane of the CLAS. Special care
should be taken when puncturing this membrane as the large blood vessels of the
heart base lie a few millimeters caudal to it.
Approach to the Ventral Hepatoperitoneal Spaces (VHPC)
The hepatoperitoneal space surrounds the liver and is divided by the dorsal and
ventral mesenteries into four compartments (right dorsal, right ventral, left dorsal,
and left ventral). The advantage of this approach is that it enables the clinician to
directly enter the VHPC and examine large areas of both the right and left liver
lobes. Liver biopsies can be collected without the need for cutting air-sac
membranes. The same approach also enables examination of the pericardium and
its drainage when necessary. Since there is no penetration of air-sacs, this
approach is reasonably safe even when pericardial or perihepatic effusion is
suspected. The entry point is on the midline, immediately caudal to the sternum.
After cutting the skin the perihepatic membrane is entered. In most cases the liver
is completely hidden under the sternum; however, some variation exists and with
hepatomegaly the liver may extend well beyond the caudal sternal border.
Examination of both lobes requires puncturing of the thin ventral mesentery
separating the left and right spaces.
Endoscopy of the Upper Gastrointestinal Tract
Prior to the procedure the clinician should familiarize himself with the anatomy of
the species (particularly that of the crop that may vary significantly between
families). The patient is anesthetized and an endotracheal tube is inserted into the
trachea. The bird is then placed in the desired recumbency (usually ventral). An
examination sheath is used and is connected to an insufflator as well as to a bag of
sterile 0.9% NaCl.
Each procedure begins with careful examination of the oral cavity (see also under
upper respiratory system). The esophagus leaves the oropharynx slightly right of
the midline. Insufflation by air or CO2 enables better viewing of the esophageal
and ingluvial wall. If the crop is not empty the bird may be turned into dorsal
recumbency to facilitate complete examination of the wall. The lower ingluvial
sphincter is located in psittacines near the midline. The size of the bird will
determine how far the endoscope reaches when entered from the oral cavity. In
larger birds (e.g. large macaws) an ingluviotomy may be necessary to reach the
proventriculus and ventriculus. Identification of the proventriculus is facilitated
by the openings of the pit-like gastric glands while the ventriculus is recognized
by the greenish to yellow colour of the koilin layer. In many cases the ventriculus
will contain grit and some food. Irrigation with saline is useful to improve
visibility and identify lesions or small foreign objects. The bird’s head should be
elevated during the procedure and during recovery from anesthesia to prevent
aspiration. An endoscopic-assisted lavage technique for removal of foreign bodies
and irritant content from the ventriculus has been recently described (10). Larger
objects are often better retrieved using the 3 or 5 F grasping forceps.
Endoscopy of the Upper Respiratory System
Endosopy of the upper respiratory system to the level of the syrinx and primary
bronchi is indicated when the history or clinical signs (e.g. sneezing, nasal
discharge, respiratory distress, voice change) point towards pathology of this
system.
The endoscope should be used to magnify and examine the nares. In the oral
cavity the choanal slit is examined and through it parts of the nasal septum and
the middle conchae can be seen. The infundibular cleft and glottis should also be
examined. The choanal margins and glottal folds are a common site for papilloma
formation.
The ability to perform a complete tracheoscopy depends on the tracheal diameter
and length. In small species an endoscope with a diameter <2.7mm may be
required while for larger long-necked species flexible bronchoscopes are best
used. A short examination does not require special preparations however longer
procedures require placement of an air-sac cannula. The clinician should be
careful not to cause trauma to the tracheal mucosa. Procedures that can be
performed inside the upper respiratory tract include removal of foreign objects
and parasites, treatment of strictures, partial removal of fungal granulomas and/or
direct placement of antifungal drugs.
Cloacoscopy and Examination of the Oviduct
This approach enables the clinician to examine the three cloacal compartments
(from cranial to caudal: coprodeum, urodeum, proctodeum), the mucosal folds
that separate these compartments, and the openings of the rectum, ureters and
genital system into the cloaca (11). The coprodeum is the largest of the three
compartments and usually contains fecal material mixed with urates. The entry of
the rectum into this compartment is usually easily visualized. In contrast, in many
species the urodeum is a very narrow space containing on its dorsal surface the
openings of the urogenital system. In species where the males have a phallus it
originates from the ventral urodeal surface. The opening of the cloacal bursa is
located on the dorsal wall of the proctodeum.
For the procedure the bird is placed in dorsal recumbency. A protective or
instrument sheath connected to a 0.9% NaCl drip is used. The endoscope and
sheath should be inserted carefully between the vent lips while infusing the
normal saline. Contact with the cloacal mucosa should be avoided to prevent
iatrogenic bleeding. The approach is especially useful for identification of early
signs of papillomatous changes that often involve the proctodeum and sometimes
also the urodeum. In laying hens examination of the oviduct and removal of egg
fragments may be possible; however, extensive flushing with fluids should be
avoided as it may result in leakage into the intestinal peritoneal space through
retrograde drainage out of the infundibulum. A technique for collection of
biopsies from the cloacal bursa through its opening to the proctodeum has been
recently described (12).
Biopsy Collection and Minimally-invasive Surgery
The instrument sheath of the endoscope enables the examiner to collect biopsies
from almost all avian organs/ tissue types. In some cases (e.g. the kidney) a
biopsy can be harvested directly from the abdominal air-sac by the use of biopsy
forceps, while for other organs (e.g. liver, spleen) the air-sac and peritoneal
membranes must be incised by scissors prior to biopsy collection. Use of the
surgical instruments requires practice. Insertion of the instruments into the
surgical sheath should be slow and careful. Once the tip of the instrument is
visible through the endoscope, the sheath and instrument should be moved as one
rather than moving just the instrument. Ideally, at least two biopsies should be
collected from each tissue of interest. Major blood vessels should be avoided and
the biopsy site should be examined to ensure proper hemostasis. When using the
biopsy forceps bleeding is usually minimal.
Minimally-invasive surgical techniques that make use of pediatric laparoscopy
equipment have been described (6-9). Unlike routine endoscopy, these procedures
require multiple entry points and simultaneous use of several surgical instruments.
Such procedures that have been described to date include orchidectomy, salpingohysterectomy, resection and ablation of fungal granulomas, and cloacopexy (6-9);
however, as these techniques continue to develop, more procedures will likely be
described.
Discussion
This paper demonstrates the versatility of applications of endoscopy in avian
medicine. The described techniques enable examination of the majority of organs
and tissue types, making them superb diagnostic and therapeutic tools. These are
especially important as the ability to diagnose diseases in birds based on clinical
signs and physical examination is often limited. Although Imaging techniques are
of great value in avian medicine, they rarely result in a specific diagnosis.
Ultrasonography in birds is challenging due to their small size, large sternum, and
extensive air-sac system. Furthermore, subtle changes in coloration of organs (e.g.
with excessive hepatic iron storage) cannot be appreciated by ultrasonography,
and the biopsy collection abilities are limited. Ultrasonography is advantageous in
birds with ascites, where endoscopy may be too risky, and may be of greater
value for diagnosis of female reproductive pathologies.
The risks associated with endoscopy include anesthetic complications,
hemorrhage, trauma to internal structures, infection, and herniation at the entry
point. These are generally rare in the hands of the experienced clinician, and are
far less serious than the risks associated with exploratory surgery. Performing
successful endoscopies requires practice as well as good knowledge of avian
anatomy and of the normal appearance of the various organs and tissues.
Endoscopy should be regarded as a highly effective “second line” of
diagnostic/therapeutic means after more basic means have been exploited.
The relatively large investment in an endoscopy system remains a major limiting
factor for private practices. Although pre-owned arthroscopy and laparoscopy
systems are widely available from the human market, finding a suitable
endoscope with sheaths and instruments is more difficult. The latter should
therefore be purchased from a single manufacturer to ensure compatibility. Using
the same equipment for other tasks (e.g. for ear canal examination in dogs and
cats or rabbit dental procedures) may make this purchase a more viable option for
the smaller practice. Recording of the examination enables the clinician to show
the findings to the clients, improving their understanding and trust.
References
1. Harrison, G. J. Endoscopic examination of avian gonadal tissue. Vet. Med.
Small. Anim. Clin. 73: 479-484, 1978.
2. Jones, D. M, Samour, J. H., Knight, J. A. and Finch, J. M. Sex determination of
monomorphic birds by fibreoptic endoscopy. Vet. Rec. 115: 596-598, 1984.
3. Taylor, M. Diagnostic applications of a new endoscopic system for birds. Proc.
Eur. Conf. Avian Med. Surg. pp. 127-131, 1993.
4. Taylor, M. Endoscopic examination and biopsy techniques. In: Ritchie, B. W.,
Harrison, G. J. and Harrison, L. R. (Eds): Avian Medicine: Principals and
Application. Wingers Publishing, Lakeworth, pp. 327-354, 1994.
5. Hernandez-Divers, S. J. and Hernandez-Divers, S. M. Avian diagnostic
endoscopy. Comp. Cont. Educ. Pract. Vet. 26: 839-852, 2004.
6. Pye, G. W., Bennett, R. A., Plunske, R. and Davidson J. Endoscopic
salpingohysterectomy of juvenile cockatiels (Nymphicus hollandicus). J. Avian.
Med. Surg. 15: 90-94, 2001.
7. Hernandez-Divers, S. J. Endosurgical Debridement and Diode Laser Ablation
of Lung and Air Sac Granulomas in Psittacine Birds. J. Avian. Med. Surg. 16:
138-145, 2002.
8. Wilson, G. H., McBride, M., Grant, K., Hernandez-Divers, S. and Ritchie, B.
Chemical castration of Pigeons via endoscopic intratesticular injection. Proc.
Assoc. Avian Vet. pp. 91-93, 2004.
9. Hernandez-Divers, S. J. Minimally invasive endoscopic surgery of birds. J.
Avian. Med. Surg. 19: 107-120, 2005.
10. Loudis, B. Endoscopic-assisted gastric lavage for foreign body retrieval. Proc.
Assoc. Avian Vet. pp. 83-88, 2004.
11.Taylor, M. Examining the avian cloaca using saline infusion cloacoscopy.
Exotic DVM, 3(3), pp 77-79, 2001,
12. Hernandez-Divers, S. J., Lester, V. K., Latimer, K. S., Wilson, G. H.,
Hernandez-Divers, S. M., Hanley, C. S., Strunk, A., Crane, M. and Ritchie, B.
Endoscopic techniques for the collection of lymphoid tissue from pigeons:
Evaluation of splenic and bursa of fabricius biopsy techniques and
histopathologic quality. Proc. Am. Assoc. Zoo Vet. pp. 269-270.