Urinary Stones
Archeologic studies show that urinary tract stone disease was an affliction of
humans earlier than 4800 BC (Shattock, 1905). Ancient Greek and Roman physicians recorded the symptoms and treatment of urologic stone disease, but little
attention was directed to localization of the stone or to the cause of its formation.
For a complete review of the historical aspects of urinary stone disease, see
Resnick and Boyce (1979).
In the 20th century, advances in technology and microscopic techniques have
led to a better understanding of the structural characteristics of calculi, their
chemical composition, and the various components of urine. Many theories have
been proposed to explain the cause and development of urologic calculi, but none
have been able to answer fully the questions concerning stone formation. In all
probability, stone disease will be found to result from the interaction of multiple
factors, many of which are as yet unknown.
Theories of Stone Formation
A. Nucleation Theory: Stone formation is initiated by the presence of a
crystal or foreign body in urine supersaturated with a crystallizing salt that favors
growth of a crystal lattice.
B. Stone Matrix Theory: An organic matrix of serum and urinary proteins
(albumin; a\- and 0:2-globulins and occasionally -γ-globulins; mucoproteins; and
matrix substance A) provides a framework for deposition of crystals.
C. Inhibitor of Crystallization Theory: Some urinary substances, eg,
magnesium, pyrophosphate, citrate, phosphocitrate, diphosphonate, mucoproteins,
and various peptides, inhibit crystal formation. Absence or low concentration of
inhibitors permits crystallization.
Most investigators acknowledge that these 3 theories describe the 3 basic
factors influencing urinary stone formation. It is likely that more than one factor
operates in causing stone disease. A generalized model of stone formation
combining these 3 basic theories has been proposed. A period of abnormal
crystalluria is required during which large crystals or aggregates of crystals are
produced in the urine. In order for these crystals to continue to grow and propagate, a certain number of chemical factors must be present, ie, the urine must be
supersaturated with thesalt of the stone-forming crystal, certain inhibitors of
crystallization must be reduced or absent from the urine, and a certain
concentration of nucleating matrix material must be present.
Additional risk factors can influence the degree and severity of clinical stone
disease. These include the metabolic state of the patient, which is influenced by
genetic background as well as the presence of certain hormonal imbalances;
environmental factors, which could lead to supersaturation of already saturated
urine; dietary excesses; and anatomic abnormalities, which could lead to chronic
infection or actually enhance the deposition of crystals in the upper urinary tract.
Anatomic Site of Stone Formation
There are several different theories as to where stone formation occurs in the
kidney: (1) deposition of calcium on the basement membrane of collecting tubules
and on the surface of papillae; (2) deposition of linear precipitates of calcium
within the renal lymphatics to produce obstruction and breakdown of the
membrane separating the lymphatics from the collecting tubules; and (3)
intratubular deposits of amorphous necrotic calcific cellular debris or organized
mi-crocalculi (or both).
DIAGNOSTIC EVALUATION
Medical History
A personal as well as a family history should be obtained for all patients. A
history of inflammatory bowel disease, recurrent urinary tract infection, prolonged
periods of immobilization, gout, or familial occurrence of certain inherited renal
diseases, eg, renal tubular acidosis or cystinuria, should be sought. Calcium oxalate
stone disease is inherited in a multifactorial manner, and hypercalciuria has been
shown to be inherited as an autosomal dominant trait. The presence of other
endocrine or metabolic disorders should also be considered.
A complete list of all medications taken should be obtained. Acetazolamide,
useful in the treatment of glaucoma, has been implicated as a cause of calcium
stones. Absorbable silicates, usually found as part of an antacid preparation, may
rarely be implicated in the formation of silicon calculi. Ascorbic acid in amounts
greater than 2 g/d may increase urinary excretion of oxalate and contribute to
formation of calcium oxalate stones. Any drug that decreases the urinary pH may
contribute to the formation of uric acid stones. Orthophosphates prescribed to
decrease calcium stone formation have been associated with an increase in the size
of struvite stones. The diuretic hydrochlorothiazide may cause uricosuria and
formation of uric acid stones, and allopurinol, a potent xanthine oxidase inhibitor
useful in the treatment of gout, may also cause precipitation and formation of
xanthine stones in certain individuals. In patients with a history of stone disease, all
methods of previous treatment, including surgery, should be documented and
details of stone composition sought.
Symptoms & Signs at Presentation
It is generally accepted that renal stones are initially formed in the proximal
urinary tract and pass progressively into the calices, renal pelvis, and ureter. Their
presentation may therefore vary from an incidental opaque shadow found on x-ray
to fulminant pyelonephrosis if obstruction and infection have occurred.
A. Symptoms Related to Stones at Specific Sites:
1. Caliceal stones-Small, asymptomatic, nonobstructing caliceal stones are
usually discovered as incidental findings on radiograms obtained for the evaluation
of other organ systems. Patients with nonobstructing caliceal stones are often
asymptomatic but may consult the physician after an episode of gross hematuria. If
the stone becomes large enough to obstruct an infundibulum, flank pain, recurrent
infection, or persistent hematuria may result.
2. Renal pelvic stones-A small stone in the renal pelvis may remain there
asymptomatically, pass into the ureter, or become impacted at the ureteropelvic
junction.
If obstruction occurs at the level of the ureteropelvic junction, the pain may be
intermittent, corresponding to the obstruction of urine flow, and may be localized
to the flank or the costovertebral angle. When urinary infection accompanies
obstruction, the patient may present with florid pyelonephritis or gram-negative
septicemia.
3. Proximal ureteral stones-A calculus small enough to pass into the ureter
can produce ureteral colic and hematuria. Beyond the ureteropelvic junction, the
ureter assumes a diameter of about 10 mm (30F), and small calculi can easily pass
to the level at which the ureter crosses over the iliac vessels. At this point, the
diameter of the ureter narrows to about 4 mm (12F), and stones at this level
commonly obstruct urine flow. The patient who presents with a stone in the upper
ureter will frequently experience a sharp, spasmodic pain of acute onset, localized
to the flank. As the stone passes down the ureter to the level of the pelvic brim, the
pain remains sharp and intermittent, corresponding to peristalsis of the ureter. The
pain frequently will radiate to the lateral flank and abdominal area and may be
accompanied by nausea and vomiting. The pain is typically intermittent, with
intense episodic intervals followed by periods of relief (' 'renal colic").
4. Distal ureteral stones-As the stone passes into the distal ureter, the pain
remains intermittent and sharp, corresponding to the intermittence of ureteral
peristalsis. In males, the pain frequently radiates along the inguinal canal into the
groin and corresponding testicle. In females, the pain may radiate to the labia.
A third area of ureteral narrowing exists at the level of the ureterovesical
junction. At this point, the ureter narrows to a diameter of 1 -5 mm and it is here
that most stones become lodged. Once a calculus reaches the distal ureter and
approaches the bladder, symptoms of vesical irritation frequently are noted.
B. Associated Nonrenal Symptoms: Owing to the arrangement of the
autonomic nervous system, which transmits visceral pain, and the similar neurologic innervation of the kidneys and stomach by the celiac ganglia, it is not unusual
for ureteral colic to be accompanied by nausea and vomiting. Abdominal distention
resulting from reflex ileus or intestinal stasis may also be present and confuse the
diagnosis. It is therefore necessary to consider other pathologic entities that may
mimic the presentation of a ureteral stone. Among these are gastroenteritis, acute
appendicitis, colitis, diverticulitis, salpingitis, and cholecystitis.
C. Variability of Symptoms: Less frequently, the passage of a stone may not
be as dramatic as noted above. Such patients may describe a ' 'dull'' ache in the
flank area that may have been present for several weeks without interfering with
their daily routine. This pain is not as localized as acute colic and may be confused
with other visceral pain.
Other less dramatic forms of presentation include persistent hematuria, either
gross or microscopic, and persistent urinary tract infection. These patients will
frequently have a struvite stone (see below).
Patients with asymptomatic stone disease may present initially for the
evaluation of hypertension, azotemia, or symptoms referable to the gastrointestinal
tract.
D. Findings on Physical Examination: A thorough physical examination is
an essential part of the initial evaluation of the patient who may have a urinary
calculus. Upon presentation to the emergency room, most patients will be
experiencing severe colic and will be in obvious distress. In contradistinction to
patients with acute peritonitis or abdominal pain, patients with ureteral colic will
toss about and be unable to find comfort in any position. Diaphoresis, tachycardia,
and tachypnea are frequent signs. Hypertension secondary to the discomfort may
also be present. Fever is usually not present unless infection is associated with
obstruction.
The abdomen should be examined carefully, with particular attention directed
to palpation of the flank, where ureteral obstruction may produce acutely a hydronephrotic kidney. The kidney or the costovertebral angle is frequently tender to
palpation. The abdomen should be carefully palpated to rule out surgical causes of
abdominal pain. It is not unusual for the bowel sounds to be hypoactive and for an
ileus to be present on radiographic examination. The bladder should also be
palpated, since urinary retention can occur secondary to acute ureteral colic.
Urinalysis and urine culture are required for all patients in whom stone
disease is suspected. Microscopic or gross hematuria is frequently present in
patients with acute ureteral colic. However, the absence of hematuria does not rule
out renal stone disease. Pyuria may be present even without urinary tract infection,
and bacteriuria is frequently seen in female patients with acute stone disease. Findings suggestive of infection may alter the therapeutic approach. The presence of
crystals should also be noted, since they often occur in the acute phase of stone
disease and may accurately reveal the type of stone present. Urinary pH should be
noted, because patients with uric acid or cystine stones usually have acidic urine
and those with struvite stones have alkaline urine.
F. Radiographic Findings:
At least 90% of all renal stones are radiopaque and therefore readily visible
on a plain film of the abdomen. Stones composed of calcium phosphate (apatite)
are the most radiopaque and have a density similar to that of bone. Calcium oxalate
is slightly less dense, followed by magnesium ammonium phosphate (struvite) and
cystine. Stones composed solely of uric acid or matrix are considered to be
radiolucent and would not appear on a plain film of the abdomen. Other
calcifications that may appear on the plain film and be confused with a urinary
calculus include calcified mesenteric lymph nodes, calcium in rib cartilage,
gallstones, foreign bodies (pills), and pelvic phleboliths. Oblique films may show
whether the calcification is in line with the normal anatomic position of the kidney
or ureter.
1. Intravenous urographyPatients whose history and physical examination are compatible with urinary
stone disease should undergo an intravenous urogram unless they are allergic to the
contrast medium. In a patient with acute ureteral colic, the most common finding
on intravenous urography is a delay in visualization of the collecting system on the
affected side. In the absence of complete ureteral obstruction or a nonfunctional
kidney, a dense nephrogram will appear, followed by visualization of the collecting
system. Delayed films should be obtained until the complete collecting system is
opacified down to the area of ureteral obstruction. Frequently, stones located in the
intramural portion of the ureter may be obscured by dye collected in the bladder.
An oblique film obtained after voiding will often show the calculus.
2. Tomography-In patients who present with acute ureteral colic, the plain
film of the abdomen often shows a paralytic ileus that may obscure existing
calculi. Plain-film tomograms may help to identify a stone otherwise obscured by
overlying gas or feces.
It is not uncommon to see perirenal or periureteral extravasation of contrast
medium in patients with obstructing ureteral calculi. The extravasation is believed
to originate from a forniceal tear and is associated with the increased pressure
caused by the obstructing stones. In the absence of infection, the condition is selflimiting and does not require further therapy. If infection is suspected, antibiotic
therapy should be instituted.
3. Retrograde urographyRetrograde pneumopyelography
Retrograde urograms are rarely needed to diagnose a stone; however, they are
indicated when the diagnosis is suspect or the patient is allergic to contrast
medium.
4. Ultrasonography-
In patients in whom it is not possible to obtain an intravenous urogram, ultrasonic evaluation of the kidneys may aid in the diagnosis of renal stones. In
pregnant women with flank pain in whom it is desirable to limit radiation exposure
or in anuric patients or patients with chronic renal failure, the presence of
hydronephrosis on acoustic shadowing may be diagnostic.
5. CT scanning- CT scanning is seldom indicated as the first diagnostic study
for the evaluation of a patient with a suspected urinary calculus. However, in cases
where the presence of a nonopaque stone or a urinary tract tumor is being
considered, CT scans have proved diagnostic.
Although a radiolucent stone cannot be detected on the plain film alone, the
diagnosis should be suspected when hydronephrosis and a radiolucent filling defect
are found on sonograms or urograms. A CT scan may help to differentiate a stone
from a blood clot or tumor.
SURGICAL TREATMENT OF RENAL STONES
Renal stones that must be surgically removed may be located in the pelvis,
infundibula, calices, or combinations thereof, and specific techniques are required
to manage each of these situations so as to effectively remove all stone fragments
and maximally preserve renal tissue.
Hypothermia in Urologic Surgery
Hypothermia reduces renal metabolism and prevents cellular damage during
periods of ischemia associated with intraoperative occlusion of the renal artery.
Renal cooling reduces cellular metabolic activity, so that the parenchyma! cells,
especially those of the proximal convoluted tubule, are better able to tolerate
ischemia. The temperature needed to prevent ischemic changes is controversial,
but experimental studies and clinical experience indicate that the kidney is
optimally protected when it is maintained at approximately 15-20 °C. Packing the
kidney in an ice slush prepared from physiologic salt solutions, applying external
cooling coils, and other methods are acceptable ways of cooling the kidney.
Intraoperative X-Rays
Intraoperative x-rays as well as sonograms obtained using portable
ultrasonographic equipment greatly aid the urologist in locating and removing
small stone fragments. Intraoperative nephroscopy and pulsatile irrigation are also
helpful in the removal of small stone fragments.
Open Surgical Procedures
A. Nephrectomy and Partial Nephrectomy:
Nephrectomy meets many objectives of surgery for removal of stones but
cannot be endorsed for treatment of stone disease, because renal tissue is
needlessly sacrificed. Indiscriminate partial nephrectomy often sacrifices
salvageable renal tissue and should be performed only in patients with severe
obstruction and parenchymal damage in whom the recovery of renal function of
that segment is expected to be minimal.
Pyelolithotomy
Simple pyelolithotomy is used for removal of calculi confined to the renal
pelvis. Minimal dissection of the renal sinus is usually needed, and exposure of the
entire kidney is not required. This procedure is not indicated for the removal of
entrapped caliceal stones or large, branched renal calculi.
C. Extended Pyelolithotomy: Trapped caliceal and branched stones usually
cannot be adequately removed through a simple pyelotomy. Dissection of the renal
sinus and exposure of the infundibula permit access to larger stones. Advocates of
extended pyelolithotomy consider it superior to anatrophic nephro-lithotomy
because it is less traumatic to the renal parenchyma. Operative blood loss is usually
minimal, so that occlusion of the renal vessels is rarely required.
D. Pyelonephrolithotomy: The removal of branched calculi located within
the lower pole infun-dibulum may be facilitated by extending a routine pyelotomy
incision through the renal parenchyma overlying the lower pole infundibulum
posteriorly. This procedure is also indicated for the removal of stones in the lower
pole of a kidney with a small intrarenal renal pelvis. The procedure is relatively
bloodless, and clamping of the renal artery is usually not necessary.
E. Coagulum Pyelolithotomy: Coagulum pyelolithotomy consists of use of a
mixture of pooled human fibrinogen and thrombin to form a clot within the renal
collecting system that effectively traps stones and facilitates their removal. The
mixture is injected into the renal pelvis before the latter is opened. The renal pelvis
is opened after 10 minutes, when the clot has formed. The main application of this
technique is in the removal of multiple small calculi in a large extrarenal renal
pelvis. It may also be useful in the removal of soft calculi that are likely to crumble
during removal.
F.
Anatrophic
Nephrolithotomy:
Intersegmental
anatrophic
nephrolithotomy (Boyce procedure; Smith and Boyce, 1967) is indicated for the
removal of multiple or branched calculi associated with infundibular stenosis. It is
also indicated in situations where pyelolithotomy is technically impossible, eg, in a
kidney with a small intrarenal renal pelvis and in cases where prior surgery has
obliterated access to the renal sinus.
Nephrolithotomy
An incision is made within the avascular plane or division between the
anterior and posterior vascular segments, the renal artery is clamped, and the
kidney is cooled to prevent ischemic changes. When the procedure is properly
performed, large renal calculi can be easily removed with minimal trauma to the
kidney. Reconstruction of the collecting system should also be done to facilitate
drainage and reduce the incidence of recurrent stone formation.
G. Radial Nephrotomy: Radial nephrotomy may be used as a primary
procedure or in conjunction with any of the other surgical procedures discussed
above. It is indicated for the removal of a solitary caliceal stone or a caliceal stone
associated with a larger intrapelvic stone. In order to decrease in-traoperative blood
loss, it is helpful to clamp the main renal artery and cool the kidney. The radial
paren-chymal incisions should be made on the convex border of the posterior
surface whenever possible, thereby minimizing damage to the intralobar vessels.
H. Ex Vivo, or "Bench," Surgery and Auto-transplantation: Nearly all
patients with renal stone disease can be successfully managed by one of the above
surgical procedures. However, "bench" surgery with autotransplantation of the
kidney may have a role in treatment of patients with recurrent stone disease and a
history of multiple surgical procedures, stenosis of the pelvis or proximal ureter, or
calculi associated with congenital renal anomalies or of patients with intractable
ureteral colic.
PERCUTANEOUS STONE REMOVAL
Cooperative efforts between urologists and radiologists have led to the
development of endourology. A nephroscope may be inserted through a
nephrostomy tract to remove a stone from the renal pelvis. An ultrasound probe
may be used to fragment a staghorn calculus.
The advantages of percutaneous methods are obvious. No incision is required,
and many of the procedures can be performed under local anesthesia. Recovery
time is shortened, and the patient can usually return to full activity in a short period
of time.
Disadvantages include the occasional need for nephrostomy drainage for up to
several weeks and the possibility of bleeding secondary to percutaneous stone
manipulation. These are new techniques, and longterm effects are still uncertain, as
is the success rate compared with that of more conventional surgical methods.
The criteria for percutaneous stone removal are identical to those for open
procedures for stone removal. Patients should have complete laboratory studies,
and all stones should be identified and located preoperatively. Antimicrobial drugs
should be used to treat urinary tract infections before stone manipulation.
The cornerstone of percutaneous manipulative procedures is the placement of
a percutaneous nephrostomy tube and the establishment of a nephrostomy tube
tract of adequate caliber to accommodate the nephroscope. Immediate dilation of
the nephrostomy tract and delayed dilation of the tract over a 1- to 2-week period
have both been successfully employed.
The methods of stone removal are varied, and the choice is based on the
experience of the surgeon and the needs of the patient. Stones can be grasped or
flushed out under fluoroscopic control or under direct vision using a nephroscope.
Stone baskets or specially designed forceps may be employed. Large stones may
be fragmented using either an ultrasonic or electrohy-draulic lithotrite under direct
vision.
The success rate for these stone removal procedures is greatest with renal
pelvic and caliceal stones, approaching 100% in some instances. Stones impacted
at the ureteropelvic junction are more difficult to remove by these techniques; the
success rate is only about 50%. Stones less than 1.5 cm in diameter can usually be
removed in a single session, whereas larger stones may require multiple operative
sessions. With experienced operators, the complications have thus far been limited.
Extracorporeal shock-wave lithotripsy permits removal of renal stones
without direct surgical intervention (Chaussy, 1981; Chaussy, Brendel, and
Schmidt, 1980). The patient is given an epidural or general anesthetic and lowered
into a tank of water at the bottom of which is placed the shock-wave electrode used
to produce the shock waves that fragment the renal stone. The shock waves
produced by the electrode are focused and directed at the stone by a 2-dimensional
radiographic scanning system and are keyed to follow the R wave of the patient's
ECG. The average patient receives 1000-1500 shock-wave pulses. After about 200
pulses, the stone begins to fragment. Small particles are passed in the urine over
the next several days.
In studies performed on dogs, the shock waves caused no tissue damage
except to the lungs, but the dosage was 50 times greater than that used on humans.
The shock waves did not damage bone tissue, because of the large protein matrix
of bone.
This technique is contraindicated in the presence of urinary tract obstruction
or radiolucent stones.
Of 206 patients who had 221 shock-wave applications, fewer than 1 %
required open surgical removal of stones and 88.5% were rendered stone-free.
Only 20% required analgesia after the treatment, and most were discharged after 4
days of hospitalization (Chaussy, 1981).
The only shock-wave unit presently available is in Munich. Several major
institutions in the USA have ordered the instruments and will institute clinical
trials. With time and further clinical experience, the indications and applications of
this technique will become apparent.
TREATMENT OF URETERAL STONES
Ureteral stones originate in the renal collecting system and pass into the
ureter, where they frequently become lodged and cause symptoms of ureteral colic.
The right and left ureters are involved with equal frequency. Management depends
on the size and location of the stone, age of the patient, presence or absence of
urinary tract infection, anatomy of the urinary tract, and degree of symptoms.
Treatment may be expectant, manipulative, or surgical.
Studies have shown that 31-93% of ureteral stones pass spontaneously. Size
and location of the stone need to be considered when planning a course of therapy.
Ninety percent of stones located in the distal ureter and measuring less than 4 mm
in diameter were found to pass spontaneously, whereas only 50% of stones 4-5.9
mm in diameter passed spontaneously. Only 20% of stones greater than 6 mm in
diameter passed without surgical intervention. Stones located in the proximal
ureter are much less likely to pass spontaneously.
Expectant Therapy
Most ureteral stones are less than 5 mm in diameter and pass spontaneously.
Expectant management consists of hydration and the liberal use of analgesics.
Patients are instructed to strain all urine and to save the stone for analysis. Plain
films of the abdomen and pelvis are obtained at 1- to 2-week intervals to monitor
progress of the stone down the ureter. If the patient develops fever associated with
a urinary tract infection, severe ureteral colic unresponsive to oral medications,
severe nausea and vomiting, complete obstruction of a solitary kidney, or
impaction of the stone, hospital admission and surgical or manipulative treatment
are indicated.
Manipulative Treatment
In the past, it was generally accepted that stone manipulation should not be
attempted when the stone was above the rim of the bony pelvis (Anderson, 1974).
With the use of fluoroscopy to guide stone extraction, small stones lodged in the
upper and mid ureter may be safely approached endoscopically with doubleballoon stone catheters and a ureteroscope.
Large stones in the renal pelvis or proximal ureter have been removed using
the ureteroscope and ultrasonic lithotriptor to disintegrate impacted stones. Stones
5-8 mm in diameter usually pass into the distal ureter to lodge at the ureterovesical
junction; this location is ideal for transurethral manipulation.
Instruments used with varying success for the removal of ureteral stones
include Councill and Johnson baskets, expandable Robinson baskets, retractable
Dormia and Pfister-Schwartz baskets, end-loop and side-loop Davis catheters,
balloon catheters including double-balloon catheters, and multiple ureteral
catheters. Success rates vary according to the skill of the surgeon and the
instrument used. There is a reported 93% success rate when the loop catheter is
used and allowed to pass spontaneously. Wire stone baskets have been successful
in about 60-70% of cases.
Complications resulting from stone manipulation are relatively rare and range
from 0.3% with loop catheters to 2% with wire stone baskets. Complications
include urinary tract infection, hematuria, ureteral perforation, breakage and
entrapment of the stone basket, and complete avulsion of the ureter.
Ureteral stones have been successfully removed via percutaneous routes.
Preliminary success in using the shock-wave machine to fragment upper ureteral
calculi has also been reported.
Stones larger than 8 mm in diameter usually require surgical intervention.
Other indications for operative stone removal include the development of urinary
sepsis, stones impacted anywhere in the ureter, unsuccessful attempts at stone
manipulation, and physical abnormalities that do not allow stone manipulation, ie,
urethral stricture. A number of different approaches to the ureter have been
described, including the modified dorsal lumbar approach or the anterior kidney
incision for stones located in the proximal ureter. Midureteral stones may be
approached by a McBurney or Gibson incision, while stones in the distal ureter
may bejemoved through a Pfannenstiel or lower midline incision. In carefully
selected patients, the transvesical or transvaginal approach may be useful in
removing distal ureteral calculi.
BLADDER STONES
Primary stones of the bladder are relatively rare in the USA but occur
commonly in children in parts of India, Indonesia, the Middle East, and China.
These stones usually occur in sterile urine. They are uncommon in girls. It is
believed that the incidence is related to diets low in protein and phosphate.
Dehydration due to hot weather and diarrhea further compounds the problem. In
areas where bladder stones are endemic, they are usually composed of ammonium
acid urate.
Benign Prostatic Hyperplasia
Secondary vesical stones form as a result of other urologic conditions. They
nearly always occur in men and are frequently associated with urinary stasis and
chronic urinary tract infection. Urinary obstruction may be due to prostatic
hyperplasia or urethral stricture. Neurogenic vesical dysfunction may be a cause of
chronic infection and urinary retention with eventual stone formation. Patients with
chronic indwelling catheters frequently develop encrustations on the catheter and
bladder calculi. Ureteral stones may pass into the bladder but fail to pass through
the urethra. Foreign bodies in the urinary tract may act as a nidus for calcium
deposition and stone formation.
Foreign bodies in the urinary tract
Diagnostic Evaluation
Patients with bladder stones frequently give a history of hesitancy, frequency,
dysuria, hematuria, dribbling, or chronic urinary tract infection unrespon-'sive to
antimicrobial drug therapy. Sudden interruption of the urinary stream associated
with the acute onset of pain radiating down and along the penis may occur when
the stone intermittently obstructs the bladder neck.
Retrograde pneumocystography
Most vesical stones are radiopaque and apparent on a plain film of the pelvis.
Oblique films may be helpful in differentiating bladder stones from calcifications
in ovaries, lymph nodes, or uterine fibroids
Cystoscopy is the most accurate means of diagnosis.
Treatment
Small bladder stones may be removed by trans-urethral irrigation. Larger
stones may be crushed by one of a variety of different manual lithotrites and
removed from the bladder by irrigation. Ultrasonic and electrohydraulic
lithotriptors are available to fragment large bladder calculi.
Stones that are too large to manage transurethrally and stones associated with
prostatic hypertrophy should be removed by a suprapubic surgical procedure which
allows for contemporaneous prostatectomy. Other urologic conditions that
contribute to formation of stones must be corrected if recurrence is to be prevented.
Chemolysis using hemiacidrin or Suby's solution G administered via a catheter
may be an effective form of treatment in patients who cannot tolerate general
anesthetics.
URETHRAL STONES
Primary urethral calculi are formed in the urethra and are rare. They are
usually found in association with an abnormality of the lower urinary tract that
typically causes stasis of urine or chronic urinary tract infection and leads to stone
formation. Patients with urethral diverticula, strictures, foreign bodies in the
urethra, chronic urethral fistulas, benign prostatic hyperplasia, and meatal stenosis
are more prone to the development of urethral stones.
Secondary urethral calculi are more common; they are formed in the kidney
or bladder and become lodged in the urethra as they progress down the urinary
tract.
Most urethral calculi (59-63%) are located in the anterior urethra and up to 11
% at the fossa navicularis. However, up to 42% may become impacted at the
membranous urethra or external urinary sphincter.
Diagnostic Evaluation
A urethral calculus should be considered when there is a history of acute
urinary retention preceded by sharp perinea! pain. Careful palpation of the urethra
may disclose the presence of a pendulous or distal urethral stone. In females, the
stone should be evident from transvaginal palpation of the urethra. Retrograde
urethrography in males will identify the presence and location of the stone.
Treatment
Management of impacted urethral stones is surgical. Therapeutic goals should
include not only removal of the stone but also repair of any urethral abnormality
leading to stone formation.