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Kitten with Vesicourachal Diverticula

 

By: Asaf Dagan, DVM, Dip. ABVP (canine&feline), CVA, LL.B.
 

Introduction

This case report involves a male domestic short hair kitten with repeated episodes of lower urinary tract disease (LUTD). The kitten had a large vesicourachal diverticulum and iatrogenic urethral tear, which required both medical and surgical treatments, including antibiotics, alpha-adrenergic blocker, fluids, diverticulectomy, indwelling urinary catheterization, and supportive care. Later on it developed a urethral stricture and had to undergo perineal urethrostomy, after which it made a complete recovery.  

Urinary tract disorders of young animals are often congenital or have a congenital predisposing factor. Anomalies of the urachus are relatively common congenital disorders of the urinary bladder in cats. The urachus is a fetal structure responsible for transferring urine from the developing urinary bladder to the placenta. It serves the essential function of urine excretion in the fetal stage. Normally, it should undergo complete atrophy to become nonfunctional at birth and it usually remains as a fibrous connective tissue remnant at the bladder vertex. In some cases, this process fails and different kinds of anomalies may develop: persistent urachus, urachal cysts, urachal sinus and vesicourachal diverticula. It is not yet known what factors are responsible for the failure of urachal atrophy and incomplete closure.

When the entire urachal canal, between the urinary bladder and the umbilicus, remains functionally patent it is referred to as a persistent (or patent) urachus. Urachal cysts may develop if secreting urachal epithelium remains in segments of a persistent urachus. This anomaly has not yet been reported in cats[1]. Urachal sinus develops when the distal urachus remains patent and is open at the umbilicus. This anomaly is asymptomatic and is rarely diagnosed[2]. Finally, when a portion of the urachus located at the bladder vertex fails to close completely it is defined as vesicourachal diverticula.

Vesicourachal diverticula are divided into two types: microscopic and macroscopic. The former is characterized by microscopic lumens lined by normal transitional epithelium that appear at the bladder vertex from the submucosa to the subserosa. Presumably, microscopic diverticula are relatively common in cats, with a prevalence of up to 40% according to one study of 80 cats1. Usually this condition is clinically silent. However, a concurrent but unrelated disease of the lower urinary tract causing inflammation may lead to obstruction or detrusor hyperactivity, which results in increased intraluminal pressure and subsequent enlargement of the microscopic lumens to become macroscopic – the second type. Diseases associated with elevated intraluminal pressure include urinary tract infection (UTI), uroliths, urethral plugs and idiopathic disease. According to this hypothesis, acquired macroscopic diverticula develop because the microscopic lumens reduce the tensile strength of the bladder wall at that location and the elevated intraluminal pressure causes them to tear and/or enlarge[3]. This is probably why many macroscopic diverticula in cats resolve spontaneously within 2-3 weeks after elimination of the concurrent urinary tract disease[4].

Macroscopic diverticula are not always a temporary enlargement of a microscopic one. Unlike the acquired type, congenital macroscopic diverticula develop before or soon after birth and may persist indefinitely. They are presumed to be caused by impaired urine outflow leading to elevated and/or sustained intraluminal pressure1. Possibilities include anatomic or functional (e.g. reflex dyssenergia) outflow obstruction, detrusor hyperactivity, or abnormal production of a large volume of urine. The incidence of congenital macroscopic diverticula in cats is unknown but is considered uncommon. They too are usually clinically silent unless associated with a concurrent UTI. However, persistent macroscopic diverticula in young cats are potential risk factors for recurrent bacterial UTI and infection-induced struvite urolithiasis3 because they are associated with urine pooling.

In one study3, macroscopic vesicourachal diverticula were identified radiographically in 23% of adult cats with hematuria, dysuria and/or urethral obstruction. They occurred twice as often in male as in female cats, with a mean age of 3.7 years (range, 1 to 11 years). Interestingly, clinical signs were not apparent before 1 year of age. No breed predisposition was detected. The higher incidence in males is probably because they are more likely to develop urethral outflow obstruction secondary to intraluminal precipitates and swelling or spasm of the urethral wall.

As explained, most times vesicourachal diverticula are clinically silent. However, when there is and association with a concurrent lower urinary tract disease, clinical signs may include reduced appetite or anorexia and weight loss, malaise, hematuria, dysuria, stranguria, pollakuria, and polyuria. The bladder may feel enlarged, painful and firm and manual expression of the bladder may be difficult or impossible if urethral obstruction exists. Complete blood count, biochemistry profile and urinalysis are usually unremarkable in the case of vesicourachal diverticula alone, but may show abnormalities due to concurrent diseases.

Vesicourachal diverticula are best identified by positive contrast cystography, either antegrade cystourethrography or retrograde urethrocystography[5]. Double-contrast cystography or excretory urography may also be utilized3. Survey radiographs and pneumocystography are less reliable diagnostically. Clues that can be identified during survey radiography include: pointed deformities of the bladder vertex; elliptic shape to the bladder when incompletely distended; and lack of typical movement of the bladder vertex toward the bony pelvis when partially- or undistended5.

For a contrast study, complete distention of the urinary bladder is usually recommended to allow proper evaluation of the thickness of the bladder wall. However, maximum distention of the bladder lumen with contrast medium may obscure small vesicourachal diverticula due to stretching of the bladder vertex. To avoid this problem it is recommended to take a series of radiographs with the bladder in various levels of distention until complete filling. Extramural diverticula are often seen as a convex or triangular protrusion from the bladder vertex. Intramural diverticula may appear as tubular duct-like structure or sac-like irregularities with a narrow neck that allows communication with the bladder lumen.

Ultrasound is also effective in detecting vesicourachal diverticula[6]. They appear as anechoic outpouchings or elongations of the wall[7]. Yet another diagnostic option is uroendoscopy – it is useful in the definitive evaluation of the lower urinary tract for various anatomical abnormalities, including vesicourachal diverticula[8]. An additional advantage of uroendoscopy is that a biopsy may be obtained from the bladder vertex which may allow for a microscopic diverticulum to be identified by histopathology. Obviously, extramural or macroscopic diverticula may be identified incidentally during laparotomy surgery for an unrelated reason (e.g. spay). 

Differential diagnosis for vesicourachal diverticula include persistent urachus (characterized by dribbling urine through the umbilicus), persistent urachal ligaments and urachal cysts.

As discussed above, macroscopic vesicourachal diverticula are usually not a primary cause of feline lower urinary tract disease (LUTD), but rather a sequela of urinary tract dysfunction. Therefore, in probably most cases of macroscopic diverticula, treatment should be directed at eliminating the underlying disease with the reasonable expectation that the diverticula will then resolve spontaneously. In other words, identification of LUTD (i.e. hematuria, dysuria, pollakuria and partial or complete urethral obstruction), in and of itself, is not an immediate indication for diverticulectomy.

Cats with bacterial UTI should be treated with appropriate antimicrobials. If the diverticulum is self-limiting, resolution of the infection will eliminate the LUTD. However, if the infection persists or recurs despite appropriate treatment, the status of the diverticulum should be reevaluated by repeated contrast radiography. If the diverticulum persists in a cat with chronic or recurring UTI, diverticulectomy should be considered5. Diverticulectomy is a simple excision of the excess abnormal tissue at the bladder vertex and is similar to partial cystectomy.

A unique dilemma arises when a cat with a diverticulum is evaluated for perineal urethrostomy (PU). The diverticulum already represents an abnormality in the cat’s local defenses against UTI. Removal of the penile urethra will further impair the host local defenses and the risk of UTI will increase. Hence, it is recommended to reconsider the need for PU in such a patient. On the other hand, if the diverticulum persists but the penile abnormality persists as well, predisposing the patient to an unacceptable recurrence of urethral obstruction, then PU may be unavoidable. If PU is performed in a patient with persistent diverticulum, it should be monitored periodically for UTI. If recurrent or chronic UTI occurs after PU, diverticulectomy should then be considered5.

Cats with struvite urocystoliths, sterile or infection-induced, and acquired diverticula may be successfully managed with medical therapy alone[9]. For cats with other types of urocystoliths surgery remains the only reliable option since a dissolution diet does not yet exist.

Urethral tear is a traumatic event that may be caused by pelvic fracture, gun shot, bite wound, urolithiasis, or it may be iatrogenic due to aggressive catheterization attempts. Ruptures of the urethra most frequently occur proximally, near its attachment to the bladder[10]. Leakage of urine into surrounding tissues produces inflammation and necrosis. If urine leaks into the abdominal cavity it may result in peritonitis, ascites, post renal azotemia, and uremia. Positive contrast urethrography is the most useful diagnostic technique to evaluate urethral injuries. Leakage of contrast material from the urethra locates the site of urethral tear and hint to the extent and distribution of urine leakage. Air should not be used as a negative contrast agent as it carries the risk for potentially fatal air emboli[11].

Small urethral tears may heal over an indwelling urinary catheter if it is left in place for 1-3 weeks10. Larger urethral tears may require surgical repair. The repair method depends on the size and location of the rupture and the character of the underlying problem. Options include: primary urethral repair, extrapelvic anastamosis of the urethra to the bladder, antepubic urethrostomy, or urinary diversion procedures. The most common complication of urethral tear is urethral stricture. It may occur secondary to inaccurate suturing or to an inappropriately-sized indwelling catheter10.

Feline perineal urethrostomy (PU) is indicated to prevent recurring urethral obstruction in males or to treat an obstruction that cannot be relieved by catheterization. It is also used to treat urethral strictures that occur following obstruction, catheterization or tears. Post operatively there is a relatively high incidence of bacterial UTI due to anatomic alterations of the urethral opening, impaired local defense mechanisms (e.g. shortening of the urethra), and the underlying uropathy. Many cats suffer permanent loss of striated urethral sphincter function following the procedure, although urinary incontinence is rare[12].  

In the obstructed cat, electrolyte and acid-base abnormalities should be corrected before induction of anesthesia. Intravenous fluid therapy should be given to restore normal hydration and perfusion and to combat post-obstructive diuresis. 0.9% saline should be used if hyperkalemia is suspected, but can be replaced by a balanced electrolyte solution if potassium level is normal. Cats that had significant uremia initially are at a risk of developing marked post-obstructive diuresis, which may lead to hypovolemia and hypokalemia. Therefore, large volume of intravenous fluids and close monitoring of serum potassium level is required. ECG should be monitored perioperatively to detect cardiac arrhythmias secondary to abnormal potassium levels.

Differential diagnosis for LUTD with urethral obstruction include constipation, oliguria or anuria, lower urinary tract rupture, spinal lesions, detrusor-urethral dyssynergia, detrusor atony, functional urethral resistance, and dysautonomia.

For PU surgery the cat is placed in sternal recumbency12. The anus is purse-stringed and the penis is catheterized if possible. The penile urethra is exposed at the level of bulbourethral glands, which is the widest part, and the incised urethral mucosa is sutured directly to the skin. It is recommended not to routinely use indwelling catheters post-operatively as it may promote stricture formation and UTI12. Long-term prognosis after PU is good.

Acupuncture is a treatment modality of traditional Chinese medicine. It is becoming increasingly popular in the west but controversy still exists as to its effectiveness. A recent systematic review of the veterinary acupuncture literature found no strong evidence to either recommend or reject its use on domestic animals, but acknowledged that some encouraging data do exist for its potential usefulness in veterinary medicine[13]. The author of this report uses acupuncture frequently as an adjunct or complimentary modality in the treatment of musculo-skeletal, neurological, digestive and urinary problems. To the best of the author’s knowledge, there are no published reports evaluating the efficacy of acupuncture for the treatment of feline LUTD.

 

Clinical report

An eleven week old, 0.6kg, male domestic short hair kitten was presented to the emergency service with a chief complaint of acute stranguria of several hours duration. The cat was adopted 3 weeks earlier from the local SPCA shelter and had already received 2 standard kitten vaccinationsa. There were no other problems in its medical history. On physical exam the kitten appeared bright and alert, its vital parameters were within the normal range, but its urinary bladder was very large, firm and painful. The rest of the physical exam was unremarkable. Attempts to gently express the bladder manually produced only a few drops. The diagnosis was urethral obstruction and bladder distention. The owner declined blood work but agreed to an unblocking procedure and a urinalysis.  

Treatment started with IV administration of 0.9% saline at 2ml/kg/hr. Anesthesia was induced with ketamine 8mg/kg combined with diazepam 0.2mg/kg given IV to effect. The urethra was unblocked with little resistance using 3.5Fr tomcat urinary catheter and about 30ml of blood tinged urine removed and submitted for urinalysis. The bladder was thoroughly lavaged with warm sterile saline. The catheter was replaced by a 3.5Fr “red rubber” urinary catheter, which was anchored to the prepuce with 2 sutures of 3-0 nylon, and connected to a closed collection system. During recovery from anesthesia the kitten had some dysphoria and hypothermia (temp 97.30F; range 100.5-102.5) and was placed on a heating pad. Once obstruction was relieved and risk of hyperkalemia abated, IV fluids were changed to lactated ringer’s solution at 80ml/kg/day. Urinalysis revealed hematuria and bacteuria (table 1) and the kitten was started on amoxicillin-clavulanate

 

Table 1: Urinalysis results (source – catheterization)

Test Result Reference range

Color

Straw

 

Turbidity

Cloudy

 

Specific gravity

1.036

1.001-1.080*

Stick    

Glucose

Negative

Negative

Bilirubin

Negative

Trace to 1+

Ketone

Negative

Negative

pH

7.5

4.5-8.5

Blood

Large

Negative

Protein

3+

Trace

Sediment    

WBC

TNTC†

0-5/hpf

RBC

TNTC†

0-5/hpf

Epithelial

2-4/hpf

Occasional/hpf

Bacteria

Rods 4+

Negative

Casts

Negative

Occasional hyaline

Crystals

rare fragments

Variable

*typical range for urine specific gravity in a cat is 1.035-1.060[14]

†TNTC – too numerous to count.

acid oral suspension 16.6mg/kg twice daily and phenoxybenzamine 0.6mg/kg orally once daily. It also received one dose of dexamethasone sodium phosphate 0.25mg/kg IV to reduce inflammation in the urinary tract. Urine output was measured and matched the fluid input.

On the next day the kitten managed to pull out the urinary catheter despite wearing an Elizabethan collar. The urinary bladder palpated moderate in size but not firm. The kitten was observed urinating on his own, albeit with a thready and unstable stream, and was otherwise stable and in good spirits. Therefore it was decided to continue with close monitoring and medications as described. In addition, acupuncture was attempted to help treat LUTD and prevent urethral spasm, stricture or re-obstruction. Dry needles were placed at acu-points “bladder 23” and “bladder 28” but the kitten reacted violently to this manipulation and the needles had to be removed after less than 1 minute. Instead, aqua-puncture was used by injecting 0.4ml lactated ringer’s solution into point “conception vessel 1”. No reaction was noted.

Several hours later the urethra became obstructed again, as was evident by frequent attempts to urinate with no success and by distention of the bladder. Again, the owner declined blood work and imaging due to financial limitations and consented to only another attempt of unblocking the urethral obstruction. The kitten received premedication consisting of 0.06mg/kg acepromazine and 0.01mg/kg buprenorphine IV. Anesthesia was induced with a combination of ketamine 8mg/kg with diazepam 0.2mg/kg given IV to effect and maintained with isoflurane. However, this time the urethral obstruction could not be relieved despite the use of retrograde hydropropulsion with different catheters, including tomcat, red rubber, olive tip, and an over-the-needle IV catheter with the stylet removed. In order to assess the cause of the blockage and to evaluate for a possible urethral tear, a positive contrast urethrography was done by injecting 0.4ml of iodinated contrast material into the urethra via a 3.5Fr red rubber catheter inserted retrograde into the distal urethra up to the point of resistance (radiographs 1A and 1B). The kitten continued to have a smooth recovery from anesthesia but remained slightly sedated and unbalanced for several hours.

Lateral and ventro-dorsal views of the caudal abdomen showed contrast material leaking into the tissue surrounding the pelvic urethra. Decreased serosal detail in the caudal abdomen indicated the presence of some free fluid in that area, or alternatively was caused by lack of intra-abdominal fat tissue, typical for a young kitten. The outline and walls of the urinary bladder were not clearly visible but a mass effect in the caudal abdomen indicated that the bladder was significantly distended. An ultrasound exam was declined by the owner. A diagnosis of iatrogenic urethral tear was established, complicated by urinary bladder distention and possible uroabdomen. It was suspected that some congenital anomaly of the lower urinary tract was present, predisposing the kitten to UTI and urethral obstruction. Possibilities included vesicourachal diverticula, urocystoliths and urethroliths, urachal cyst, congenital urethral stricture, and neoplasia1. Other non-congenital causes considered were primary bacterial cystitis and urethritis, trauma, and idiopathic LUTD.

   

Since it was impossible to relieve the obstruction by retrograde catheterization, cystocentesis was done to empty the bladder. Almost 40ml of urine were aspirated from the bladder and a urinalysis of that sample showed hematuria, improving bacteuria, and crystaluria (table 2). The sample was submitted for culture and sensitivity. Afterwards the bladder palpated to be in normal size and shape. A point-of-care blood analyzerb results had minor and clinically insignificant changes (table 3). Attempts for abdominocentesis did not yield any free fluid. The kitten was otherwise bright and alert and the remainder of the physical exam had no abnormal findings. Surgery to fix the urethral tear was scheduled for the next morning since the kitten was stable and an emergency procedure was not necessary. Overnight the kitten was under close observation to monitor for bladder distention and stability of vital parameters.

On the next morning, the kitten was prepped for surgery. Premedication included only 0.01mg/kg buprenorphine given subcutaneously (acepromazine was avoided because of the prolonged recovery from the previous procedure). 20mg/kg ampicillin was given IV since the kitten did not receive its oral antibiotics that day. Anesthesia was induced with a combination of ketamine 8mg/kg with diazepam 0.2mg/kg given IV to effect and maintained with isoflurane. Continuous monitoring included heart rate, respiratory rate, indirect blood pressure, ECG, pulse-oxymetry, end-tidal CO2 and temperature (the same parameters were monitored in all general anesthetic procedures described in this report). IV fluids (LRS) were administered at 10mg/kg/hr. The kitten was placed in dorsal recumbancy and laparotomy was performed through a caudal abdominal ventral midline approach. Immediately upon examining the urinary bladder a very large vesicourachal diverticulum was identified at the vertex.


Table 2: Urinalysis results (source – cystocentesis)

Test Result Reference range

Color

Light straw

 

Turbidity

Cloudy

 

Specific gravity

1.019

1.001-1.080*

Stick    

Glucose

Negative

Negative

Bilirubin

Negative

Trace to 1+

Ketone

Negative

Negative

pH

7.5

4.5-8.5

Blood

Large

Negative

Protein

1+

Trace

Sediment    

WBC

10-15/hpf

0-5/hpf

RBC

15-20/hpf

0-5/hpf

Epithelial

4-6/hpf

Occasional/hpf

Bacteria

Few rods

Negative

Casts

Negative

Occasional hyaline

Crystals

2+ struvite

Variable

 

Table 3: i-Stat blood test results

Test Result Reference range Units

Hemoglobin

8.8

6.0-12.9

g/dL

Hematocrit

26

24-37.5

%

BUN

19

7-25

mg/dL

Glucose

149

77-120

mg/dL

Sodium

143

145-154

mEq/L

Potassium

4.0

2.7-5

mEq/L

Chloride

114

115-125

mEq/L

TC