Causes, Investigation, and Diagnosis of Lower Urinary Tract Disease in Cats
World Small Animal Veterinary Association Congress Proceedings, 2017
Roswitha Dorsch, DECVIM-CA, Dr med vet, Dr habil
Center for Clinical Veterinary Medicine, Ludwig Maximilian University, Munich, Germany

Feline lower urinary tract disease (FLUTD) is a common reason for cat owners to seek veterinary care. Cats with any disease of the lower urinary tract present with similar clinical signs, such as hematuria, pollakiuria, stranguria, voiding outside the litter box, and/or urethral obstruction. In the literature, there is a consensus that feline idiopathic cystitis (FIC) is the most common diagnosis in cats with FLUTD and is responsible for the symptoms in 55 to 69% of cats.1-3 The proportion of cats with cystouroliths is reported to be 15 to 30%. The proportion of cats with urinary tract infections (UTI), however, differs across the literature. Studies from the United States show that less than 3% of young and middle-aged cats with signs of FLUTD suffer from UTI3, while studies performed in Europe (Switzerland, Norway, Germany) reveal a higher proportion of 8 to 20%2,4,5. One possible reason is that the European studies included a higher number of first opinion cases whereas the USA studies were performed in referral hospitals.

There are significant age-related differences in the incidence of the various causes of FLUTD.5,6 It has been shown that in cats younger than 10 years, FIC is diagnosed in 65% of patients with FLUTD but only in 35% of cats older than 10 years. UTI and neoplasia were significantly more common in cats over 10 years than in younger cats (UTI 42% vs. 13.4%, neoplasia 12.9% vs. 1%). Another study in geriatric cats also revealed a high proportion of cats with UTI of 46%. Seventeen per cent of these old cats suffered from urolithiasis and UTI, 10% from uroliths, 7% had urethral plugs, 5% FIC, and 3% neoplasia.

A diagnostic work-up must be performed to identify the cause of FLUTD. This includes a urinalysis (dipstick, urine sediment, aerobic urine culture), abdominal radiographs to identify radio-dense cystoliths or urethroliths, and ultrasound of the urinary tract to exclude radiolucent cystoliths and focal bladder abnormalities such as polyps or neoplasms. If no specific cause can be identified, the disease is classified as idiopathic cystitis. Double contrast cystoscopy and transurethral cystoscopy are also helpful to exclude radiolucent cystoliths and confirm the presence of FIC.

Urethral obstruction is a common complication associated with FLUTD in male cats and has been reported in 55–57% of cats with idiopathic cystitis and 67–76% of cats with urolithiasis.1,5 The treatment of cats with obstructive FLUTD includes circulatory support, treatment of metabolic complications such as hyperkalemia and metabolic acidosis, analgesia, and reestablishment of urine flow by urinary catheterization with or without previous decompressive cystocentesis. Due to the low percentage of UTIs causing urethral obstruction, treatment with antibiotics is rarely necessary.

Opinions on the use of decompressive cystocentesis are divided. Possible risks associated with decompressive cystocentesis include: bladder rupture caused by puncture of an already compromised, ischemic bladder wall, additional damage to the already inflamed urinary bladder, and iatrogenic damage to the aorta or another abdominal organ. On the other hand, benefits of decompressive cystocentesis include immediate relief of patient discomfort due to bladder overdistension and relief of back pressure of urine to the kidney. There is more time for patient stabilization for sedation and catheterization of the urinary bladder. In addition, by lowering intraluminal pressure, it facilitates passage of a transurethral catheter and flushing of intraluminal plugs or debris back into the urinary bladder. Two studies have shown that the risk of bladder rupture following decompressive cystocentesis is low.7,8 One study included 47 cats that had been treated with decompressive cystocentesis once before urinary catheterization. In this study, no cat was diagnosed with bladder rupture. The current recommendation by Hall et al. (2015) is to perform a single cystocentesis with a small needle 22 g attached to an extension set with a three-way stopcock to avoid repeated punctures. The needle should be placed in the region of the bladder neck at a 45° angle. With the needle in this position, it will not slide out of the bladder while emptying it. After cystocentesis, a small 3.5 French transurethral catheter should be placed to keep the bladder small and minimize the risk of possible urine leakage from the cystocentesis site.

Complications After Treatment of Urethral Obstruction

1.  Post-obstructive diuresis
Post-obstructive diuresis (POD) is observed in 46–74% of cats within 12 hours of relief of urethral obstruction and urine production up to 14 ml/kg/h has been documented.9,10 Cats with metabolic acidosis have a higher risk of POD and there is a correlation between the severity of POD after 4 hours and venous blood pH. POD needs to be addressed by adequate fluid therapy particularly initially when patients are severely compromised and do not compensate for fluid loss by food intake and drinking. After 48 hours, 80 to 100% of cats have urine production of > than 2 ml/kg/h, but the amount of urine produced exceeded the amount of intravenous fluids in only 37% of cats. At later time points it therefore appears that intravenous fluid therapy could be the driving force for the increased urine production. One way to avoid excessive fluid therapy is to decrease the rate of intravenous fluids and see whether the urine output drops accordingly. If so, fluid therapy can be tapered continuously. If urine production is higher than fluid rate, the IV fluids need to be increased and reduction of the fluid rate should be attempted later.

2.  Bacterial urinary tract infection
Prophylactic antimicrobial therapy for the prevention of UTI in catheterized animals is never indicated. One third of cats with an indwelling urinary catheter for 48 hours develop significant bacteriuria.11 Only cats with significant bacteriuria should be treated with antimicrobial agents. Unless there is evidence of pyelonephritis or septicemia, antibiotics should be administered after removal of the indwelling catheter. At the time the catheter is removed, a urine sample is again sent for culture and sensitivity testing.

3.  Trauma to the urethra with formation of strictures
An uncommon complication of urethral catheterization is trauma to the urethra causing a urethral tear. With a catheter in place to limit the contact of the injured tissue and prevent leakage of urine in the periurethral tissue, tears can heal spontaneously.

4.  Repeated urethral obstructions
Repeated urethral obstructions are seen in 17–58% of cats. These can be caused by debris in the bladder that move into the urethra causing a new urethral plug, by spasm of the urethra due to urethritis, urethral injury and stricture formation, and a urethral calculus. The fact that a urinary catheter can be passed does not exclude the presence of a urethral calculus. Documentation of the site and extent of urethral strictures or urethral neoplasia are best accomplished by positive contrast urethrography. Two studies have revealed a lower risk of recurrent urethral obstruction with the use of smaller catheters, indwelling catheters for more than 26 hours, and the use of prazosin compared to phenoxybenzamine.

References

1.  Gerber B, Bore WFS, Kley S, Laluha P, Muller C, Sieber N, et al. Evaluation of clinical signs and causes of lower urinary tract disease in European cats. J Small Anim Pract. 2005;46(12):571–577.

2.  Saevik BK, Trangerud C, Ottesen N, Sorum H, Eggertsdottir AV. Causes of lower urinary tract disease in Norwegian cats. J Feline Med Surg. 2011;13(6):410–417.

3.  Lekcharoensuk C, Osborne CA, Lulich JP. Epidemiologic study of risk factors for lower urinary tract diseases in cats. J Am Vet Med Assoc. 2001;218(9):1429–1435.

4.  Gerber B, Bore WFS, Kley S, Laluha P, Muller C, Sieber N, et al. Evaluation of clinical signs and causes of lower urinary tract disease in European cats. J Small Anim Pract. 2005;46(12):571–577.

5.  Dorsch R, Remer C, Sauter-Louis C, Hartmann K. Feline lower urinary tract disease in a German cat population. A retrospective analysis of demographic data, causes and clinical signs. Tierarztl Prax (K). 2014;42(4):231–239.

6.  Bartges JW, Barsanti JA. Bacterial urinary tract infections in cats. In: Bonagura JD, ed. Current Veterinary Therapy XIII. Philadelphia, PA: Elsevier/Saunders; 2000:880–883.

7.  Hall J, Hall K, Powell LL, Lulich J. Outcome of male cats managed for urethral obstruction with decompressive cystocentesis and urinary catheterization: 47 cats (2009–2012). J Vet Emerg Crit Care. 2015;25(2):256–262.

8.  Cooper ES, Owens TJ, Chew D, J Buffington CA. A protocol for managing urethral obstruction in male cats without urethral catheterization. J Am Vet Med Assoc. 2010;237(11):1261–1266.

9.  Francis BJ, Wells RJ, Rao S, Hackett TB. Retrospective study to characterize post-obstructive diuresis in cats with urethral obstruction. J Feline Med Surg. 2010;12(8):606–608.

10.  Fröhlich L, Hartmann K, Sautter-Louis C, Dorsch R. Post-obstructive diuresis in cats with naturally occurring lower urinary tract obstruction: incidence, severity and association with laboratory parameters on admission. J Feline Med Surg. 2015;18(10):809–817.

11.  Hugonnard M, Chalvet-Monfray K, Dernis J, Pouzot-Nevoret C, Barthelemy A, Vialard J, et al. Occurrence of bacteriuria in 18 catheterised cats with obstructive lower urinary tract disease: a pilot study. J Feline Med Surg. 2013;15(10):843–848.

Speaker Information
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R. Dorsch, DECVIM-CA, Dr. med. vet., Dr. habil.
Medizinische Kleintierklinik, Department of Klinische Tiermedizin
Ludwig Maximilian University of Munich
M√ľnchen, Germany


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