Unless clinical signs of bacterial infection develop, antimicrobial therapy is not used prophylactically while a urinary catheter is in place.

UTI can occur in spite of prophylactic antibiotics. Infection in cats receiving antibiotics will be with more highly antibiotic resistant organisms. Opportunistic fungal infections of the urine and bladder have also been reported in association with frequent urethral obstruction and antibiotic administration. Instead of prophylactic antibiotics, a urine sample is collected for urinalysis and culture when the catheter is removed. If bacterial infection is present, antibiotic therapy is instituted for 10 days. A urine culture should be performed again three to five days after the antibiotic regimen is completed to ensure that the infection was eliminated. In evaluating culture results when the urinary catheter is removed, any bacteria isolated should be considered significant as long as the sample was collected from the catheter or by cystocentesis. Aseptic technique should be used.

Optimal medical care should include measurement of BUN, serum creatinine, and serum electrolytes daily until these normalize. Fluid therapy should be continued until the azotemia is resolved. Subcutaneous fluids can be substituted for intravenous fluids once the uremic signs abate and serum potassium is normal (usually within four to 24 hours).

If hypokalemia is suspected, it should be confirmed by measurement of serum potassium concentration. If present, potassium supplementation can be given orally if the cat is not vomiting or 16 mEq KCL can be added to each liter of balanced electrolyte solution. If hypokalemia is severe (<3.0 mEq/L), additional potassium supplementation may be needed.

A potential consequence of urethral obstruction is damage to the bladder detrusor muscle by prolonged over distention. Loss of the tight junctions between muscle fibers prevents spread of motor nerve impulses that permit bladder contraction. Thus, even after relief of obstruction, the cat cannot voluntarily empty its bladder, but the bladder can be expressed manually with a good urine stream, indicating that no outflow obstruction exists. Treatment is directed toward keeping the bladder empty so that the tight junctions can reform. This can be done by frequent manual expression or by use of an indwelling urinary catheter. Time required for return of bladder function varies with degree of injury.

Another reason for inability to urinate after relief of obstruction is outflow resistance. Physical examination shows that even with adequate manual compression, the urine stream is weak. Causes of such outflow resistance include recurrence of intraluminal obstruction, extraluminal obstruction or urethral spasm. Physical obstructions should be ruled out by urethrography. If urethral spasm is present, drug therapy may be of benefit, but has not been well evaluated in cats. A drug to consider would be phenoxybenzamine to block urethral alpha-adrenergic receptors. Side effects of phenoxybenzamine, such as hypotension, are related to alpha-adrenergic blockade. The drug should not be used in cats with cardiovascular disease.

Prevention

Recurrence rates for idiopathic cystitis have been 40-65 percent, depending perhaps on how closely the owner observes the cat. Only three prospective studies have been done to evaluate the efficacy of treatment regimens to prevent recurrence of idiopathic cystitis. One study compared the efficacy of a dry versus a wet acidifying diet (diets identical except for water content). Incidence of recurrence was lower on the wet diet (11 percent versus 39 percent), indicating the importance of increasing water intake. Methods to increase water intake include feeding canned food, dry food mixed with water, providing water the cat likes (such as fresh water), and providing bouillon, soups or broths from cooking. The second study evaluated oral glucosamine versus a placebo. Recurrence rates were the same in both groups, although there were four cats of 20 in the glucosamine group that relapsed whenever the drug was discontinued and improved again when it was reinstituted, suggesting some cats may be responsive. Interestingly, owners of cats in this study changed the cats' diets. Prior to the study, 95 percent of the cats were fed at least 50 percent dry food; within one month of starting the six-month course of therapy, more than 80 percent were fed solely wet food, and their urine specific gravity dropped accordingly. Cats in both groups improved during the six-month study, providing further support that the most effective treatment option may be to change from dry to wet food. The third study compared the use of feline facial pheromone in the environment versus placebo for two months. No significant difference was found, although the study involved only nine cats.

Dr. Hoskins is owner of DocuTech Services. He is a diplomate of the American College of Veterinary Internal Medicine with specialities in small animal pediatrics. He can be reached at (225) 955-3252, fax: (214) 242-2200, or e-mail: jdhoskins@mindspring.com
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