Lower urinary tract disease is among the most common concerns in feline medicine. Inappropriate urination is one of the most frequent reasons for presentation of a cat to a veterinary clinic, and a major reason for euthanasia or surrender of a cat. While new drugs, diets, and techniques have entered the market in recent years to help prevent and treat lower urinary disease, this remains a frustrating condition for cat owners and veterinarians alike. Urethral obstruction is the most dramatic presentation of lower urinary disease, whereby cats are unable to urinate due to blockage of the urethra and enter kidney failure.

The wall of the bladder is lined by a protective layer of proteoglycans and glycosaminoglycans (GAGs)- oily substances that prevent damage and bacterial growth and reduce inflammation in the bladder wall. In states of disease such as bladder stones or crystals, infection, or idiopathic cystitis, this protective wall is often damaged or disrupted. This allows for a vicious cycle of inflammation to occur. Defects in this GAG layer have been associated with bladder inflammation in both cats and humans. Feline Idiopathic Cystitis (FIC) is a disease of cats characterized by inflammation of the bladder wall in the absence of an obvious inciting cause. Cats with FIC have been shown to have decreased levels of urinary GAGs.

Due to the important role of GAGs in bladder health, there has been significant interest in investigating the use of synthetic GAGs to prevent or treat lower urinary disease. Pentosan polysulfate sodium (PSS) is a semi-synthetic GAG that may have an ability to replace defective GAGs in the bladder wall. In human women, PSS instilled into the bladder has been shown to decrease the signs of interstitial cystitis. Anecdotally, PSS has been used extensively for the treatment of lower urinary disease in cats with little evidence for efficacy. Studies in cats have previously shown no decrease in the recurrence of clinical signs or pain scores with oral or subcutaneous PSS.

The aim of this study was to determine the efficacy of PSS instilled directly into the bladder in reducing inflammation and the recurrence of urinary obstruction in cats with FIC. Cats presenting to a veterinary hospital with signs of lower urinary obstruction were diagnosed with FIC on the basis of exclusion of other causes (complete urinalysis, aerobic culture, abdominal radiographs and abdominal ultrasound). CBC, serum chemistry, T4, and retrovirus testing were also performed. Cats with any evidence of inciting urinary disease, other systemic disease, or treatment with steroids, antibiotics, or GAGS in the previous 14 days were excluded. 44 cats were enrolled and randomized to be treated with either PSS or placebo in addition to standard care (IV fluids, pain control, antispasmodics, catheterization, bladder flushing).

Prior to treatment, the urinary bladder was drained and the cat’s de obstructed and flushed copiously. The cat’s were catheterized and 30mg of PSS in 10mL sterile NaCl was instilled into the urinary bladder and the catheter was clamped for 30 minutes. This was repeated after 24 and 48 hours of catheterization, and the catheters removed. Cats were monitored for signs of recurrence, pain, and urine parameters.

There was no significant difference found in the recurrence of obstruction and need for re catheterization between treatment and placebo groups. Both groups showed a general improvement in pain, appetite, and general demeanor over the course of the study. No differences were seen in any urinalysis parameters between groups.

The results of this study found that the use of intravesicular pentosan polysulfonate did not change the outcome for cats with lower urinary obstruction. These results are suggestive that PSS likely has no efficacy in the treatment of lower urinary obstruction due to FIC. Further studies may be warranted to determine if increased doses or time in the bladder improve efficacy. There may also be improved efficacy in non-obstructed cats. While it is always disappointing to find that a treatment is not effective, this is important information in the search for the ideal treatment for FIC and urinary obstruction in general. (MRK)