In cats, idiopathic cystitis (IC) causes chronic clinical signs such as changes in urinary frequency, urinary urgency, and inappropriate urination. In this study, urodynamic parameters in 11 female cats with IC were evaluated and compared with previously published data for healthy cats. Complete physical examination, CBC, serum biochemical analysis, urinalysis, urine bacteriologic culture, and abdominal radiography or cystoscopy were performed in all cats. A diagnosis of IC was made based on a disease-compatible history and exclusion of other diagnoses such as urolithiasis, infection, and neoplasia. Two sequential cystometrograms and urethral pressure profiles were then obtained for each cat. Tracings were evaluated for evidence of overactive urinary bladder. Other metrics included maximum urethral pressure (MUP), maximum urethral closure pressure (MUCP), and functional profile length. Results indicated that cats with IC had significantly higher MUP in the smooth and skeletal muscle portions of the urethra than did healthy cats. The MUCP was also significantly higher in cats with IC than in healthy cats. None of the cats with IC had evidence of overactive bladder, which suggests that use of anticholinergic drugs is likely to have minimal benefit in cats suspected of having IC. The high MUCP in cats with IC suggested that α1–adrenoceptor antagonists or skeletal muscle relaxants may be of therapeutic value. Further study is required to determine whether these results can be extrapolated to male cats with recurrent obstructive IC.

Commentary: This  is the first study to evaluate cystometrogram data in cats with IC, and the results provide important information about the pathophysiology of this complex disease. Compared with normal female cats, those with IC required higher intravesicular pressures to trigger bladder contraction. These findings suggest that increased detrusor contractility is not part of the pathophysiology of IC and may help explain why response to anticholinergic treatment has been poor. On the other hand, urethral pressure profilometry in affected cats demonstrated higher closure pressures in both the smooth and skeletal muscle portions of the urethra, suggesting that increased outflow resistance contributes to the commonly observed pollakiuria, dysuria, and stranguria. If these results are extrapolated to male cats with IC, the use of a1–adrenoceptor antagonists and/or skeletal muscle relaxants may help manage clinical signs as well as recurrent urethral obstruction.—Gregory F. Grauer, DVM, MS, Diplomate ACVIM

Urodynamic evaluation of female cats with idiopathic cystitis. Wu CH, Buffington CA, Fraser MO, Westropp JL. AM J VET RES 72:578-582, 2011.