Evaluation of urethral orifice cross-section dimensions following perineal urethrostomy in male cats.

OBJECTIVES: The aims of this study were: (1) To evaluate the urethral orifice cross‐section size immediately and 12 days post‐operatively following a perineal urethrostomy procedure. (2) To assess the correlation between the cross‐section size and stricture formation during a 6‐month period following the perineal urethrostomy. ANIMALS: Twenty‐four male cats with feline lower urinary tract disease that failed to respond to medical treatment and underwent perineal urethrostomy. MATERIALS AND METHODS: The urethral orifice cross‐section size was estimated by the largest size of the urinary catheter that was possible to insert facilely through the urethrostomy site. The urethral orifice cross‐section size was measured in three different times: Pre‐operative (LUCpr), immediately post‐operative (LUCi) and 12 days post‐operative (LUCp). Urinary obstruction recurrence and urethrostomy site stricture formation were documented for 6 months after the surgical procedure. The probabilities for obstruction recurrence in cases of LUCi ≤ 8Fr and LUCi > 8Fr were calculated. RESULTS: Urinary obstruction and urethrostomy site stricture occurred in 5 of 24 (~20%) of the operated cats at an average of 92 ± 25 days post‐perineal urethrostomy. LUCi ranged from 6 to 10 (median 10) Fr and the LUCp ranged from 4 to 10 (median 8) Fr. There was a significant decrease of 0.15 ± 0.09 mm² of the urethral orifice cross‐section area 12 days post‐operative compared to the measurements taken immediately post‐operative. The probabilities for post‐operative urinary obstruction of the LUCi ≤ 8Fr cases (intra‐operative urethral orifice cross‐section area equal or larger than 5.5 mm²) and in the LUCi > 8Fr cases were 44 and 6%, respectively. Recurrence of obstruction was documented in all cases (three cats) in which LUCi was 6Fr. CONCLUSION AND CLINICAL SIGNIFICANCE: The largest size of the urinary catheter that is possible to insert during surgery is a simple method to evaluate urethrostomy cross‐section size. Contraction of the urethral orifice diameter is expected during the wound healing phase. Post‐operative urinary obstruction is more likely in cases where LUCi < 8Fr.