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.