Urethral compliance in hypospadias operated by tubularized incised urethral plate (TIP) with and without a dorsal inlay graft: an experimental controlled study

Abstract

Abnormal uroflowmetries are common after tubularized incised plate urethroplasties (TIP), perhaps due to low compliance. We hypothesized that (1) abnormal uroflowmetries after TIP might be caused by segmental lower compliance; (2) by adding a graft to the raw area in the incised plate (TIPG), compliance might be improved by preventing secondary intention healing of the dorsal incision. A standardized penectomy was performed in 27 adult male rabbits: 9 normal non-operated controls (G1), 6 weeks after TIP (G2: n = 9) or TIPG (G3: n = 9). A standardized isolated segment (including the whole urethroplasty in G1 and G2) was progressively distended with air (1, 2 and 3 ml) in the 3 groups. The respective intraluminal pressures were measured with a tensiometer. Pressure measurements were feasible and reproducible for this model. Mean pressures tended to be higher in the experimental groups (G1: 59.7 mmHg vs. G2: 79.6 mmHg vs. G3: 100.1 mmHg for 1 ml injections; G1: 233.1 mmHg vs. G2: 241 mmHg vs. G3: 308.4 mmHg for 2 ml injections and G1: 457.3 mmHg vs. G2: 429 mmHg vs. G3: 520 mmHg for 3 ml injections) without reaching the statistical significance. In this model, the elasticity of the TIP or TIPG neourethras tended to be reduced when compared to controls. The placement of an inlay graft on the dorsal incised area did not increase the compliance. This model allows the measurement of segmental intraluminal urethral pressures generated by controlled air distension and may be a useful tool to evaluate the experimental urethroplasty models.