How much does the midline incision add to urethral diameter after tubularized incised plate urethroplasty? An experimental animal study.

Abstract

We objectively quantified the gain in urethral diameter and the effect of stenting after tubularized incised plate urethroplasty in a rabbit hypospadias model. We created a hypospadias model in 12 New Zealand white male rabbits by excising the ventral urethra. A 3 cm tattoo line was made longitudinally in the dorsal urethral plate midline. Two weeks later a 2 cm relaxing incision was made in the middle part of the tattooed line. The stretched incision width between the tattooed edges was measured, followed by urethral plate tubularization. Six rabbits were stented and 6 were nonstented. Two weeks later the animals were sacrificed and the distance separating the tattoo was measured at the midpoint of the tattooed line. Transverse sections at this point were examined histologically. All animals survived the procedures. Stents were removed at 7 days in 4 rabbits and fell out in 2 at 4 and 2 days, respectively. The mean ± SD incision width of 5.5 ± 1.6 mm (range 3 to 8) at tubularization became 2 ± 0.5 mm (range 1 to 3) after healing (p <0.002). Mean width of the healed incision was 1.7 ± 0.4 (range 1 to 2) vs 2.3 ± 0.5 mm (range 1.5 to 3) in the nonstented and stented groups, respectively (p <0.06). Rabbits with a stenting duration of less than 7 days were excluded from the last analysis. Histologically all incisions healed completely with an intact epithelium. The initial width of the midline relaxing incision significantly decreased after complete epithelialization. The average gain in urethral width was only 2 mm. Stenting appeared to increase the width of the healed incisions but not in a statistically significant manner.