Urethral complex thickness and thickness index are the independent risk factors for urethroplasty complications after tubularized incised plate hypospadias repair

Abstract

In tubularized incised plate urethroplasty, the depth of the mid-line relaxing incision is the key factor for urethral plate tubularization without tension. The incision depths will be different from one case to the other even if they have been done by the same surgeon. This difference in depths resulted from the different thicknesses of the urethral plate and the underlying corpus spongiosum (urethral complex). To evaluate the urethral complex thickness and thickness index as risk factors for the complications of TIPU in penile shaft hypospadias repair. All primary penile shaft (distal and mid-penile) hypospadias (with or without mild penile chordee) were operated with TIPU between March 2018 and February 2021. We measured the urethral complex thickness in the hypospadiac and proximal normal parts of urethra pre-operatively with superficial U/S probe. Intraoperative, we measured the urethral plate width before and after the midline relaxing incision, calculate the relative increase in urethral plate width (RIUPW). Stepwise logistic regression assessed the effect of different variables on the complication rate. These variables include; urethral plate width before and after incision, urethral complex thickness, thickness index, RIUPW, site of hypospadiac meatus and patients ages. 10 cases had 11 complications (12.7%). Fistulae were the commonest complication (8.9%). Complication rate has significant negative correlations with many variables on Univariate analysis. Stepwise logistic regression shows that urethral plate thickness and thickness index are the independent risk factors for complications after TIPU in penile shaft hypospadias. Urethral plate width was suggested to be a risk factor for TIPU complications. In our study, Univariate analysis shows that complications were more with plate width ˂8mm but without significant difference (P=0.487). Also it shows that post incision width and RIUPW have significant negative correlation with complications rate. Multivariate analysis showed that the urethral complex thickness and thickness index are the independent risk factors for complications after TIPU hypospadias repair (AUC 0.94 95% CI 0.894-0.972P˂0.001 and 0.965 95% CI 0.921-0.996, respectively). The thickness of the urethral plate and the underlying spongiosum is the determining factor for TIPU success. We can use it as an objective reproducible assessment tool for urethral plate quality and to predict TIPU complications.