A comparison of 467 uroflowmetry results in repaired hypospadias vs. normal male flows

Abstract

Introduction: There are currently no clinical criteria for obstructed urinary flow after hypospadias repair surgery. Previous studies have utilized adult and pediatric nomograms and flow shapes to define obstruction, however these methods are limited by a lack of standardization and lack of interrater reliability when determining flow shapes, respectively. The idealized voider derived flow indexes offer a way to track uroflowmetry results in a volume and age agnostic manner.

Objective: We sought to evaluate all our hypospadias patients over a 10-year period and identify patients without complications and those with complications and determine their respective flow parameters. Our secondary objective is to identify which uroflowmetry parameters are the most significant predictors of urethral stricture and meatal stenosis at the time of the uroflowmetry study.

Study design: Retrospective chart review was used to compile demographic information, details of hypospadias repair surgeries, and uroflowmetry results from pediatric hypospadias repair patients. Subjects were divided into distal, midshaft, and proximal groups based on the initial location of their urethral meatus. Flows from the hypospadias repair groups were compared to flows from normal age matched controls from a previous study. We compared flows from hypospadias repair patients with no complications present with those who had urethral stricture or meatal stenosis present at the time of uroflowmetry. Binary logistic regression and ROC analysis was used to assess different uroflowmetry parameters' ability to detect the presence of obstructed urine flow.

Results: 467 uroflowmetry studies from 200 hypospadias repair patients were included in the database. Compared to controls, the hypospadias repair groups tended to have significantly lower Qmax, Qavg, Qmax FI, Qavg FI, and longer ttQmax. Significant differences in flow parameters were observed when comparing hypospadias repair patients with and without flow obstructing complications at the time of uroflowmetry. Binary logistic regression including various uroflowmetry parameters showed Qmax FI had a significant effect on the odds of observing the absence of a stricture in proximal and distal hypospadias cases.

Discussion: Of the uroflowmetry parameters analyzed, binary logistic regression and the likelihood ratio of a positive result all point to Qmax FI as the better parameter to use to detect the presence of complications in patients who have undergone distal or proximal hypospadias repair surgery.

Conclusion: We have established normal parameters for post-operative hypospadias repair patients which can be used to follow patients over time and allow for the identification of complications by keeping track of flow indexes which are volume and age agnostic.

Keywords: Flow index; Hypospadias; Stricture; Urethroplasty; Uroflowmetry.