Introduction: Uroflowmetry is a noninvasive method used to assess for possible obstruction after hypospadias surgery. While numerous publications on this topic are available, few compare flows to age matched normals or to pediatric nomograms and most have small numbers of cases. Our aim is to establish normal flow values in patients after repair of varying degrees of hypospadias and to identify if there are reliable differences between those with complications and those without.
Methods: A retrospective review of ICD-10 codes for all patients with hypospadias and uroflowmetry was performed over a 10 year history. Flow parameters were compiled in a database and patients were grouped by the pre-operative location of their urethral meatus. Critical parameters evaluated were Qmax, Qavg, voided volume, PVR, Qmax flow index (FI), and Qavg FI. We compared hypospadiac flows to 1,081 normal age matched male flows from a previous study. Our benchmark normal was a bell shaped curve in both normal and hypospadiacs. Descriptive statistics and Kruskal-Wallis tests with Bonferroni correction were performed using SPSS.
Results: Original urethral meatal locations were recorded as distal, midshaft and proximal with 134 flows from 90 patients, 47 flows from 23 patients, and 277 flows from 109 patients, respectively, and 1,081 flows from 656 normal patients. As outlined in table 1, repaired hyspospadiacs with bell curves had lower Qmax and Qmax FI compared to normal bells. Only proximal hyposadiacs had lower Qavg and Qavg FI compared to normal. When comparing all voids, the hypospadiacs were significantly different than normal. When comparing patients with complications and those without, there were differences between the different urethral positions as noted in table 2.
Conclusions: We have established useful normal parameters which can be used to follow postoperative hypospadias patients over time, allowing for the identification of complications by simply keeping track of flow indexes which are volume and age agnostic.