Achieving goal capacity for continence surgery: A cumulative event analysis of bladder exstrophy patients

Background: Following successful closure of patients with classic bladder exstrophy (CBE), the next major milestone is the establishment of urinary continence. Prior to determining the most appropriate continence surgery, it is imperative to reach an adequate bladder capacity minimum of 100 cc in order to make the decision between bladder neck reconstruction (BNR) or continent stoma, with or without augmentation cystoplasty (AC). Objective: To examine the timing of when patients achieve threshold bladder capacity for BNR eligibility. We hypothesize most patients will achieve an adequate bladder capacity (100 cc) by 7 years old when continence surgeries will begin to be considered. Study design: An institutional database of 1388 exstrophy patients was retrospectively reviewed for CBE patients after successful primary bladder closure. Bladder capacities were measured via gravity cystography and data presented as descriptive statistics. The cohort was stratified by location, neonatal (≤28 days) or delayed closure period and osteotomy status. The bladder capacities were categorized to either reaching goal or not and a cumulative event analysis was performed. The event being reaching 100 cc capacity or greater and time being the number of years between bladder closure and attainment of goal capacity.[Formula presented] Results: 253 patients met inclusion criteria between 1982 and 2019. The majority were of male gender (72.9%), had their closure performed at the authors' institution (52.5%), within the neonatal period (80.7%), and without an osteotomy (51.7%). 64.9% of patients reached goal bladder capacity. There were no significant differences in those who did or did not achieve goal except for clinical follow up. Cumulative event analysis demonstrated a median time of 5.73 years (95% CI 5.2–6.20) corresponded with a 50% event probability of reaching goal capacity. Cox-proportional hazards showed location of closure was significantly associated with hazards of reaching goal bladder capacity (HR = 0.58, CI 0.40–0.85, p = 0.005). Based on this model, the median time to event would be 5.20 years (95% CI 4.76–5.80) for cases done at the authors’ hospital and 6.26 years for those performed at an outside hospital (95% CI 5.77–7.24). Conclusions: These findings help surgeons counsel families appropriately on the odds of attaining goal capacity at various ages. For those who do not reach 100 cc by five years of age, it helps further characterize the odds of requiring a continent stoma with bladder augmentation and the best timing for reconstructive surgery in order to safely gain urinary continence. Families may also be assured that most patients would have the breadth of surgical options when it comes to continence as more than half of patients reached the bladder capacity threshold.