Does cystoscopy method affect the investigation of bladder pain syndrome/interstitial cystitis?

INTRODUCTION AND HYPOTHESIS: Cystoscopic investigation to identify associated histological findings of increased mast cells in the detrusor muscle has been recommended by the European Society for the Study of Bladder Pain Syndrome (ESSIC) in the investigation of bladder pain syndrome/interstitial cystitis (BPS/IC). The aim of this study was to identify if the cystoscopy approach impacts the biopsy results when investigating women presenting with symptoms of BPS/IC. METHODS: We performed a single-centre retrospective analysis of 300 bladder biopsy reports from 2015 to 2018 from women undergoing cystoscopy for BPS/IC. Biopsies obtained using closed cup forceps through a flexible (FC) or rigid cystoscope (RC) were compared. RESULTS: Fifty-eight FC biopsies were compared with 242 RC biopsies. FC biopsies had a smaller mean diameter (1.6 mm vs 2.9 mm p < 0.01) and volume (4.1 mm3 vs 9.6 mm(3) p < 0.001) compared with RC biopsies. There was no significant difference in the histological depth of sampling to the muscularis propria. A total of 292 samples had CD117 immunohistochemical staining for mast cell count (MCC) analysis. The MCC/mm(2) was significantly lower in FC biopsies (p < 0.01). Sixteen percent of FC samples compared with 60% of RC samples had a high MCC >28/mm(2) (p < 0.01). There was no significant difference in positive microbiology culture between FC (21%) and RC (28%) sampling. CONCLUSION: Rigid and flexible cystoscopy can be used to investigate BPS/IC as recommended by international societies. However, the biopsy method impacts the mast cell count analysis, which can influence diagnosis and management. Therefore, RC would be the optimal investigation.