MP07-11 INTERSTITIAL CYSTITIS / BLADDER PAIN SYNDROME - DETRUSOR MAST CELL COUNT IS ASSOCIATED WITH HYDRODISTENTION CLINICAL RESPONSE

INTRODUCTION AND OBJECTIVE: Interstitial Cystitis / Bladder Pain Syndrome (IC/BPS) is, presumably, an umbrella term for several disorders, with hypothesized differences in pathomechanisms and response to treatment. Clinical guidelines are disputed whether bladder biopsies are indicated as a part of standard IC/BPS patient evaluation or only for ruling out differential diagnoses. Abnormal mast cell activation in the detrusor has long been suggested as a mechanism for IC/BPS symptoms, but their role in patient evaluation is unclear. Our aim was to find out if detrusor mastocytosis in bladder biopsies has clinical implications, specifically if it can predict clinical symptom improvement and its duration, following treatment with hydrodistention. METHODS: In a retrospective study, we examined bladder biopsies taken from patients with complaints concordant with IC/BPS during cystoscopy and hydrodistention under anesthesia. We correlated pathological findings with patient reported symptom improvement or resolution and its duration. We used t-test, chi-square, and multivariate linear regression to define the relations between detrusor mastocytosis (≥20 mast cells / mm2) and symptom improvement. RESULTS: 31 Patients, 27 female and 4 male, mean age 59±17.6 years, underwent cystoscopy under anesthesia for suspected IC/BPS between 2013 and 2019. For 24 patients (21 female, 3 male, mean age 59±17.5 years), bladder biopsies with mast cell count were available. Eight (33%) had detrusor mastocytosis. The median follow-up was 9.6 [range: 2.3-61.4] months. Mastocytosis was associated with symptom improvement (p=0.03) and patients with detrusor mastocytosis experienced an average additional 6.8 months (95% CI 1.6-12.1, p=0.014) of improvement, compared with patients without. In a univariate regression model, improvement duration was positively correlated with detrusor mastocytosis (p=0.005), age (p=0.047) and follow-up duration (0.002), but not with gender (p=0.25), Charlson comorbidity score (p=0.61), Hunner lesion presence (p=0.14) or bladder capacity under anesthesia (p=0.20). In a multivariate model, mastocytosis was the only factor correlated with improvement duration (p=0.025). CONCLUSIONS: Detrusor mastocytosis in bladder biopsies was associated with symptom improvement after hydrodistention in IC/BPS patients. This finding may improve disease phenotyping and treatment choice direction. Mast cell activity may be a target for future research on noninvasive test development for IC/BPS phenotyping. Source of Funding: none.