IUC24396-89 The fate of the hydronephrotic kidney in muscle-invasive bladder cancer

Abstract Background Hydronephrosis is an independent predictor of poor clinical outcomes in muscle-invasive bladder cancer (MIBC), associated with higher rates of extravesical disease and reduced survival. However, its impact on renal function remains unclear. This study evaluates changes in serum creatinine over 2 years and assesses whether de-obstruction at diagnosis influences renal function. Methods We conducted a retrospective analysis of patients diagnosed with MIBC and hydronephrosis (2020-2024). Inclusion criteria were ≥T2 disease and serum creatinine measurements at diagnosis and 2 years post-diagnosis. Patients without oncologic intervention, those who died within 1 year, or decompression after initial treatment were excluded. Data were extracted from hospital records. Results Among 52 patients (mean age 68.5, 30 males), most had T2/T3 disease; 19 had nodal involvement (N+), and 11 had metastases (M+). Treatment included cystectomy (n = 25), chemoradiotherapy (n = 23), radiotherapy (n = 10), and chemotherapy alone (n = 4). Creatinine increased by a mean of 15 µmol/L (P = .0325) at one year in all treatment groups, but there was no significant difference at 2 years. In cystectomy patients, creatinine increased significantly at one year (13 µmol/L, P = .04) but not at 2 years. This was primarily driven by patients who were de-obstructed before cystectomy (Cr + 29.80 µmol/L, P = .01). Non-surgical treatments showed no impact on renal function. Most de-obstruction was pre-chemoradiotherapy. Conclusions Patient selection for de-obstruction is critical, particularly in those receiving chemotherapy, as there is evidence that renal function can be preserved. Our findings suggest de-obstruction can be avoided when cystectomy is planned, as it may help preserve renal function at 1 year.