ObjectiveTo compare the safety and efficacy of bipolar vs monopolar transurethral resection of bladder tumour (TURBT) in patients maintained on low-dose aspirin with tumours >3cm. Patients and methodsA prospective randomised single-centre study was performed including 200 patients with bladder tumours of >3cm, as measured by ultrasonography. All patients were using low-dose aspirin (81mg/day), which was not stopped in the perioperative period. Patients were randomised into two groups: Group A, monopolar TURBT (M-TURBT); Group B, bipolar TURBT (B-TURBT). The primary endpoint of the study was the decrease in postoperative haemoglobin (Hb) concentration measured using an automated cell counter. The secondary endpoints of the study were intraoperative blood transfusion or the occurrence of urethral trauma during cystoscopy and the need for re-coagulation. ResultsThe postoperative reduction in Hb concentration, was significantly lower in the B-TURBT group [mean (SD) 0.55 (0.26) g/dL] compared with the M-TURBT group [mean (SD) 1.24 (0.61) g/dL] (P<0.001). There was also a significant difference (in favour of B-TURBT) between the groups in the mean postoperative reduction in haematocrit and the mean postoperative hospital stay. There was no significant difference between the groups for the occurrence of obturator jerk, bladder perforation, and the need for blood transfusion. ConclusionB-TURBT in patients maintained on low-dose aspirin is better than M-TURBT for minimising postoperative drop in Hb concentration.