Introduction:
The aim of the study was to identify predictors of surgical complications of transurethral resection of bladder tumour (TURBT).

Material and methods:
We prospectively recruited 983 consecutive patients undergoing TURBT within 7 months in six academic institutions. All patients were followed up from the surgery up to 30 days postoperatively with at least one telephone contact at the end of the observation. The primary study endpoint was any intra- or postoperative surgical complication. For the identification of predictors of complications, univariate and multivariate logistic regression models were used. Trial registration: ClinicalTrials.gov (NCT03029663). Registered 24 January 2017.

Results:
Surgical complications were noticed in 228 (23.2%) patients, including 83 (8.4%) patients with more than one complication and 33 cases of Clavien-Dindo grade 3 complications (3.3%). The most common in-hospital complications were bleeding (n = 139, 14.1%) and bladder perforation (n = 46, 4.7%). In a multivariate analysis, nicotine use, high ASA score, and the presence of high-grade tumour were the most significant predictors of high-grade complications. The stage of the disease was the strongest predictor of bleeding, while the presence of muscle in the specimen and resident surgeon were the strongest predictors for bladder perforation.

Conclusions:
TURBT poses a significant risk of surgical complications, the majority of which are of low grade.