Background: Prostate biopsy is one of the most frequently performed procedures in urology. Recently, there has been a nationwide shift towards offering transperineal (TP) biopsies due to a reduced rate of infectious complications compared to the transrectal (TR) route. While infection may be reduced, TP biopsy is not without complication, most notably, acute urinary retention (AUR). Estimates vary as to the true rate of AUR following TP biopsy. Further, some studies have reported higher rates of AUR following TP biopsy than TR. Here we report the rate of AUR following TP biopsy at a single academic institute and relate it to risk factors for developing AUR. Methods: Retrospective case-control study. All biopsies performed with TR ultrasound (TRUS) guidance using TP technique under general anesthesia in dorsal lithotomy with a grid template. TRUS volumes were recorded during the procedure, and MRI volumes were calculated by a trained radiologist pre-biopsy. Charts of men undergoing TP biopsy from 2012 to present were reviewed. AUR was defined as patients who reported inability to urinate within 72 hours post-biopsy and underwent thorough evaluation including PVR and relevant H&P and required catheter placement. Independent samples t-test was run to relate AUR to risk factors pre/post-biopsy. Results: A total of 767 TP biopsies were completed in the study window, but not all had TRUS/MRI data. Total rate of AUR was 5.48% (N=42/767). Risk factors for AUR were increased TRUS (p=0.009, [6.49, 42.30]) and MRI prostate volumes (p=0.027, [2.90, 43.13]). Age, number of cores taken, and number of previous biopsies were not associated with AUR. Conclusions: While data is scant, the rate of AUR at our institution is consistent with current estimates in the literature. There is a growing body of evidence that the rate of AUR post-TP biopsy is higher than TR, but more investigation is needed. There is also a gap in the literature on risk factors predicting AUR after TP biopsy, however our findings are relatively consistent with the few studies currently published. Urologists must recognize patients presenting for TP biopsy with large volume prostates and consider altering management to prevent AUR.

N represents the total number of biopsies in each variable category. The mean difference is the average difference between no acute urinary retention versus acute urinary retention groups.