Urethral Injury in Rectal Cancer Surgery: A Comprehensive Study Using Cadaveric Dissection, Imaging Analyses, and Clinical Series

Male urethral injury during rectal cancer surgery is rare but significant. Scant information is available about the distances between the rectourethral space and neighboring structures. The aim of this study is to describe the anatomical relations of the male urethra. This three-pronged study included cadaveric dissection, retrospective MRI analysis, and clinical cases. Measurements included the R-Mu distance (shortest distance between the rectum and the membranous urethra), R-Am distance (distance from the anterior rectal wall to anal margin nearest to the membranous urethra), and the anal canal-rectum axis angle. The clinical study analyzed the incidence of urethral injury and associated factors among 244 consecutive men from January 2016 to January 2023. The overall incidence of urethral injury in our series was low (0.73%), but in men with tumors < 10 cm from the anal margin, it was 4% in abdominoperineal resection and 3.2% in TaTME. On preoperative MRI, the median R-Mu distance was 1 cm (IQR, range, 0.2-2.3), the median R-Am distance was 4.3 cm (range, 2-7.3), and the median anorectal angle was 128(degrees) (range, 87-160). In the cadaveric study (nine adult male pelvises), the mean R-Mu distance was 1.18 cm (range 0.8-2), and the mean R-Am distance was 2.64 cm (range 2.1-3). Avoiding urethral injury is crucial. The critical point for injury lies 2-7.3 cm from the anal margin, with a 0.2-2.3 cm distance between the rectum and the membranous urethra. Collaborating with anatomists and radiologists improves surgeons' anatomy knowledge.