Quantifying displacement of urogenital organs after abdominoperineal resection for rectal cancer

Aim: This study aimed to quantify displacement of urogenital organs after abdominoperineal resection (APR), and to explore patient and treatment characteristics associated with displacement. Method: Patients from 16 centres who underwent APR for primary or recurrent rectal cancer (2001–2018) with evaluable preoperative and 6–18 months postoperative radiological imaging were included in the study. Anatomical landmarks on sagittal images were related to a coordinate system based on reference lines between fixed bony structures and absolute displacements were calculated using the Pythagorean theorem. Rotation of landmarks was measured relative to a pubic-S5 reference line. Results: There were 248 patients included of which 171 were men and 77 women. The median displacement of the internal urethral orifice was 25 mm in men (maximum 65), and 17 mm in women (maximum 50). Rotation of the internal urethral orifice was in a caudal direction in 160/170 (94%) of men and 65/73 (89%) of women, with a median of 32 degrees (maximum 85) and 33 degrees (maximum 83), respectively. Displacements of the posterior bladder wall, distal end of prostatic urethra and cervix were significantly correlated with the internal urethral orifice. In linear regression analysis, biological mesh reconstruction of the pelvic floor and visceral interposition were significantly associated with increased displacement of the internal urethral orifice, and female gender and any filling of the presacral space with decreased displacement. Conclusions: Substantial absolute displacement and rotation of urogenital organs after APR for rectal cancer were observed, but with high variability among both men and women, and being significantly associated with reconstructive interventions.