Lateral Presentation of the Sacral Flexure of the Male Rectum

Description

Seen in lateral profile, the distal sigmoid colon descends from the left iliac fossa and continues as the rectum as it crosses the pelvic brim, with the rectal ampulla expanding inferiorly before narrowing toward the anal canal. The sacral flexure of the rectum (flexura sacralis recti) forms a gentle anteroposterior curve that follows the concavity of the sacrum and coccyx, keeping the upper rectum posterior while the lower segment lies more anterior within the lesser pelvis. Posterior relationships are dominated by the sacrum, and the anterior rectal wall is oriented toward the prostate and seminal vesicles in the male pelvis. That curvature is not an academic detail. During rigid sigmoidoscopy, transanal endoscopic microsurgery, or stapled low anterior resection, the sacral flexure influences instrument trajectory and the line of sight, and it partly explains why excessive force can lead to posterior wall injury against the sacrum. It also frames the surgical planes used in total mesorectal excision, where staying in the avascular fascia propria of the rectum preserves the presacral venous plexus posteriorly and protects the autonomic nerves that course along the pelvic sidewall. Use this artwork for gross anatomy teaching on the hindgut and pelvic viscera, for colorectal surgery atlases illustrating rectal curves and endoscopic navigation, or for radiology and gastroenterology publications correlating lateral pelvic anatomy with rectal catheter placement and distal colorectal pathology. Anatomical accuracy verified by SciePro's Medical Advisory Board.