Lateral Flexure of the Male Rectum

Description

Curving through the posterior pelvis, the male rectum is shown in profile with emphasis on its lateral flexure (flexura lateralis recti) and the transition at the rectosigmoid junction. The ampulla recti widens inferiorly as the canal approaches the pelvic floor, while the transverse rectal folds (plicae transversales recti, valves of Houston) project into the lumen and interrupt the otherwise smooth contour. Posteriorly, the rectal wall follows the sacral concavity (flexura sacralis), bringing the rectum into close relationship with the sacrum and coccyx as it descends toward the anorectal angle. This curvature is not academic. The rectosigmoid curve and lateral flexure create predictable points of resistance during digital rectal examination, rigid proctoscopy, colonoscopy, and transanal instrumentation, and they influence how the rectum distends during fecal loading. The transverse rectal folds can trap the tip of a scope or catheter and are a common site of minor mucosal trauma, while the sacral curve helps explain why rectal perforation risk increases when force is applied without following the natural posterior then anterior sweep. Surgical educators and endoscopy trainers can use this image to teach safe rectal and rectosigmoid navigation, including the direction of insertion relative to the sacrum and the expected feel of the valves. It also suits anatomy courses covering hindgut development, pelvic viscera, and the anorectal region, as well as clinical publications discussing proctologic examination technique and complications of instrumentation. Anatomical accuracy verified by SciePro's Medical Advisory Board.