Evaluation of the Effect of Rectal Dilatation on Bowel Function by Sagittal CT Imaging

Rectal dilatation strongly affects bowel function. However, the relationship between rectal dilatation and bowel function remains unclear. Since January 2024, we have attempted to evaluate this relationship by using sagittal computed tomography (CT) imaging.

Sixty patients with colon cancer, excluding obstructive cancer, who underwent surgical procedures at our hospital were retrospectively registered in this study from January 2024 to March 2025. Rectal dilatations were evaluated by using axial and sagittal CT imaging. A rectal diameter greater than that of the fifth lumbar vertebral body diameter was considered long. The diameter of the upper rectum was measured at the inferior border of the second sacral vertebra, and that of the lower rectum was measured at the inferior border of the fourth sacral vertebra.

Rectal dilatations were detected in 26 (43.3%) of the patients. Twenty-two (36.7%) patients were administered laxatives orally for constipation. In nineteen (86.4%) of the twenty-two patients, dilatation in both the upper and lower rectum was detected simultaneously, and the patients were administered laxatives. No patient experienced dilatation only in the upper rectum. Thirty-eight (63%) patients with no rectal dilatation above the inferior border of the third sacral vertebra were not treated with any laxative.

Sagittal CT imaging is very useful for evaluating anatomical changes in the rectum. The diameter of the rectum at the inferior border of the third sacral vertebra on sagittal CT images may be a clinical diagnostic criterion for patients with anorectal motility disorders.