Poor Neorectal Evacuation as a Cause of Impaired Defecatory Function After Low Anterior Resection: A Study Using Scintigraphic Assessment

Purpose. Patients who have undergone low anterior resection (LAR) of the rectum occasionally complain of symptoms related to impaired neorectal evacuation. Using scintigraphy, we assessed neorectal evacuation in 22 patients who underwent LAR and straight anastomosis, and correlated the results with clinical defecatory function, clinical factors, and anorectal manovolumetric parameters. Methods. After the introduction of an artificial stool containing ^99mTc-DTPA into the neorectum, sequential lateral gamma images were obtained. From the time–activity curve of radioactivity in the whole pelvis, the time taken to eva-cuate half of the introduced artificial stool (T _1/2) and the percentage of artificial stool evacuated in 1 min (Evac₁) were calculated. Results. The Evac₁ was significantly lower in the patients who had undergone LAR than in reference normal volunteers. A long T _1/2 was significantly associated with worse defecatory function. The Evac₁ was also significantly lower in patients with a low anastomosis. The rectal sensory threshold was significantly greater in patients with a shorter T _1/2. The maximum tolerable volume of the neorectum was significantly greater in patients with a shorter T _1/2 and a higher Evac₁. Conclusion. Poor neorectal evacuation is associated with impaired defecatory function after LAR. Therefore, it is suggested that optimizing both reservoir function and evacuation of the neorectum would improve defecatory function after LAR. Received: January 19, 2001 / Accepted: July 17, 2001