THE INTERNAL ANAL SPHINCTER RESPONSE: MANOMETRIC STUDIES ON ITS NORMAL PHYSIOLOGY, NEURAL PATHWAYS, AND ALTERATION IN BOWEL DISORDERS*

Abstract

An internal anal reflex which can be elicited at will, is regularly reproducible, and cannot be inhibited by voluntary effort, is demonstrated by manometric technics. This reflex consists of the transient relaxation of the internal anal sphincter in response to balloon distention of the rectum or recto-sigmoid. While an intact recto-sigmoid is needed for this response, neither intramural ganglia nor spinal cord connections are required for its medication; nor does an ideomuscular transmission appear to be involved. An abnormal sphincter response occurs with patients with fecal incontinence after proctosigmoidectomy, whereas patients with functional incontinence have a normal response. A normal reflex in Hirschsprung''s disease indicates that constipation and megacolon in this disorder are not due to an unyielding anal sphincter. The possible application of this test to diagnosis of Hirschsprung''s disease is suggested.