Congenital segmental dilatation (SD) of the intestine is a rare lesion defined as limited bowel dilatation with a 3- to 4-fold increase in size with an abrupt transition between the normal and dilated bowel and no intrinsic or extrinsic barrier distal to the dilatation. This condition is complicated by the obstruction of the intestines or chronic constipation from birth. It was first described in 1959 by Swenson and Rathauser1 as “a new entity,” which is distinct from Hirschsprung’s disease in terms of the pathological finding of normal ganglion cells. Sine then, over 100 cases were reported in the world literature in 2006.2 Thereafter, the number of case reports on patients with this condition has increased. Despite the large number of reports, the etiology of the disease remains elusive. Although the current study attempts to evaluate the roles of interstitial cells of Cajal, the enteric nervous system, and the smooth muscle in SD of the small bowel, the etiology has not been clarified.