ABSTRACT
Congenital megacolon also referred to as Hirschsprung’s disease or aganglionic megacolon is characterized by the absence of nerve plexus in the colon, it rarely affects the small intestine. Whereas acquired megacolon is a constant dilatation of the large intestine in the absence of disease but occurs due to various factors such as infections, emotional disturbances, stress, or secondary to inflammatory bowel diseases (IBD) such as ulcerative colitis, Crohn’s disease, and proctocolitis. In the present case, we report here an unusual form of megacolon. The sigmoid colon was significantly enlarged but twisting or volvulus was not detected. The ascending, transverse, and remaining part of descending colon and mesentery appeared normal, The possibility of false rotation of the gut was excluded. Interestingly, the artery supplying the left one-third of the transverse colon and descending colon originated from a branch of the middle colic artery. This anomalous artery was found to form a communication with the trunk of the inferior mesenteric artery, the Arc of Riolan, and gave branches that supplied the descending colon. The left colic artery was absent. The transverse colon showed a stricture between its right 2/3rd and left 1/3rd, confirming with vascular accidents, resulting in anomalous blood supply and aganglionosis. The dilated part of the sigmoid colon was found to be with ganglion cells, while the distal part after the megacolon, lacked ganglion cells in all layers of the sigmoid colon. This case documents a very rare finding which will make the surgeons aware of a newer arterial pattern associated with congenital megacolon.