A Case of Chronic Idiopathic Megacolon

Abstract

Case: A 42 year old female presents with chronic diarrhea, bloating and increasing abdominal distention for 6 months. A CT scan showed massive colonic dilation with findings concerning for an internal herniation versus sigmoid volvulus. She underwent colonoscopy for decompression which showed diffuse colonic dilation but no evidence of a volvulus. She was managed initially with prokinetic agents and nasogastric and rectal tube decompression. Her celiac panel, vitamin b12, HSV, EBV, CMV, sedimentation rate, hemoglobin a1c, electrolytes, ANA, TSH were unremarkable. Anorectal manometry revealed no evidence of Hirschsprung's disease and an intact rectoanal inhibitory reflex. Unfortunately, the colonic dilation worsened despite conservative measures and she underwent an exploratory laparotomy and subtotal colectomy. Intraoperative findings revealed diffusely dilated colon with a maximum diameter of 15 cm and serosal tears in the transverse colon but without evidence of internal herniation, volvulus or obstruction. Pathology showed edema and congestion without significant inflammation. There was no evidence of fungal elements, spirochete-like organisms, CMV, HSV, amyloidosis or fibrosis. Immunostains revealed the presence of interstitial cells of Cajal, nerves, ganglion cells, and a normal distribution of lymphoid cells. At this point she was thought to have chronic acquired idiopathic megacolon. Discussion: Chronic megacolon is a rare condition and typically manifests as intractable constipation, abdominal pain, and bloating. It is caused by diseases that involve the smooth muscle cells, enteric or extrinsic nervous system, or the connective tissue component of the colonic wall. It is idiopathic in the majority of cases. Secondary causes include myopathic disorders such as Duchenne's muscular dystrophy, and neuropathic disorders such as Hirschsprung's disease and Chagas disease. Some diseases such as Parkinson's disease or diabetes, may cause either extrinsic denervation or intrinsic neuropathy, causing megacolon. Chronic megacolon is also observed in patients with connective tissue disorders such as Ehlers-Danlos syndrome, amyloidosis, and scleroderma. In general, the treatment of chronic megacolon is similar to that of intractable constipation. Short term treatment options include prokinetic agents and acetylcholinesterase inhibitors. Many patients eventually require a colectomy because of failed medical therapy.Figure 1Figure 2Figure 3