Proximal Megacolon in an Adult
Authors: Priya Vijayvargiya, Michael Camilleri
Journal: Clinical Gastroenterology and Hepatology (2013)

A44-year-old woman, born and residing in the United States, presented with medically nonresponsive chronic constipation, requiring 1 gallon of polyethylene glycol electrolyte solution weekly to induce bowel movements. She consistently experienced incomplete evacuation. She was hospitalized once for suspected sigmoid volvulus that spontaneously resolved. Physical examination showed a distended tympanitic abdomen with palpable stool in the left lower quadrant. Rectal examination revealed a high resting anal sphincter tone and no coordinated perineal descent during simulation of defecation; these features were confirmed on anorectal manometry (high squeeze anal sphincter pressure and requirement of 200 g to facilitate 50-mL balloon evacuation from the rectum). Gastric emptying was normal, and colonic transit was delayed. She was diagnosed with pelvic floor dyssynergia and symptoms improved somewhat after biofeedback therapy. A plain abdominal radiograph (Figure A) showed a dilated colon, confirmed on computerized tomography scan. Sagittal views of the abdominal computerized tomography (Figure B) showed an elongated, dilated proximal colon with a decompressed rectum. Direct endoscopic visualization of the intersection of the dilated and nondilated colon showed no mass or constrictions. Because of persistent symptoms and megacolon, she underwent colectomy at another hospital. Figure C shows the resected specimen with a dilated ascending and transverse colon, normal-caliber descending colon and rectum, and no constricted transition zone between dilated and normal-caliber segments. No pathologic examination of the colon was available. The enteric nervous system is derived from vagal and sacral neural crest cells. Vagal neural crest cells migrate caudally through the entire length of the gastrointestinal tract and provide the majority of neurons and glia. The sacral neural crest cells migrate rostrally and contribute to the innervation of the distal colon and rectum.1Burns A.J. Le Douarin N.M. The sacral neural crest contributes neurons and glia to the post-umbilical gut: spatiotemporal analysis of the development of the enteric nervous system.Development. 1998; 125: 4335-4347Crossref PubMed Google Scholar Colonic dysganglionosis presents as a continuous spectrum, ranging anatomically from hypoganglionosis in colonic sections of different lengths and distributions to a localized constriction with proximal dilatation in Hirschsprung disease (HD). Hypoganglionosis is a decrease vs a complete lack of ganglia, and it can present as localized or generalized megacolon, or it may occur concomitantly with HD.2Kim H.J. Kim A.Y. Lee C.W. et al.Hirschsprung disease and hypoganglionosis in adults: radiologic findings and differentiation.Radiology. 2008; 247: 428-434Crossref PubMed Scopus (39) Google Scholar These disorders present with long-term constipation refractory to medical therapy.2Kim H.J. Kim A.Y. Lee C.W. et al.Hirschsprung disease and hypoganglionosis in adults: radiologic findings and differentiation.Radiology. 2008; 247: 428-434Crossref PubMed Scopus (39) Google Scholar Although approximately 95% of HD cases are diagnosed before the age of 5,3Ikeda K. Goto S. Diagnosis and treatment of Hirschsprung's disease in Japan. An analysis of 1628 patients.Ann Surg. 1984; 199: 400-405Crossref PubMed Scopus (183) Google Scholar less severe cases may present after 10 years of age and are considered adult HD. Long-segment HD, with a transition zone proximal to the splenic flexure,2Kim H.J. Kim A.Y. Lee C.W. et al.Hirschsprung disease and hypoganglionosis in adults: radiologic findings and differentiation.Radiology. 2008; 247: 428-434Crossref PubMed Scopus (39) Google Scholar is a variant seen in 0.4% to 4% of adults with HD.4Higashi M. Ieiri S. Teshiba R. et al.Hirschsprung's disease patients diagnosed at over 15 years of age: an analysis of a Japanese nationwide survey.Pediatr Surg Int. 2009; 25: 945-947Crossref PubMed Scopus (7) Google Scholar, 5Doodnath R. Puri P. A systematic review and meta-analysis of Hirschsprung's disease presenting after childhood.Pediatr Surg Int. 2010; 26: 1107-1110Crossref PubMed Scopus (53) Google Scholar In summary, the endoscopic radiologic features and gross pathology of the resected colon are consistent with proximal megacolon, probably caused by hypoganglionosis, not HD.