Background: Chronic megacolon is a rare disease of the colonic motor function characterized by a permanent increase in colonic diameter. Methods: We reviewed electronic medical records of all patients diagnosed with chronic megacolon from 1999 to 2014 at Mayo Clinic. Our aim was to summarize clinical and motility features, including colonic compliance and tone measured by colonic barostat-controlled 10-cm-long infinitely compliant balloon. Colonic compliance curves were compared to healthy control (40) and disease (47) control groups. Results: Among 24 identified patients, the mean maximal colonic diameter on abdominal radiograph was 12.7 ± 0.8 cm. The cause of megacolon was idiopathic in 16 of 24 and secondary in 8 of 24. A relatively high prevalence (10/24) of comorbid pelvic floor dyssynergia was identified. At the time of this report, 16 patients had undergone colectomy. In general, megacolon presented high fasting colonic volume at relatively low pressures (16–20 mmHg), suggesting high colonic compliance; similarly, volumes at operating pressures that ensured apposition of the balloon to the colonic wall suggested low colonic tone. Median balloon volume at 44 mmHg distension was 584 mL (IQR 556.5–600) in patients with megacolon compared to 251 mL (212–281) in healthy, 240 mL (207–286) in functional constipation, and 241 mL (210.8–277.5) in diarrhea-predominant irritable bowel syndrome controls. Colon’s tonic response to feeding was generally intact, and there was frequently maintained phasic contractile response to feeding. Conclusions: Chronic megacolon is a severe colonic dysmotility, manifesting radiologically with increased colonic diameter; it can be proven by measuring colonic compliance and typically requires colectomy because of failed medical therapy.
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