Medically Refractory Constipation With Colonic Hypercompliance: Comparison With Megacolon and Healthy Colon

BACKGROUND: Chronic megacolon is an uncommon neurogastrointestinal disorder typically characterized by a persistent increase in colonic diameter. METHODS: Our aim was to identify adults with medical treatment-refractory constipation without radiographic criteria for megacolon but with increased colonic compliance (refractory constipation with colonic hypercompliance (RCCH)), and to compare the colonic compliance in 7 identified patients with "RCCH" to colonic compliance in 10 patients with chronic megacolon by radiographic criteria (i.e., megacolon) and 40 healthy volunteers. After endoscopic placement, compliance of left or transverse colon was measured using a 10-cm-long infinitely compliant balloon connected to an electronically controlled rigid piston barostat. The barostat inflated the balloon from 0 to 44 mmHg in 4-mmHg steps at 30-s intervals to measure colonic compliance (pressure-volume relationship). Eligibility criteria for inclusion were increased colonic compliance based on a functional assessment without meeting radiographic criteria for megacolon (i.e., RCCH). In the three groups, we compared colonic volumes at intra-balloon pressure of 8, 16, 20, 32, and 44 mmHg, the pressure at half maximum volume, and the slope of the colonic compliance curve using ANOVA on ranks and Dunn's pairwise comparison test. Other features of colonic motility were documented. RESULTS: Colonic volumes at all pressures (8-44 mmHg) and the pressure at half maximum volume were significantly greater in patients with megacolon and RCCH than in healthy controls (p < 0.001 for both), but compliance was not significantly different between RCCH and megacolon. CONCLUSION: A subset of patients with medically-refractory chronic constipation has colonic compliance similar to that of patients with megacolon.