Empty colon: a pitfall in the assessment of colonic transit time

We report a misleading outcome of colonic transit time (CTT) assessment in an adolescent girl with functional constipation. We found prolonged total and right segmental CTT despite high doses of oral polyethylene glycol 4000 and repeated treatment with polyethylene glycol–electrolyte solution (Klean-Prep®) by nasogastric tube. A colonoscopy aiming at disimpaction of a possible faecal mass revealed an empty colon with dozens of radio-opaque markers adhered to the colonic wall. This report shows that the result of a CTT cannot be accepted blindly. Especially the clustering of many markers within narrow margins might point at entrapment of markers in mucus against the colonic wall.