Validity of segmental transit studies used in routine clinical practice, to characterize defaecatory disorder in patients with functional constipation

Objective Segmental colonic transit can be determined by performing regional counts of radio-opaque markers on an abdominal radiograph. It has been claimed that the pattern of markers can be used to characterize the type of constipation, with a concentration of markers seen in the rectosigmoid region in patients with defaecatory disorders. The aim of our study was to examine this hypothesis in a cohort of patients with functional constipation. Method Consecutive patients presenting to a specialist constipation clinic and satisfying inclusion criteria were studied. All patients had the following assessments: radio-opaque marker study performed according to a standard protocol; proforma-based symptom assessment using Likert scoring; and radioisotope defaecating proctogram. Transit study data included total transit time, rectosigmoid transit time and geometric mean of markers. Symptom scores were recorded for straining, incomplete evacuation and digitation, together with a cumulative symptom score. Evidence of outlet obstruction from the proctogram included four previously described parameters. Results A total of 108 patients with functional constipation according to the Rome criteria with a median age of 41 years were studied. Neither rectosigmoid transit time nor the geometric centre of markers could differentiate patients with a functional defaecatory disorder (FDD). There was no correlation between the pattern of marker distribution and any of the parameters denoting outlet obstruction. Conclusion Our data do not support the hypothesis that assessment of segmental transit, using standard methods applicable to routine clinical practice can determine the type of constipation. In particular, patients exhibiting evidence of FDD are no more likely to have recto-sigmoid retention of markers than those without.