Assessing constipation: the devil is in the details.

Constipation is one of the most common complaints seen in Western populations and a fixture in the clinical practice of most gastroenterologists. Although prevalence estimates vary on the basis of the definitions used, up to 28% of the population may be affected. Although only a minority of these patients present to the medical establishment, this minority still accounts for 2.5 million physician visits per year. In addition, the economic impact is substantial, with laxative sales accounting for $800 million and diagnostic testing estimated to be as high as $6.9 billion annually. For the majority of patients, symptoms are mild and intermittent. Management is often self-directed or directed by primary care physicians through the use of lifestyle changes and over-the-counter laxatives. However, for those patients with more severe symptoms who do not have clinical improvement despite empiric therapy, further clinical testing is often carried out. In the absence of alarm symptoms or as a screening modality in patients over the age of 50 years, the diagnostic yield for colonoscopy is reasonably low. To evaluate further, the American Gastroenterological Association recommends diagnostic testing of both colonic transit and anorectal function to evaluate specifically for slow-transit constipation (colonic inertia) and defecatory dysfunction. Of those patients with idiopathic constipation, how frequently are slow-transit constipation and defecatory dysfunction observed? The classic paper evaluating this question was written by Pemberton and colleagues from the Mayo Clinic in 1991. During this study, the investigators performed radiopaque marker transit studies and pelvic floor function tests in 277 patients referred for symptoms of severe constipation. They identified slow-transit constipation in 29 patients (10.5%), defecatory dysfunction in 37 patients (13.4%), combined slow-transit and defecatory dysfunction in 14 patients (5.1%), and no discernable abnormalities in 197 patients (71.1%). The same group later expanded this analysis to 1009 patients and used scintigraphic transit testing for a portion of the patients (with the remaining patients undergoing radiopaque marker transit studies). In this subsequent analysis, more patients with defecatory dysfunction were identified (24.7%); however, the percentage of patients with slowtransit constipation remained similar to their previous analysis. Other investigators have examined this issue, with varying results. Iantorno et al retrospectively evaluated 215 subjects with idiopathic constipation. Colonic transit was assessed using radiopaque marker transit studies and was noted to be abnormal in 18 patients (8.4%). Sadik et al used a different radiopaque marker transit protocol and reported slow transit in 34% of 70 patients with reported constipation. A recent report fromMayo Clinic investigating whole-gut scintigraphy identified slow colonic transit in 31 of 118 patients (26.3%) with reported constipation. In this issue of Journal of Clinical Gastroenterology, Shahid et al present their experience with 212 patients who underwent motility evaluation for refractory constipation at Temple University. During their workup, these patients underwent whole-gut transit scintigraphy, anorectal manometry, electromyography, balloon expulsion testing, and defecography. The first key finding of their study was that slow-transit constipation seemed to be significantly more prevalent than recorded by other institutions. Slow-transit constipation was identified in 91 patients (42%), defecatory dysfunction in 25 patients (12%), combined slow-transit and defecatory dysfunction in 53 patients (25%), and no discernable abnormalities in only 43 patients (20%). In total, 144 patients (68%) in their study had slow-transit constipation. Their second key finding was that the majority of these patients also had proximal motility abnormalities on whole-gut scintigraphy. Of note, although these findings differ significantly from those of other institutions (as detailed above), they are similar to a prior report from the investigators in 2000, using a smaller sample size.