Transit Time Measurement

Abstract

A technique for measuring colonic transit time is a useful tool in the evaluation of patients with complaints of severe constipation. Objective measurement of transit times provides a portion of the information necessary to pursue a logical form of treatment and to monitor outcome. Techniques used to measure colonic transit time can be classified as radiological, colorimetric, particulate, chemical and isotopic (see also Chap. 12). The ideal marker should be inert and non-toxic, remain completely unabsorbed and unmetabolised, be easily measured, have no appreciable bulk and mix well with intestinal contents. The use of radio-opaque markers has the advantage that the passage of the markers can be simply observed by making serial radiographs either of the abdomen or of the stools. The progression time of markers along the colon is an objective indication of colonic transit time. Direct proof that markers are travelling at the same rate as food residues is difficult and has not been obtained for any marker. But the observations that these markers have a similar specific gravity (1.05) to the gut content and that they travel at similar rates to a liquid and finely powdered marker are good indirect evidence [1]. A single value for transit time is obtained if a single solid marker is studied. But, since in constipation the stools tend to be infrequent, it is most convenient to give more markers and to record the passage of a large fraction of them.