[Total and segmental colonic transit times. Measurements by radio-opaque markers]

Measurement of the transit time by addition of a marker to the natural alimentary bolus permits an overall evaluation of colonic motricity. Bismuth and barium salts, dyes and radioactive compounds have been used, each of these methods having its own drawbacks, such as insufficient or impossible quantification, influence on transit or partial intestinal absorption. Radio-opaque pellets do not modify transit, are not absorbed, provide quantification readily and measure transit selectively in the ascending colon, the descending colon, the sigmoid colon and the rectum. The progression of pellets is followed by radiography of the abdomen. The number of radiograms can be reduced to 3 or even 1 by graded administration of the pellets over 3 consecutive days. The results obtained in normal subjects are similar in different studies; they are not influenced by age or by the amount of fibrous material present in food. Total and right segmental transit times are longer in women than in men. Measurement of the colonic transit time is indicated in severe constipation to differentiate between colonic inertia and terminal obstruction which have different mechanisms and treatments. Such measurements are also useful for an objective evaluation of constipation.