Gastrointestinal Radiology > Procedures > Colon Transit Time

Transit Time (Colon Motility Test)


The simplest and most easily interpreted colonic transit evaluation is performed with a plain abdominal radiograph on day 5 after the patient has ingested a gelatin capsule containing radiopaque markers (SITZMARKS™, Konsyl Pharmaceuticals, Fort Worth, TX). Each capsule contains 24 radiopaque polyvinyl chloride o-rings of 1 mm x 4.5 mm. The test is inexpensive and well tolerated by patients.


Adult patients with severe constipation but otherwise negative G.I. evaluations


  1. On day 0, direct the patient to take one SITZMARKS capsule by mouth with water, preferably with observation by office personnel. Instruct the patient to use no laxatives, enemas, or suppositories for 5 days.
  2. On day 5, obtain a plain abdominal radiograph (KUB). Determine the number and location of remaining radiopaque rings.
  3. Patients who expel at least 80% of the markers by 5 days (5 or fewer rings remaining) have grossly normal colonic transit.
  4. For patients who retain 6 or more markers, one may elect to get a follow-up radiograph on day 7, when normally 100% of marker should have been expelled.

Interpretation of Results

  1. If over 80% of the radiopaque markers (19 or more) are passed by day 5, colonic transit is grossly normal.

  2. If 6 or more of the markers remain on day 5, this is abnormal:

    1. If remaining markers are scattered about the colon, the problem is most likely colonic hypomotility or inertia.

    2. If remaining markers are accumulated in the rectum or rectosigmoid, the condition is most likely functional outlet obstruction, such as rectal intussusception or anismus.


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