Colon Transit Study

Constipation in simple terms is a condition in which there is difficulty in emptying the bowels, usually associated with hardened feces with high level of constraint or restriction. Constipation is common in general population with rates varying from 2-30%.

Clinically less than three bowel movements per week and or straining more than 75% of occasions represent constipation. It can also identified by the usage of Bristol stool chart. In the early major causes includes insufficient dietary fiber intake, inadequate fluid intake, decreased physical activity, side effects of medications, hypothyroidism, and obstruction by colorectal cancer.

Colonic transit time (CTT) is defined as the time it takes for stool (feces) to pass through the colon, Colon study is the most basic and primary tool in pathologic diagnosis and for planning management in patients with constipation. Colon transit times are generally shorter in normal Asian populations than in Westerners. In studies from Korea, average colon transit time was 20-30 hours in normal subjects. Dietary differences may make a difference in colon transit time between Asian and Westerners.

It is a very simple study done by swallowing a series of small inert plastic markers over a three-day period then having an x-ray of the abdomen.

The standard measurement of colon transit time is by measuring movement of radio-opaque markers through the gut. It is reliable and reproducible. It is simple to perform as well as being cost effective in the evaluation of chronic constipation. It allows to assess both the severity of the problem and the response to therapy.

You will be given three capsules (labelled 1, 2 and 3) when you make your appointment. Each capsule contains 20-inert radio-opaque markers.

Don't Open the capsule but swallow it whole with water as follows:

Day 1: Take capsule 1 in the morning by 08:00AM after breakfast.

Day 1: Take capsule 2 at night by 08:00PM after dinner.

Day 2: Take capsule 3 in the morning by 08:00AM after breakfast.

Day 2: Appointment for abdominal x-ray (Erect) by 08:00PM.

Day 3: Appointment for abdominal x-ray (Erect) by 08:00PM.

(This is a modified protocol for Indian patients based on normal average colon transit time)

- It is important for the success of the study to take each capsule on the designated day and at the same time as specified.

- Continue with your normal diet and activities but it is important not to take any prokinetics , laxatives, suppositories or enemas to help your bowels move.

Note: Because this procedure is done under x-ray guidance, you should notify your doctor prior to booking an appointment if you are pregnant or suspect you may be pregnant.

Delayed transit is defined as > 20% retention of markers. Colon transit times in each segment and through the entire colon are calculated by multiplying the number of markers by 1.2.

Patients can be categorized according to patterns of marker movement:

- Transit in the right colon or left colon is delayed in patients with slow transit constipation.

- Colonic inertia (Hypomotility) has equal distribution of markers throughout the colon.

- Markers progress normally through the proximal colon but stagnate in the rectum in those with outlet delay/dysfunction/dysynergia.

Retention of more than 12 markers on day 3 is considered abnormal and indicative of slow transit constipation. Dysynergic defecation may also retain markers, a diagnosis of slow transit constipation should only be made after excluding dysynergia.

Depending on the category of the patients motility pattern observed he will be benefited by prokinetics (for slow transit) or laxatives or surgery for resistant cases.

Radionuclide scintigraphy and wireless motility capsules are other techniques used to measure colon transit time.

Article by Dr. Vadivel Kumaran, MD(GEN.MED).,DM(MED. GASTRO)
Consultant Medical Gastroenterologist And Hepatologist, Kauvery Hospital, Chennai

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