CTT (OATT) – Considerations for units preferring a strict single X-ray method

About 80% of the constipated patients undergoing CTT measurement are women, about 20% men. In general, most patients considered for CTT have already tried some therapies like food changes, bulking agents or osmotic laxatives but with insufficient effect.

Assessment of colonic transit is indicated to see if the patient has a transit abnormality or not. If abnormal, the test should disclose the type of disturbance.

Points to be considered:

1. Select a single X-ray method that can distinguish between normal and delayed CTT in both men and women. This limit, defined as percentile 95 in healthy subjects, is near 2.5 days (55-60 hours) in men but around 3.9-4.0 days (approx. 95 hours) in women.

The Transit-Pellets principle with repeated, regular marker doses is the only single X-ray method to meet this requirement: Numerical CTT values are obtained over the full transit range. In addition, the method yields segmental transit value, thus giving a complete colonic transit profile.

2. After the CTT measurement, at follow up, discuss the results with the patient and show the transit profile obtained. Discuss the transit profile in relation to the patient’s symptoms.

3. A normal transit value is seen in most patients with IBS-C and is important to discuss with the patient. Show the normal OATT and the normal transit profile the patient has along the colon, despite his/her feeling of severe constipation. This will help the patient understand that abnormal sensitivity is a cause and help eliminate the patient’s fear of having a dangerous disease. According to the founder of the Gothenburg IBS school (Ringstrom et al., 2010) this is a key point in patient education for IBS-C and helps reducing symptoms.

Note that this assessment requires a method that can measure gender specific normal values. For example, a transit time in the order of 3.0 – 3.6 days is a delay in male patients but completely normal in female patients.

4. In patients having a delayed recto-sigmoid transit time, consider the possibility of an outlet obstruction disorder. For further exploration of such disorders special investigation may be needed such as balloon expulsion test, ano-rectal manometry, etc.

5. A considerable part of the patients with constipation and slow transit have delay in left colon. If the patient has already tried the usual measures (see above), the transit value and transit profile obtained motivate attempts with recently developed laxatives.

6. Some patients with notoriously therapy refractory constipation have a delay also in the right colon with a caecum-ascendens transit time in the order of 2-3 days, thus, severe colonic inertia. In this group, usually refractory also to the newer laxatives, unconventional drugs may be tried before surgery is considered.

7. Colonic surgery, e.g., colectomy with ileo-rectal anastomosis, to treat drug refractory constipation, is a rare operation today, but still performed in very selected cases by some specialized colorectal surgeons. In general, this procedure is only considered in patients with a long transit time also in the right colon (see point 6).

Hasse Abrahamsson, 2020
Professor of Gastroenterology
Sahlgrenska Academy, University of Gothenburg