Colonic Transit Study Technique and Interpretation: Can These Be Uniform Globally in Different Populations With Non-uniform Colon Transit Time?

TO THE EDITOR: We read with great interest the review article entitled " How to interpret a functional or motility test: colon transit study " by Kim et al. 1 The authors reviewed colonic transit study using radio-opaque markers, scintigraphy and wireless mo-tility capsule in evaluation of colonic motility. 1 They described the method and criteria to differentiate between slow and normal transit constipation and fecal evacuation disorders. However, it is important to note that the method they described for assessment of colonic transit using radio-opaque markers, initially described by Hinton et al 2 as early as 1969 may not suit the population with rapid gut transit such as in India. The authors referred to several studies in which either single or multiple capsule techniques were used. 1 In single capsule technique , after ingestion of markers contained in capsules, several abdominal X-rays are performed until all markers are defecated or a single abdominal X-ray on day 5 (120 hours later). Similarly, in multiple capsule-technique, capsules are taken daily for 3 days followed by abdominal X-rays on day 4 and 7 or only on day 7. In single capsule technique, when more than 20% of markers are retained , it is defined as delayed transit. 3 Most of these series are from the West where mean colonic time was found to be 30-40 hours, with upper normal limit of 70 hours. 4-8 However, this method was not found suitable in some Asian population especially in India where gut transit is fast. Gut transit time is quite fast in Indian population. Though stool frequency of up to 3 per week is considered normal in Western population, 9 99% of Indians pass at least 1 stool per day. 10 Average stool weight in 514 healthy Indians older than 15 years was 311 g per day. 11 In contrast, stool weight greater than 200 g per day is diagnostic of diarrhea in Western population. 12 Median mouth to cecum transit time was 65 minutes among 12 healthy Indians 13 and total colonic transit time was 15.8 hours among 25 subjects. 14 Considering fast gut transit among Indians, the protocol for assessment of colonic transit time using radio opaque markers is likely to be different in this population. When the Western protocol for assessment of transit time by administration of 20 radio-opaque markers each at 0, 24 and 48 hours followed by an abdominal …