Transit colonic

Two 5-HT receptor sub-types, 5-HT3 and 5-HT4, are involved in gut motility, visceral sensitivity, and gut secretion. The 5-HT3 receptors slow colonic transit and increase fluid absorption, whereas 5-HT4 receptor stimulation results in accelerated colonic transit. 

AM Metcalf, SF Phillips, AR Zinsmeister, RL Mac-Carty, RW Beart, BG Wolff. Simplified assessment of segmental colonic transit. Gastroenterology 92 40-47, 1987. 

DA Akin, SS Davis, RA Sparrow, IR Wilding. Colonic transit of different sized tablets in healthy subjects. J Controlled Release 23 147-156, 1993. 

BMI 19.8-36.0 kg m-2) were studied. All transit variables were unaffected by gender. The older subjects had a slower mean colonic transit time of radiolabeled plastic particles than the young subjects (p < 0.05), while BMI affected the gastric emptying of fiber but not other gastrointestinal variables [22]. In a more recent study, comparison was made between cohorts of young and elderly males, but no age-related effect could be determined [23]. 

Tab. 23.2. Colonic transit times (h) of single unit dosage forms [37],...

Bouchoucha et al. characterized colonic transit time in 30 healthy subjects and in 43 patients with inflammatory bowel disease using X-ray opaque markers. The response to food was different in the two populations in controls, the cecum and ascending colon emptied and filled the distal bowel, whereas in the patients only the splenic flexure and left transverse colon emptied. Movement through both the right and left colon in patients was observed to be much slower than in controls, both before and after a meal [55]. 

R. C., Watts, P. J., Melia, C. D., Davies, M. C., Wilson, C. G., Scintigraphic demonstration of accelerated proximal colon transit by lactulose and its modification by gelling agents, Gastroenterology 1992, 103, 1167-1173. 

Rao et al. [140] described a study using a commercial pH sensitive radio-telemetry capsule (RTC) to evaluate small bowel and colonic transit time in athletes with gastrointestinal symptoms. The RTC (type 7006 Remote Control Systems, London, UK) consists of a glass electrode with an integral reference cap and battery. RF transmissions from the capsule are detected by a solid-state receiver worn on the belt of the patient. The recorder samples the pH from the capsule at 6 second intervals for a period of 24 hours. They used pH changes as an indication of the pH capsule s movement. A sharp rise in pH from around pH 2 to pH 6 indicates that the capsule has moved into the duodenum from the stomach. Then the pH progressively rises to a plateau around pH 8, which indicates that the capsule has moved into the terminal ileum. Another commercially available wireless pH sensor (Bravo) from Medtronic Inc. has been used to measure esophageal pH for a period of 48 hours and it will be discussed later. 

K.A. Rao, E. Yazaki, D. F. Evans and R. Carbon, Objective evaluation of small bowel and colonic transit time using pH telemetry in athletes with gastrointestinal symptoms. J. Sports Med. 38, 482-487... 

Sharma SS, Bhaigava N, Mathur SC Effect of oral erythromycin on colonic transit in patients with idiopathic constipation. A pilot study. Dig Dis Sci 1995 40 2446-2449. 

Colonic transit time is only slightly affected by food, but is redueed under stress. Studies have shown that drugs, which act on the parasympathetie or sympathetie nervous system, affeet the propulsive motor aetivity, thereby influeneing the eolonie transit time [12]. Although not significantly affected by most diseases [13], the transit time is shorter in patients who complain of diarrhea and longer in patients with eonsti-pation. 

Alosetron, a 5-HTj receptor antagonist, retards colonic transit (58) and is used to treat diarrhea-predominant IBS. Although genetic variants in the 5-HT receptors have been discovered, their physiological relevance has yet to be determined. 

Fig. 13.4 Response of colonic transit to treatment with alosetron is greater in homozygous long vs heterozygous SERT-P genotype. 5-HT, serotonin. (Reproduced from ref. 63.)...

Viramontes, B. E., Camilleii, M., McKinzie, S., Pardi, D. S., Burton, D., and Thomforde, G. M. (2001) Gender-related differences in slowing colonic transit by a 5-HT3 antagonist in subjects with diarrhea-predominant irritable bowel syndrome. Am. J. Gastroenterol. 96, 2671-2676. 

In London, the Guy s Hospital group d wished to see if they could extrapolate validly from OT-treated acromegalic patients to those with sporadic gallstone disease. They also wished to study further the mechanism whereby prolongation of colonic transit might influence DCA metabolism, biliary cholesterol secretion and saturation, and therefore the risk of cholesterol gallstone formation. To study this, Thomas et developed a working hypothesis... 

Given the large number of variables, Thomas et argued that it was important to carry out both univariate and multi-variate analyses of the data. Both types of analysis showed that LBTT, the activity of the 7a-dehydroxy-lation, and the distal colonic luminal pH were all significant risk factors for high proportions of DCA in serum (and by implication, in bile). Based on these results, the authors concluded that there was indeed prolonged colonic transit in conventional gallstone patients and that this, in turn, was likely to result in increased DCA formation, solubilisation (and therefore bioavailability) and absorption. 

Simple antidiarrhoeals are generally contra-indicated, they do not help to reduce mucosal efflux, and may, by reducing colonic transit, predispose to megacolon development. Despite the strong association between non-smoking and the occurrence of ulcerative colitis nicotine patch treatment has shown little evidence of value. 

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