Systemic factors are trophic in Thiry-Vella loop in the absence of luminal contents

Mucosal histology, crypt cell proliferation and brush border enzymes were measured in rats with varying degrees of Thiry-Vella fistulas, in order to compare the effect of systemic and luminal factors on adaptive growth and differentiation (brush border enzymes) in small intestinal epithelium.

Twenty-four male Wistar rats (300-350 g) were divided with three groups of eight which underwent the following operations: 20% Thiry-Vella fistula, 80% Thiry-Vella fistula and sham operation.

80% Thirty-Vella fistulas caused a functional short gut; in intestine remaining in continuity there were significant increases in segmental weight, protein, Alp activity and villus height, compared with sham-operated controls and 20% Thiry-Vella fistulas. There was a significant fall in villus height, crypt cell production in loops of 20% Thiry-Vella fistula rats not exposed to luminal contents compared with control segments of sham-operated rats. In contrast, loops of the 80% Thiry-Vella fistula rats were not atrophied despite the much greater distance from luminal nutrients; the villus height and PCNA-LI were higher than in 20% Thiry-Vella fistula rats, and at least as great as in sham-operated rats.

This study indicates that atrophy does not occur in loops after 80% Thiry-Vella fistula because crypt cell proliferation is maintained in Thiry-Vella fistulas. Thus, the atrophic effect of diversion of luminal nutrients can be counteracted by systemic growth factors released as part of the adaptive response; luminal factors are not essential for maintenance of normal cellular turnover when there is a powerful stimulus to cell proliferation.