Intestinal bypass in the rat: a model for growth failure, liver disease, and jejunal bacterial overgrowth in marasmus and kwashiorkor.

The role of small intestinal bacterial colonisation on growth, liver function, and survival was examined in young rats, by comparing the effects of 90% small intestinal resection (resulting in nutritional disturbance from loss of absorptive surface) with equivalent small intestinal bypass (where the nutritional disturbance is accompanied by bacterial overgrowth in the long bypassed segment of jejunoileum). Weight loss in bypass rats was double that seen in resected animals. This was not due to enhanced malabsorption, but was the result of reduced food intake. In addition, bypass rats developed hepatocellular dysfunction, the early onset of hypoproteinaemia (occasionally accompanied by ascites), and had high mortality. Adverse effects were due to bacterial overgrowth in the long excluded segment of small bowel, as they were modified by antibacterial drugs, and were not seen in rats with nutritional disturbance (resection) alone, which adapted well and had negligible postoperative mortality. Persistent bacterial overgrowth in the small intestine can adversely affect the host's appetite, growth, liver function, and survival. These abnormalities, which developed shortly after intestinal bypass in the rat, are reminiscent of marasmus and kwashiorkor, and suggest that bacterial overgrowth, rather than dietary deficiency, may be primarily responsible for the development of infant "malnutrition" in the developing world.