Bile Intestinal bypass

Since intestinal mucosa, especially in ileum, appears to synthesize cholesterol at a high rate even in man and since this synthesis is increased by the absence of bile acids (223), it is to be expected that in patients with intestinal bypass mucosal cholesterol production is markedly increased in the bypassed portion of the gut and should contribute to serum cholesterol. Ileal or more extensive intestinal resections, on the other hand, prevent this increase in synthesis and should reduce serum cholesterol more effectively than the sole bypass does. However, animal experiments indicate that in monkeys prevention of dietary-induced hypercholesterolemia is less effective by ileal resection... 

Clinical stresses which interfere with vitamin metabohsm, can result in calcium deficiency leading to osteomalacia and osteoporosis (secondary vitamin D deficiency). These stresses include intestinal malabsorption (lack of bile salts) stomach bypass surgery obstmctive jaundice alcoholism Hver or kidney failure decreasing hydroxylation of vitamin to active forms inborn error of metabohsm and use of anticonverdiants that may lead to increased requirement. 

Enteric hyperoxaluria refers to a state in which oxalate is over-absorbed in the bowel because of a defect in absorption of fat and bile adds. In those patients, suffering from Crohn s disease or patients with jejunoileal bypass [14, 15], Ca is complexated to fatty (bile) acids by which Ca-oxalate is no longer formed making oxalate available for intestinal absorption. Daily oxalate excretion is in between that of healthy volunteers and... 

The most common situations in which bile salts are deficient in the small intestine are (1) T-tube drainage of the common bile duct and (2) partial or complete interruption of ileal absorption, as in regional enteritis or ileal resection or bypass. In the former group, bile drainage is usually incomplete and temporary, so that most patients tolerate this period well without... 

Cholesterol and fat-soluble vitamins require bile acid induced micellar solubilization for absorption, which takes place in the upper small intestine (c/. 32,116-118). Accordingly, in bile salt deficiency states, cholesterol absorption should be markedly impaired and fecal neutral sterol excretion increased. The fact that fecal neutral steroid excretion on a low-cholesterol diet is actually normal, as after ileal resection, ileal bypass, and cholestyramine treatment, or even decreased, as in cirrhosis of the liver or biliary occlusion (11), is due to a markedly reduced biliary secretion of cholesterol. In gluten enteropathy, in which no excessive bile salt loss usually exists, fecal neutral sterol excretion is markedly augmented (119). However, in occasional cases in which fecal bile salt elimination is markedly enhanced, the fecal neutral steroid excretion is quite normal, probably owing to decreased biliary cholesterol secretion as a consequence of low biliary bile salt secretion. Detailed information on the role of bile salts in both intraluminal and mucosal phases of fat and sterol absorption is presented in many recent reviews (6,10,113,114,117). 

Ileal bypass (see Section VB2) performed for hypercholesterolemic patients (269) increased cholesterol elimination in the study by Moore et al. (156) about fivefold as bile acids and threefold as neutral steroids according to the isotopic balance technique. Serum cholesterol reduction was about 40 %. In our own series, consisting of patients with familial hypercholesterolemia only, similar results have been obtained by the chemical balance technique except that elimination of cholesterol increased solely as bile acids (11,63,127). The fecal bile salt loss was associated with a 35 % fall in the serum cholesterol level, a severalfold increased cholesterol synthesis, impaired micellar solubilization of digested lipids, reduced intestinal bile salt concentrations, and decreased cholesterol level in the intestinal contents. The last suggests that biliary secretion of cholesterol was markedly decreased so that, despite impaired cholesterol reabsorption, fecal neutral steroid excretion remained quite unchanged. An increased fecal bile salt loss associated with stimulated cholesterol production has been reported also by Grundy et al. (94). 

Cholestyramine is an ion-exchange resin that traps the bile salts and thereby secures their elimination in the intestine. The bile salts are continuously excreted in the intestine bile acid formation from cholesterol increases, and serum cholesterol levels drop. Existing evidence indicates that cholestyramine administration and ileal bypass are the most effective measures available to reduce serum cholesterol in hypercholesterolemic patients. 

Bile acids and lipids are lost in the feces when a large portion of the intestine is bypassed because disease has caused obstruction (for example, in obstruction by cancer), or because the intestinal seg-... 

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