the enterohepatic circulation of bile acids will lower cholesterol. bile acid sequestrants bind bile acids in the gut, preventing reabsorption. in so doing, more endogenous cholesterol is shunted into the production of bile acids, thereby lowering cholesterol levels. the sequestered bile acids are then excreted in the feces. cholestasis tests for bile acids are useful in both human and veterinary medicine, as they aid in the diagnosis of a number of conditions, including types of cholestasis such as intrahepatic cholestasis of pregnancy, portosystemic shunt, and hepatic microvascular dysplasia in dogs. structural or functional abnormalities of the biliary system result in an increase in bilirubin (jaundice) and in bile acids in the blood. bile acids are related to the itching (pruritus) which is common in cholestatic conditions such as primary biliary cirrhosis (pbc), primary sclerosing cholangitis or intrahepatic cholestasis of pregnancy. treatment with ursodeoxycholic acid has been used for many years in these cholestatic disorders. gallstones main article: gallstones the relationship of bile acids to cholesterol saturation in bile and cholesterol precipitation to produce gallstones has been studied extensively. gallstones may result from increased saturation of cholesterol or bilirubin, or from bile stasis. lower concentrations of bile acids or phospholipids in bile reduce cholesterol solubility and lead to microcrystal formation. oral therapy with chenodeoxycholic acid and/or ursodeoxycholic acid has been used to dissolve cholesterol gallstones. stones may recur when treatment is stopped. bile acid therapy may be of value to prevent stones in certain circumstances such as following bariatric surgery. bile acid diarrhea excess concentrations of bile acids in the colon are a cause of chronic diarrhea. it is commonly found when the ileum is abnormal or has been surgically removed, as in crohn's disease, or cause a condition that resembles diarrhea-predominant irritable bowel syndrome (ibs-d). this condition of bile acid diarrhea/bile acid malabsorption can be diagnosed by the sehcat test and treated with bile acid sequestrants. bile acids and colon cancer bile acids may have some importance in the development of colorectal cancer. deoxycholic acid (dca) is increased in the colonic contents of humans in response to a high fat diet. in populations with a high incidence of colorectal cancer, fecal concentrations of bile acids are higher, and this association suggests that increased colonic exposure to bile acids could play a role in the development of cancer. in one particular comparison, the fecal dca concentrations in native africans in south africa (who eat a low fat diet) compared to african americans (who eat a higher fat diet) was 7.30 vs. 37.51 nmol/g wet weight stool. native africans in south africa have a low incidence rate of colon cancer of less than 1:100,000, compared to the high incidence rate for male african americans of 72:100,000. experimental studies also suggest mechanisms for bile acids in colon cancer. exposure of colonic cells to high dca concentrations increase formation of reactive oxygen species, causing oxidative stress, and also increase dna damage. mice fed a diet with added dca mimicking colonic dca levels in humans on a high fat diet developed colonic neoplasia, including adenomas and adenocarcinomas (cancers), unlike mice fed a control diet producing one-tenth the level of colonic dca who had no colonic neoplasia. the effects of ursodeoxycholic acid (udca) in modifying the risk of colorectal cancer has been looked at in several studies, particularly in primary sclerosing cholangitis and inflammatory bowel disease, with varying results partly related to dosage. genetic variation in the key bile acid synthesis enzyme, cyp7a1, influenced the effectiveness of udca in colorectal adenoma prevention in a large trial. dermatology bile acids may be used in subcutaneous injections to remove unwanted fat (see mesotherapy). deoxycholic acid as an injectable has received fda approval to dissolve submental fat. phase iii trials showed significant responses although many subjects had mild adverse reactions of bruising, swelling, pain, numbness, erythema, and firmness around the treated area.