One function of the liver is the synthesis of urea from various sources of ammonia, most of which come from protein-splitting bacteria in the GI tract. In cirrhosis, there is extensive liver cell destruction and fibrous tissue replacement of areas between nodules of irregularly regenerating liver cells. This architectural distortion also distorts the hepatic venous […]
Bile acids are water-soluble components of bile that are derived from cholesterol metabolism by liver cells. Two primary bile acids are formed: cholic acid and chenodeoxycholic acid. Both are conjugated with glycine or taurine molecules and excreted from liver cells into bile in a manner similar but not identical to bilirubin excretion. The conjugated bile […]
In certain situations the prothrombin time can be a useful liver test. The liver synthesizes prothrombin but needs vitamin K to do so. Vitamin K is a fat-soluble vitamin that is present in most adequate diets and is also synthesized by intestinal bacteria; in either case, it is absorbed from the small bowel in combination […]
GGT (formerly gamma-glutamyltranspeptidase) is located mainly in liver cells, to a lesser extent in kidney, and in much smaller quantities in biliary tract epithelium, intestine, heart, brain, pancreas, and spleen. Some GGT activity seems to reside in capillary endothelial cells. The serum GGT level is increased in the newborn but declines to adult levels by […]
Lactic dehydrogenase (LDH) is found in heart, skeletal muscle, and RBCs, with lesser quantities in lung, lymphoid tissue, liver, and kidney. A considerable number of conditions can elevate total LDH levels. For that reason, serum total LDH has not been very helpful as a liver function test. However, in some cases isoenzyme fractionation by electrophoresis […]
ALT is an enzyme found predominantly in liver but with a moderate-sized component in kidney and small quantities in heart and skeletal muscle. In general, most ALT elevations are due to liver disease, although large amounts of tissue damage in the other organs mentioned may also affect serum levels. In fact, severe myositis or rhabdomyolysis […]
Serum aspartate aminotransferase (AST; formerly SGOT) is an enzyme found in several organs and tissues, including liver, heart, skeletal muscle, and RBCs. AST elevation from nonhepatic sources is discussed elsewhere. AST elevation originating from the liver is due to some degree of acute liver cell injury. Following onset of acute hepatocellular damage from any etiology, […]
Alkaline phosphatase (ALP) is a group of closely related enzymes with maximal activity when the pH is about 10. ALP is found in many tissues, with highest concentrations in liver and biliary tract epithelium, bone, intestinal mucosa, and placenta. Liver and bone are the two tissues most commonly responsible for ALP elevation. ALP is composed […]
These tests follow much the same pattern as conjugated and unconjugated bilirubin. After bile reaches the duodenum, intestinal bacteria convert most of the bilirubin to urobilinogen. Much urobilinogen is lost in the feces, but part is absorbed into the bloodstream. Once in the blood, most of the urobilinogen goes through the liver and is extracted […]
Bilirubin is formed from breakdown of hemoglobin molecules by the reticuloendothelial system. Newly formed (unconjugated) bilirubin circulates in blood bound nonpermanently to serum albumin and is carried to the liver, where it is extracted by hepatic parenchymal cells, conjugated first with one and then with a second glucuronide molecule to form bilirubin diglucuronide, and then […]
