Surgical history should be taken, especially if the patient has an extensive abdominal past surgical history as well as family history is important to see there are any inherited disorders (Dubin-Johnson and Rotor syndrome). Bilirubinuria has been seen in patients taking the drug phenazopyridine or the nonsteroidal anti-inflammatory etodolac. All prescribed and over the counter medications, including dietary supplements and vitamins, should be recorded since they might alter liver function. Thus, bilirubinuria is an important early sign of a pathological process.Ī thorough medical history involving assessment of any condition that may be related to hepatobiliary diseases such as fatty liver disease, pregnancy, viral hepatitis, alcoholic liver disease, celiac disease, thyroid disease, and right-sided heart failure should be obtained. If there is hepatocellular dysfunction or biliary obstruction, some of the direct conjugated bilirubin escapes into the bloodstream, gets filtered by the kidneys, and excreted in the urine. In a normal physiological state, conjugated bilirubin is not passed in urine. From the remaining twenty percent, ten percent of it is excreted in the urine as urobilin, given the urine its unique color, and ninety percent of it is unconjugated and undergoes enterohepatic circulation. In the intestines, the bilirubin gets metabolized by the colonic bacteria into urobilinogen, eighty percent of which gets excreted into feces as stercobilin, given its unique color. The conjugated/soluble bilirubin is transported through the biliary and cystic ducts to the gallbladder where it gets stored, or it passes through the ampulla of Vater to enter the duodenum. The canalicular excretion of bilirubin is the rate-liming step of hepatic bilirubin metabolism accumulation of conjugated bilirubin in blood signifies hepatocellular dysfunction when the canalicular excretion of bilirubin is overwhelmed or obstruction of the bile duct. The conjugated bilirubin is then excreted into bile. Once in the hepatocyte, the unconjugated bilirubin is taken to the endoplasmic reticulum, where it is conjugated with a sugar via the enzyme glucuronosyltransferase and is then soluble in the aqueous bile. Once it reaches the hepatocyte, the albumin-bilirubin bond is broken, and the bilirubin is taken by the hepatocyte using a carrier-membrane transport. The bilirubin released from the reticuloendothelial system that reaches the hepatocyte is unconjugated/insoluble and is bound to albumin. Through a series of reactions, heme becomes biliverdin, which is then transformed into bilirubin and transported from the plasma to the liver for conjugation. 80 percent of heme is generated from the catabolism of RBC, and the remaining 20 percent is generated from ineffective erythropoiesis and breakdown of muscle myoglobin. The body produces 4 mg per kg of bilirubin from the metabolism of heme. To understand the presence of bilirubin in the urine, it is important to understand the physiology behind bilirubin metabolism which can be divided into three phases: prehepatic, hepatic, and posthepatic. Therefore, bilirubinuria is a marker of conjugated hyperbilirubinemia and can be the earliest sign of hepatic or biliary disease. In a healthy individual with normal liver function and bile duct anatomy, bilirubin is not detectable in the urine. Patients may describe their urine as tea or cola-colored when they have jaundice and conjugated hyperbilirubinemia due to liver or biliary disease. On the other hand, conjugated bilirubin is water-soluble and thus can be renally excreted and detected in the urine. Unconjugated hyperbilirubinemia is characterized by acholuric jaundice as urine is not darkened by urinary bilirubin as bilirubin is not detected in the urine in such cases. Unconjugated bilirubin is soluble in fat but insoluble in water and thus cannot be renally excreted. Bilirubin in the body exists as either conjugated/direct or unconjugated/indirect. Bilirubin and related breakdown metabolites are well known for causing the characteristic coloring in bile and stool however, its presence in the urine is not normal, and for it to be present there, it must be water-soluble and excreted by the kidney. It can be detected by the standardized urine dipstick, mostly referred to as urinalysis in most hospitals worldwide. Bilirubinuria is the presence of bilirubin in the urine.
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