From the Guidelines
Bilirubinuria, or high bilirubin in urine, is typically caused by an underlying liver or bile duct problem, and the most common causes include hepatitis, liver cirrhosis, gallstones blocking bile ducts, or certain medications affecting liver function, as supported by the most recent study 1.
Causes of Hyperbilirubinemia
The causes of hyperbilirubinemia can be broadly categorized into two types: unconjugated and conjugated hyperbilirubinemia. Unconjugated hyperbilirubinemia is usually due to hemolysis or impaired conjugation, whereas conjugated hyperbilirubinemia is typically due to parenchymal liver disease or obstruction of the biliary system 1.
- Unconjugated hyperbilirubinemia can be caused by:
- Hemolysis
- Impaired conjugation, such as in Gilbert's syndrome
- Conjugated hyperbilirubinemia can be caused by:
- Parenchymal liver disease, such as hepatitis or liver cirrhosis
- Obstruction of the biliary system, such as gallstones blocking bile ducts
- Certain medications affecting liver function
Evaluation and Management
If you notice dark or tea-colored urine, you should consult a healthcare provider promptly for proper evaluation. No specific home treatment exists for bilirubinuria itself, as it's a symptom rather than a disease. Your doctor will likely order blood tests, including liver function tests, complete blood count, and possibly imaging studies like ultrasound or CT scans to determine the cause. While awaiting medical care, it is essential to:
- Stay well-hydrated
- Avoid alcohol and medications that can stress the liver, such as acetaminophen
- Follow a healthy diet low in processed foods
Pathophysiology
Bilirubinuria occurs because conjugated bilirubin, which is normally excreted through bile into the intestines, backs up into the bloodstream when liver or bile duct problems exist, allowing it to be filtered by the kidneys into urine. This differs from normal physiology, where only minimal amounts of bilirubin appear in urine. According to the study published in the Journal of the American College of Radiology 1, the most common causes of jaundice, which can lead to bilirubinuria, include hepatitis, alcoholic liver disease, blockage of the common bile duct by a gallstone or tumor, and toxic reaction to a drug or medicinal herb.
From the Research
Causes of Hyperbilirubinemia
The causes of hyperbilirubinemia, which is characterized by elevated bilirubin levels in the urine, can be attributed to various factors. These include:
- Excess bilirubin production, such as in pathologic hemolysis 2
- Impaired liver uptake, leading to elevation of indirect bilirubin 2
- Impaired conjugation, resulting from a defect in the UDP-glucuronosyltransferase 2
- Bile clearance defect, causing elevation of direct bilirubin due to defects in clearance proteins or inability of bile to reach the small bowel through bile ducts 2
- Liver lesions, which can reduce hepatocyte cell number and impair the uptake of indirect bilirubin from plasma and diminish direct bilirubin transport and clearance through the bile ducts 2
- Alcoholic liver disease, biliary strictures, choledocholithiasis, drug-induced liver injury, hemolysis, or hepatitis 3
- Bile cast nephropathy, a condition where high bilirubin levels can cause a functional proximal tubulopathy or precipitate into casts associated with acute tubular injury 4
Diagnostic Evaluation
The diagnostic evaluation of hyperbilirubinemia involves a comprehensive medical history, review of systems, and physical examination 3, 5. Laboratory tests, such as assays for bilirubin (total and fractionated), complete blood cell count, aspartate transaminase, alanine transaminase, gamma-glutamyltransferase, alkaline phosphatase, albumin, prothrombin time, and international normalized ratio, can help determine the underlying cause of hyperbilirubinemia 3. Imaging studies, including ultrasonography of the abdomen, computed tomography with intravenous contrast media, and magnetic resonance cholangiopancreatography, may also be necessary to evaluate the biliary tree and liver 3, 5.
Classification of Hyperbilirubinemia
Hyperbilirubinemia can be classified into two types: conjugated and unconjugated. Conjugated hyperbilirubinemia is an unusual situation where Rotor and Dubin-Johnson Syndromes should be considered 6. Non-conjugated hyperbilirubinemia can be caused by hemolysis, ineffective erythropoiesis, Gilbert or Crigler-Najjar syndromes 6. Measuring fractionated bilirubin allows for determination of whether the hyperbilirubinemia is conjugated or unconjugated 3.