Icterus

Icterus, commonly known as jaundice, is the yellow discoloration of the skin, sclerae, and mucous membranes caused by elevated bilirubin in the blood. It reflects an imbalance between bilirubin production, hepatic processing, and biliary excretion. Bilirubin exists as unconjugated (indirect) bilirubin, which is not water-soluble, and conjugated (direct) bilirubin, which is water-soluble after hepatic conjugation.

Causes are usually grouped by site: prehepatic (increased bilirubin production from hemolysis or ineffective erythropoiesis), hepatic (impaired conjugation as in Gilbert or Crigler-Najjar syndromes; hepatocellular injury from hepatitis, cirrhosis, or drugs), and posthepatic (obstruction of bile flow from gallstones, tumors, or strictures leading to conjugated hyperbilirubinemia and cholestasis).

Neonatal jaundice is common in newborns due to immature bilirubin metabolism; severe unconjugated hyperbilirubinemia risks kernicterus if untreated.

Clinical features include yellowing of the skin and sclera, dark urine, and pale stools in cholestasis; pruritus may occur in cholestatic disease. Physical examination may reveal hepatomegaly or splenomegaly.

Diagnosis involves measuring total and direct bilirubin, liver function tests, complete blood count, and coagulation studies; imaging such as ultrasound or MRCP assesses biliary obstruction. In neonates, risk assessment and bilirubin nomograms guide management.

Management targets the underlying cause: neonatal phototherapy or exchange transfusion for severe unconjugated jaundice; treatment of hemolysis or hepatitis; relief of biliary obstruction via endoscopic or surgical means; avoidance of hepatotoxic drugs.

Prognosis depends on etiology and timeliness of treatment; significant risk of kernicterus remains for untreated severe neonatal hyperbilirubinemia.