43. Mechanical jaundice (icterus mechanicus)

Mechanical jaundice (obstructive jaundice)

Obstructive jaundice results from impaired bile flow due to extrahepatic or intrahepatic mechanical obstruction, causing conjugated hyperbilirubinaemia.
Extrahepatic causes include common bile duct stones, pancreatic head cancer, cholangiocarcinoma, ampullary tumour, benign stricture and chronic pancreatitis.
Intrahepatic duct obstruction may occur with primary sclerosing cholangitis, infiltrative disease or selected drug-related conditions; distinguish mechanical obstruction from hepatocellular jaundice.

Conjugated bilirubin refluxes into blood and is excreted in urine, causing dark urine. Reduced intestinal bile causes pale stools and impaired fat absorption; retained bile salts contribute to pruritus.
Features include yellow sclera/skin, dark urine, pale stools, pruritus, steatorrhoea and weight loss. Fever and RUQ pain suggest cholangitis or gallstone disease.
Painless progressive jaundice with weight loss and a palpable gallbladder (Courvoisier sign) raises suspicion of malignant obstruction, but is not diagnostic.

Check total/direct bilirubin, ALP, GGT, ALT/AST, full blood count, coagulation, albumin and renal function. Cholestatic enzymes are commonly elevated.
Ultrasound is the first-line test to identify biliary dilatation, gallstones and gallbladder pathology.
Contrast CT assesses pancreatic and biliary malignancy and staging. MRCP non-invasively maps biliary anatomy; EUS assesses distal duct/pancreatic lesions and permits sampling.
ERCP is mainly therapeutic for drainage, stone extraction, stenting and selected tissue sampling because it carries risks including pancreatitis, bleeding and cholangitis.
Differential diagnosis includes hepatocellular jaundice, haemolysis, drug-induced cholestasis and sepsis-associated cholestasis.

Treat the cause and severity. If cholangitis or sepsis is present, give urgent IV antibiotics and biliary drainage.
CBD stones are managed by ERCP extraction or other duct-clearance techniques, followed by cholecystectomy when indicated.
Malignant obstruction may require endoscopic or percutaneous stenting for drainage, with resection for selected operable cancers and systemic/palliative treatment for advanced disease.
Correct vitamin K deficiency/coagulopathy when appropriate, manage pruritus and nutritional deficiencies, and assess for fat-soluble vitamin deficiency in prolonged cholestasis.
Complications include cholangitis, biliary cirrhosis, coagulopathy, malnutrition and renal dysfunction.