Jaundice with pruritus, dark urine, a cholestatic pattern (high conjugated bilirubin, ALP 3x ULN, only mild transaminase rise) suggests extrahepatic obstruction (e.g. pancreatic head tumour, CBD stone). The initial test is abdominal ultrasound, which shows whether the bile ducts are dilated and often the level/cause. CT then stages a pancreatic mass, MRCP/MRI is second-line if ultrasound is inconclusive, and ERCP is invasive and reserved for therapy or when obstruction is already established.