Clinical scenario: Chronic diarrhea/ pruritis/jaundice
A 15-year-old boy with a 2-year history of ulcerative colitis, currently in clinical remission on mesalamine, is evaluated for persistent fatigue and generalized pruritus. He denies abdominal pain or worsening diarrhea. Examination reveals mild scleral icterus and hepatomegaly without splenomegaly. Laboratory investigations show: total bilirubin 2.4 mg/dL, ALT 82 U/L, AST 76 U/L, alkaline phosphatase 640 U/L, and γ-glutamyl transferase (GGT) 420 U/L. Abdominal ultrasonography demonstrates no gallstones or biliary dilatation.
Which of the following is the most appropriate next investigation to confirm the diagnosis?
A. Endoscopic retrograde cholangiopancreatography (ERCP)
B. Liver biopsy
C. Magnetic resonance cholangiopancreatography (MRCP)
D. Percutaneous transhepatic cholangiography (PTC)
E. Serum antimitochondrial antibody
Correct answer & Explanation:
Item #1
Correct Answer: C. Magnetic resonance cholangiopancreatography (MRCP)
Explanation: Primary sclerosing colangitis
This adolescent has a cholestatic pattern of liver injury (marked elevation of alkaline phosphatase and GGT) together with ulcerative colitis, which strongly suggests primary sclerosing cholangitis (PSC).
MRCP is the investigation of choice to establish the diagnosis because it non-invasively demonstrates the characteristic multifocal strictures and segmental dilatation (“beading”) of the intrahepatic and/or extrahepatic bile ducts.
Why the other options are incorrect
A. Endoscopic retrograde cholangiopancreatography (ERCP)
ERCP is not recommended as the initial diagnostic test because it is invasive and carries risks such as pancreatitis and cholangitis. It is mainly reserved for therapeutic interventions (e.g., dilating dominant strictures).
B. Liver biopsy
Not routinely required to diagnose classic PSC. It is mainly indicated when small-duct PSC or PSC–autoimmune hepatitis overlap syndrome is suspected.
C. Magnetic resonance cholangiopancreatography (MRCP)
Correct. MRCP is the first-line imaging modality for diagnosing PSC because of its high diagnostic accuracy and non-invasive nature.
D. Percutaneous transhepatic cholangiography (PTC)
Rarely used today for diagnosis and generally reserved when MRCP and ERCP are not feasible.
E. Serum antimitochondrial antibody
This antibody is associated with primary biliary cholangitis (PBC), not PSC. PBC is extremely uncommon in children.
Learning Point
Primary sclerosing cholangitis should be suspected in any child or adolescent with ulcerative colitis who develops:
- Persistent cholestatic liver enzyme elevation (especially GGT and alkaline phosphatase)
- Pruritus
- Fatigue
- Jaundice
The diagnostic investigation of choice is MRCP, while ERCP is reserved primarily for therapeutic intervention, not routine diagnosis.
