11.4 Cholestatic Liver Disease: PBC and PSC

Disorders of the biliary tree and pancreas frequently feature in the MRCP(UK) Part 1 examination. Candidates are expected to differentiate between autoimmune cholestatic hepatopathies, manage gallstone-related biliary emergencies, master the diagnostic and prognostic criteria of acute pancreatitis, and direct the investigation and enzyme replacement therapy of chronic pancreatic exocrine insufficiency.

1. Cholestatic Liver Diseases

Primary Biliary Cholangitis (PBC)

• Epidemiology & Associations: Striking female preponderance (~9:1); typical age of onset 40–60 years. Associated with autoimmune conditions including Sjögren's syndrome (~70%), Hashimoto's thyroiditis, systemic sclerosis (CREST syndrome), and coeliac disease.
• Immunopathogenesis: T-cell mediated autoimmune destruction of the cholangiocytes lining intrahepatic interlobular and septal bile ducts (small ducts <100 um diameter). The extrahepatic biliary tree is completely spared. Progressive ductopenia leads to chronic cholestasis, accumulation of cytotoxic bile salts, portal inflammation, and biliary cirrhosis.
• Clinical Features: Insidious onset. The two cardinal early symptoms are disabling fatigue and intractable pruritus (typically worse at night, prominent on palms and soles, and often preceding jaundice by several years). Physical signs include excoriations, xanthelasma / xanthomas (due to severe hypercholesterolaemia with high HDL), cutaneous hyperpigmentation, and late jaundice. Significant risk of osteoporosis / osteopenia (malabsorption of fat-soluble vitamin D and osteoblast suppression), mandating baseline bone mineral density (DEXA) scanning.
• Diagnostic Hallmarks:
  • Biochemical Profile: Markedly elevated Alkaline Phosphatase (ALP) and Gamma-Glutamyl Transferase (GGT); transaminases (AST/ALT) are normal or mildly elevated. Serum bilirubin rises late and signifies advanced ductopenia and poor prognosis.
  • Serology: Antimitochondrial Antibodies (AMA) are positive in >95% of patients (specificity >98%). Specifically targeted against the E2 subunit of the pyruvate dehydrogenase complex (PDC-E2). Markedly elevated serum immunoglobulin M (IgM) is classic.
  • Liver Biopsy: Rarely required if ALP is elevated and AMA is positive. Histopathology demonstrates florid duct lesions: chronic granulomatous inflammation destroying interlobular bile ducts, ductopenia, and bridging fibrosis.
• Therapeutic Management:
  • First-Line Disease-Modifying Agent: Ursodeoxycholic acid (UDCA) (13–15 mg/kg/day orally). A hydrophilic tertiary bile acid that replaces toxic endogenous bile acids, stimulates bicarbonate secretion, and exerts anti-apoptotic effects. Halts histological progression, delays need for liver transplantation, and improves transplant-free survival.
  • Second-Line Agents: Obeticholic acid (farnesoid X receptor [FXR] agonist) or fibrates (bezafibrate, PPAR-alpha agonist) for patients with incomplete biochemical response or intolerance to UDCA.
  • Pruritus Management: First-line is colestyramine (bile acid sequestrant; must be dosed 2–4 hours before or after UDCA to avoid binding the drug); second-line agents include rifampicin, oral naltrexone, and sertraline.

Primary Sclerosing Cholangitis (PSC)

• Epidemiology & Associations: Male predominance (~2:1); typical age of onset 30–50 years. 70–80% of patients have underlying Inflammatory Bowel Disease, overwhelmingly Ulcerative Colitis (typically pancolitis with rectal sparing and backwash ileitis). Conversely, ~5% of patients with UC develop PSC.
• Immunopathogenesis: Chronic idiopathic fibroinflammatory obliterative cholangiopathy affecting both intrahepatic and extrahepatic bile ducts (large and small ducts). Characterized by periductal fibrosis, diffuse stricturing, and biliary cirrhosis.
• Clinical Presentation: Often asymptomatic, detected via persistent ALP elevation during routine IBD monitoring. Symptomatic patients experience fatigue, intermittent fluctuating jaundice, pruritus, right upper quadrant ache, and recurrent episodes of acute ascending bacterial cholangitis.
• Diagnostic Hallmarks:
  • Biochemical Profile: Cholestatic pattern (elevated ALP and GGT).
  • Serology: Perinuclear antineutrophil cytoplasmic antibodies (p-ANCA) positive in 60–80% (atypical nuclear pattern). Serum IgG4 should be measured to rule out IgG4-related sclerosing cholangitis, a steroid-responsive mimic.
  • Diagnostic Imaging of Choice: Magnetic Resonance Cholangiopancreatography (MRCP). Demonstrates multifocal segment-like strictures and intervening saccular dilatations involving intra- and extrahepatic bile ducts—the classic "beaded" appearance (string of beads).
  • Liver Biopsy: Rarely necessary; characteristically reveals concentric periductal fibrosis ("onion-skin" fibrosis) causing complete luminal obliteration and fibrous cords.
• Malignancy Risks & Surveillance Protocols:
  • Cholangiocarcinoma (CCA): Lifetime risk of 10–15% (~1.5% annual incidence). Manifests as rapid clinical decompensation, weight loss, worsening jaundice, or an acute "dominant stricture". Surveillance: annual MRCP and serum carbohydrate antigen 19-9 (CA 19-9).
  • Colorectal Carcinoma (CRC): 4- to 5-fold higher risk than in UC alone, with high propensity for right-sided colonic neoplasia. Mandatory guideline rule: Annual surveillance colonoscopy with chromoendoscopy and targeted/random biopsies from the time of PSC diagnosis, regardless of whether bowel disease is quiescent.
  • Gallbladder carcinoma: Annual ultrasound; cholecystectomy indicated for any gallbladder polyp >8 mm.
• Management: No medical therapy halts progression (UDCA does not improve survival). Endoscopic balloon dilatation (with or without temporary stenting) for dominant strictures. Orthotopic liver transplantation is the only curative option for decompensated disease (recurs in 20–25% of allografts).