Diagnostic testing for hepatobiliary and pancreatic conditions

Definition / Overview

The hepatobiliary and pancreatic (HPB) system encompasses the liver parenchyma, biliary tree (intra- and extrahepatic ducts, gallbladder), and pancreas (head, neck, body, tail, uncinate process). Diagnostic evaluation spans a broad spectrum, from incidentally identified benign lesions requiring surveillance to life-threatening malignancies demanding urgent MDT review. Selecting the right test requires understanding what each modality answers, its sensitivity/specificity in context, and how the result will change management.

Pathophysiology and Mechanism

Why Accurate Diagnosis Matters

• The HPB field contains conditions where tissue diagnosis, vascular mapping, and functional assessment are all simultaneously relevant.
• Benign and malignant lesions can appear radiologically similar; misclassification leads either to overtreatment (unnecessary major hepatectomy) or undertreatment (missed curative window for resectable cancer).
• Obstructive jaundice from any cause demands systematic evaluation to separate choledocholithiasis, benign stricture, malignancy, and inflammatory conditions before irreversible complications occur.

Pathophysiological Principles Guiding Test Selection

• Cholestasis vs. hepatocellular injury: pattern of LFT derangement directs the diagnostic pathway.
• Tumour biology: vascularity, enhancement pattern, and ductal involvement distinguish adenocarcinoma from neuroendocrine tumour, cholangiocarcinoma, and benign lesions.
• Vascular anatomy: determines resectability before any planned HPB resection; CT/MR angiography defines portal vein, hepatic artery, and SMA involvement.

Clinical Features / Diagnosis

Symptom-Based Diagnostic Frameworks

Investigation / Monitoring

Biochemical Investigations

Liver Function Tests and Synthetic Markers

• Bilirubin (total, direct/indirect): conjugated hyperbilirubinaemia indicates hepatocellular or obstructive pathology; unconjugated suggests haemolysis or Gilbert's.
• ALP and GGT: disproportionate elevation relative to transaminases points to biliary obstruction or infiltrative disease.
• AST/ALT: hepatocellular injury; ratios >2:1 (AST:ALT) raise suspicion of alcoholic hepatitis.
• Albumin, INR/prothrombin time: synthetic function; critical for Child-Pugh and MELD scoring before hepatic resection.
• Platelet count: thrombocytopaenia suggests portal hypertension; informs resection risk.

Serum Tumour Markers

Pancreatic Cyst Fluid (obtained via EUS-FNA)

• CEA >192 ng/mL: suggests mucinous cyst (MCN/IPMN); does not distinguish benign from malignant.
• Amylase: markedly elevated in pseudocysts and communicating IPMNs.
• Cytology: low sensitivity for malignancy (~50%) but high specificity when positive.
• Molecular analysis (KRAS/GNAS mutations): KRAS mutation highly specific for mucinous lineage; GNAS mutation specific for IPMN.

Functional Pancreatic Tests

• Faecal elastase-1: first-line non-invasive test for exocrine insufficiency; values <100 μg/g indicate severe insufficiency.
• HbA1c and fasting glucose: endocrine function; new-onset diabetes in a patient >50 years without risk factors should prompt pancreatic cancer evaluation.

Imaging

Ultrasound (USS)

• First-line for suspected biliary disease, acute right upper quadrant pain, and liver lesion characterisation.
• Advantages: no radiation, widely available, real-time, sensitive for gallstones (>95%), biliary dilatation, and large lesions.
• Limitations: operator-dependent; poor for distal CBD, pancreatic tail, and lesions obscured by bowel gas.
• CEUS (contrast-enhanced ultrasound): useful for characterising haemangioma vs. metastasis; immediate lesion characterisation in experienced centres without radiation.

Computed Tomography (CT)

CT Pancreas Protocol (Triphasic/Dual-Phase)

• Acquisition in arterial and portal venous phases with thin slices through the pancreas.
• Defines: primary tumour, ductal dilation ("double-duct sign"), vascular involvement (SMA, celiac, portal/SMV confluence), and lymphadenopathy.
• Vascular staging: CT can reliably assess vessel encasement and contact; sensitivity ~80-90% for detecting vascular invasion, informing borderline vs. locally advanced vs. resectable classification.
• Pulmonary, hepatic, and peritoneal metastases identified simultaneously.

CT Liver with Contrast (Triphasic)

• Essential for HCC: arterial hyperenhancement + portal venous washout = LI-RADS 5 (highly suggestive of HCC); fulfils criteria for diagnosis without biopsy in appropriate context (cirrhotic liver).
• Liver metastases: typically hypovascular in portal venous phase (CRC mets); neuroendocrine liver metastases are hypervascular in arterial phase.

MRI / MRCP

• MRCP (MR cholangiopancreatography): gold standard non-invasive imaging of the biliary tree; depicts stricture location, duct calibre, choledocholithiasis, and intraductal filling defects.
• MRI liver with hepatobiliary contrast (gadoxetic acid / Gd-EOB-DTPA): superior to CT for detection of small HCC, liver metastases, and characterisation of FNH (uptake in hepatobiliary phase) vs. adenoma (no uptake) vs. malignancy.
• MRI pancreas: superior to CT for cystic lesion characterisation (IPMN morphology, mural nodules, communication with main duct), and for soft-tissue characterisation of periampullary lesions.
• Primary sclerosing cholangitis: MRCP demonstrates the "string and bead" pattern of multifocal strictures and dilatations; combined with AMA and IgG4 serology to exclude PBC and IgG4-associated cholangitis.

Endoscopy-Based Investigations

ERCP (Endoscopic Retrograde Cholangiopancreatography)

• Predominantly therapeutic in contemporary practice; reserve diagnostic-only ERCP for situations where intervention is simultaneously planned.
• Provides: biliary drainage (stenting), brushings for cytology (sensitivity ~30-50% for CCA), and intraductal biopsies.
• Cholangioscopy (SpyGlass): direct visualisation of bile duct mucosa; guided biopsy increases diagnostic yield for indeterminate biliary strictures.
• Indicated when: obstructive jaundice with high suspicion of CBD stone, biliary decompression before surgery, tissue sampling of hilar/biliary strictures.

EUS (Endoscopic Ultrasound)

• High-resolution imaging of the pancreatic head, distal CBD, and peripancreatic nodes, superior to CT for lesions <2 cm.
• EUS-FNA/FNB: tissue acquisition for solid pancreatic lesions (sensitivity ~85-90%), lymph nodes, and cyst fluid sampling.
• Determines T and N staging of periampullary tumours; defines relationship to portal vein and SMA.
• Preferred when CT/MR equivocal for a small pancreatic mass or when tissue is required prior to neoadjuvant therapy.

Nuclear Medicine

Staging Laparoscopy

• Indicated before planned resection for pancreatic adenocarcinoma, gallbladder carcinoma, and cholangiocarcinoma when CT suggests resectable or borderline resectable disease.
• Detects occult peritoneal, omental, and small liver surface metastases not seen on cross-sectional imaging.
• Yield is highest when CA 19-9 is markedly elevated (>150-200 U/mL), when primary is locally advanced, or when there is ascites on imaging.
• Laparoscopic ultrasound can be added to assess intrahepatic metastases and vascular involvement intraoperatively.

Management: Selecting the Appropriate Test Pathway

Incidental Liver Lesion, Algorithm

1. History: cirrhosis/viral hepatitis risk → HCC surveillance pathway; known malignancy → metastasis evaluation; OCP use in young woman → consider adenoma or FNH.
2. Serology: AFP, LFTs, hepatitis B/C serology, INR/albumin.
3. If cirrhotic liver: triphasic CT or MRI liver, LI-RADS classification; if LI-RADS 5, proceed to MDT without biopsy.
4. If non-cirrhotic liver: MRI with gadoxetic acid for characterisation; biopsy considered if diagnosis remains uncertain and will change management.
5. Haemangioma suspected: confirm with CEUS or MRI, peripheral nodular enhancement with centripetal fill-in; no further workup if classic.
6. FNH: central scar, spoke-wheel vascularity on MRI, hepatobiliary phase uptake; no intervention required if asymptomatic.
7. Adenoma: characterise subtype (HNF1α-mutated, β-catenin-mutated, inflammatory); β-catenin-mutated adenomas carry malignant potential, resection generally recommended.

Obstructive Jaundice, Algorithm

1. Bloods: FBC, LFTs, coagulation, bilirubin, blood cultures if febrile, CA 19-9, CEA.
2. USS abdomen: biliary dilatation present? Stone vs. mass vs. no discrete lesion.
3. MRCP: defines level and cause of obstruction; proceed to ERCP only when intervention planned.
4. CT pancreas protocol: if malignancy suspected, staging and vascular assessment.
5. EUS ± FNA: small pancreatic head mass, equivocal CT, tissue required pre-neoadjuvant.
6. ERCP + stenting: if cholangitis, symptomatic jaundice requiring decompression before resection, or tissue sampling required.

Cystic Pancreatic Lesion, Algorithm

1. MRCP/MRI pancreas for morphological characterisation: main duct IPMN, branch duct IPMN, MCN, SCN.
2. High-risk features (Fukuoka guidelines): main duct involvement, mural nodules, obstructive jaundice, positive cytology → surgical resection.
3. Worrisome features: cyst >3 cm, thickened wall, abrupt duct calibre change, lymphadenopathy → EUS for further evaluation.
4. EUS-FNA: cyst fluid for CEA, amylase, cytology; molecular testing if equivocal.
5. SCN: lobulated, microcystic, central scar on CT/MRI, near-certain benign; serial imaging unless symptomatic.
6. Pseudocyst: clinical context of pancreatitis + amylase-rich fluid; no resection; drain if symptomatic.

Complications & Special Considerations

Pitfalls in HPB Diagnosis

• False-negative CA 19-9: Lewis antigen-negative individuals; always interpret in context of imaging.
• IgG4-elevated pancreatic mass: autoimmune pancreatitis can mimic pancreatic adenocarcinoma; steroid trial diagnostically appropriate after exclusion of malignancy by multidisciplinary review and tissue sampling.
• Biliary brushings for CCA: low sensitivity; fluorescence in situ hybridisation (FISH) increases yield; cholangioscopy-directed biopsy is now preferred in expert centres.
• ERCP risk in suspected CCA: biliary stenting before staging may increase perioperative infection risk and complicate subsequent hilar dissection; coordinate stenting with surgical plan.
• Incidental pancreatic lesion on CT: do not dismiss small hypodense lesion in the pancreatic head, reformat with pancreas protocol CT or proceed to MRI/EUS.

Special Populations

• Cirrhotic patients: biopsy of liver lesions carries bleeding risk and seeding risk; use LI-RADS criteria to avoid biopsy when HCC diagnosis is radiologically secure.
• Post-cholecystectomy incidental gallbladder cancer (T1b+): requires formal staging CT chest/abdomen/pelvis, CA 19-9, CEA, and MDT review before deciding on re-resection.
• Suspected PSC: MRCP + IgG4 + AMA; liver biopsy for fibrosis staging; ELF test and LSM (FibroScan) for non-invasive fibrosis monitoring.
• Biliary trauma or post-operative bile leak: HIDA scan to confirm and characterise leak; MRCP to delineate ductal anatomy before repair.

Perioperative Management and MDT Integration

Preoperative Optimisation Before Major HPB Resection

• Nutritional assessment: malnutrition common in HPB malignancy; consider 7-10 days preoperative enteral nutritional support if severely malnourished (weight loss >10-15%, albumin <30 g/L).
• Obstructive jaundice management: biliary drainage prior to major hepatectomy may be required if future liver remnant (FLR) is at risk, coordinate with interventional radiology or endoscopy; avoid routine preoperative drainage before pancreaticoduodenectomy unless delay to surgery >2 weeks or cholangitis.
• Portal vein embolisation (PVE): if FLR <20-25% in otherwise normal liver, or <30-40% in cirrhotic or chemotherapy-damaged liver; assess volumetry on CT; resect 4-6 weeks after PVE.
• Cardiopulmonary fitness: formal assessment with functional capacity history ± CPET for patients undergoing major resections; optimise cardiorespiratory comorbidities.

MDT Decision-Making Checklist for HPB Malignancy

• Confirm diagnosis (radiological ± tissue).
• Stage disease (T, N, M, disease-specific staging system).
• Assess resectability against vascular criteria.
• Evaluate FLR volume and quality.
• Determine fitness for surgery and perioperative risk.
• Agree on neoadjuvant strategy if borderline resectable.
• Plan approach (open / laparoscopic / robotic) based on anatomy, expertise, and tumour biology.
• Schedule post-operative surveillance and adjuvant therapy.

Summary Table: Modality Selection by Clinical Question

Sources

• RACS position statements & curriculum (Royal Australasian College of Surgeons)
• ANZGOSA (Australia & NZ Gastric & Oesophageal Surgery Association)