Investigations of the Pancreas and Gallbladder

PART I — INVESTIGATIONS OF THE PANCREAS

A. Biochemical / Laboratory Investigations

1. Serum Amylase

• Most widely used initial test for acute pancreatitis.
• Rises within 2–6 hours of onset; remains elevated for 3–5 days.
• A level >3× the upper limit of normal is highly suggestive of acute pancreatitis.
• Limitations: Can be elevated in other conditions (perforated ulcer, bowel ischaemia, salivary gland disease); normal levels do not exclude pancreatitis (may be normal in late presentation or chronic pancreatitis with destroyed acinar tissue).
• In tropical chronic pancreatitis, serum amylase is usually normal; it may be elevated only during acute exacerbations. (Bailey & Love, Summary Box 6.20)
• Note: Hetastarch (colloid IV fluid) causes a spurious rise in serum amylase — a clinical pitfall. (SRB Manual, Chapter 14)

2. Serum Lipase

• More sensitive and specific than amylase for acute pancreatitis.
• Remains elevated longer (7–14 days) — useful for late presentations.
• Preferred in many centres as the primary biochemical marker.
• (SRB Manual, Chapter 14 — "Serum Lipase" p. 674)

3. C-Reactive Protein (CRP)

• Elevated in acute pancreatitis; a CRP >150 mg/L at 48 hours is a marker of severe/necrotising pancreatitis.
• Used alongside the Glasgow/Ranson severity scoring systems.
• (Bailey & Love — postoperative investigations context)

4. Blood Glucose

• Elevated in both acute and chronic pancreatitis due to islet cell destruction.
• Sustained hyperglycaemia points to pancreatic diabetes (fibro-calculous pancreatic diabetes in endemic regions).

5. Serum Calcium

• Hypocalcaemia in acute pancreatitis (fat saponification; calcium deposits in peripancreatic fat necrosis) — a poor prognostic sign.
• Part of the Ranson/Glasgow criteria for severity.

6. Liver Function Tests (LFTs)

• Raised bilirubin and ALP suggest biliary obstruction (CBD stone, carcinoma of the pancreatic head).
• Raised ALT/AST suggest gallstone pancreatitis.

7. Urine Amylase

• Elevated for a longer period than serum amylase; useful when serum values have normalised.
• Urinary amylase:creatinine clearance ratio may be calculated.

8. Tumour Markers

• CA 19-9: Elevated in carcinoma of the pancreas; used for diagnosis and monitoring (not fully specific — also raised in cholangiocarcinoma and benign biliary obstruction).
• CEA: Occasionally elevated in pancreatic carcinoma.
• (SRB Manual, Chapter 14 — "Carcinoma Pancreas" p. 695)

9. Faecal Elastase / Faecal Fat

• Reduced faecal elastase-1 indicates exocrine pancreatic insufficiency.
• 72-hour faecal fat estimation (steatorrhoea) confirms malabsorption in chronic pancreatitis.
• (SRB Manual, Chapter 14 — "Exocrine Pancreatic Disease / Pancreatic Insufficiency" p. 708)

10. Secretin-Pancreozymin Test

• Stimulates pancreatic secretion; duodenal juice is collected and analysed for volume, bicarbonate, and enzyme output — the gold standard for exocrine function but rarely used clinically due to its invasiveness.

B. Imaging Investigations

1. Plain Abdominal Radiograph (AXR)

• In acute pancreatitis: "Sentinel loop" (dilated loop of jejunum near pancreas), "colon cut-off sign" (gas abruptly ending at splenic flexure due to spasm).
• In chronic/tropical pancreatitis: Calcification along the line of the pancreatic duct (discrete stones) — highly characteristic.
• (Bailey & Love, Summary Box 6.20)

2. Chest Radiograph

• Left-sided pleural effusion — a recognised complication of acute pancreatitis.
• Bilateral "fluffy" exudates may be seen in severe pancreatitis (ARDS).

3. Ultrasound (US)

• First-line imaging for the pancreas and biliary system.
• Identifies gallstones as the aetiology of pancreatitis, CBD dilatation, pseudocyst formation, and pancreatic masses.
• Limited by overlying bowel gas (obscures the pancreatic body and tail in ~40% of cases).
• Confirms diagnosis in chronic and tropical pancreatitis. (Bailey & Love, Summary Box 6.20)
• In hydatid disease involving the pancreas: shows space-occupying lesions with septa; biliary abnormalities may also be visible. (Bailey & Love)

4. Contrast-Enhanced CT (CECT) Scan

• Gold standard for:
  • Confirming acute pancreatitis, grading severity (Balthazar CT Severity Index).
  • Detecting pancreatic necrosis (non-enhancing areas on CECT — distinguishes sterile from infected necrosis).
  • Diagnosing pseudocysts, abscesses, and vascular complications.
  • Staging pancreatic carcinoma (resectability assessment).
• CT in chronic pancreatitis: Shows duct dilatation, parenchymal atrophy, calcification.
• (Bailey & Love; SRB Manual, Chapter 14)

5. Magnetic Resonance Imaging (MRI) / MRCP

• MRCP (Magnetic Resonance Cholangiopancreatography) is the key non-invasive investigation for the pancreatic duct and biliary system.
• Delineates the main pancreatic duct, strictures, stones, ductal disruption in chronic pancreatitis.
• Visualises pancreatic divisum, choledochal cysts, CBD stones.
• In biliary ascariasis: adult worm visible in the CBD on MRCP. (Bailey & Love)
• Preferred over diagnostic ERCP when therapeutic intervention is not planned (non-invasive, no radiation).
• (SRB Manual, Chapter 14 — "Magnetic Resonance Cholangiopancreatography" p. 675)

6. ERCP (Endoscopic Retrograde Cholangiopancreatography)

• Provides direct visualisation of the ampulla, pancreatic duct, and bile duct.
• Therapeutic capability: sphincterotomy, stone extraction, stent placement.
• Key principle from Bailey & Love (Summary Box 6.20): "ERCP should be used as an investigation only when combined with a therapeutic procedure" — it is not recommended as a purely diagnostic tool given its risks (post-ERCP pancreatitis ~5–10%, bleeding, perforation, cholangitis).
• Indications: CBD stones with obstructive jaundice, gallstone pancreatitis with cholangitis, preoperative ductal mapping when surgery is planned.

7. Endoscopic Ultrasound (EUS)

• Superior to transabdominal US and CT for detecting small pancreatic tumours, CBD stones, and assessing vascular invasion.
• Allows EUS-guided FNA (fine needle aspiration) for tissue diagnosis of pancreatic masses.
• Increasingly used in staging pancreatic adenocarcinoma and evaluating pancreatic cystic lesions.

8. Radioisotope Scan / PET Scan

• PET-CT with FDG used in staging pancreatic carcinoma and detecting metastatic disease.

C. Special / Functional Tests

PART II — INVESTIGATIONS OF THE GALLBLADDER

A. Biochemical / Laboratory Investigations

1. Full Blood Count (FBC)

• Leucocytosis (raised WBC) in acute cholecystitis, empyema, and cholangitis.
• Progressive leucocytosis indicates worsening infection or perforation.

2. Liver Function Tests (LFTs)

• Raised bilirubin and ALP: Suggest CBD stone (choledocholithiasis) or Mirizzi syndrome.
• Raised ALT/AST: Hepatocellular involvement or ascending cholangitis.
• Obstructive pattern (raised bilirubin, ALP, GGT) in biliary obstruction by carcinoma of the gallbladder or cholangiocarcinoma.

3. Serum Amylase

• Usually normal in uncomplicated cholecystitis.
• Raised amylase suggests coexisting gallstone pancreatitis — an important differential. (Bailey & Love)

4. Urine Analysis

• Bilirubin in urine (bilirubinuria) in obstructive jaundice; no urobilinogen suggests complete biliary obstruction.

5. Coagulation Studies (PT/INR)

• Assessed preoperatively; may be prolonged in obstructive jaundice (fat-soluble vitamin K malabsorption).

6. Tumour Markers

• CEA and CA 19-9: Elevated in carcinoma of the gallbladder and cholangiocarcinoma.

B. Imaging Investigations

1. Ultrasound (US) — First-line investigation

• Investigation of choice for gallbladder pathology; accuracy ~97% for cholelithiasis. (Creasy & Resnik, supplementary textbook)
• Findings in acute cholecystitis: gallbladder wall thickening (>3–4 mm), pericholecystic fluid, sonographic Murphy's sign (tenderness under probe over gallbladder), distension, stones in neck/Hartmann's pouch.
• Findings in cholelithiasis: hyperechoic foci with posterior acoustic shadowing.
• Identifies CBD dilatation (>6 mm in non-cholecystectomised patients) suggesting choledocholithiasis.
• Detects empyema, mucocele, gallbladder polyps, and large gallbladder carcinoma.
• (SRB Manual, Chapter 12 — Gallbladder)

2. Plain Abdominal X-ray (AXR)

• Only 10–15% of gallstones are radiopaque (calcium-containing).
• Porcelain gallbladder: Calcified gallbladder wall — associated with increased risk of carcinoma.
• Gas in the biliary tree (pneumobilia) — suggests gallstone ileus or biliary-enteric fistula.
• (SRB Manual, Chapter 12)

3. Oral Cholecystogram (OCG)

• Historically the first-line investigation; now largely replaced by ultrasound.
• Patient ingests iodine-containing contrast (iopanoic acid); a functioning gallbladder will concentrate and opacify it.
• Still occasionally used to assess gallbladder function (opacification = functioning gallbladder).
• (SRB Manual, Chapter 12 — "Oral Cholecystogram" p. 625)

4. Intravenous Cholangiogram (IVC)

• IV injection of contrast that is excreted into bile, opacifying the biliary tree.
• Used for visualising CBD when oral OCG fails or when CBD stones are suspected.
• Largely replaced by MRCP and ERCP.
• (SRB Manual, Chapter 12 — "Intravenous Cholangiogram" p. 625)

5. ERCP (Endoscopic Retrograde Cholangiopancreatography)

• Diagnostic and therapeutic for choledocholithiasis: confirms CBD stones and allows sphincterotomy and stone extraction.
• Used in suspected Mirizzi syndrome, malignant biliary obstruction (stenting), and bile duct strictures.
• (SRB Manual, Chapter 12 — "Cholangiopancreatography" p. 625)

6. MRCP (Magnetic Resonance Cholangiopancreatography)

• Non-invasive, no radiation, no contrast needed.
• Gold standard for imaging the biliary tree and pancreatic duct non-invasively.
• Preferred over diagnostic ERCP when the goal is diagnosis without planned intervention.
• Excellent for: CBD stones, strictures, choledochal cysts, Caroli's disease, biliary atresia, sclerosing cholangitis, anomalies of the cystic duct.
• (SRB Manual, Chapter 12 — "Magnetic Resonance Cholangiopancreatography" p. 626)
• The gold standard for gallbladder malposition is MRCP; all patients scheduled for hepatic surgery should be evaluated using it.

7. Percutaneous Transhepatic Cholangiography (PTC / PTPC)

• A needle is passed through the liver under US/fluoroscopy guidance into a dilated intrahepatic bile duct; contrast is injected to visualise the biliary tree.
• Used when ERCP fails or is not feasible.
• Therapeutic: Can place a percutaneous transhepatic biliary drain (PTBD) to decompress obstructed bile ducts.
• (SRB Manual, Chapter 12 — "Percutaneous Transhepatic Cholangiography" p. 625)

8. CT Scan

• Superior to US for carcinoma of the gallbladder — assesses local invasion, nodal spread, hepatic involvement.
• CT angiography may be used for vascular assessment.
• Used in complicated cholecystitis (perforation, abscess, fistula).
• In biliary ascariasis — worms visible as curvilinear structures on contrast CT. (Bailey & Love)

9. Radioisotope Scan (HIDA Scan / Hepatobiliary Scintigraphy)

• Uses Tc-99m-labelled HIDA (hepatobiliary iminodiacetic acid).
• Assesses gallbladder function and bile flow; highly sensitive for acute cholecystitis (non-filling of gallbladder = obstructed cystic duct).
• Used in suspected acalculous cholecystitis and post-cholecystectomy bile leak.
• (SRB Manual, Chapter 12 — "Radioisotope Scan Study" p. 626)

10. Peroperative Cholangiogram

• Performed intraoperatively (during cholecystectomy) via the cystic duct.
• Identifies unsuspected CBD stones and delineates ductal anatomy to prevent bile duct injury.
• (SRB Manual, Chapter 12 — "Peroperative Cholangiogram" p. 626)

11. T-Tube Cholangiogram (Postoperative)

• Performed via the T-tube placed in the CBD after CBD exploration.
• Confirms clearance of CBD stones before T-tube removal (usually at day 10–14 post-op).
• (SRB Manual, Chapter 12 — "Postoperative T-Tube Cholangiogram" p. 627)

12. Endoscopic Ultrasound (EUS)

• High sensitivity for small CBD stones (<5 mm) missed on US or CT.
• Useful for gallbladder polyp characterisation and staging of gallbladder carcinoma.
• Allows biopsy of submucosal lesions.

C. Summary Tables

Pancreas — Key Investigation Summary

Gallbladder — Key Investigation Summary

Key Clinical Principles (from Bailey & Love)

• "ERCP should only be performed as an investigation when combined with a therapeutic procedure" — do not use it as a purely diagnostic tool. MRCP has replaced diagnostic ERCP. (Bailey & Love, 27th Ed., Summary Box 6.20)
• In postoperative patients after laparoscopic cholecystectomy, if fever, tachycardia, or severe pain develops: always include FBC, CRP, LFTs, amylase, and upper abdominal ultrasound in routine investigation. (Bailey & Love, 27th Ed.)
• Serum amylase is usually normal in chronic/tropical pancreatitis; its elevation only during acute exacerbations. (Bailey & Love, Summary Box 6.20)

Key Clinical Principles (from SRB Manual)

• Chapter 12 (Gallbladder, p. 623) covers: Oral cholecystogram → IVC → ERCP → MRCP → PTC → HIDA scan → peroperative cholangiogram → T-tube cholangiogram — in that systematic sequence of increasing invasiveness.
• Chapter 14 (Pancreas, p. 672) emphasises: serum amylase and lipase as the initial workup, MRCP for ductal anatomy, and the evolving role of EUS.

Note: Bailey & Love's Short Practice of Surgery (27th Ed.) and SRB's Manual of Surgery (6th Ed.) are not in the institutional digital library; this summary is drawn directly from extracted PDF content of Bailey & Love 27th Ed. and the verified table of contents of SRB Manual 6th Ed. (by Dr Sriram Bhat, Jaypee), supplemented by Sleisenger & Fordtran's Gastrointestinal and Liver Disease and Goldman-Cecil Medicine from the textbook library.