Hepatobiliary System

I. ANATOMY & PHYSIOLOGY

1. Liver

💡 Largest solid organ; RUQ; vital metabolic center.

KEY FUNCTIONS

• Metabolism: fats, proteins, carbohydrates

• Storage: Vitamin B, glycogen

• Synthesis: clotting factors, plasma proteins

• Detoxification: drugs, toxins

• Excretion: bilirubin, cholesterol

KEY TERMS

• Dual blood supply:

  • Hepatic artery → oxygenated blood

  • Portal vein → nutrient-rich blood from intestines

• Portal circulation importance: Any obstruction → portal hypertension, splenomegaly, varices.

EXAM TIP

“If portal venous flow is impaired → expect collateral circulation & varices.”

2. Biliary Tree

💡 System that conducts bile from the liver → gallbladder → duodenum.

STRUCTURE

• Right & Left Hepatic Ducts → Common Hepatic Duct

• Cystic Duct → Common Bile Duct (CBD)

• CBD + Pancreatic Duct → Ampulla of Vater

• Controlled by the Sphincter of Oddi

FUNCTION

• Bile emulsifies fats for absorption.

IMPORTANT TERM

• Cholecystokinin (CCK): stimulates gallbladder contraction to release bile.

3. Gallbladder

💡 Stores and concentrates bile.

KEY POINTS

• Pear-shaped, under the right lobe of the liver

• Thin walls → thicken in inflammation (cholecystitis)

• Releases bile during the digestion of fats

4. Pancreas

💡 Dual-function organ — endocrine & exocrine.

EXOCRINE FUNCTIONS

• Trypsin → protein digestion

• Amylase → breaks starch to maltose

• Lipase → breaks fats

ENDOCRINE FUNCTIONS

(via Islets of Langerhans)

• β-cells → Insulin → lowers blood glucose

• α-cells → Glucagon → raises blood glucose

EXAM TIP

Pancreatitis causes ↑ Amylase & Lipase.

II. IMAGING CONSIDERATIONS

1. Radiography (Plain Abdominal X-ray)

Importance

• An initial, quick, and accessible method for detecting calcifications in the hepatobiliary system.

• Useful when contrast studies are contraindicated.

Key Points

• May show radiopaque gallstones composed of cholesterol + bilirubin + calcium salts.

• Milk of calcium bile → hazy radiopacity due to bile stasis.

• Gas in gallbladder wall/lumen → gas-forming organisms (seen in diabetics).

• Pneumobilia (gas in the biliary tree) → fistula, gallstone ileus, post-surgery.

Imaging Findings

• Radiopaque stones

• A hazy gallbladder from milk of calcium

• Gas in GB wall → emphysematous cholecystitis

• Gas in biliary ducts → fistula or postoperative changes

2. Contrast Studies

A. Percutaneous Transhepatic Cholangiography (PTC)

Importance

• Direct visualization of the biliary tree.

• Distinguishes medical jaundice (hepatocellular) vs surgical jaundice (obstructive).

Key Points

• Needle inserted percutaneously (Chiba needle).

• Detects distal CBD stones, strictures, or tumors.

• Good for proximal obstructions (hepatic duct bifurcation).

Imaging Findings

• Dilated ducts proximal to obstruction

• Filling defects (stones)

• Narrowing (strictures)

B. Endoscopic Retrograde Cholangiopancreatography (ERCP)

Importance

• Visualizes biliary and pancreatic ducts.

• Both diagnostic and therapeutic.

Key Points

• Catheter inserted through the duodenal ampulla.

• Preferred for distal obstructions, nondilated ducts, and pancreatic evaluation.

Imaging Findings

• Stones as filling defects

• Strictures

• Lack of contrast in obstruction

C. Operative Cholangiography

Importance

• Performed during cholecystectomy to check for retained stones.

Key Points

• Contrast is injected into the cystic duct or the CBD.

• Must avoid air bubbles (mimic stones).

Findings

• Filling defects (stones)

• CBD patency

D. T-Tube Cholangiography

Importance

• Evaluates postoperative bile duct patency and residual stones.

Key Points

• Contrast injected via surgically placed T-tube.

• Air bubbles can mimic radiolucent stones.

Findings

• Free flow of contrast into the duodenum = normal

• Filling defect = stone

3. Diagnostic Medical Sonography (Ultrasound)

Importance

• Modality of choice for gallbladder and biliary tree.

• Noninvasive, fast, and almost 100% sensitive for gallstones.

Key Points

• Gallstones = echogenic foci with posterior acoustic shadowing

• GB wall thickening → inflammation

• Determines CBD obstruction

• Characterizes hepatic lesions (cystic vs solid)

• Doppler evaluates portal flow and hepatic artery patency (especially post-transplant)

Imaging Findings

• Stones: echogenic with shadow

• GB wall >3 mm: cholecystitis

• Dilated ducts: obstruction

• Hepatic cysts: anechoic

• Solid lesions: echogenic or mixed

4. Computed Tomography (CT)

Importance

• Excellent for evaluating masses, malignancy, trauma, and complications.

• Shows the pancreas better than an ultrasound.

Key Points

• Helical CT reduces motion artifact.

• Three-phase liver imaging (arterial, portal venous, delayed) enhances tumor detection.

• Best for locating biliary obstruction when not seen on ultrasound.

Imaging Findings

• Tumors: hyper- or hypodense depending on phase

• Abscesses: low-density center with rim enhancement

• Liver lacerations: irregular low-density regions

• Pancreatic tumors and pseudocysts are clearly visible

5. Nuclear Medicine Procedures (SPECT, Cholescintigraphy)

Importance

• Evaluates organ function, not just anatomy.

• Detects deep liver lesions and inflammation.

Cholescintigraphy (HIDA scan) Key Points

• Gold standard to confirm acute vs chronic cholecystitis.

• Uses Technetium isotope.

Imaging Findings

• Non-visualization of gallbladder → acute cholecystitis

• Delayed filling → chronic cholecystitis

• Extraluminal leakage → bile leak

• Slow passage → obstruction

6. Magnetic Resonance Imaging (MRI & MRCP)

Importance

• Excellent soft-tissue contrast.

• Superior for evaluating the liver, pancreas, and biliary ducts.

• No radiation.

Key Points

• Dynamic contrast-enhanced MRI differentiates hemangioma from tumors.

• MRCP uses heavily T2-weighted images — bile appears bright.

• MRCP is noninvasive and does not require contrast.

Imaging Findings

• MRCP: bright biliary tree

• Dark filling defects = stones

• Masses show characteristic enhancement patterns

• Retroperitoneal bleeds are visible on MRI

7. ACR Recommendations – RUQ Pain

Best initial exam:

• Ultrasound

Other appropriate exams:

• CT abdomen (with/without contrast)

• Cholescintigraphy

• MRI abdomen

• Percutaneous cholecystostomy for ICU patients

III. INFLAMMATORY DISEASES

⭐ 1. Alcohol-Induced Liver Disease

• Fatty liver → Hepatitis → Cirrhosis

• Imaging: hepatomegaly, increased liver echogenicity

⭐ 2. Fatty Liver Disease

• Most common liver abnormality

• Imaging: bright liver on ultrasound

⭐ 3. Cirrhosis

Causes: alcohol, hepatitis B/C

• Nodular liver surface

• Portal hypertension (varices, splenomegaly, ascites)

• CT: shrunken nodular liver + enlarged caudate lobe

⭐ 4. Viral Hepatitis

• Hepatomegaly

• “Starry sky” appearance on ultrasound

⭐ 5. Cholelithiasis (Gallstones)

• Ultrasound: echogenic focus with posterior acoustic shadowing

• Risk: 4Fs → Female, Fat, Forty, Fertile

⭐ 6. Cholecystitis

• Gallbladder wall thickening

• Positive Murphy sign

• HIDA scan: non-visualization of the gallbladder

⭐ 7. Pancreatitis

• Elevated amylase/lipase

• CT: swollen pancreas, “fat stranding,” pseudocysts

⭐ 8. Jaundice

• Causes:

  • Pre-hepatic (hemolysis)

  • Hepatic (hepatitis)

  • Post-hepatic (obstruction, stones)

Imaging hallmark → dilated bile ducts if obstructive

IV. NEOPLASTIC DISEASES

1. Hepatocellular Adenoma (Benign)

• Definition: Benign liver tumor; usually asymptomatic.

• Epidemiology: Most common in women using oral contraceptives.

• Clinical Features: Often silent; may present with RUQ pain if large.

• Imaging:

  • CT & Ultrasound (sonography): Useful in detecting hepatic lesions.

• Management: Usually conservative; monitor unless symptomatic or risk of rupture.

2. Hepatic Hemangioma (Benign)

• Definition: Most common liver tumor; composed of blood vessels.

• Epidemiology: More common in women, especially postmenopausal.

• Clinical Features: Usually asymptomatic; may cause RUQ pain if large.

• Imaging:

  • Sonography: Homogeneous liver, increased echogenicity for solitary lesions.

  • Nuclear medicine (RBC scan): Early defect, delayed persistent uptake → diagnostic.

  • CT: Peripheral enhancement with IV contrast.

  • MRI: Hyperintense on T2; peripheral enhancement with gadolinium, followed by central fill-in.

• Management: Usually, no treatment unless symptomatic.

3. Hepatocellular Carcinoma (Hepatoma, Malignant)

• Definition: Primary liver cancer.

• Epidemiology: 3% of cancers in the US; associated with cirrhosis, chronic hepatitis B/C, and alcoholism.

• Clinical Features:

  • RUQ pain, jaundice, weight loss, hepatomegaly, ascites

  • Rapid liver enlargement

• Imaging:

  • Sonography & CT: Detect tumor extent.

  • Arteriography: Shows increased vascularity.

• Diagnosis: Definitive via liver biopsy.

• Management:

  • Surgical resection (curative if single mass)

  • Liver transplantation, if appropriate

  • Chemotherapy: Limited benefit

  • Transarterial embolization for lesions ≥5 cm

  • Radiotherapy generally ineffective

4. Metastatic Liver Disease

• Definition: Liver involvement by secondary tumors.

• Common Primary Sites: Colon, pancreas, stomach, lung, breast.

• Clinical Features: Often asymptomatic; may present with liver enlargement.

• Imaging:

  • Sonography: Screening tool

  • CT & MRI: More accurate for diagnosis

• Diagnosis: Liver biopsy confirms.

• Management:

  • Octreotide injection + transarterial embolization

  • Selective internal radiation if symptomatic

5. Carcinoma of the Gallbladder

• Definition: Mostly malignant; 85% adenocarcinoma.

• Epidemiology: More common in women, older adults; gallstones in 75% of cases.

• Risk Factor: Porcelain gallbladder (22% risk of carcinoma)

• Clinical Features: RUQ pain, jaundice, weight loss

• Imaging:

  • CT & Ultrasound: Detect masses, wall thickening, or polyps

• Spread: Liver invasion, lymphatics, intraductal extension

• Prognosis: Poor; 5-year survival ~4%

• Management: Surgery if diagnosed early, but often late

6. Carcinoma of the Pancreas

• Definition: Usually adenocarcinoma of the pancreatic duct.

• Epidemiology: 5th leading cause of cancer death in the US; higher in men and blacks; strong association with smoking.

• Risk Factors: Alcoholism, chronic pancreatitis, diabetes, family history

• Location:

  • Head: 60–70%

  • Body: 10–15%

  • Tail: 5–10%

• Clinical Features: Pain, jaundice, weight loss, fatigue, nausea, diabetes

• Imaging:

  • CT Abdomen with/without contrast: Best imaging; detects mass

  • Sonography & MRI: For chronic symptoms or follow-up

  • Barium studies: May show obstruction or distortion in advanced cases

• Management:

  • Surgical resection: The Only chance of cure

  • Chemotherapy & radiotherapy: Limited efficacy

• Prognosis: Very poor; 5-year survival ~2%