JC63B (Surgery) - Imaging for hepatobiliary system

Question 1

List 5 main imaging modalities for abdominal exam

Answer 1

Plain AXR
USG 
Cholangiography 
CT 
MRI

Question 2

Plain AXR
- Abdominal pathologies identified
-

Answer 2

Abdominal pathologies identified:

• Calcified Gallstones
• Air in biliary tree or gallbladder wall
• Soft tissue mass, Abscesses
• Bowel dilatation, Ileus and SBO

Question 3

US abdomen

Advantages and disadvantages for hepatobiliary system evaluation

Answer 3

Advantages:

• No ionizing radiation
• Cheap, safe, portable, fast
• Gallbladder wall evaluation
• Sensitive and accurate extra-hepatic bile duct assessment
• Image guided intervention

Disadvantages:
- Operation dependent
- Anything that affects contact between probe and abdominal wall:
Pneumobilia, soft pigment stones impair visualization
Previous operations with scars, clips and tubes impair visualization
Duodenal gas/ ileus impair visualization

Question 4

Normal gallbladder and CBD thickness on USG

Gallstone appearance on USG

Answer 4

Gallbladder wall: <0.3cm thick

CBD: <0.6cm in diameter*

CBD becomes thicker with age and Increase by 1mm every decade after 60 years old e.g. 0.9cm in 90 years old is ok

Gallstones: Mobile, Echogenic with acoustic shadowing

Question 5

Causes of gallbladder wall edema

Typical gallbladder wall thickness on USG

Answer 5

Gallbladder wall thickness >3mm

Causes of gallbladder wall edema:

• Hepatitis
• CHF
• Nearby viscera inflammation e.g. pyelonephritis/ perforated peptic ulcer
• Low albumin
• Tumor

Question 6

Cholangiography

Major types

Answer 6

Endoscopic Retrograde Cholangiopancreatogram - ERCP

Percutaneous transhepatic cholangiogram - PTC

MRCP

T-tube cholangiogram

Question 7

Function of T-tube cholangiogram

Answer 7

Performed after cholescystectomy

Explore CBD to look for residual stones

Question 8

CT scan for hepatobiliary assessment

Pros and cons
Indication

Answer 8

Pros:
Cross-sectional display of intra-abdominal organs, good anatomical detail
Not limited by gas, clips, drainage pipes (cf USG)
Detects wide-range of pathologies

Cons: 
Ionizing radiation 
IV contrast complications 
Not sensitive for cholangitis 
Expensive, not portable 

Indication:

• Sub-optimal USG
• HPB complications: GB perforation with pericholecystic abscess, empyema
• CT-guided interventions
• Find other extra-HPB system pathologies

Question 9

MRI for HPB examination

Pros and cons
Indications
Types

Answer 9

Pros: 
No ionizing radiation 
True multi-planar image with high soft tissue detail 
Higher contrast resolution than CT scan 
Tissue characterization with T1,2W

Cons:
Worse Spatial resolution than CT scan
Long scan time
Availability and accessibility
Patient cooperation needed, Claustrophobic
C/I medical implants: pacemakers, cochlear implants

Types:
MRI abdomen
MRI cholangiopancreatogram

Indications:
Unsuccessful ERCP
Contraindicated ERCP - previous gastric/ bypass operation with altered anatomy
Evaluation of other abdominal pathologies