Imaging

Choledocholithiasis

Preliminary Diagnosis: Choledocholithiasis

I. What imaging technique is first-line for this diagnosis?

Transabdominal right upper quadrant ultrasound. Ideally, patient is NPO for 8 hours to empty the duodenum/stomach and optimize visualization of the distal common bile duct.

II. Describe the advantages and disadvantages of this technique for diagnosis of choledocholithiasis.

Advantages

  • Ultrasound is safe, fast, and cheap.

  • May directly show gallstone in common bile duct, but more likely demonstrates a dilated common bile duct, which suggests the presence of an obstructing stone

Disadvantages

  • Transabdominal ultrasound has low to moderate sensitivity at detecting signs of choledocholithiasis.

  • Effectiveness decreases with obese body habitus.

III. What are the contraindications for the first-line imaging technique?

No contraindications to transabdominal ultrasound.

IV. What alternative imaging techniques are available?

  • Contrast-enhanced MR cholangiopancreatography (MRCP)

  • Endoscopic ultrasound (EUS)

  • CT cholangiography (IV contrast infusion)

V. Describe the advantages and disadvantages of the alternative techniques for diagnosis of choledocholithiasis.

Contrast-enhanced MRCP

Advantages

  • Indicated when transabdominal ultrasound is not diagnostic and clinical suspicion for choledocholithiasis is low to moderate

  • Has high sensitivity and specificity for identifying gallstones in the common bile duct

  • Noninvasive and does not expose patient to radiation

Disavantages

  • Expensive. Optimal with IV contrast, but not required

EUS

Advantages

  • Indicated when transabdominal ultrasound is not diagnostic and clinical suspicion for choledocholithiasis is moderate to high

  • Has high sensitivity and specificity for identifying gallstones in the common bile duct, and higher resolution than MRCP

  • EUS is generally considered equally or slightly more effective than MRCP.

Disadvantages

  • More invasive than MRCP and requires sedation

CT cholangiography (IV contrast infusion)

Advantages

  • Less expensive and faster than MRCP or EUS.

Disadvantages

  • Newer method, which has slightly lower or equal sensitivity and specificity compared with MRCP or EUS

  • Exposes patient to radiation

VI. What are the contraindications for the alternative imaging techniques?

MRCP

  • Contrast enhanced requires administration of gadolinium. In general, gadolinium is contraindicated with GFR < 60. MRCP may be done without contrast, but will lower sensitivity and specificity.

  • MR imaging is also contraindicated in patients with metallic foreign bodies (AICD, pacemaker, stents, etc).

EUS

  • Contraindicated in patients who cannot undergo sedation and in patients with altered anatomy (e.g., roux-en-Y gastric bypass)

CT cholangiography (IV contrast infusion)

  • Due to radiation exposure, it should be used conservatively in the pediatric population and is contraindicated in pregnancy

  • Requires IV contrast infusion, which is contraindicated in patients with renal insufficiency

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