From the Guidelines
Ultrasound is the recommended first-line imaging for suspected choledocholithiasis, offering good visualization of the biliary system with high sensitivity for ductal dilation. This approach is supported by the fact that trans-abdominal ultrasound still has its role as a first imaging test in initial evaluation due to its wide availability 1. If ultrasound shows dilated bile ducts but no definitive stones, magnetic resonance cholangiopancreatography (MRCP) should be performed next as it provides detailed images of the biliary tree without radiation or contrast, with an accuracy of detecting CBD stones surpassing 90% 1.
Some key points to consider in the imaging of choledocholithiasis include:
- The sensitivity of ultrasound in detecting CBD stones ranges from 25 to 63% 1, but it has high diagnostic accuracy in demonstrating biliary dilatation.
- MRCP has an accuracy of detecting CBD stones surpassing 90%, though there is a clinically significant weakness in the detection of small stones 1.
- Endoscopic ultrasound (EUS) is a minimally invasive endoscopic procedure superior to endoscopic retrograde cholangiography (ERC) in detecting malignant causes of cholestasis and is at least equal to ERC in terms of stone detection 1.
- Computed tomography has its clinical value above all in unstable patients with high suspicion of underlying malignancy or suspicion of hepatic abscesses 1, but noncontrast abdominal CT has very limited value in the context of suspected choledocholithiasis 1.
The choice of imaging depends on clinical presentation, laboratory findings (particularly elevated liver enzymes), and the pre-test probability of choledocholithiasis. Patients with jaundice, right upper quadrant pain, and elevated liver enzymes should undergo prompt imaging to prevent complications like cholangitis or pancreatitis. MRCP is excellent for detection of cholelithiasis/choledocholithiasis with reported sensitivity of 85% to 100%, specificity of 90%, and accuracy of 89% to 90% 1, making it a crucial diagnostic tool in the management of suspected choledocholithiasis.
From the Research
Imaging Modalities for Choledocholithiasis
- Unenhanced spiral CT and US are useful for evaluating suspected common bile duct stones, with a sensitivity of 86% and 82%, and a specificity of 98% and 98%, respectively 2.
- Magnetic resonance cholangiopancreatography (MRCP) has a high diagnostic accuracy for choledocholithiasis, with a sensitivity of 91%, specificity of 98%, and diagnostic accuracy of 97% 3.
- MRCP is highly accurate in the diagnosis of choledocholithiasis and has the potential to replace diagnostic ERCP, but it may underestimate the number of bile duct stones present 3.
- Endoscopic ultrasound (EUS) is recommended for patients with an intermediate likelihood of choledocholithiasis, and can help reduce the number of unnecessary ERCPs 4.
Diagnostic Accuracy of Imaging Modalities
- MRCP has a sensitivity of 90%, specificity of 88%, and accuracy of 89% in diagnosing choledocholithiasis, with higher accuracy for stones larger than 6 mm 5.
- Ultrasound has a sensitivity of 38%, specificity of 100%, and diagnostic accuracy of 89% in the diagnosis of choledocholithiasis, but is less accurate than MRCP 3.
- EUS and MRCP should be used in sequence, depending on the pre-test probability of choledocholithiasis, with ERCP reserved for cases with a high pre-test probability 6.
Clinical Practice Guidelines
- The European Society for Gastrointestinal Endoscopy (ESGE) guideline recommends stratifying patients with suspected choledocholithiasis into low-, intermediate-, and high-likelihood groups, and using EUS or MRCP prior to ERCP in the intermediate group 4.
- Adherence to the ESGE guideline can help reduce the number of unnecessary ERCPs and improve patient outcomes 4.