From the Guidelines
Abdominal ultrasound is indicated as the first-line imaging study for patients with jaundice to evaluate for biliary obstruction and identify its potential causes. This non-invasive test should be performed early in the diagnostic workup of jaundiced patients to distinguish between obstructive and non-obstructive causes. Ultrasound can effectively detect dilated bile ducts (suggesting obstruction), gallstones, masses in the pancreatic head, and liver abnormalities that may cause jaundice. The procedure is particularly valuable because it is readily available, relatively inexpensive, does not use radiation, and can be performed at the bedside for critically ill patients.
Key Points
- Ultrasound findings help guide subsequent management decisions, such as whether to proceed with more invasive procedures like ERCP or MRCP for therapeutic intervention or further diagnostic clarification.
- In patients with obstructive jaundice, early identification and intervention are crucial to prevent complications like cholangitis or progressive liver damage.
- While ultrasound has limitations in visualizing the distal common bile duct due to overlying bowel gas and may miss small stones or tumors, its high sensitivity for biliary dilation makes it an essential first step in evaluating jaundiced patients, as supported by the American College of Radiology 1.
Limitations and Considerations
- The cause of the obstruction (benign or malignant) is less often definitively seen on US, particularly in the distal CBD.
- False-negative US studies are typically due either to the inability to visualize the extrahepatic biliary tree (often from interposed bowel gas or large body habitus) or to the absence of biliary dilation in the presence of acute obstruction.
- US is less accurate than either CT or MRCP for determining the site and the cause of obstruction, but it remains a valuable initial imaging modality due to its non-invasive nature and availability.
From the Research
Indications for Ultrasound Abdomen in Jaundice
The following are indications for performing an ultrasound of the abdomen in patients with jaundice:
- To confirm or exclude biliary dilatation 2
- To evaluate patients with obstructive jaundice and determine the etiology, location, level, and extent of disease 2
- As a screening modality to choose patients for further imaging, such as MRCP examination 2
- To detect mechanical biliary obstruction and stone disease, although it may be less sensitive for detecting obstructing tumors 3
- To evaluate the biliary tract in patients presenting with right upper quadrant pain or jaundice 3
- As a first-line option for patients presenting with jaundice, depending on the suspected underlying etiology 4
Diagnostic Accuracy of Ultrasound
The diagnostic accuracy of ultrasound in patients with jaundice is:
- 88% sensitive in diagnosing benign diseases, compared to 100% for MRCP and 54.55% for CT scan 2
- 79.17% sensitive in diagnosing malignant diseases, compared to 95.83% for MRCP and 91.67% for CT scan 2
- Useful in detecting choledocholithiasis, biliary stricture, or tumor, although less sensitive for detecting obstructing tumors 3
Clinical Context
In patients with jaundice, ultrasound is often used in conjunction with other imaging modalities, such as: