Endoscopic ultrasound versus magnetic resonance cholangiopancreatography for the diagnosis of common bile duct stones

Cochrane: Bile, produced in the liver and stored temporarily in the gallbladder, is released into the small bowel on eating fatty food. The common bile duct (CBD) is the tube through which bile flows from the gallbladder to the small bowel. Stones in the CBD (CBD stones) are usually formed in the gallbladder before migration into the bile duct. They can obstruct the flow of bile leading to jaundice (yellowish discolouration of skin, whites of the eyes, and dark urine), infection of the bile (cholangitis), and inflammation of the pancreas (pancreatitis), which can be life threatening.

Various diagnostic tests can be performed for the diagnosis of CBD stones. Depending upon the availability of resources, these stones are removed endoscopically (usually the case) or may be removed as part of the operation performed to remove the gallbladder (it is important to remove the gallbladder since the stones continue to form in the gallbladder and can cause recurrent problems). Prior to removal, invasive tests such as endoscopic retrograde cholangiopancreatography (ERCP) or intraoperative cholangiography (IOC) can be performed to detect CBD stones. However, before performing such invasive tests to diagnose CBD stones, non-invasive tests such as endoscopic ultrasound (EUS) (using ultrasound attached to the endoscope) and magnetic resonance cholangiopancreatography (MRCP) are used to identify people at high risk of having CBD stones so that only those at high risk can be subjected to further tests.
 

Study characteristics
We performed a thorough search for studies that reported the accuracy of EUS or MRCP in the diagnosis of CBD stones. We included a total of 18 studies involving 2532 participants. Eleven studies evaluated EUS alone, five studies evaluated MRCP alone, and two studies evaluated both tests. A total of 1537 participants were included in the 13 studies that evaluated EUS and 995 participants were included in the seven studies that evaluated MRCP. Most studies included patients who were suspected of having CBD stones based on abnormal blood tests, abnormal ultrasound, or symptoms such as jaundice or pancreatitis, or a combination of the above. The proportion of participants who had undergone previous gallbladder removal varied across studies.
 

Key results
Based on an average sensitivity of 95% for EUS, on average 95 out of 100 people with CBD stones will be detected while the remaining 5 people will be missed and will not receive appropriate treatment. The average number of people with CBD stones detected using EUS may vary between 91 and 97 out of 100 people. The average specificity of 97% for EUS means that on average 97 out of 100 people without CBD stones will be identified as not having CBD stones; 3 out of 100 would be false positives and would not receive appropriate treatment. The average number of false positives could vary between 1 and 6 out of 100 people. For MRCP, an average sensitivity of 93% means that on average 93 out of 100 people with CBD stones will be detected while the remaining 7 people will be missed and will not receive appropriate treatment. The average number of people with CBD stones detected using MRCP may vary between 87 and 96 out of 100 people. With an average specificity of 96% for MRCP, 96 out of 100 people without CBD stones will be identified as not having CBD stones; 4 out of 100 would be false positives and would not receive appropriate treatment. The average number of false positives could vary between 2 and 10 out of 100 people. This means that some people with CBD stones can be missed by EUS and MRCP. Although most people with a negative EUS or MRCP do not need to undergo further invasive tests, in the presence of persistent symptoms further testing with MRCP if the patient had undergone EUS or EUS if the patient had undergone MRCP, ERCP, or IOC may be indicated. There is little to choose between EUS and MRCP in terms of diagnostic accuracy.
 

Quality of evidence
All the studies were of low methodological quality, which may undermine the validity of our findings.
 

Future research
Further studies of high methodological quality are necessary.

 

 

Authors' conclusions: 

Both EUS and MRCP have high diagnostic accuracy for detection of common bile duct stones. People with positive EUS or MRCP should undergo endoscopic or surgical extraction of common bile duct stones and those with negative EUS or MRCP do not need further invasive tests. However, if the symptoms persist, further investigations will be indicated. The two tests are similar in terms of diagnostic accuracy and the choice of which test to use will be informed by availability and contra-indications to each test. However, it should be noted that the results are based on studies of poor methodological quality and so the results should be interpreted with caution. Further studies that are of high methodological quality are necessary to determine the diagnostic accuracy of EUS and MRCP for the diagnosis of common bile duct stones.