Background
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.
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.
Endoscopic ultrasound (EUS) and magnetic resonance cholangiopancreatography (MRCP) are tests used in the diagnosis of common bile duct stones in patients suspected of having common bile duct stones prior to undergoing invasive treatment. There has been no systematic review of the accuracy of EUS and MRCP in the diagnosis of common bile duct stones using appropriate reference standards.
To determine and compare the accuracy of EUS and MRCP for the diagnosis of common bile duct stones.
We searched MEDLINE, EMBASE, Science Citation Index Expanded, BIOSIS, and Clinicaltrials.gov until September 2012. We searched the references of included studies to identify further studies and of systematic reviews identified from various databases (Database of Abstracts of Reviews of Effects (DARE), Health Technology Assessment (HTA), Medion, and ARIF (Aggressive Research Intelligence Facility)). We did not restrict studies based on language or publication status, or whether data were collected prospectively or retrospectively.
We included studies that provided the number of true positives, false positives, false negatives, and true negatives for EUS or MRCP. We only accepted studies that confirmed the presence of common bile duct stones by extraction of the stones (irrespective of whether this was done by surgical or endoscopic methods) for a positive test, and absence of common bile duct stones by surgical or endoscopic negative exploration of the common bile duct or symptom free follow-up for at least six months for a negative test, as the reference standard in people suspected of having common bile duct stones. We included participants with or without prior diagnosis of cholelithiasis; with or without symptoms and complications of common bile duct stones, with or without prior treatment for common bile duct stones; and before or after cholecystectomy. At least two authors independently screened abstracts and selected studies for inclusion.
Two authors independently collected the data from each study. We used the bivariate model to obtain pooled estimates of sensitivity and specificity.
We included a total of 18 studies involving 2366 participants (976 participants with common bile duct stones and 1390 participants without common bile duct stones). Eleven studies evaluated EUS alone, and five studies evaluated MRCP alone. Two studies evaluated both tests. Most studies included patients who were suspected of having common bile duct stones based on abnormal liver function tests; abnormal transabdominal ultrasound; symptoms such as obstructive jaundice, cholangitis, or pancreatitis; or a combination of the above. The proportion of participants who had undergone cholecystectomy varied across studies. Not one of the studies was of high methodological quality. For EUS, the sensitivities ranged between 0.75 and 1.00 and the specificities ranged between 0.85 and 1.00. The summary sensitivity (95% confidence interval (CI)) and specificity (95% CI) of the 13 studies that evaluated EUS (1537 participants; 686 cases and 851 participants without common bile duct stones) were 0.95 (95% CI 0.91 to 0.97) and 0.97 (95% CI 0.94 to 0.99). For MRCP, the sensitivities ranged between 0.77 and 1.00 and the specificities ranged between 0.73 and 0.99. The summary sensitivity and specificity of the seven studies that evaluated MRCP (996 participants; 361 cases and 635 participants without common bile duct stones) were 0.93 (95% CI 0.87 to 0.96) and 0.96 (95% CI 0.90 to 0.98). There was no evidence of a difference in sensitivity or specificity between EUS and MRCP (P value = 0.5). From the included studies, at the median pre-test probability of common bile duct stones of 41% the post-test probabilities (with 95% CI) associated with positive and negative EUS test results were 0.96 (95% CI 0.92 to 0.98) and 0.03 (95% CI 0.02 to 0.06). At the same pre-test probability, the post-test probabilities associated with positive and negative MRCP test results were 0.94 (95% CI 0.87 to 0.97) and 0.05 (95% CI 0.03 to 0.09).