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Diagnosis

Magnetic resonance cholangiography was sensitive and specific for evaluation of the biliary tract

ACP J Club. 1996 Sept-Oct;125:45. doi:10.7326/ACPJC-1996-125-2-045


Source Citation

Soto JA, Barish MA, Yucel EK, et al. Magnetic resonance cholangiography: comparison with endoscopic retrograde cholangiopancreatography. Gastroenterology. 1996 Feb;110:589-97. [PubMed ID: 8566608]


Abstract

Objective

To determine the diagnostic accuracy of 3-dimensional fast spin-echo magnetic resonance cholangiography (MRC) for the evaluation of biliary tract abnormalities.

Design

Blinded comparison of the results of MRC with direct cholangiography, the diagnostic standard.

Setting

Department of Radiology at the Boston University Medical Center, Boston, USA.

Patients

46 patients (mean age 51 y, 67% women) randomly recruited from referrals for elective endoscopic retrograde cholangiopancreatography (ERCP).

Description of test and diagnostic standard

Data from MRC were acquired using commercially available software in a clinical magnetic resonance scanner using a body coil. The MRC images were evaluated independently by 2 radiologists with experience in biliary tract imaging. The common bile duct was considered dilated if it measured > 6 mm (except for postcholecystectomy patients for whom the upper limit of normal was set at 8 mm). The degree of dilatation was graded subjectively as mild, moderate, or severe. The level of obstruction was divided into suprapancreatic, intrapancreatic, and periampullary. The presence and number of stones in the common bile duct were recorded. The intrahepatic biliary tree was evaluated for the presence of dilatation. All patients had direct cholangiography within 24 hours of the completion of MRC. The same criteria described above for MRC were used for the evaluation and scoring of direct cholangiography.

Main outcome measures

Sensitivity, specificity, and likelihood ratios.

Main results

MRC images of diagnostic quality were obtained in 44 patients (96%). MRC correctly identified normal-caliber common bile duct and common hepatic and intrahepatic bile ducts in 16 of 17 patients (specificity 94.1%, {95% CI 71.3% to 99.8%}*). MRC correctly showed the presence of bile duct dilatation and the site of obstruction in 26 of 27 patients (sensitivity 96.3%, {CI 81.0% to 99.9%}*). {The likelihood ratio for a positive test result for biliary ductal dilatation was 16.3, and the likelihood ratio for a negative test result was 0.04.}* The sensitivity of MRC for biliary strictures (n = 10) and intraductal abnormalities (n = 7) was 90% and 100%, respectively.

Conclusion

3-dimensional fast spin-echo magnetic resonance cholangiography was highly sensitive and specific in the evaluation of the biliary tract.

Source of funding: Philips Medical Systems, Shelton, Connecticut.

For article reprint: Dr. E.K. Yucel, Brigham & Woman's Hospital, Surgical Planning Lab, Boston, MA, USA. FAX 617-582-6033.

*Numbers calculated from data in article.


Commentary

MRC is emerging as the latest imaging technology to evaluate the biliary tree. This noninvasive method is used to visualize these structures without using a contrast agent. Because the magnetic resonance images can be directly acquired in any plane, 3-dimensional representation of biliary tract anatomy and pathology can be accurately obtained. Patients receive no radiation exposure and unlike other imaging modalities, such as ultrasonography, ERCP, or percutaneous transhepatic cholangiography, MRC does not rely on operator skill. The limitations of MRC include imaging artifact caused by metallic surgical clips and air in the biliary tree. Additionally, MRC does depend on technology that requires a multicoil device for better spatial resolution, which is currently not widely available (1).

Should MRC be used in the routine diagnosis of biliary tract disease, and where does it fit in the diagnostic work-up? Although Soto and colleagues should be commended for their efforts, it is difficult to conclude that the clinical role of MRC has been defined because the number of patients in each diagnostic category in their study was small.

Large, controlled, prospective clinical studies are necessary to examine the role of MRC in specific diseases (e.g., detection of choledocholithiasis or selection of drainage procedure for proximal biliary strictures) in addition to cost-effectiveness and outcome analysis data (2). New imaging technology, such as MRC, should be shown to improve patient management or reduce health care costs before it replaces diagnostic ERCP as a routine diagnostic test.

Irving Waxman, MD
Harvard Medical SchoolBoston, Massachusetts, USA


References

1. Meakem TJ 3d, Schnall MD. Magnetic resonance cholangiography. Gastroenterol Clin North Am. 1995;24:221-38.

2. Van Dam J. Magnetic resonance cholangiography: a field with attraction. Gastroenterology. 1995;108:1948-50.