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THE DIAGNOSTIC ACCURACY OF MAGNETIC RESONANCE CHOLANGIOPANCREATOGRAPHY (MRCP) AND ULTRASOUND COMPARED WITH DIRECT CHOLANGIOGRAPHY IN THE DETECTION OF CHOLEDOCHOLITHIASIS
Clinical Radiology (2000) 55, 579 doi:10.1053/crad.1999.0426, available online at http://www.idealibrary.com on
Correspondence Letters are published at the discretion of the Editor. Opinions expressed by correspondents are not necessarily those of the Editor. Unduly long letters may be returned to the authors for shortening. Letters in response to a paper may be sent to the author of the paper so that the reply can be published in the same issue. Letters should be typed double spaced and should be signed by all authors personally. References should be given in the style specified in the Instructions to Authors at the front of the Journal.
THE DIAGNOSTIC ACCURACY OF MAGNETIC RESONANCE CHOLANGIOPANCREATOGRAPHY (MRCP) AND ULTRASOUND COMPARED WITH DIRECT CHOLANGIOGRAPHY IN THE DETECTION OF CHOLEDOCHOLITHIASIS SIR – The paper by Varghese et al. [1] confirms the high sensitivity and specificity of MRCP in the detection of bile duct stones. The paper compares the diagnostic accuracy of MRCP and ultrasound using direct cholangiography as the gold standard. The sensitivity of ultrasound (38%) for the detection of bile duct stones in their study was extremely low and the authors cite five publications in the 1980s showing the sensitivity of ultrasound varying between 20 and 80%. It is interesting to note that very little has been published in the 1990s about the diagnostic accuracy of ultrasound in this clinical situation, despite the improvements in image resolution due to developments such as harmonic imaging. In 1990 a study was published from this hospital, in which ultrasound and ERCP findings in 208 patients were compared. In this study most of the ultrasound examinations were performed by a single operator. Of the 49 patients with choledocholithiasis there were 40 true positive, three false positive and nine false negative results on ultrasound, giving a sensitivity for ultrasound of 82% and a specificity of 98.5%. A recent audit was undertaken of 100 patients undergoing ERCP and ultrasound in which multiple ultrasound operators were involved. This revealed a sensitivity for ultrasound of 48% and a specificity of 100%. It is absolutely clear that the diagnostic accuracy of ultrasound in this clinical situation varies enormously from one operator to another. It is essential that individual operators, when drawing up a diagnostic strategy for the investigation of biliary tract disorders, first undertake a study of their own accuracy using ultrasound. No strategy should be based on the published work of others. For individuals with a high sensitivity for the detection of bile duct stones, only a relatively small number of patients will need to undergo MRCP (a more expensive and time-consuming examination than ultrasound) and then only when strict clinical indications and criteria have been fulfilled. An individual with a low sensitivity but high specificity for ultrasound in the detection of choledocholithiasis could adopt the strategy proposed by Varghese et al. Should an individual have both a low sensitivity and specificity for ultrasound, then there is very little point in
0009-9260/00/070579+01 $35.00/0
undertaking the ultrasound examination at all and MRCP should become the examination of first choice. D.R.M. LINDSELL
Department of Radiology John Radcliffe Hospital Oxford OX3 9DU, U.K. References
1 Varghese JC, Liddel RP, Farrell MA, Murray FE, Osborne H, Lee MJ. The diagnostic accuracy of magnetic resonance cholangiopancreatography and ultrasound compared with direct cholangiography in the detection of choledocholithiasis. Clin Radiol 1999;54:604–614. 2 Lindsell DRM. Ultrasound imaging of pancreas and biliary tract. Lancet 1990;390–393. REPLY TO DR LINDSELL SIR – We agree with Dr Lindsell’s comments regarding the sensitivity and specificity of ultrasound for the detection of choledocholithiasis. The advent of MRCP will enable radiologists who have access to both ultrasound and MRCP to determine their own sensitivity and specificity for the identification of common bile duct stones. The sensitivity of 38% for the ultrasound detection of common bile duct stones in our study reflects a large number of patients in whom the ultrasound examination was performed at outside institutions. They were then referred for ERCP. As part of our assessment of MRCP, we performed MRCP on all of these patients before ERCP. Therefore, the low sensitivity for ultrasound in our study almost certainly reflects the large number of operators and the variety of hospitals in which the ultrasound was performed. Of course, we still believe that ultrasound remains the first line investigation for the assessment of the biliary tract. Access to MRCP is limited and ultrasound will remain the first port of call in the algorithm for assessment of the biliary tree for some time to come. M.J. LEE
Department of Radiology Beaumont Hospital and Royal College of Surgeons in Ireland Dublin, Ireland
q 2000 The Royal College of Radiologists
Correspondence Letters are published at the discretion of the Editor. Opinions expressed by correspondents are not necessarily those of the Editor. Unduly long letters may be returned to the authors for shortening. Letters in response to a paper may be sent to the author of the paper so that the reply can be published in the same issue. Letters should be typed double spaced and should be signed by all authors personally. References should be given in the style specified in the Instructions to Authors at the front of the Journal.
THE DIAGNOSTIC ACCURACY OF MAGNETIC RESONANCE CHOLANGIOPANCREATOGRAPHY (MRCP) AND ULTRASOUND COMPARED WITH DIRECT CHOLANGIOGRAPHY IN THE DETECTION OF CHOLEDOCHOLITHIASIS SIR – The paper by Varghese et al. [1] confirms the high sensitivity and specificity of MRCP in the detection of bile duct stones. The paper compares the diagnostic accuracy of MRCP and ultrasound using direct cholangiography as the gold standard. The sensitivity of ultrasound (38%) for the detection of bile duct stones in their study was extremely low and the authors cite five publications in the 1980s showing the sensitivity of ultrasound varying between 20 and 80%. It is interesting to note that very little has been published in the 1990s about the diagnostic accuracy of ultrasound in this clinical situation, despite the improvements in image resolution due to developments such as harmonic imaging. In 1990 a study was published from this hospital, in which ultrasound and ERCP findings in 208 patients were compared. In this study most of the ultrasound examinations were performed by a single operator. Of the 49 patients with choledocholithiasis there were 40 true positive, three false positive and nine false negative results on ultrasound, giving a sensitivity for ultrasound of 82% and a specificity of 98.5%. A recent audit was undertaken of 100 patients undergoing ERCP and ultrasound in which multiple ultrasound operators were involved. This revealed a sensitivity for ultrasound of 48% and a specificity of 100%. It is absolutely clear that the diagnostic accuracy of ultrasound in this clinical situation varies enormously from one operator to another. It is essential that individual operators, when drawing up a diagnostic strategy for the investigation of biliary tract disorders, first undertake a study of their own accuracy using ultrasound. No strategy should be based on the published work of others. For individuals with a high sensitivity for the detection of bile duct stones, only a relatively small number of patients will need to undergo MRCP (a more expensive and time-consuming examination than ultrasound) and then only when strict clinical indications and criteria have been fulfilled. An individual with a low sensitivity but high specificity for ultrasound in the detection of choledocholithiasis could adopt the strategy proposed by Varghese et al. Should an individual have both a low sensitivity and specificity for ultrasound, then there is very little point in
0009-9260/00/070579+01 $35.00/0
undertaking the ultrasound examination at all and MRCP should become the examination of first choice. D.R.M. LINDSELL
Department of Radiology John Radcliffe Hospital Oxford OX3 9DU, U.K. References
1 Varghese JC, Liddel RP, Farrell MA, Murray FE, Osborne H, Lee MJ. The diagnostic accuracy of magnetic resonance cholangiopancreatography and ultrasound compared with direct cholangiography in the detection of choledocholithiasis. Clin Radiol 1999;54:604–614. 2 Lindsell DRM. Ultrasound imaging of pancreas and biliary tract. Lancet 1990;390–393. REPLY TO DR LINDSELL SIR – We agree with Dr Lindsell’s comments regarding the sensitivity and specificity of ultrasound for the detection of choledocholithiasis. The advent of MRCP will enable radiologists who have access to both ultrasound and MRCP to determine their own sensitivity and specificity for the identification of common bile duct stones. The sensitivity of 38% for the ultrasound detection of common bile duct stones in our study reflects a large number of patients in whom the ultrasound examination was performed at outside institutions. They were then referred for ERCP. As part of our assessment of MRCP, we performed MRCP on all of these patients before ERCP. Therefore, the low sensitivity for ultrasound in our study almost certainly reflects the large number of operators and the variety of hospitals in which the ultrasound was performed. Of course, we still believe that ultrasound remains the first line investigation for the assessment of the biliary tract. Access to MRCP is limited and ultrasound will remain the first port of call in the algorithm for assessment of the biliary tree for some time to come. M.J. LEE
Department of Radiology Beaumont Hospital and Royal College of Surgeons in Ireland Dublin, Ireland
q 2000 The Royal College of Radiologists