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The efficacy of magnetic resonance cholangiography for the evaluation of patients with suspected choledocholithiasis before laparoscopic cholecystectomy
The Efficacy of Magnetic Resonance Cholangiography for the Evaluation of Patients with Suspected Choledocholithiasis Before Laparoscopic Cholecystectomy Terrence H. Liu, MD, Eileen T. Consorti, MD, Akira Kawashima, MD, Randy D. Ernst, MD, C. Thomas Black, MD, Philip H. Greger, Jr., MD, Ronald P. Fischer, MD, PhD, David W. Mercer, MD, Houston, Texas
BACKGROUND: Endoscopic retrograde cholangiography is the most commonly utilized tool for the identification of common bile duct stones (CBDS) before laparoscopic cholecystectomy, whereas the role of magnetic resonance cholangiography (MRC) for patient evaluation before laparoscopic cholecystectomy is currently undefined. METHODS: We prospectively evaluated the efficacy of MRC for the identification of CBDS among patients with high risk for choledocholithiasis. Patient selection was based on clinical, sonographic, and laboratory criteria. Standard cholangiograms were obtained when possible for verification of MRC results. RESULTS: Ninety-nine patients underwent evaluation with preoperative MRC. CBDS was visualized in 30% of patients. MRC sensitivity, specificity, positive predictive value, negative predictive value, and accuracy were 85%, 90%, 77%, 94%, and 89%, respectively. CONCLUSIONS: MRC is useful for the evaluation of patients with suspected choledocholithiasis. Advantages of MRC include its noninvasive nature, ease of application, and accuracy in identifying and estimating the size of CBDS. Application of MRC in this setting reduces the need for diagnostic endoscopic retrograde cholangiography. Future investigations should be directed at the development of cost-effective utilization strategies for MRC application. Am J Surg. 1999;178: 480 – 484. © 1999 by Excerpta Medica, Inc.
T
he incidence of choledocholithiasis ranges from 8% to 20% among patients who undergo cholecystectomy.1–3 The approach to the diagnosis and management of common bile duct stones (CBDS) in these patients varies significantly, depending on patient preference, physician preference, expertise of surgical, endoscopic, radiologic personnel, and resource availability. Definitive diagnosis of choledocholithiasis before laparoscopic cholecystectomy (LC) provides physicians with the opportunity to formulate an optimal treatment plan. Clinical, ultrasonographic, and serum chemistry parameters are associated with 96% to 98% sensitivity but low specificity for the identification of patients with CBDS.1– 6 When patients are selected for preoperative endoscopic retrograde cholangiography (ERC) based on these criteria, 40% to 75% of patients have no CBDS found at ERC.1 The low yield of diagnostic ERC and the procedure-related complication rate of 0.8% to 10%, including sedation-related complications, pancreatitis, cholangitis, perforations, and bleeding, have led some investigators to explore magnetic resonance cholangiography (MRC) as a diagnostic modality for the detection of choledocholithiasis.1 Magnetic resonance imaging techniques have been utilized for the evaluation of patients with suspected pancreatic and biliary tract pathology.7 With T2-weighted, twodimension fast-spin echo MRC, bile produces brighter signal intensity than the surrounding tissue and fluid, while biliary stones produce a signal void. Utilizing these techniques, early reports of MRC have demonstrated high sensitivity and specificity for the detection of CBDS and CBD strictures.8 –12 An example of MRC is shown in Figure 1. This study was undertaken to determine the efficacy of MRC for diagnosing choledocholithiasis in a population of patients at high risk for CBDS.
METHODS From the Departments of Surgery (THL, ETC, CTB, PHG, RPF, DWM) and Radiology (AK, RDE), The University of Texas, Houston Health Science Center at Lyndon B. Johnson General Hospital, Houston, Texas. Requests for reprints should be addressed to Terrence H. Liu, MD, Department of Surgery, Suite 30S 62 008, 5656 Kelley St., Houston, Texas 77026-1967. Presented at the 51st Annual Meeting of the Southwestern Surgical Congress, Coronado, California, April 18 –21, 1999.
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© 1999 by Excerpta Medica, Inc. All rights reserved.
Between August 1, 1997 and December 31, 1998, a total of 421 patients underwent cholecystectomy at the University of Texas, Houston Health Science Center/Lyndon B. Johnson General Hospital, which is a 250-bed teaching hospital primarily serving the medical indigent patients of Harris County, Texas. The preoperative evaluation for all patients included an abdominal ultrasound for determination of cholelithiasis and estimation of CBD size, and serum chemistry determination of bilirubin, alkaline phosphatase, transaminase (AST/ALT), and amylase. Patients 0002-9610/99/$–see front matter PII S0002-9610(99)00224-X
MAGNETIC RESONANCE CHOLANGIOGRAPHY BEFORE CHOLECYSTECTOMY/LIU ET AL
Figure 1. Coronal and axial views of MRC scan demonstrating the presence of a 3-mm stone within the lumen of a 7-mm CBD. The arrow indicates the location of stone.
TABLE I Factors for the Determination of Patients With “High Risk” for Choledocholithiasis A. History of jaundice, cholangitis, or biliary pancreatitis B. CBD size by ultrasound ⬎5 mm in diameter C. Serum chemistry abnormalities Total bilirubin ⬎1.5 mg/dL Alkaline phosphatase ⬎150 U/L AST ⬎100 U/L ALT ⬎100 U/L Determination of high risk for choledocholithiasis is based on evidence present from categories A, B, and C. The presence of factors from two or more of the above categories indicated “high risk.”
were considered to have high suspicion for choledocholithiasis on the basis of criteria described in Table I. Before the utilization of MRC at our institution, patients who were determined to have high risk for having CBDS underwent preoperative evaluation with ERC. During the study period, patients with high suspicion for CBDS were evaluated with MRC before LC. MRC scans obtained were breath-hold, heavily T2-weighted, two-dimension fast-spin echo MRC performed on a 1.5T scanner (Horizon LX; GE Medical Systems, Milwaukee, WI). MR images were filmed in the axial and coronal planes in increments of 3 to 5 mm.
An average duration of 15 min was required for each MRC study. Patients whose MRC revealed no CBDS underwent LC/ intraoperative cholangiography (IOC) without further evaluations. During the initial portion of the study, all patients whose MRC demonstrated CBDS underwent further evaluation and CBD clearance with ERC. However, during the latter portion of the study, preoperative ERC was not performed when patients were detected to have small, asymptomatic CBDS by MRC, because we felt that these patients would not have benefited from the procedure. Cholangiography was performed at ERC or cholecystectomy, for verification of MRC result. All patient data was prospectively collected and entered into a database. Radiographic studies were interpreted by a radiologist. All patients were followed for evidence of CBDS-related complications. This study was conducted with the approval of The Committee for the Protection of Human Subjects at University of Texas-Houston Medical School.
RESULTS During a 17-month period, 99 patients were evaluated with MRC before cholecystectomy. Eighty-eight of the patients were female and 11 patients were male. The patient age ranged from 17 to 67 years, with a mean age of 35.3 years. Diagnoses among the patients were acute/ chronic cholecystitis in 38 patients (38%), biliary pancre-
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COMMENTS
TABLE II CBDS Visualization by MRC Diagnosis Cholecystitis Pancreatitis Jaundice Cholangitis Biliary colic All patients
Actual Numbers
Percentage
11/38 6/37 12/17 1/1 0/6 30/99
29% 16% 71% 100% 0% 30%
The actual numbers and percentages of patients with CBDS visualized by MRC, grouped by admitting diagnosis and total. CBDS, common bile duct stones; MRC, magnetic resonance cholangiography.
atitis in 37 patients (37%), obstructive jaundice in 17 patients (17%), biliary colic in 6 patients (6%), and cholangitis in 1 patient (1%). CBD dilation was defined as a duct diameter of greater than 5 mm measured by ultrasound, and this was observed in 61% of all patients. Among patients with choledocholithiasis, 98% of these patients had a CBD diameter of greater than 5 mm. CBDS was detected by MRC in 30 patients (30%) (Table II). The CBDS identified by MRC ranged in size from 2 to 16 mm in diameter. Twenty-two patients with CBDS detected by MRC underwent ERCP before cholecystectomy, and CBDS was found in 20 out of 22 of these patients (92%). Seven patients had small CBDS (2 to 3 mm) identified by MRC, however, no CBDS were identified at the time of standard cholangiography. In our opinion, the small CBDS most likely had passed spontaneously before ERC or LC. Nevertheless, these results were tabulated as false-positive MRC findings. Sixty-five patients had true-negative MRC, which was confirmed by IOC and clinical follow-up in 49 patients. The remaining 16 patients who did not have IOC performed had confirmation by clinical follow-up. Four patients were found to have false-negative MRC. One of the patients had a small CBDS and nonobstructed CBD demonstrated by IOC, which resolved with postoperative ERC/ES. The second patient’s MRC was interpreted as demonstrating sludge in the distal CBD; however, at the time of an attempted LC and IOC, an impacted CBDS was found at the ampulla. This patient required a CBD exploration for clearance of this stone. The third patient had a poor-quality IOC performed during LC, which was misinterpreted. This patient developed clinical and chemical evidence of CBD obstruction, which resolved spontaneously; a follow-up ERC in this patient revealed no CBDS. The fourth false-negative MRC occurred in a patient whose MRC was interpreted as demonstrating a cystic duct impacted by a 5-mm stone. This patient’s IOC showed an impacted CBDS at the junction of the cystic duct and CBD, and the patient required an open CBD exploration. The overall results were 65 true-negative, 23 true-positive, 7 false-positive, and 4 false-negative studies. MRC sensitivity was 85%, specificity was 90%, negative predictive value was 77%, positive predictive value was 94%, and accuracy was 89% for the detection of CBDS. 482
The optimal approach to the management of patients with CBDS and cholelithiasis remains controversial. One of the factors leading to this controversy is the lack of an accurate, noninvasive method for the diagnosis of choledocholithiasis. An alternative approach is to establish the diagnosis of CBDS at the time of operation with ultrasound or contrast cholangiography, and the CBDS can be resolved by laparoscopic, open CBD exploration, or postoperative ERC. IOC has a false-positive rate of 2% to 16%, which can lead to unnecessary CBD explorations. Furthermore, cholangiography may be unobtainable in 5% to 45% of cases.8 –11 The approach we have adapted in our practice is to diagnose and manage CBDS before LC. This approach has been adapted to accommodate the high volume of operative caseloads, limited operative time, and the large number of patients with suspected choledocholithiasis encountered in our county hospital. With the addition of MRC as a screening modality for patient selection for ERC/ES, there has been significant reduction in the number of ERCs performed for diagnostic purposes, and the management of patients with suspected choledocholithiasis has been greatly expedited. The MRC sensitivity of 85%, specificity of 90%, and accuracy rate of 89% observed by us are similar to those published in previous reports.12–17 These MRC results reported are comparable with the diagnostic capabilities of ERC, which is associated with a sensitivity of 84% to 89%, specificity of 97%, and a success rate of 95%.1 The pitfalls associated with MRC may be categorized as technical or interpretive pitfalls. Pneumobilia, duct tortuosity, cystic duct insertion, and sphincter contraction can be sources for false-positive MRC.18 It is our belief that most of the false-positive results encountered in our study occurred as a result of spontaneous passage of small CBDS before ERC or LC/IOC. The four false-negative MRCs encountered in our patients probably resulted from inadequate imaging angles in 3 patients leading to segments of CBD containing CBDS to be missed. The remaining false-negative MRC was obtained in a patient who had an impacted CBDS near the insertion of the cystic duct, which was erroneously interpreted as a stone impacted in the cystic duct. It is difficult to assess the true hospital cost of MRC, because a major portion of hospital cost incurred is associated with the purchasing and installation of the magnetic resonance imaging (MRI) equipment. The hospital charge for each MRI machine in our facility is $995. The finding of CBDS in only 30% of patients who underwent MRC evaluation indicates over-utilization and reflects the low specificity of traditional clinical, chemical, and ultrasonographic indicators of choledocholithiasis. Clearly, the occurrence of choledocholithiasis differed among patients with different admission diagnoses. CBDS was identified in 71% of patients presenting with jaundice, 27% of patients with cholecystitis, 16% of patients with pancreatitis, 0% of patients with biliary colic, and 100% of patients with cholangitis. The patients with biliary colic who underwent evaluation with MRC were imaged because of concern with unexplained asymptomatic CBD dilation by ultrasound. Since none of these patients was
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Figure 2. Proposed algorithm for improved MRC utilization. LC, laparoscopic cholecystectomy; CBDS, common bile duct stone; U/S, ultrasound; LFT, liver functions test; IOC, intraoperative cholangiogram; ERC, endoscopic retrograde cholangiography.
found to have CBDS, we no longer image patients with asymptomatic dilation of the CBD. The high incidence of choledocholithiasis identified among the patients presenting with cholangitis or jaundice indicate that MRC evaluation is unnecessary; therefore, we believe that these patients should be referred for ERC once the ultrasounds demonstrate CBD dilation. We believe that MRC evaluation can be most useful for the preoperative evaluation of patients with cholecystitis or biliary pancreatitis, in association with CBD dilation and elevation in liver functions test. Conclusions MRC is a useful imaging modality for the screening of patients with suspected CBDS before LC. MRC performed in this setting provides valuable information regarding the presence or absence of CBDS, as well as the size of CBDS if present. Moreover, the information obtained from MRC can be utilized to select for patients who would benefit from preoperative ERC. Using the information, we have developed a modified algorithm, shown in Figure 2. The selective use of MRC based on the proposed algorithm will improve utilization of this imaging modality, while minimizing the need for nontherapeutic ERC.
REFERENCES 1. Paul A, Millat B, Holthausen U, et al. Diagnosis and treatment of common bile duct stones (CBDS): results of a consensus development conference. Surg Endosc. 1998;12:856 – 864. 2. Golub R, Cantu Jr R, Tan M. The prediction of common bile duct stones using a neural network. J Am Coll Surg. 1998;187:584 – 590.
3. Trondsen E, Ewin B, Faerden AE, et al. Prediction of common bile duct stones prior to cholecystectomy. Arch Surg. 1998;133: 162–166. 4. Welbourn CRB, Haworth JM, Leaper DJ, Thompson MH. Prospective evaluation of ultrasonography and liver function tests for the preoperative assessment of the bile duct. Br J Surg. 1995;82: 1371–1373. 5. Houdart R, Perniceni T, Darne B, et al. Predicting common bile duct lithiasis: determination and prospective validation of a model predicting low risk. Am J Surg. 1995;170:38 – 43. 6. Hauer-Jensen M, Karesen R, Nygaard K, et al. Predictive ability of choledocholithiasis indicators: a prospective validation. Ann Surg. 1985;202:64 – 87. 7. Soto JA, Barish MA, Ferrucci JT. Magnetic resonance imaging of the bile ducts. Sem Roent. 1997;32:188 –201. 8. Mills JL, Beck DE, Harford FJ Jr. Routine operative cholangiogram. Surg Gynecol Obstet. 1985;161:343–345. 9. Doyle PJ, Ward-McQuaid JN, McEwe SA. The value of routine perioperative cholangiography: a report of 4000 cholecystectomies. Br J Surg. 1982;69:617– 619. 10. Kelley WE, Sheridan VC. Laparoscopic choledoscopy with small caliber endoscope. Surg Endosc. 1995;9:293–296. 11. Bagrato VJ. Laparoscopic choledochoscopy and choledocholithotomy. Surg Laparosc Endosc. 1993;3:164 –166. 12. Becker CD, Grossholz M, Becker M, et al. Choledocholithiasis and bile duct stenosis: diagnostic accuracy of MR cholangiopancreatography. Radiology. 1997;205:523–530. 13. Pavone P, Laghi A, Lomanto D, et al. MR cholangiography (MRC) in the evaluation of CBD stones before laparoscopic cholecystectomy. Surg Endosc. 1997;11:982–985. 14. Dwerryhouse SJ, Brown E, Vipond MN. Prospective evaluation of magnetic resonance cholangiography to detect common bile duct stones before laparoscopic cholecystectomy. Br J Surg. 1998; 85:1364 –1366.
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15. Musella M, Barbalace G, Capparelli G, et al. Magnetic resonance imaging in evaluation of the common bile duct. Br J Surg. 1998;85:16 –19. 16. Lomanto D, Pavone P, Laghi A, et al. Magnetic resonance cholangiopancreatography in the diagnosis of biliopancreatic diseases. Am J Surg. 1997;174:33–38.
17. Adamek HE, Albert J, Weitz HB, et al. A prospective evaluation of magnetic resonance cholangiopancreatography in patients with suspected bile duct obstruction. Gut. 1998;43:680 – 683. 18. Fulcher AS, Turner MA. Pitfalls of MR cholangipancreaography (MRCP). J Comput Assist Tomography. 1998;22:845– 850.
DISCUSSION
starting to go back to taking care of this as primarily a surgical problem and not even bothering with the ERCP or postoperative evaluations?
Byron McGregor, MD (Reno, Nevada): Dr. Liu and his associates are to be commended for a refreshingly honest evaluation of what is, in essence, a phase II clinical trial of a new diagnostic tool. If they found discrepancies between their MR findings and what they found in the operating room, they chose to regard those as false positives, even though the authors believed they represented were stones that had previously passed. Many, if not most, of the medical centers represented by this audience do not yet have the technology to perform scans like we just saw, either for hardware reasons like the big magnets or for software needs to perform the rapid-spin echo cycles. Questions of this study take two tacks. The first are very mundane: 1) Did you use antispasmodics to reduce bowel motility? 2) The same question regarding secretion if you are looking at the pancreatic duct; and 3) what do you do with those pesky little problems like previous surgical clips and hemobilia? More interesting, though, will be the group’s more philosophical musings about the proper role for this $1,000 study in the evaluation of biliary tracts. Should we look at the sensitivities, meaning the true positives, and if that number is high in a population, why should we just not perform the ERCP initially and take advantage of it’s therapeutic value? Or should we emphasize the specificity, meaning the true negatives, and if so, then how do we justify to an insurance company why we did the test at all? Thomas A. Broughan, MD (Tulsa, Oklahoma): We have gone from the debate over selective versus routine intraoperative cholangiography and we have added ERCP and then we added ultrasound, and now we are adding infusion cholangiography with CT scanning, and now magnetic resonance cholangiography. I think cost is an issue here. Whatever happened to the simple intraoperative cholangiogram? Does your group believe that it still has the advantages of perhaps avoiding injury during laparoscopic cholecystectomy, and failing that, at least identifying sooner, at least at the time of operation, the majority of these injuries? And, does magnetic resonance cholangiography offer you any advantages in that area? Raymond Price, MD (Salt Lake City, Utah): I am not sure we need the admission of another expensive test in the area of laparoscopic surgery. We went initially to laparoscopic cholecystectomy with ERCP, and we are now going to laparoscopic surgery with trans-cystic common bile duct explorations when stones are found on cholangiography, and not even needing to use the ERCP or putting our patients at risk for the complications of the ERCP. How would this really fit into today’s management of common bile duct stones in an era where we are now
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CLOSING Terrence H. Liu, MD: With regards to Dr. McGregor’s questions, we did not use antispasmodics for any of the patients. This was a rapid single breath-hold study as opposed to some of the other techniques. So, with this technique, we did not see very much artifacts in regards to bowel motility. As far as the problems with clips and hemobilia, which are two of the known causes of false-positive MRCs, we have actually performed MRCs in some of our patients postsurgery and found that, even though the standard radiology literature says that MRC should not be performed for at least a week after surgery, in some of our patients the radiologists have done that without hurting the patient and moving those clips that are newly placed; and as long as they are informed that this was a post-op patient, they can take it into account that these clips are outside the duct area and they incorporate that into the interpretation. We have not had much problems with the imaging of these patients, fortunately, because of the expertise our radiologists have. I agree with your last comment regarding the sensitivity and specificity. That is one of the reasons why we moved to a modified algorithm. During the initial phase of our study, we really were interested to know how good we were in finding stones. Therefore, we included a number of patients who clearly had a common duct stone. Now, having gone through these patients, we can say with greater certainty that these patients do not need MRC before their ERCP or whatever the definitive procedure may be. Our group does not perform routine IOCs. I think that question has been debated in the literature quite a bit, and we are taking the side that routine IOCs probably would not prevent intraoperative injury. With regard to the future role of MRC, during this time of rapid development of laparoscopic common bile duct exploration, I am aware of the emerging reports supporting the use of laparoscopic common bile duct exploration resulting in more cost-effective treatment of the patients. However, I think most studies still discuss that there is a role for some patients, such as the higher medical risk patient, including the ASA III and ASA IV patients, who may benefit from an expedited intraoperative course. Clearly, these patients may benefit from MRC evaluation before surgery to minimize time in the operating room. So, I perceive that may be the direction in which this technology will be heading at this point.
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BACKGROUND: Endoscopic retrograde cholangiography is the most commonly utilized tool for the identification of common bile duct stones (CBDS) before laparoscopic cholecystectomy, whereas the role of magnetic resonance cholangiography (MRC) for patient evaluation before laparoscopic cholecystectomy is currently undefined. METHODS: We prospectively evaluated the efficacy of MRC for the identification of CBDS among patients with high risk for choledocholithiasis. Patient selection was based on clinical, sonographic, and laboratory criteria. Standard cholangiograms were obtained when possible for verification of MRC results. RESULTS: Ninety-nine patients underwent evaluation with preoperative MRC. CBDS was visualized in 30% of patients. MRC sensitivity, specificity, positive predictive value, negative predictive value, and accuracy were 85%, 90%, 77%, 94%, and 89%, respectively. CONCLUSIONS: MRC is useful for the evaluation of patients with suspected choledocholithiasis. Advantages of MRC include its noninvasive nature, ease of application, and accuracy in identifying and estimating the size of CBDS. Application of MRC in this setting reduces the need for diagnostic endoscopic retrograde cholangiography. Future investigations should be directed at the development of cost-effective utilization strategies for MRC application. Am J Surg. 1999;178: 480 – 484. © 1999 by Excerpta Medica, Inc.
T
he incidence of choledocholithiasis ranges from 8% to 20% among patients who undergo cholecystectomy.1–3 The approach to the diagnosis and management of common bile duct stones (CBDS) in these patients varies significantly, depending on patient preference, physician preference, expertise of surgical, endoscopic, radiologic personnel, and resource availability. Definitive diagnosis of choledocholithiasis before laparoscopic cholecystectomy (LC) provides physicians with the opportunity to formulate an optimal treatment plan. Clinical, ultrasonographic, and serum chemistry parameters are associated with 96% to 98% sensitivity but low specificity for the identification of patients with CBDS.1– 6 When patients are selected for preoperative endoscopic retrograde cholangiography (ERC) based on these criteria, 40% to 75% of patients have no CBDS found at ERC.1 The low yield of diagnostic ERC and the procedure-related complication rate of 0.8% to 10%, including sedation-related complications, pancreatitis, cholangitis, perforations, and bleeding, have led some investigators to explore magnetic resonance cholangiography (MRC) as a diagnostic modality for the detection of choledocholithiasis.1 Magnetic resonance imaging techniques have been utilized for the evaluation of patients with suspected pancreatic and biliary tract pathology.7 With T2-weighted, twodimension fast-spin echo MRC, bile produces brighter signal intensity than the surrounding tissue and fluid, while biliary stones produce a signal void. Utilizing these techniques, early reports of MRC have demonstrated high sensitivity and specificity for the detection of CBDS and CBD strictures.8 –12 An example of MRC is shown in Figure 1. This study was undertaken to determine the efficacy of MRC for diagnosing choledocholithiasis in a population of patients at high risk for CBDS.
METHODS From the Departments of Surgery (THL, ETC, CTB, PHG, RPF, DWM) and Radiology (AK, RDE), The University of Texas, Houston Health Science Center at Lyndon B. Johnson General Hospital, Houston, Texas. Requests for reprints should be addressed to Terrence H. Liu, MD, Department of Surgery, Suite 30S 62 008, 5656 Kelley St., Houston, Texas 77026-1967. Presented at the 51st Annual Meeting of the Southwestern Surgical Congress, Coronado, California, April 18 –21, 1999.
480
© 1999 by Excerpta Medica, Inc. All rights reserved.
Between August 1, 1997 and December 31, 1998, a total of 421 patients underwent cholecystectomy at the University of Texas, Houston Health Science Center/Lyndon B. Johnson General Hospital, which is a 250-bed teaching hospital primarily serving the medical indigent patients of Harris County, Texas. The preoperative evaluation for all patients included an abdominal ultrasound for determination of cholelithiasis and estimation of CBD size, and serum chemistry determination of bilirubin, alkaline phosphatase, transaminase (AST/ALT), and amylase. Patients 0002-9610/99/$–see front matter PII S0002-9610(99)00224-X
MAGNETIC RESONANCE CHOLANGIOGRAPHY BEFORE CHOLECYSTECTOMY/LIU ET AL
Figure 1. Coronal and axial views of MRC scan demonstrating the presence of a 3-mm stone within the lumen of a 7-mm CBD. The arrow indicates the location of stone.
TABLE I Factors for the Determination of Patients With “High Risk” for Choledocholithiasis A. History of jaundice, cholangitis, or biliary pancreatitis B. CBD size by ultrasound ⬎5 mm in diameter C. Serum chemistry abnormalities Total bilirubin ⬎1.5 mg/dL Alkaline phosphatase ⬎150 U/L AST ⬎100 U/L ALT ⬎100 U/L Determination of high risk for choledocholithiasis is based on evidence present from categories A, B, and C. The presence of factors from two or more of the above categories indicated “high risk.”
were considered to have high suspicion for choledocholithiasis on the basis of criteria described in Table I. Before the utilization of MRC at our institution, patients who were determined to have high risk for having CBDS underwent preoperative evaluation with ERC. During the study period, patients with high suspicion for CBDS were evaluated with MRC before LC. MRC scans obtained were breath-hold, heavily T2-weighted, two-dimension fast-spin echo MRC performed on a 1.5T scanner (Horizon LX; GE Medical Systems, Milwaukee, WI). MR images were filmed in the axial and coronal planes in increments of 3 to 5 mm.
An average duration of 15 min was required for each MRC study. Patients whose MRC revealed no CBDS underwent LC/ intraoperative cholangiography (IOC) without further evaluations. During the initial portion of the study, all patients whose MRC demonstrated CBDS underwent further evaluation and CBD clearance with ERC. However, during the latter portion of the study, preoperative ERC was not performed when patients were detected to have small, asymptomatic CBDS by MRC, because we felt that these patients would not have benefited from the procedure. Cholangiography was performed at ERC or cholecystectomy, for verification of MRC result. All patient data was prospectively collected and entered into a database. Radiographic studies were interpreted by a radiologist. All patients were followed for evidence of CBDS-related complications. This study was conducted with the approval of The Committee for the Protection of Human Subjects at University of Texas-Houston Medical School.
RESULTS During a 17-month period, 99 patients were evaluated with MRC before cholecystectomy. Eighty-eight of the patients were female and 11 patients were male. The patient age ranged from 17 to 67 years, with a mean age of 35.3 years. Diagnoses among the patients were acute/ chronic cholecystitis in 38 patients (38%), biliary pancre-
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COMMENTS
TABLE II CBDS Visualization by MRC Diagnosis Cholecystitis Pancreatitis Jaundice Cholangitis Biliary colic All patients
Actual Numbers
Percentage
11/38 6/37 12/17 1/1 0/6 30/99
29% 16% 71% 100% 0% 30%
The actual numbers and percentages of patients with CBDS visualized by MRC, grouped by admitting diagnosis and total. CBDS, common bile duct stones; MRC, magnetic resonance cholangiography.
atitis in 37 patients (37%), obstructive jaundice in 17 patients (17%), biliary colic in 6 patients (6%), and cholangitis in 1 patient (1%). CBD dilation was defined as a duct diameter of greater than 5 mm measured by ultrasound, and this was observed in 61% of all patients. Among patients with choledocholithiasis, 98% of these patients had a CBD diameter of greater than 5 mm. CBDS was detected by MRC in 30 patients (30%) (Table II). The CBDS identified by MRC ranged in size from 2 to 16 mm in diameter. Twenty-two patients with CBDS detected by MRC underwent ERCP before cholecystectomy, and CBDS was found in 20 out of 22 of these patients (92%). Seven patients had small CBDS (2 to 3 mm) identified by MRC, however, no CBDS were identified at the time of standard cholangiography. In our opinion, the small CBDS most likely had passed spontaneously before ERC or LC. Nevertheless, these results were tabulated as false-positive MRC findings. Sixty-five patients had true-negative MRC, which was confirmed by IOC and clinical follow-up in 49 patients. The remaining 16 patients who did not have IOC performed had confirmation by clinical follow-up. Four patients were found to have false-negative MRC. One of the patients had a small CBDS and nonobstructed CBD demonstrated by IOC, which resolved with postoperative ERC/ES. The second patient’s MRC was interpreted as demonstrating sludge in the distal CBD; however, at the time of an attempted LC and IOC, an impacted CBDS was found at the ampulla. This patient required a CBD exploration for clearance of this stone. The third patient had a poor-quality IOC performed during LC, which was misinterpreted. This patient developed clinical and chemical evidence of CBD obstruction, which resolved spontaneously; a follow-up ERC in this patient revealed no CBDS. The fourth false-negative MRC occurred in a patient whose MRC was interpreted as demonstrating a cystic duct impacted by a 5-mm stone. This patient’s IOC showed an impacted CBDS at the junction of the cystic duct and CBD, and the patient required an open CBD exploration. The overall results were 65 true-negative, 23 true-positive, 7 false-positive, and 4 false-negative studies. MRC sensitivity was 85%, specificity was 90%, negative predictive value was 77%, positive predictive value was 94%, and accuracy was 89% for the detection of CBDS. 482
The optimal approach to the management of patients with CBDS and cholelithiasis remains controversial. One of the factors leading to this controversy is the lack of an accurate, noninvasive method for the diagnosis of choledocholithiasis. An alternative approach is to establish the diagnosis of CBDS at the time of operation with ultrasound or contrast cholangiography, and the CBDS can be resolved by laparoscopic, open CBD exploration, or postoperative ERC. IOC has a false-positive rate of 2% to 16%, which can lead to unnecessary CBD explorations. Furthermore, cholangiography may be unobtainable in 5% to 45% of cases.8 –11 The approach we have adapted in our practice is to diagnose and manage CBDS before LC. This approach has been adapted to accommodate the high volume of operative caseloads, limited operative time, and the large number of patients with suspected choledocholithiasis encountered in our county hospital. With the addition of MRC as a screening modality for patient selection for ERC/ES, there has been significant reduction in the number of ERCs performed for diagnostic purposes, and the management of patients with suspected choledocholithiasis has been greatly expedited. The MRC sensitivity of 85%, specificity of 90%, and accuracy rate of 89% observed by us are similar to those published in previous reports.12–17 These MRC results reported are comparable with the diagnostic capabilities of ERC, which is associated with a sensitivity of 84% to 89%, specificity of 97%, and a success rate of 95%.1 The pitfalls associated with MRC may be categorized as technical or interpretive pitfalls. Pneumobilia, duct tortuosity, cystic duct insertion, and sphincter contraction can be sources for false-positive MRC.18 It is our belief that most of the false-positive results encountered in our study occurred as a result of spontaneous passage of small CBDS before ERC or LC/IOC. The four false-negative MRCs encountered in our patients probably resulted from inadequate imaging angles in 3 patients leading to segments of CBD containing CBDS to be missed. The remaining false-negative MRC was obtained in a patient who had an impacted CBDS near the insertion of the cystic duct, which was erroneously interpreted as a stone impacted in the cystic duct. It is difficult to assess the true hospital cost of MRC, because a major portion of hospital cost incurred is associated with the purchasing and installation of the magnetic resonance imaging (MRI) equipment. The hospital charge for each MRI machine in our facility is $995. The finding of CBDS in only 30% of patients who underwent MRC evaluation indicates over-utilization and reflects the low specificity of traditional clinical, chemical, and ultrasonographic indicators of choledocholithiasis. Clearly, the occurrence of choledocholithiasis differed among patients with different admission diagnoses. CBDS was identified in 71% of patients presenting with jaundice, 27% of patients with cholecystitis, 16% of patients with pancreatitis, 0% of patients with biliary colic, and 100% of patients with cholangitis. The patients with biliary colic who underwent evaluation with MRC were imaged because of concern with unexplained asymptomatic CBD dilation by ultrasound. Since none of these patients was
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Figure 2. Proposed algorithm for improved MRC utilization. LC, laparoscopic cholecystectomy; CBDS, common bile duct stone; U/S, ultrasound; LFT, liver functions test; IOC, intraoperative cholangiogram; ERC, endoscopic retrograde cholangiography.
found to have CBDS, we no longer image patients with asymptomatic dilation of the CBD. The high incidence of choledocholithiasis identified among the patients presenting with cholangitis or jaundice indicate that MRC evaluation is unnecessary; therefore, we believe that these patients should be referred for ERC once the ultrasounds demonstrate CBD dilation. We believe that MRC evaluation can be most useful for the preoperative evaluation of patients with cholecystitis or biliary pancreatitis, in association with CBD dilation and elevation in liver functions test. Conclusions MRC is a useful imaging modality for the screening of patients with suspected CBDS before LC. MRC performed in this setting provides valuable information regarding the presence or absence of CBDS, as well as the size of CBDS if present. Moreover, the information obtained from MRC can be utilized to select for patients who would benefit from preoperative ERC. Using the information, we have developed a modified algorithm, shown in Figure 2. The selective use of MRC based on the proposed algorithm will improve utilization of this imaging modality, while minimizing the need for nontherapeutic ERC.
REFERENCES 1. Paul A, Millat B, Holthausen U, et al. Diagnosis and treatment of common bile duct stones (CBDS): results of a consensus development conference. Surg Endosc. 1998;12:856 – 864. 2. Golub R, Cantu Jr R, Tan M. The prediction of common bile duct stones using a neural network. J Am Coll Surg. 1998;187:584 – 590.
3. Trondsen E, Ewin B, Faerden AE, et al. Prediction of common bile duct stones prior to cholecystectomy. Arch Surg. 1998;133: 162–166. 4. Welbourn CRB, Haworth JM, Leaper DJ, Thompson MH. Prospective evaluation of ultrasonography and liver function tests for the preoperative assessment of the bile duct. Br J Surg. 1995;82: 1371–1373. 5. Houdart R, Perniceni T, Darne B, et al. Predicting common bile duct lithiasis: determination and prospective validation of a model predicting low risk. Am J Surg. 1995;170:38 – 43. 6. Hauer-Jensen M, Karesen R, Nygaard K, et al. Predictive ability of choledocholithiasis indicators: a prospective validation. Ann Surg. 1985;202:64 – 87. 7. Soto JA, Barish MA, Ferrucci JT. Magnetic resonance imaging of the bile ducts. Sem Roent. 1997;32:188 –201. 8. Mills JL, Beck DE, Harford FJ Jr. Routine operative cholangiogram. Surg Gynecol Obstet. 1985;161:343–345. 9. Doyle PJ, Ward-McQuaid JN, McEwe SA. The value of routine perioperative cholangiography: a report of 4000 cholecystectomies. Br J Surg. 1982;69:617– 619. 10. Kelley WE, Sheridan VC. Laparoscopic choledoscopy with small caliber endoscope. Surg Endosc. 1995;9:293–296. 11. Bagrato VJ. Laparoscopic choledochoscopy and choledocholithotomy. Surg Laparosc Endosc. 1993;3:164 –166. 12. Becker CD, Grossholz M, Becker M, et al. Choledocholithiasis and bile duct stenosis: diagnostic accuracy of MR cholangiopancreatography. Radiology. 1997;205:523–530. 13. Pavone P, Laghi A, Lomanto D, et al. MR cholangiography (MRC) in the evaluation of CBD stones before laparoscopic cholecystectomy. Surg Endosc. 1997;11:982–985. 14. Dwerryhouse SJ, Brown E, Vipond MN. Prospective evaluation of magnetic resonance cholangiography to detect common bile duct stones before laparoscopic cholecystectomy. Br J Surg. 1998; 85:1364 –1366.
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15. Musella M, Barbalace G, Capparelli G, et al. Magnetic resonance imaging in evaluation of the common bile duct. Br J Surg. 1998;85:16 –19. 16. Lomanto D, Pavone P, Laghi A, et al. Magnetic resonance cholangiopancreatography in the diagnosis of biliopancreatic diseases. Am J Surg. 1997;174:33–38.
17. Adamek HE, Albert J, Weitz HB, et al. A prospective evaluation of magnetic resonance cholangiopancreatography in patients with suspected bile duct obstruction. Gut. 1998;43:680 – 683. 18. Fulcher AS, Turner MA. Pitfalls of MR cholangipancreaography (MRCP). J Comput Assist Tomography. 1998;22:845– 850.
DISCUSSION
starting to go back to taking care of this as primarily a surgical problem and not even bothering with the ERCP or postoperative evaluations?
Byron McGregor, MD (Reno, Nevada): Dr. Liu and his associates are to be commended for a refreshingly honest evaluation of what is, in essence, a phase II clinical trial of a new diagnostic tool. If they found discrepancies between their MR findings and what they found in the operating room, they chose to regard those as false positives, even though the authors believed they represented were stones that had previously passed. Many, if not most, of the medical centers represented by this audience do not yet have the technology to perform scans like we just saw, either for hardware reasons like the big magnets or for software needs to perform the rapid-spin echo cycles. Questions of this study take two tacks. The first are very mundane: 1) Did you use antispasmodics to reduce bowel motility? 2) The same question regarding secretion if you are looking at the pancreatic duct; and 3) what do you do with those pesky little problems like previous surgical clips and hemobilia? More interesting, though, will be the group’s more philosophical musings about the proper role for this $1,000 study in the evaluation of biliary tracts. Should we look at the sensitivities, meaning the true positives, and if that number is high in a population, why should we just not perform the ERCP initially and take advantage of it’s therapeutic value? Or should we emphasize the specificity, meaning the true negatives, and if so, then how do we justify to an insurance company why we did the test at all? Thomas A. Broughan, MD (Tulsa, Oklahoma): We have gone from the debate over selective versus routine intraoperative cholangiography and we have added ERCP and then we added ultrasound, and now we are adding infusion cholangiography with CT scanning, and now magnetic resonance cholangiography. I think cost is an issue here. Whatever happened to the simple intraoperative cholangiogram? Does your group believe that it still has the advantages of perhaps avoiding injury during laparoscopic cholecystectomy, and failing that, at least identifying sooner, at least at the time of operation, the majority of these injuries? And, does magnetic resonance cholangiography offer you any advantages in that area? Raymond Price, MD (Salt Lake City, Utah): I am not sure we need the admission of another expensive test in the area of laparoscopic surgery. We went initially to laparoscopic cholecystectomy with ERCP, and we are now going to laparoscopic surgery with trans-cystic common bile duct explorations when stones are found on cholangiography, and not even needing to use the ERCP or putting our patients at risk for the complications of the ERCP. How would this really fit into today’s management of common bile duct stones in an era where we are now
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CLOSING Terrence H. Liu, MD: With regards to Dr. McGregor’s questions, we did not use antispasmodics for any of the patients. This was a rapid single breath-hold study as opposed to some of the other techniques. So, with this technique, we did not see very much artifacts in regards to bowel motility. As far as the problems with clips and hemobilia, which are two of the known causes of false-positive MRCs, we have actually performed MRCs in some of our patients postsurgery and found that, even though the standard radiology literature says that MRC should not be performed for at least a week after surgery, in some of our patients the radiologists have done that without hurting the patient and moving those clips that are newly placed; and as long as they are informed that this was a post-op patient, they can take it into account that these clips are outside the duct area and they incorporate that into the interpretation. We have not had much problems with the imaging of these patients, fortunately, because of the expertise our radiologists have. I agree with your last comment regarding the sensitivity and specificity. That is one of the reasons why we moved to a modified algorithm. During the initial phase of our study, we really were interested to know how good we were in finding stones. Therefore, we included a number of patients who clearly had a common duct stone. Now, having gone through these patients, we can say with greater certainty that these patients do not need MRC before their ERCP or whatever the definitive procedure may be. Our group does not perform routine IOCs. I think that question has been debated in the literature quite a bit, and we are taking the side that routine IOCs probably would not prevent intraoperative injury. With regard to the future role of MRC, during this time of rapid development of laparoscopic common bile duct exploration, I am aware of the emerging reports supporting the use of laparoscopic common bile duct exploration resulting in more cost-effective treatment of the patients. However, I think most studies still discuss that there is a role for some patients, such as the higher medical risk patient, including the ASA III and ASA IV patients, who may benefit from an expedited intraoperative course. Clearly, these patients may benefit from MRC evaluation before surgery to minimize time in the operating room. So, I perceive that may be the direction in which this technology will be heading at this point.
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