gallstones are among the most prevalent clinical problems all around the world . based on published studies , the prevalence of gall stones in europe is about 5 - 20% in the general population , rising with age .
the incidence of gallstones is three times more common in women than in men ( 13 ) .
twelve percent of patients with symptomatic gall stone disease have common bile duct stones ( 4 ) .
choledocholithiasis may be asymptomatic ; or it may cause serious problems , such as obstructive jaundice , pancreatitis and cholangitis , which can complicate disease management , especially in older patients . according to previous studies , it is recommended that common bile duct investigation should be done in order to rule out choledocholithiasis in all patients with symptomatic cholelithiasis .
bile duct calculi in majority of cases are predictable on the basis of clinical , biochemical and radiological examinations .
ultra - sonography ( uss ) is an available , low cost , non - invasive test , with no need for ionizing radiation .
uss can measure the diameter of intra and extra hepatic bile ducts , indicating whether it is dilated or not .
however , it misses approximately 65% of bile duct stones because of the interference with bowel gas and also because ultra - sonography is a procedure highly operator dependent ( 36 ) .
intra - operative cholangiography ( ioc ) is the gold standard procedure in the diagnosis of bile duct stones .
but it is invasive , needs anesthesia , elongate the duration of operation and anesthesia and may increase intra and post - operative complications .
studies recommend trying to move to a procedure much safer , more cost effective with less complication .
magnetic resonance cholangiopancreatography ( mrcp ) is a non - invasive procedure that gives high resolution images of the biliary tree without any exposure to ionizing radiation ( 3 , 7 ) .
its role in identifying uncertain anatomy and visualizing the bile duct stones is well - established ( 8) .
investigations show that comparing to direct cholangiography , mrcp has found to be sensitive and specific ( 3 , 7 , 9 , 10 ) .
therefore , given that ioc is an invasive procedure with probable complications , it would seem that mrcp could replace the direct cholangiography when it used for diagnostic purposes based on studies indicate that it is a sensitive and specific diagnostic procedure ( 7 ) .
we performed this study to compare the efficacy of ioc and mrcp in patients thought to have biliary stones , considering the sensitivity , specificity , positive predictive value and negative predictive value of these two procedures . through this study
we can help answering the question below : can pre - operative mrcp obviate the need for ioc ?
fifty - nine consecutive inpatients with suspected common bile duct ( cbd ) stones admitted to the surgery unit of imam hossein medical center , tehran , iran , were recruited in the study over a period of 24 months .
patients had the mean age of 556 sd years ( range 36 - 68 ) .
we studied them after obtaining their approval from the ethics committee of the university hospital , imam hossein hospital , tehran , iran . after taking a history and examination , blood tests and routine biochemical assays including serum liver enzymes , bilirubin , amylase and alkaline phosphatase
an abdominal uss was performed to look for the presence of gallstones and any signs of a cbd stone or bile duct dilation .
patients included in this study all had normal sonography but higher than normal alkaline phosphatase level ( alph > 200 ) and were clinically suspicious to common bile duct ( cbd ) stones . any patient with derangement in other liver tests ( such as bilirubin ) or
documented biliary stone diagnosed by uss were excluded from the study . if in a patient scheduled for cholecystectomy according to these investigations there was a strong suspicion to choledocholithiasis , the patient received preoperative mrcp , and then undergone ioc along with subsequent cholecystectomy .
all mrcp scans were analyzed by a radiologist who was unaware of ioc and lab test results .
cholecystectomies were performed in a standard manner by one surgeon , the operating surgeon initially assessed ioc , and the film was subsequently reported by one , blinded radiologist who was unaware of mrcp scan results either . based on recorded data , specificity , sensitivity , positive and negative predictive values were individually calculated for both procedures ( mrcp and ioc ) .
sensitivity was the ability to identify patients with cbd stones using the number of positive mrcp diagnoses divided by the total number of patients with confirmed cbd stones by ioc .
specificity was the ability to identify patients without cbd stones using the number of negative mrc diagnoses as a percentage of the total number of patients without ioc - proven cbd stones .
positive and negative predictive values of mrc were determined by the proportion of mrcp diagnoses ( positive or negative ) confirmed by ioc .
fifty - nine consecutive inpatients with suspected common bile duct ( cbd ) stones admitted to the surgery unit of imam hossein medical center , tehran , iran , were recruited in the study over a period of 24 months .
patients had the mean age of 556 sd years ( range 36 - 68 ) .
we studied them after obtaining their approval from the ethics committee of the university hospital , imam hossein hospital , tehran , iran . after taking a history and examination , blood tests and routine biochemical assays including serum liver enzymes , bilirubin , amylase and alkaline phosphatase
an abdominal uss was performed to look for the presence of gallstones and any signs of a cbd stone or bile duct dilation .
patients included in this study all had normal sonography but higher than normal alkaline phosphatase level ( alph > 200 ) and were clinically suspicious to common bile duct ( cbd ) stones . any patient with derangement in other liver tests ( such as bilirubin ) or
documented biliary stone diagnosed by uss were excluded from the study . if in a patient scheduled for cholecystectomy according to these investigations there was a strong suspicion to choledocholithiasis , the patient received preoperative mrcp , and then undergone ioc along with subsequent cholecystectomy .
all mrcp scans were analyzed by a radiologist who was unaware of ioc and lab test results .
cholecystectomies were performed in a standard manner by one surgeon , the operating surgeon initially assessed ioc , and the film was subsequently reported by one , blinded radiologist who was unaware of mrcp scan results either . based on recorded data , specificity , sensitivity , positive and negative predictive values were individually calculated for both procedures ( mrcp and ioc ) .
sensitivity was the ability to identify patients with cbd stones using the number of positive mrcp diagnoses divided by the total number of patients with confirmed cbd stones by ioc .
specificity was the ability to identify patients without cbd stones using the number of negative mrc diagnoses as a percentage of the total number of patients without ioc - proven cbd stones .
positive and negative predictive values of mrc were determined by the proportion of mrcp diagnoses ( positive or negative ) confirmed by ioc .
in this study the mean age of the patients was 55 with the standard deviation of 6 years .
mean level of alkaline phosphtase was 492 with the standard deviation of 26 ( table 1 ) .
statistics and its relative 95% confidence interval tp= true positive , tn= true negative , fp = false positive , fn = false negative , ppv= positive predictive value , npv = negative predictive value , da= diagnostic accuracy , lr= likelihood ratio , do= diagnostic odds the positive predictive value for ioc was 88% , comparing to mrcp which was 43% .
the difference was significant with the p - value less than 0.05 ( p = 0.04 ) .
these findings show that we had lots of false positive results performing mrcp comparing with ioc .
the diagnostic accuracy difference of these two procedures were significant either ( p = 0.02 ) which means ioc is much more accurate .
there were no significant and meaningful differences between the sensitivity and specificity statistics based on statistical analysis ( table 2 ) . 
 
the incidence of common bile duct ( cbd ) stones among the patients undergoing cholecystectomy is reported as approximately 12% .
there are some symptoms , signs and invesigations that should arouse suspicion of a cbd stones including derangement in liver function test ( lft)s , dilated cbd in ultrasound ( us ) .
routine intra - operative cholangiography ( ioc ) is performed , by some surgeons , for several reasons .
firstly through this procedure we can confirm that cbd is clear and find unsuspected stones in cbd . but according to the evidences 1% of patients with normal lft and ultra - sonography have stones in their cbd and 75% of these stones passes spontaneously ( 4 , 1921 ) .
the disadvantage of this procedure is that we force an unnecessary cbd exploration to the patient and prolongation of the operation , because of the radiography and also because of surgical dissection and cannulation .
preoperative evaluation of the biliary tree has assumed a great importance in patients suspicious to choledocolithiasis and may help us avoiding intra - operative difficulties . performing a confident assessment of the cbd prior to the surgery may reduce or obviate the need for hazardous and timeconsuming ioc ( 3 , 11 ) .
several diagnostic and therapeutic strategies have been suggested for clinical diagnosis and management of cbd stones such as routine mrcp , selective endoscopic retrograde cholangiopancreatography ( ercp ) , routine ioc or endoscopic us with cbd exploration .
however no single method is both risk free , highly sensitive and specific currently in use(1114 ) .
results from different studies demonstrate that sensitivity and specificity of mrcp for detection of cbd stones is high and the resolution of the biliary tree images is excellent .
these investigations confirm the accuracy of mrcp in diagnosis of cbd stones ( 1517 ) .
recent studies comparing mrcp with ioc or ercp confirmed that mrcp has the accuracy up to 95% ( 7 , 22 , 23 ) .
studies comparing ercp with mrcp indicates that reliance upon mrcp findings may have reduced the requirement for ercp and sphincterotomy by up to 75% ( 22 , 24 ) . in our study
there were no significant differences in sensitivity , specificity between the two procedures mrcp and ioc . but based on our study the diagnostic accuracy of ioc was higher than mrcp ( 98% vs 85% ) and this difference was statistically significant ( p = 0.02 ) .
the positive predictive value of ioc was 88% , compared to mrcp that was 43% ( p = 0.04 ) .
these findings indicates that mrcp has significant false positive results compare to the ioc and based on mrcp only , we may perform unnecessary operations to a few number of patients .
considering these results , we feel that although using pre operative mrcp reduces the duration of operation and is less invasive comparing with routine ioc ( 7 , 9 , 10 , 18 ) , it does not have the diagnostic accuracy of the ioc .
it may reduce unpredictable damages to the cbd during the ioc but it has significant false positive cases .
dalton et al ( 7 ) reported that mrcp should be the only modality used to exclude cbd stones 
so individual centers must design their own strategies based on local factors including geographical location , personnel , equipment and facilities such as ercp and mrcp , economic factors ( time resources , private or teaching hospital ) and the experience of the operating team . in conclusion
the suggestion advocating routine use of mrcp instead of ioc or as a substitute for ioc needs further investigations on more patients . not only should we consider all the advantages and disadvantages of these two procedures ( ioc , mrcp ) but also we should perform some further investigations in order to find out which of these two procedures is the most cost - effective based on local circumstances in different centers . with further studies we may be able to choose a procedure less invasive , less expensive , with lower rate of complications and of course more diagnostic accuracy
 aimthis study was performed to compare the efficacy of preoperative magnetic resonance cholangiopancreatography ( mrcp ) and intra - operative cholangiography ( ioc ) methods in patients suspicious to gall stones.backgroundaccording to previous studies , it is recommended that common bile duct investigation should be done in order to rule out choledocholithiasis in all patients with symptomatic cholelithiasis . 
 ioc is an invasive procedure with probable complications , it would seem that mrcp could replace the direct cholangiography.patients and methodsin a diagnostic clinical trial , fifty - nine patients with symptomatic biliary stones or cholecystitis were recruited in this study . 
 the included patients had normal size biliary ducts in sonography but high serum alkaline phosphatase level . 
 preoperative mrcp and ioc were performed for the patients and the obtained results were analyzed and compared.resultsthe positive predictive value for ioc was 88% and for mrcp was 43% . 
 the diagnostic accuracy of ioc and mrcp were 98% and 85% respectively , suggesting that ioc is much more diagnostically accurate . 
 there were no significant difference in specificity and sensitivity of these two methods.conclusionaccording to the results , we can conclude that mrcp may not obviate the need for ioc . 
 the suggestion for routine use of mrcp instead of ioc and as a substitution of that procedure needs further investigations on more patients . 
Introduction
Patients and Methods
Patient Selection
Results
Discussion