ROLE OF MRCP IN HEPATOBILIARY PATHOLOGY IN CORRELATION WITH ERCP.

hepatobiliary Aim: To determine diagnostic accuracy of MRCP as compared to ERCP for evaluating biliary duct disorders using the specificity, sensitivity, positive and negative predictive values. examination reveals moderately differentiated adenocarcinoma hilar stricture and undergone biliary sphincterotomy stent


ISSN: 2320-5407
Int. J. Adv. Res. 6(4), 1388-1407 1389 The new modes of MR sequencing provide clear projectional images that are similar to images obtained during ERCP, while routinely performed by experienced gastroenterologists, is still associated with adverse effects like pancreatitis, bile leak, hemorrhage, gastro duodenal perforation and sepsis with a morbidity rate of 7% and a mortality rate of 1% [36].
The development of fast imaging sequences and the improvements in the quality of abdominal images have generated a new interest in magnetic resonance evaluation of biliary & pancreatic diseases [35].With the help of advanced imaging sequences, we can get the images equal that of ERCP [17].
Most researchers have reported that these new MRCP sequences are even better than ERCP because they accurately diagnoses pancreatobiliary diseases [24,3,9].MRCP is a less costly, non-invasive, and sensitive technique for evaluating the biliary and pancreatic ductal systems.
In MRCP, multiplanar images are obtained parallel to the orientation of the biliary tree, using an MR sequence that is sensitive to static fluid without the need for exogenous contrast agents. Fluid in the ducts appears bright against the darker tissue. MRCP can diagnose the presence of bile duct obstruction and the level of obstruction in most cases.
MRCP is unique due to its accuracy and noninvasive nature and its ability to depict ducts proximal to a high-grade obstruction. As a result, at some centers, ERCP is now used primarily as a means of gaining access for interventions such as stent placements instead of as a diagnostic tool.
The major disadvantage of MRCP is that it is entirely diagnostic, in contrast to ERCP, which provides diagnostic information as well as access for therapeutic interventions.
Other disadvantages of MRCP include decreased spatial resolution and the quality of imaging in patients who are in a physiological, non-distended state .
In this retrospective and prospective study we predict the accuracy, sensitivity and specificity of MRCP as compared to ERCP, which is considered as a gold standard for evaluation of hepatobiliary Objectives:-To evaluate and correlate the accuracy between Magnetic Resonance Cholangio-Pancreatography and endoscopic retrograde cholangiopancreatography in diagnosing suspected cases of biliary obstruction .

Materials And Methods:-
During the period January 2010 to july 2016, 168 patients with suspected biliary pathology who underwent MRCP and ERCP, were included in this prospective and retrospective observational study.
This cross-sectional study was designed to include former and current patients with clinical features of biliary pathology who subsequently underwent MRCP and ERCP over a 12 month period.
The study participants were divided in to four main groups. Normal into group I, stone disease into group II, tumors/cysts into group III and others into group IV.
The sensitivity, specificity, and positive and negative predictive values For MRCP were calculated as compared to the ERCP.

Conclusion:-
From this study, we conclude MRCP is an alternative to ERCP in the diagnosis of pancreaticobiliary pathology. Due to high sensitivity and specificity we recommend the use of MRCP for diagnosis of biliary pathologies and can be performed rapidly and non invasively Materials And Methods:-Study Design:-During the period January 2010 to july 2016, 168 patients with suspected biliary pathology who underwent MRCP and ERCP, were included in this prospective and retrospective observational study.The sample size was estimated to 168 patients Our study was performed at the MRI and the ERCP units of Kasturba medical college Ambedkar circle, Manipal University, Mangalore. In all the patients included in this study MRCP was performed prior to ERCP.

Inclusion Criteria:-
The study included  Patients referred to the department of radiodiagnosis with clinical suspicion of biliary tract and gallbladder pathology.  Patients detected with biliary tract pathology on ultrasonography Exclusion Criteria:-The study excluded  Pregnant women.  Patients allergic to contrast.  Patients who underwent recent interventional procedures on the biliary tract.  Patients with cardiac pacemakers  Severe claustrophobia Ethical Consideration:-Numerous ethical considerations were considered in the process of this research. Kasturba medical college hospital ethical committee was requested to approve the research proposal. Patient's personal information e g. names were not to be used in the study in order to uphold confidentiality. Information acquired would not be used for any other purpose besides in the clinical management of patients and academics. The study was approved by the institute's ethical committee.Patients were requested to provide an informed consent in writing.
Single shot fast spin echo (SSFSE) with an adequate field of view was used to get the axial images. Spin echo axial T2 images were acquired using a TE of 102, Field of view (FOV) of 28 to 38cm, slice thickness of 8mm, with a spacing of 2mm. Frequency encoding was done from right to left. Phase encoding FOV was 8cm. Long TE was used to perform thick slabs to image the biliary and pancreatic ducts.

ERCP technique:
Fluoroscopy: A GE OEC 850 was used for screening and taking hard copy plain films. Duodenoscopy: An Evis Olympus JF type 180 side view duodenovideoscope was used. The procedure was performed with patients under conscious sedation or short general anesthesia, depending on the individual evaluation of the patients by the anesthetist.
Patients were positioned in the prone position and ERCP performed by an experienced surgical endoscopist. The endoscopist had no access to information from the prior MRCP.
Image Analysis:-Both MRCP and ERCP images were retrospectively interpreted by experienced radiologists and gastroenterologists respectively in a blinded fashion.

Data Collection:-
Qualified radiologists diagnosis and gastroenterogist's intra-operative findings were filled in the pretested questionnaire by the researcher.
Statistical Analysis:-Statistical Package for Social Scientists (SPSS) was used for data analysis. Subsequently , tables, pie charts and graphs were used to present the data. Images, when available were presented for some cases.  In many recent studies, MRCP has been shown to have a diagnostic accuracy comparable to that of ERCP, with the ability to demonstrate small biliary stones and the advantage of not using ionizing radiation [30,33] In our department ,Study of the biliary tract is performed using axial and coronal half-Fourier acquisition single-shot turbo spin-echo T2-weighted images(HASTE) with long TR and MRCP 3D -A navigator triggered heavily T2W1 high resolution 3-dimensional scan which provide a cholangiographic display. The coronal plane is used to provide a cholangiographic display and the axial plane is used to evaluate the pancreatic duct and the distal common bile duct [24] Group II: Stone disease:-In our study MRCP identified stone disease in 67 patients, but confirmed ERCP shows stone disease in 63 patients .Out of 67 patients,3 had cholelithiasis with choledocholithiasis which was accurately detected in MRCP.

Results:-
In our study MRCP had a 94.09% sensitivity and a 94.03 % specificity and accuracy rate of 94 % in detection of stone disease. In a study done by D Hurter et al [16] on 52 patients they found a sensitivity, and specificity of MRCP 87 % and 80 % for the detection of choledocholithiasis. The paper concluded that MRCP due to its non invasive nature, less complications rates and comparable sensitivity to ERCP for detection of biliary duct pathologies, has the potential to replace ERCP as a diagnostic test. This study, however, had a small sample size.
WenChen et al [5]analysed 25 publications which include 2310 with suspected CBD calculus and 738 with CBD stones. Sensitivity and specificity of MRCP in detecting CBD stones were 90% and 95 % respectively.The article concludes that MRCP has high diagnostic accuracy for the detection of choledocholithiasis and MRCP should be the method of choice for suspected cases of CBD stones.
In systematic review done by Kats J et al CBD stones were diagnosed by MRCP in 25 patients confirmed by ERCP in 24 patients.. Sensitivity and specificity of MRCP in detecting stones were 100% and 96% respectively [23].
In another systematic review done by Kenneth M. Vitellas et al [31] MRCP findings are seen correlation with ERCP in detection of CBD calculus and superior to CT or ultrasonography. Sensitivities and specificities for MRCP are 81%-100% and 85%-100% respectively.MRCP offers a number of advantages compared with ERCP, which is the standard of reference for imaging the biliary tract and pancreatic duct.
Unlike ERCP, MRCP is performed rapidly and does not expose patients to ionizing radiation or iodinated contrast material. The major disadvantageof MRCP is that it is entirely diagnostic, and this is in contrast to ERCP, which provides diagnostic information as well as access for therapeutic interventions [14].
Diagnostic pitfalls include air,blood, and signal loss due to surgical clips after cholecystectomy.High signal from adjacent fluid collections, ascites, or edema may also interfere with biliary signal. Arterial pulsatile compression and flow artifacts may mimic filling defects. Coronal and axial T2-weighted images are helpful in avoiding these pitfalls.
CBD calculi which are smaller than the slice thickness used in MRCP sequence can be easily missed. Motion artifacts due to physiological movements like respiration/ peristalsis/ pulsation artifacts also lead to degradation of the image quality, hence, non visualization of small CBD calculi.Differentiation of choledocholithiasis from malignant biliary obstruction has been one of the challenges in MRCP examinations.
Abrupt termination of the bile duct and the absence of typical signs of biliarylithiasis have a high correlation with malignancy (Fig.8 ,9). These features can be visualized through coronal T2-weighted images or by correlation with sequential axial images.Currently, the primary role of ERCP is to provide access to the pancreaticobiliary tract for stone extraction, stent placement, balloon dilatation and other interventions [Fig 8 b]..
ERCP has long been considered the standard of reference for examination of common bile duct stones, but MRCP has proven to be superior to ERCP for the diagnosis of intrahepatic bile duct stones, because ERCP cannot opacify the biliary duct system upstream to a stenosis.

1393
The ability of MRCP to visualize peripheral intrahepatic bile ducts makes this technique well suited to the evaluation of stones in this site.One of our patient with caroli's disease with intrahepatic biliary stones was demonstrated clearly in MRCP images (Fig-4) Many studies on MRCP shows high sensitivity (60% -100%) and specificity (90 -100%) tool for stone disease [32,34].NPV values of MRCP are high, 92.80% -99.84%. [19] So, if MRCP shows negative for common duct stones, one can be confident that stones are not present in most cases and ERCP can be avoided.One of the major benefits of MRCP in the case of suspicious biliary stone is the reduction of ERCP [29].
Pitfall of MRCP is whenever slice thickness were more than 5 mm, there were chances of missing tiny calculi. The false negative occur whenever a calculus is smaller than 5 mm which happened in 4 of our stone disease patients.
Radiologists should be aware that maximum intensity projection reconstructed images can obscure small filling defects and that source images remain indispensable for radiologists in order to make the correct diagnosis False-positive diagnoses may be due to pneumobilia, cystic duct insertion into the bile duct and extrinsic compression by an adjacentartery. [9,19] Kim & colleagues [28] recommended that MRCP can be performed before cholecystectomy in an effort to decrease morbidity associated with undetected choledocholithiasis and reduced the performance of purely diagnostic ERCP.

Group III: Tumours/cysts
Out of 39 patients with tumours, periampullary mass was seen in 11, Klatskin tumour in 10 , distal cholangiocarcinoma in 13 , IPMN--2,carcinoma head of pancreas -1 and caroli's disease-2 .MRCP had a sensitivity ,specificity ,PPV , NPV and total accuracy rates of 92.31% , 95.35%, 85.71, 97.62, and 94.64% respectively for 39 patients with tumours. MRCP helps in evaluating cholangiocarcinoma in general and hilar cholangiocarcinoma in particular.Because MRCP readily depicts ducts proximal to high-grade obstructions that are often not opacified at ERCP, MRCP typically is superior in determining disease extent and resectability [19,26].
Two of our patients with klatskin tumour presented as hilar stricture (Fig 9).5 of our patients with distal cholangiocarcinoma also presented as stricture.Although morphological features of benign and malignant strictures are defined, differentiation may be difficult at times.
It is difficult to distinguish between large stones and cholangiocarcinomas on ERCP, but even in MRCP without contrast we can diagnose stone disease because of the typical hypointense nature of stones on T2-weighted images [23].
The 'double-duct sign' on MRCP is helpful in diagnosing pancreatic carcinoma [27] which was seen in one of our patient with pancreatic head malignancy. In our study, three of the cases were interpreted as periampullary mass and final diagnosis by ERCP made as IPMN.
Communication between the duct and the abnormal cystic structure can be shown with MRI and MRCP .But it was not so possible in our cases and was merely reported as perimpullary mass.

MRCP
reliably detects choledochal cysts and provides details equivalent to ERCP without the risk of complications.Two of our cases were Caroli's disease which was correctly diagnosed by MRCP (Fig 4).
C.Matos et al [34] did a prospective study with the data provided with ERCP and MRCP in 8 patients with choledochal cysts. 7 of the 8 patients had relapsing pancreatitis. Similarity was observed between ERCP and MRCP for defining the anatomic characteristics of the cyst (7 type I cysts, 1 type IV cyst) and the presence of an abnormal pancreaticobiliary junction (PBJ) (6 cases) 1394

Group IV: Others
Most false positive cases in our study were due to detection of benign strictures when they were not present. Arterial pulsation artifacts and defects caused by the crossing of hepatic artery over CBD can result in false interpretation of MRCP images and over diagnosis of biliary duct strictures.In one of our case it was reported as mid CBD stricture,but there was no stricture detected in ERCP (Fig:10) Edematous bile duct secondary to passage of calculi was misinterpreted as a stricture on MRCP images in 2 of our cases Edematous ampulla was mistaken for periampullary nodule/mass in 4 of our cases. Sensitivity for detection of periampullary/ampullary lesions can be increased by doing a conventional post contrast MRI abdomen imaging in addition to MRCP, in which enhancing small periampullary/ampullary lesions are can be easily picked up and will not be confused with non enhancing lesions like sludge ball or edematous ampulla due to passage of calculi. Terminal segment of the bile duct at the ampulla of Vater contains less fluid within its lumen, therefore it becomes difficult to identify a small impacted calculi or a small periampullary nodule, and moreover sometimes the bulging duodenal papilla can mimic a papillary tumor.
MRCP provides accurate delineation of theductal manifestations of chronic pancreatitis, which is of utmost importance in determining disease extent and in planning surgical drainage procedures. One of the patient had calcific pancreatitis which had good correlation with ERCP.
Conclusion:-From this study, it is recommended that MRCP is an efficient diagnostic procedure for detection of presence, level, cause of obstruction and routinely advocated before any intervention is planned.
We conclude that MRCP has been shown to have a wide range of clinical applications, and it has been accepted as an accurate technique for non-invasive imaging of the pancreaticobiliary tract because it offers a number of advantages compared with ERCP, the reference standard for imaging the biliary tract and pancreatic ducts.