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1. Introduction
Evaluation of biliary obstructions is still a common clinical problem. The first problem is often to distinguish intrahepatic and extrahepatic obstruction and to reveal the character of benign or malignant obstruction. Choledocholithiasis and pancreatobiliary malignancies are the most frequent cause of extrahepatic obstruction. In addition, benign strictures, chronic pancreatitis, papillary stenosis, metastatic lymph nodes in liver hilus, and primary sclerosing cholangitis may lead to bile duct obstruction. In most cases, with medical history, physical examination, and clinical and laboratory data, the presence of bile duct obstruction could be determined. However, imaging modalities are needed to fully evaluate the biliary obstruction. With these imaging modalities, the presence, location, and causes of obstruction are determined, and this forms the basis of appropriate treatment plan. Although abdominal USG and CT are the first performed imaging methods, for definite diagnosis, direct cholangiographic methods such as ERCP ve PTC are commonly referred [1–5].
ERCP, since first appearance in 1970, in the evaluation of biliary tree, also protects its therapeutic feature and continues to be gold standard imaging method. But, today, in addition to high diagnostic accuracy of MRCP, as an invasive methods the morbidity and mortality rate of ERCP reaches about 7% and 1%, and this limits the use of ERCP for diagnosis. Also, in the case of hepaticojejunostomy and choledochojejunostomy, ERCP cannot be performed; in the case of gastric resection, retroperitoneal neoplasm, duodenal diverticulum, and ampullary edema, performing ERCP is hard. ERCP, dependent on the practitioner, in some of the cases is failed (3%–18%) or inadequate [6–11].
In MRCP technique, reconstructed 3-dimensional coronal MIP images are similar with cholangiographic images obtained with percutaneous or endoscopic way. In addition, in situations where ERCP and PTC are failed or inadequate, MRCP is an alternative method in which diagnostic images can be obtained without the need for contrast material injection, ionizing radiation, and invasive procedure. In total occlusion, compared to ERCP and PTC, significant advantage of MRCP is, MRCP can demonstrate the upper and lower section of the biliary duct at obstruction and real size of the obstruction. In ERCP and PTC, the use of high pressure contrast material to overcome the obstruction may cause the perception of more dilatation. MRCP reflects the natural state of the channel system [6–13].