A Nurman 150 * Department of Internal Medicine, Medical Faculty, Trisakti University Correspondence Dr. A. Nurman, Ph.D, Sp.PD, KGEH Department of Internal Medicine, Medical Faculty, Trisakti University Jl.Kyai Tapa 260-Grogol Jakarta 11440. Phone: 021-5672731 ext. 2707 Email: nurman_achmad@yahoo.com Univ Med 2008; 27: 150-6 Magnetic resonance cholangiopancreatography: practical experience in 30 subjects October-December, 2008October-December, 2008October-December, 2008October-December, 2008October-December, 2008 Vol.27 - No.4 Vol.27 - No.4 Vol.27 - No.4 Vol.27 - No.4 Vol.27 - No.4 ABSTRACT UNIVERSA MEDICINA A. Nurman* Magnetic resonance cholangiopancreatography (MRCP) is a noninvasive method of imaging the biliary and pancreatic ducts. No special patient preparation is required but the usual contraindications to MR scanning apply. The diagnostic performance of MRCP in most biliary tract diseases is similar to that of more invasive techniques of direct cholangiography such as endoscopic retrograde cholangiopancreatography (ERCP). The objectives of this study were to investigate the diagnostic efficacy of MRCP in patients with abdominal pain with lesser likelihood of having choledochal stone and to determine whether use of MRCP could eliminate the need for purely diagnostic endoscopic retrograde cholangio-pancreatography (ERCP). A total of 30 patients with suspected biliopancreatic pathology from several hospital was studied retrospectiely between January 2007 and December 2008 in Jakarta. The sensitivity and specificity of MRCP was 92.59% (95% Confidence Interval, 74.25 - 98.71%) and 66.67% (95% Confidence Interval, 12.53 – 98.23%), respectively. The positive predictive value of MRCP for all biliary pathology was 96.15% (95% Confidence Interval, 78.42 – 99.79%) The negative predictive value of MRCP was 50.00% (95% Confidence Interval, 9.19 – 90.81%). MRCP seems to be effective in diagnosing patients with abdominal pain with lesser likelihood of having choledochal stone. Keywords : Magnetic resonance cholangiopancreatography, biliary, pancreatic INTRODUCTION Cholangiography is often used in patients suspected of having biliary tract and pancreatic disorders to uncover the exact diagnoses of the disease. Endoscopic retrograde cholangio- pancreatography (ERCP) was considered the golden standard method for the diagnosis of these diseases, but carries a potential risk of c o m p l i c a t i o n s , i n c l u d i n g p a n c r e a t i t i s , haemorrhage, particularly from sphyncterotomy s i t e s , a n d d u o d e n a l p e r f o r a t i o n . ( 1 - 3 ) T h e procedure may not always be successful. ERCP is highly sensitive and specific, but is invasive 151 Nurman Cholangiopancreatography and inconvenient for the patient, requiring sedation and contrast (with minimal risk of a l l e r g i c r e a c t i o n ) , a n d a s s o c i a t e d w i t h significant morbidity (5–10%) and mortality ( < 1 % ) . ( 4 ) A t p r e s e n t m a g n e t i c r e s o n a n c e cholangiopancreatography (MRCP) begins to r e p l a c e E R C P a s a s c r e e n i n g m e t h o d f o r p a t i e n t s s u s p e c t e d o f h a v i n g b i l i a r y obstruction due to biliary calculus. MRCP was first described by Wallner et al. in 1991.(5) The use of single-shot fast sequences in a breath- hold period provides heavily T2-weighted sequences allowing thick slices and avoiding secondary reconstructions and artifacts. This t e c h n o l o g i c d e v e l o p m e n t h a s l e d t o i t s widespread use.(6,7) As a result, MRCP is an easy, quick, noninvasive test accessible to all patients who do not have contraindications. MRCP is also useful in patients with failed or incomplete ERCP. There is also a role for MRCP in the e v a l u a t i o n o f p a t i e n t s p r i o r t o s u r g i c a l procedures, to plan what kind of surgical p r o c e d u r e w i l l b e u n d e r t a k e n , a n d t o demonstrate the alteration the bile ducts after biliodigestive surgery. MRCP is non-invasive for studying the biliary tree and requires no ionizing radiation or iodinated contrast. It gives high-resolution projectional images of the common bile duct (CBD) with no known hazards in the absence of incompatible foreign bodies. The aim of this study was to investigate the diagnostic validity of MRCP in assessing symptomatic patients suspected of having hepatopancreaticobiliary diseases. METHODS Study design This was a retrospective cohort study of a consecutive group of patients who underwent MRCP during a period of 2 years (2007 – 2008). Patients Patients were identified from several hospitals in Jakarta over a total period of 24- m o n t h s . C o l l e c t e d d a t a i n c l u d e d c l i n i c a l presentation, liver function tests, abdominal ultrasound, and MRCP findings, and procedure- related complications. MRCP Technique All MRCP images were obtained by using a 1.5-T superconducting magnet with a gradient s t r e n g t h o f 5 0 m T / m ( G e n e r a l E l e c t r i c , Milwaukee, Wis, USA), with a body-phased array coil through the liver and pancreas. The mean time of the MRCP examination with e v a l u a t i o n w a s 1 5 m i n u t e s . M R C P w a s performed by using thick slab single shot fast spin echo (SSFSE), with selective fat saturation. The first sequence afforded a single image with a dimension of 40 mm, and exhibited the following parameters: TR/TE/FA (2800/1100/ 180), matrix 240 x 256, field of view of 300 mm, and acquisition time of 7 seconds. The second sequence yielded 13 contiguous 5-mm slices and presented the following parameters: TR/TE/FA (10.92/87/180), matrix 256 x 224, field of view of 280 mm, and acquisition time of 19 seconds. Statistical analysis The data were entered in a Microsoft Excel database. The results of MRCP were analysed a g a i n s t l a b o r a t o r y f i n d i n g s , u l t r a s o u n d examinations and the final diagnoses for the entire study population. Sensitivity, specificity, positive and negative predictive values were individually calculated in the usual manner. RESULTS Thirty patients underwent MRCP and were eligible for further evaluation during the 24- month period studied, of whom 15 (50%) were 152 Univ Med Vol.27 - No.4 female and 15 (50%) were male with median a g e o f 5 6 y e a r s ( r a n g e 2 6 – 7 5 y e a r s ) . Abdominal pain was the predominant symptom at presentation (90%) with 5 subjects having associated jaundice. Pancreatitis (n=6) and c h o l a n g i t i s ( n = 2 2 ) w e r e t h e o t h e r m o s t common features. Ultrasound U l t r a s o u n d s c a n o f t h e h e p a t o b i l i a r y system was the primary investigation in 30 patients, of whom 10 (33.3%) showed evidence of cholelithiasis and 2 (6.7%) of biliary sludge. Other abnormalities seen were dilated CBD, liver cirrhosis (LC), dilated gall bladder (GB), dilated extrahepatic bile duct (EHBD), dilated intrahepatic bile duct (IHBD), and choledochal cyst in fifteen patients. No abnormality was observed in 3 patients. MRCP O f 3 0 p a t i e n t s r e f e r r e d , M R C P w a s s u c c e s s f u l l y p e r f o r m e d i n a l l ( 1 0 0 . 0 % ) patients. Final diagnosis The final diagnoses of the patients were: i) choledochal cysts in 3 patients (10%); ii) c h o l e d o c h a l s t o n e / s l u d g e i n 5 p a t i e n t s (16.7%); iii) gall bladder stone in 8 patients (26.7%) (Figure 1); iv) intrahepatic stone 1 patient (3.3%);v) distal obstruction of the common bile duct due to mass in 7 cases (23.3%), and follow up CT scan/MRI revealed c a r c i n o m a o f t h e p a n c r e a s i n 5 p a t i e n t s (16,7%) and carcinoma of the papilla in 2 patients (6.7%); vi) stricture of the common bile duct post laparoscopic cholecystectomy in 1 patient (3.3%); viii) Klatskin tumor in 1 patient (Figure 2); (3,3%); viii) post hepatico- jejunostomy operation in choledochal cyst in 1 patient (3%); and ix) no abnormality in 3 (10%) patients (Figure 3). Figure 3. Normal MRCP Figure 2. Klatskin tumor Figure 1. MRCP in gall bladder stone 153 Nurman Cholangiopancreatography Accuracy of MRCP A t o t a l o f 3 0 p a t i e n t s w i t h c o m p l e t e comparative data were considered for detailed analysis. The sensitivity and specificity of MRCP was 92.59% (95% Confidence Interval, 74.25 – 98.71%) and 66.67% (95% Confidence Interval, 12.53 – 98.23%), respectively. The positive predictive value (having the disease) of MRCP for all biliary pathology was 96.15% (95% Confidence Interval, 78.42 – 99.79%) The negative predictive value of MRCP (truly disease free) was 50.00% (95% Confidence Interval, 9.19 – 90.81%) (Table 1). T h e r e w e r e 1 8 g a l l b l a d d e r s t o n e s , choledochal cyst, and common bile duct sludge among various positive diagnoses, based on all investigations (Table 2). DISCUSSION MRCP is a noninvasive method of imaging the biliary and pancreatic ducts and until now this technique continues to be improved. The basic principle underlying MRCP is that body fluids, such as bile and pancreatic secretions, h a v e h i g h s i g n a l i n t e n s i t y i n h e a v i l y T 2 - weighted magnetic resonance (i.e. they appear white), whereas background tissues such as the surrounding liver and flowing blood generate little signal (i.e. they appear dark). As a result of this combination of imaging characteristics, MRCP provides optimal contrast between the hyperintense signal of the bile and pancreatic secretions and the hypointense signal of the Table 1. Sensitivity and specificity of MRCP as evidenced against gold standard procedures Final diagnosis MRCP Positive Negative Total Positive Negative 25 2 1 2 26 4 Total 27 3 30 background tissue (solid organs), while blood vessels have no measurable signal. On these images the intrinsic fluids of the the biliary and pancreatic ducts make up the cholangiogram and pancreatogram. At present, ERCP is considered the gold standard method for the diagnosis of ductal c a l c u l u s , b u t c a r r i e s a p o t e n t i a l r i s k o f complications, including pancreatitis, and bleeding, particularly from sphincterotomy sites and duodenal perforation.(8) Most of the patients presented with the chief complaint of right upper quadrant or epigastric pain, with or without jaundice, or were jaundiced patients w i t h o r w i t h o u t u p p e r a b d o m i n a l p a i n . Abdominal ultrasound (US) and CT scan were mostly used as an initial evaluation in these patients. In these cases the roadmap of the biliary tract and the pancreatic duct is needed. The next examination will be the choice of to decide on ERCP or MRCP.(9) Diagnosis Number True positive Gall bladder stone Choledochal cyst Carcinoma pancreas Obstructed hepatojejunistomy False negative Common bile duct sludge Gall bladder stone 13 3 7 2 1 1 Total 27 Table 2. Different diagnoses among true positive and false negative of results of MRCP 154 Univ Med Vol.27 - No.4 If the compaint was due to biliary disease, i.e. choledochal stone or stricture/dilatation obstruction of the bile or pancreatic disease, it was easy to find the dilatation of the bile duct on abdominal US/CT. In these cases ERCP will be the choice because it can be followed by therapeutic endoscopy i.e. sphincterotomy and s t o n e e x t r a c t i o n , s t e n t / n a s o b i l i a r y t u b e installment etc.The choice of imaging will be E R C P w h e n i t i s a s s u m e d t h a t i t w i l l b e followed by therapeutic endoscopy.(10) If the complaints were due parenchymal liver disease, there would be no dilatation nor abnormality of the biliary tract or pancreatic duct, such that it will not be followed by therapeutic endoscopy, thus MRCP would be the choice. MRCP would be chosen when the likelihood for therapeutic intervention were l e s s , h e n c e u n n e c e s s a r y E R C P i s h e r e b y avoided. This study showed that the sensitivity and positive predictive value of MRCP for the diagnosis is extremely high, being 92.59% (95% Confidence Interval, 74.25 - 98.71%) and 96.15% (95% Confidence Interval, 78.42 – 99.79%) respectively. A prospective study in Spain found that MRCP had a sensitivity of 91% and positive predictive value of 89%, similar to our study.(11) But the specificity of 66.67% (95% Confidence Interval, 12.53 – 98.23%) was lower than that obtained in the study by Calco et al (84%). The negative predictive value in the present study was also low (50.0%; 95% Confidence Interval, 9.19 – 90.81%), compared to the Spanish study (88%). No special patient preparation is required, but the usual contraindications to MR scanning apply.(1,12) Patients with cardiac pacemakers, neurostimulators, or ferromagnetic aneurysm clips are excluded. The examination is usually performed after the patient has fasted for several hours to allow filling of the gallbladder and e m p t y i n g o f t h e s t o m a c h . N o s e d a t i o n i s required, and no hospitalization is needed. In s o m e p a t i e n t s c l a u s t r o p h o b i a m i g h t b e a p r o b l e m . ( 1 3 ) O r a l c o n t r a s t a g e n t s a r e n o t administered, no intravenous contrast agents are needed, and there is no radiation exposure.(10) MRCP is an ideal imaging method for patients with allergies to iodide/iodine-based contrast, or those with a general history of atopy, and f o r p r e v e n t i n g t h e o c c u r e n c e o f c o n t r a s t nephropathy.(10) In this study as in that from a different center,(10) the procedures were performed with the indication as screening in patients with right u p p e r q u a d r a n t / e p i g a s t r i c p a i n w i t h n o dilatation/equivocal dilatation of the common bile duct with/without gall bladder stone, or with normal/disturbed liver function test, with the goal to avoid unnecessary ERCP. In acute pancreatitis ERCP is avoided, because ERCP carries potential risk of complication including p a n c r e a t i t i s , b l e e d i n g p a r t i c u l a r l y f r o m s p h i n c t e r o t o m y s i t e s , a n d d u o d e n a l perforation.(14) If dilatation of bile duct was found then ERCP would be the choice and subsequent sphincterotomy and extraction of choledochal stone will be retrogradely performed. MRCP is an alternative to diagnostic ERCP for the imaging of the bile tree and the pancreatic ducts. A major feature of MRCP is that is not a therapeutic procedure, while in contrast ERCP is used for both diagnosis and treatment.(1) MRCP is the only modality that allows imaging of these ducts in the basal state, as extrinsic contrast agents are not used,(10) hence more accurately displays the native calibre of the duct than ERCP. Because of its noninvasive nature, it does not carry the risks and complications a s s o c i a t e d w i t h E R C P a n d P e r c u t a e o u s Transhepatic Cholangiography (PTC).(1) In MRCP there is no morbidity nor mortality like in ERCP/PTC. MRCP is particularly useful w h e r e E R C P i s d i ff i c u l t , h a z a r d o u s o r impossible(12) to perform, ie in patients with 155 Nurman Cholangiopancreatography anatomical/structural abnormalities, such as gastroenteric anastomosis or gastrojejunostomy. In this series MRCP was performed in a patient a f t e r h e p a t i c o j e j u n o s t o m y b e c a u s e i t w a s impossible to perform ERCP in this setting. In some situations MRCP maybe preferable to ERCP, such as situations where MRCP may give more informations than ERCP (eg hilar b i l i a r y s t r i c t u r e s , l e s i o n s a s s o c i a t e d w i t h complete pancreatic or biliary duct cut-off). MRCP is a non invasive tool that is suitable in p a t i e n t s s u s p e c t e d o f h a v i n g t o h a v e pancreaticobiliary disease, where there is no l i k e l i h o o d o r l i t t l e p o s s i b i l i t y t o p e r f o r m t h e r a p e u t i c i n t e r v e n t i o n , e g p a t i e n t s w i t h asymptomatic cholelithiasis without clinical evidence of clinical bile duct disease, like the presence of jaundice and abnormalities of liver fuction tests. MRCP is a non invasive imaging technique, seems to be highly accurate for the presense of o b s t r u c t i o n , ( 1 5 , 1 6 ) b u t i s l e s s a c c u r a t e a t differentiating malignant from benign causes of obstruction.(10) It is almost as good as ERCP in the diagnoses of common bile duct stones (CBDS), although the ability of MR to detect s m a l l s t o n e s i n n o n d i l a t e d d u c t s m a y b e limited.(10,17) MRCP may be considered as a new gold standard for the investigation of CBDS and permits reservation of ERCP to patients with a high probability of therapeutic intervention.(10) The Eropean Association of Laparoscopic Surgeons consider MRCP to be the standard diagnostic test for patients with an intermediate p r o b a b i l i t y o f C B D S . 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