| Abstract|| |
Background: Many imaging modalities are available today for the evaluation of patients with suspected biliary obstruction including Ultrasonography, Computed Tomography and Invasive cholangiography. Magnetic resonance cholangiopancreatography is a relatively new technique, which has gained popularity because of its excellent diagnostic capabilities in the evaluation of biliary obstruction.
Aims: The aim of the present study was to compare the diagnostic accuracy of Ultrasonography, Computed Tomography, Endoscopic retrograde cholangiopancreatography/ Percutaneous transhepatic cholangiography and Magnetic resonance cholangiopancreatography in assessing the level and cause of obstruction in patients with obstructive jaundice.
Patients & Methods: One hundred patients with clinical and laboratory features suggestive of biliary obstruction were included in this study. At least two imaging modalities were used in each patient. The level and cause of obstruction was evaluated by each modality. The findings were corroborated with the operative and/or histopathological findings.
Results: Magnetic resonance cholangiopancreatography showed the best results in detecting the cause of obstruction and was second only to Endoscopic retrograde cholangiopancreatography in detecting the level of biliary obstruction.
Conclusions: With its excellent diagnostic capabilities, Magnetic resonance cholangiopancreatography has certainly carved a niche for itself in the non-invasive evaluation of the patient with obstructive jaundice.
Keywords: Magnetic resonance cholangiopancreatography, Ultrasonography, Computed tomography, Biliary obstruction
|How to cite this article:|
Upadhyaya V, Upadhyaya D N, Ansari M A, Shukla V K. Comparative assessment of imaging modalities in biliary obstruction. Indian J Radiol Imaging 2006;16:577-82
|How to cite this URL:|
Upadhyaya V, Upadhyaya D N, Ansari M A, Shukla V K. Comparative assessment of imaging modalities in biliary obstruction. Indian J Radiol Imaging [serial online] 2006 [cited 2013 May 18];16:577-82. Available from: http://www.ijri.org/text.asp?2006/16/4/577/32273
| Introduction|| |
Many imaging modalities are available today for the evaluation of patients with suspected biliary obstruction. Commonly used procedures include Ultrasonography (USG), Computed Tomography (CT), Endoscopic retrograde cholangiopancreatography (ERCP) and Percutaneous transhepatic cholangiography (PTC). The limitations of these modalities have led to the increasing popularity of Magnetic resonance cholangiopancreatography (MRCP). This is a relatively new technique which has generated a lot of interest because of its excellent diagnostic capabilities in the diagnosis of bile duct obstruction and its causes.
The aim of the present study was to compare the diagnostic accuracy of these modalities (USG, ERCP/PTC, CT Scan and MRCP) in assessing the level and cause of obstruction in patients with obstructive jaundice.
| Patients and Methods|| |
One hundred patients with clinical and laboratory features suggestive of biliary obstruction were included in this study which was carried out from January 2001 to March 2003. At least two imaging modalities were used in each patient. In all these cases, USG was the initial screening investigation followed by any one of the remaining three (depending on the clinical desirability, the attending clinician's preference and the financial status of the patient) so that comparisons could be made later on based on the findings of the respective investigations.
The level and cause of obstruction was evaluated by each modality. The levels of obstruction were divided into the following types- intrahepatic, at the porta, suprapancreatic and intrapancreatic common bile duct (CBD). The findings were corroborated with the operative and/or histopathological findings, these were considered the standard of reference of the study.
(A) Ultrasonography: Patients were scanned with real time ultrasound scanners LOGIQ 200 and LOGIQ 400 (Wipro GE) using 3.5 MHz and 5 MHz sector transducers after an overnight fast. The liver, gallbladder, pancreas, intrahepatic and extrahepatic bile ducts were evaluated. Any additional findings namely, ascites, enlarged lymph nodes were also evaluated.
(B) Endoscopic Retrograde Cholangiopancreatography: The patients were kept on overnight fast and prophylactic antibiotics were given. Premedication with intramuscular pentazocine and Diazepam was given. The Olympus TJF 2D side viewing endoscope was used. Buscopan was administered slow intravenously when the second part of duodenum was entered. The papilla of Vater was identified and Urograffin 60% was injected under fluoroscopic control to fill the biliary and pancreatic ducts.
ERCP images were evaluated for evidence of intrahepatic or extrahepatic ductal dilatation, strictures and intraductal abnormalities.
(C) Percutaneous Transhepatic Cholangiography: It was done using flexible Chiba needle (23 G) under fluoroscopic control, after bleeding time, clotting time and prothrombin time were checked. Prophylactic antibiotics were administered before the procedure. The site of insertion of the Chiba needle was the 7th, 8th or 9th intercostal space (site of maximum liver dullness on percussion), in the mid-axillary line. After removal of the stylet, contrast (60%Urograffin) was injected. PTC was analysed for evidence of intrahepatic or extrahepatic ductal dilatation, strictures or intraductal abnormalities.
(D) Computed Tomography: CT Scan was done on Wipro GE Sytec 4000i machine. Both plain and contrast enhanced CT was performed by taking 10 mm contiguous axial sections from the domes of the diaphragm to the iliac crests after bowel opacification with oral contrast. Further 5mm and/or 3mm sections were taken in the region of interest. The liver, gall bladder, pancreas, intrahepatic and extrahepatic ductal systems were evaluated. Any additional findings were also noted.
(E) Magnetic Resonance Cholangiopancreatography: MRCP was done using commercially available software in a clinical MR scanner. A T2 weighted fast spin echo (FSE) sequence was performed on the axial plane to locate the dilated biliary and pancreatic ducts. For MRCP imaging, a three dimensional, fat suppressed, heavily T2 weighted FSE sequence with multislab acquisition mode was used. Slice thickness was 1 cm with a 37-inch field of view and 256x192 matrix. All sequences were performed during breath holding (10 seconds). 3D reconstruction algorithms were applied to produce images of the entire biliary tree and pancreatic duct. No contrast or anti-peristaltic drugs were used. Any evidence of intrahepatic, extrahepatic or pancreatic ductal dilatation, strictures or intra-ductal abnormalities was noted. Gall bladder was also assessed.
| Results|| |
The study included 100 patients in which 53 were females and 47 were males. Mean age of presentation was 48.14 ± 12.55 years (range 15-72 years). Most of the patients were in the 5th decade of life. Presenting complaints included yellowish discoloration of eyes/urine, pain abdomen, abdominal lump, itching, fever, vomiting, anorexia and weight loss. History of previous surgical intervention was present in 15 patients. Examination findings included icterus, hepatomegaly, palpable gall bladder, ascites, splenomegaly and axillary lymphadenopathy. The levels and causes of obstruction in this study have been shown in [Table - 1],[Table - 2].
(1) USG: Ultrasound could not correctly detect the level in one case in which obstruction was intrahepatic. All cases of obstruction at the porta were identified. At the suprapancreatic level, USG diagnosis was inconclusive in 3 and incorrect in 4. At the intrapancreatic level, it was inconclusive in 4 and incorrect in 5. USG was able to identify all cases of choledochal cysts, carcinoma gall bladder, lymphadenopathy leading to biliary obstruction and a case of hepatic hydatid cyst having ruptured into the biliary tree. Identification of CBD calculi was possible in 61.30%, benign CBD stricture in 66.67%, cholangiocarcinoma in 88.89% [Figure - 1], carcinoma head of pancreas in 77.78% and periampullary carcinoma in 80%.
(2) ERCP/PTC: ERCP was done in 42 cases while PTC was used to evaluate 6 cases. These detected the level in all cases in which obstruction was intrahepatic, at the porta and suprapancreatic. The level was incorrectly diagnosed in 2 cases in which obstruction was at the intrapancreatic level. ERCP/PTC could detect all cases of benign CBD stricture, choledochal cyst, sclerosing cholangitis and periampullary carcinoma. 92.5% accuracy for the detection of choledocholithiasis was noted [Figure - 2]. In cases of carcinoma gall bladder, lymphadenopathy and daughter cysts in the biliary tree leading to obstruction, it could only detect the level but was unable to identify the cause.
(3) CT Scan: It identified correctly all cases of obstruction at the porta and suprapancreatic levels but at intrapancreatic level it was inconclusive in 1 case and gave the incorrect diagnosis in 3 cases. Most of the cases evaluated by CT in our setup were those of suspected malignant obstruction. Of these, CT could detect all cases of carcinoma gall bladder, periampullary carcinoma [Figure - 3] and cholangiocarcinoma. All except one case of carcinoma head pancreas was detected. Only one case of choledocholithiasis was evaluated by CT Scan and the calculus was not picked up. One of two cases of benign CBD stricture was correctly identified. One case of enlarged peripancreatic lymph nodes was mistaken for a mass lesion in the head of the pancreas.
(4) MRCP: MRCP could detect the level in all cases of obstruction at the porta and suprapancreatic levels and at the intrapancreatic level, all cases except one were correctly identified. Here, a calculus at the distal end was causing minimal proximal dilatation which had been missed. MRCP was able to correctly diagnose all cases of benign CBD stricture, choledochal cyst, cholangiocarcinoma [Figure - 4] and periampullary carcinoma. It could not detect one case each of choledocholithiasis, carcinoma head of pancreas and carcinoma gall bladder.
The overall diagnostic accuracy for detection of level of obstruction was maximum for ERCP/PTC (95.83%), followed by MRCP (95.45%), CT (85.71%) and USG (83.50%).For assessing the cause, MRCP had the highest accuracy (87.5%), followed by CT Scan (85.71%), USG (77%) and ERCP/PTC (75%). (Table 3)
| Discussion|| |
When evaluating a case of obstructive jaundice, the aim of the radiologist is to confirm the presence of obstruction and to identify its location, extent and probable cause. USG has traditionally been used as the initial screening procedure because of its many advantages, which include its ready availability, its cost effectiveness, and no requirement of contrast material and lack of ionizing radiation. However, although it is well suited to visualize the Common Hepatic Duct (CHD) and proximal CBD, one of its major limitations is assessment of the distal CBD and pancreas, which are often obscured by overlying bowel gas in about 30-50% of the patients ,. Obesity is also an important limiting factor.
In the present study, USG missed many cases of CBD calculi. Other cases missed by USG were stricture, sclerosing cholangitis and cases of small mass lesions involving the head of pancreas. Many of these were due to inadequate visualization of the entire CBD due to bowel gas and obesity. Besides this, although majority of cases with choledocholithiasis demonstrate an enlarged CBD, in some patients the bile ducts are not dilated which makes sonographic detection difficult since bile does not surround the stone.
In sclerosing cholangitis, it has been noted that ducts may appear falsely normal on USG and cholangiographic comparison reveals multiple strictures and pruning, but no dilatation .
USG was able to identify the level in 83.50% and cause in 77% cases in the study. Other studies have reported a variation of 27%-95% in detecting level and 18%-85% in detecting the cause of obstruction ,,,,.
If the ultrasound is technically unsatisfactory, findings are not clear or staging of malignancies is required, then CT Scan is performed before more invasive procedures are considered. In recent years, the improved spatial resolution and contrast sensitivity available with current CT Scanners has increased their capability for evaluating the biliary system. However, it requires the use of I.V. contrast and exposes the patient to ionizing radiation.
In our study, CT showed good results in detecting the malignant causes of obstruction. However, one case of peripancreatic lymphadenopathy was incorrectly diagnosed as mass in the head of the pancreas. Among benign causes, it misinterpreted a case of benign CBD stricture as cholangiocarcinoma and failed to detect a case of CBD calculus. Usually only 20% duct stones are of homogenous high attenuation on CT  and ~ 50% of stones are of faint attenuation, slightly greater than the surrounding bile and often similar to that of the adjacent soft tissues of the pancreas. Hence, detection of these stones is difficult. The reported sensitivity of CT in detecting common duct stones varies from 45%-90% ,,,.
CT was able to detect both the level and the cause in 85.71% of the cases. Other studies have reported a variation of 80%-97% in detecting the level and 63%-94% in detecting the cause of obstruction ,,,.
The advent of ERCP dramatically changed the diagnosis and treatment of biliary and pancreatic diseases. It currently remains the standard of reference for imaging the bile duct and the pancreatic duct. PTC is particularly useful when proximal pathology is suspected based on previous screening studies. A major drawback of these procedures is their invasive nature which may result in complications. ERCP is associated with a morbidity of 1%-7%. ,,,,.
In the present study, ERCP/PTC were able to identify obstruction at all levels except for two cases where small calculi in the intrapancreatic CBD causing minimal proximal dilatation escaped detection. In cases of carcinoma gall bladder, lymphadenopathy and daughter cysts leading to obstruction, it could only detect the level but failed to identify the cause. ERCP/PTC could detect the level in 95.83% but cause in only 75% cases in the study.
MRCP is a rapidly developing non-invasive modality for evaluation of pancreatico-biliary diseases. Its development has been one of the greatest successes of modern radiology. Biliary obstruction represents one of the main indications for MRCP. It is able to produce highly accurate cholangiographic images, similar to that at direct cholangiography and yet combine the patient comfort and safety associated with ultrasound. Complete mapping of the ductal system, non-invasiveness, no requirement of intra-venous contrast and lack of exposure to ionizing radiation are some of its important features. Its inability to offer therapeutic intervention is its only drawback when compared to ERCP ,,.
In our study, MRCP was able to detect the level of obstruction in all cases except one, where the duct was minimally dilated due to a small calculus in the distal CBD which was not detected. This difficulty in detecting small stones in a non-dilated or minimally dilated duct has been reported by others ,. Besides this, it failed to detect a case of small gall bladder mass and misinterpreted a pancreatic head mass as cholangiocarcinoma.
MRCP was able to detect the level of obstruction in 95.45% and the cause in 87.50% cases. Other studies have also reported very good results with ability to detect the level ranging from 85% to 100% ,,,. In this study MRCP had the best results in detecting the level and cause of biliary obstruction. With its excellent diagnostic capabilities, it has certainly carved a niche for itself in the non-invasive evaluation of the patient with obstructive jaundice.
| References|| |
|1.||Ferruci JT, Jr. Body Ultrasonography. N Engl J Med 1979; 300:590-602. |
|2.||Taylor KJW, Rosenfield AT, de Graaff CS. Anatomy and pathology of the biliary tree as demonstrated by ultrasound. Clinics in Diagnostic Ultrasound 1979; 1:103-21. |
|3.||Majoie CB, Smits NJ, Phoa SS, Reeders JW, Jansen PL. Primary sclerosing cholangitis : sonographic findings. Abdom Imag 1995; 20: 109-12. |
|4.||Malini S, Sabel J. Ultrasonography in obstructive jaundice. Radiology 1977; 123:429-33. [PUBMED] |
|5.||Baron R L, Stanley RJ, Lee JKT, Koehler RE, Melson GE, Balfe DM et al. A prospective comparison of the evaluation of biliary obstruction using computed tomography and ultrasonography. Radiology 1982; 145: 91-8. |
|6.||Khandelwal KC, Merchant NH, Udani RJ, Joshi MS, Parikh VP, G Pradipkumar et al. Role of ultrasonography in obstructive jaundice. Ind J Radiol Imag 1991; 1: 17-20. |
|7.||Zagoni T, Benko Z, Telegdy L, Antony A, Keleti G, Peter Z. Diagnostic value of abdominal ultasonography and endoscopic retrograde cholangiopamcreatography in obstructive jaundice. Orv Hetil 1995; 136 (28): 1483-6. |
|8.||Kumar M, Prashad R, Kumar A, Sharma R, Acharya SK, Chattopadhyay TK. Relative merits of ultrasonography, computed tomography and cholangiography in patients of surgical obstructive jaundice. Hepatogastroenterology 1998; 45(24): 2027-32. |
|9.||Baron RL. Common bile duct stones: re-assessment of criteria for CT diagnosis. Radiology 1987; 162: 419-24. [PUBMED] |
|10.||Jeffrey RB Jr, Federle MP, Laing FC, Wall S, Rego J, Moss AA. Computed tomography of choledocholithiasis. AJR 1983; 140: 1179-83. |
|11.||Pedrosa CS, Casanova R, Lezana AH, Fernandez MC. Computed tomography in obstructive jaundice. Part II: The cause of obstruction. Radiology 1981;139:635-45. |
|12.||Pedrosa CS, Casanova R, Rodriguez R. Computed tomography in obstructive jaundice. Part I: The level of obstruction. Radiology 1981; 139:635-45. |
|13.||Bilbao MK, Dotter CT, Lee TG, Katon RM. Complications of endoscopic retrograde cholangiopancreatography. A study of 10,000 cases. Gastroenterology 1976; 70: 314-20. |
|14.||Hamilton I, Lintott DJ, Rothwell J, Axon ATR. Acute pancreatitis following Endoscopic retrograde cholangiopancreatography. Clin Radiol 1983; 34: 543-6. |
|15.||Thoeni RF, Fel SC, Goldberg HI.CT detection of asymptomatic pancreatitis following ERCP. Gastrointest Radiol 1990; 15: 291-5. |
|16.||Lo SK, Chen J. The role of ERCP in choledocholithiasis. In MR cholangiography in symptomatic gallstones: diagnostic accuracy according to clinical risk group. Kim JH, Kim MJ, Park SI, Chung JJ, Song SY, Kim KS et al. Radiology 2002; 224:410-16. |
|17.||Masci E, Toti G, Mariani A, Curioni S, Lomazzi A, Dinelli M, et al. Complications of diagnostic and therapeutic ERCP: A prospective multicenter study. In MR cholangiopancreatography. Fulcher AS, Turner MA. Radiol Clin N Am 2002;40:1363-76. |
|18.||Soto JA, Yucel EK, Barish MA, Chuttani R, Ferrucci JT. MR cholangio-pancreatography after unsuccessful or incomplete ERCP. Radiology 1996; 199:91-8. [PUBMED] |
|19.||Soto JA, Barish MA, Yucel EK, Siegenberg D, Ferrucci JT, Chuttani R. Magnetic resonance cholangiography : comparison with endoscopic retrograde cholangio-pancreatography. Gastroenterology 1996; 110:589-97. [PUBMED] [FULLTEXT]|
|20.||Magnuson TH, Bender JS, Duncan MD, Ahrendt SA, Harmon JW, Regan F. Utility of magnetic resonance cholangiography in the evaluation of biliary obstruction. J Am Coll Surg 1999; 189(1): 63-71. |
|21.||Varghese JC, Liddell RP, Farrell MA, Murray FE, Osborne DH, Lee MJ. Diagnostic accuracy of magnetic resonance cholangiopancreatography and ultrasound compared with direct cholangiography in the detection of choledocholithiasis. Clin Radiol 2000; 55: 25-35. [PUBMED] [FULLTEXT]|
|22.||Regan F, Smith D, Khazan R, Bohlman M, Schultze-Haakh H, Campion J, et al. MR cholangiography in biliary obstruction using half-Fourier acquisition. J Comput Assist Tomogr 1996; 20(4): 627-32. |
|23.||Georgopoulos SK, Schwartz LH, Jarnagin WR, Gerdes H, Breite I, Fong Y,et al. Comparison of magnetic resonance and endoscopic retrograde cholangio-pancreatography in malignant pancreaticobiliary obstruction. Arch Surg 1999; 134: 1002-7. [PUBMED] [FULLTEXT]|
|24.||Adamek HE, Breer H, Karschkes T, Albert J, Riemann JF. Magnetic resonance imaging in gastroenterology: Time to say good-bye to all that endoscopy? Endoscopy 2000; 32(5): 406-10. |
V K Shukla
Department of General Surgery, Institute of Medical Sciences, Banaras Hindu University, Varanasi - 221 005
[Figure - 1], [Figure - 2], [Figure - 3], [Figure - 4]
[Table - 1], [Table - 2], [Table - 3]