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Primary sclerosing cholangitis: Evaluation with MR cholangiopancreatography (MRCP)
The Egyptian Journal of Radiology and Nuclear Medicine (2011) 42, 351–356
Egyptian Society of Radiology and Nuclear Medicine
The Egyptian Journal of Radiology and Nuclear Medicine www.elsevier.com/locate/ejrnm www.sciencedirect.com
ORIGINAL ARTICLE
Primary sclerosing cholangitis: Evaluation with MR cholangiopancreatography (MRCP) Mohamed Eid a, Khaled Aly Matrawy a b
b,*
Department of Radiodiagnosis, Faculty of Medicine, Alexandria University, Egypt Department of Radiodiagnosis, Medical Research Institute, Alexandria University, Egypt
Received 5 September 2011; accepted 30 September 2011 Available online 16 November 2011
KEYWORDS Magnetic resonance cholangiopancreatography; Primary sclerosing cholangitis
Abstract Objective: To highlight the diagnostic features of PSC on MRCP studies in patients with biochemical cholestasis. Conclusion: MRCP enables accurate detection and localization of PSC and in defining the extent of disease. Ó 2011 Egyptian Society of Radiology and Nuclear Medicine. Production and hosting by Elsevier B.V. All rights reserved.
1. Introduction Primary sclerosing cholangitis (PSC) is an idiopathic, chronic cholestatic disease of possible autoimmune origin that is characterized by diffuse cholangitis and progressive fibrosis of the extra- and intrahepatic bile ducts. PSC typically manifests in Abbreviations: MRCP, magnetic resonance cholangiopancreatography; PSC, primary sclerosing cholangitis * Corresponding author. Tel.: +20 123377159; fax: +20 32466656. E-mail address: [email protected] (K.A. Matrawy). 0378-603X Ó 2011 Egyptian Society of Radiology and Nuclear Medicine. Production and hosting by Elsevier B.V. All rights reserved. Peer review under responsibility of Egyptian Society of Radiology and Nuclear Medicine. doi:10.1016/j.ejrnm.2011.09.007
Production and hosting by Elsevier
the fourth or fifth decade. There is a distinct male preponderance (1). The classic imaging findings of PSC include multifocal strictures, ectasias, ductal wall thickening, and irregular beading of the intra- and extrahepatic bile ducts (2,3). A strong association with the inflammatory bowel disease, especially ulcerative colitis, is noted (70% of cases) (4). The rate of progression is unpredictable, with up to 49% of symptomatic patients eventually developing biliary cirrhosis and liver failure. Treatment is usually palliative and includes medical therapy with orally administered agents such as ursodiol (ursodeoxycholic acid) or endoscopic or percutaneous mechanical dilation of dominant strictures. Currently, orthotopic liver transplantation is the only curative therapy for PSC (5). The chronic inflammation of PSC predisposes to the development of cholangiocarcinoma (CCA), the most dreaded complication of PSC (1). CCA develops in 10% of patients with PSC. The incidence of CCA in patients with PSC is 0.6–1.5% per year, with the highest incidence in the first 2 years after diagnosis of PSC. Patients with PSC develop CCA approximately 2–3 decades earlier than patients without PSC (6).
352 Cholangiographic features that suggest cholangiocarcinoma include irregular high grade ductal narrowing with shouldered margins, rapid progression of strictures, marked ductal dilatation proximal to strictures, and polypoid lesions. Secondary sclerosing and nonsclerosing processes can mimic primary sclerosing cholangitis at cholangiography (7). In a small percentage of patients, focal segmental involvement of PSC manifesting as a focal short-segment stricture without the classic imaging findings makes it difficult to distinguish from the periductal-infiltrating type of CCA (8). Secondary sclerosing cholangitis syndromes are a heterogeneous group of chronic cholestatic disorders that are morphologically similar to PSC but result from distinct pathologic processes. The wide spectrum of secondary sclerosing cholangitis entities includes recurrent pyogenic cholangitis, acquired immunodeficiency syndrome (AIDS) cholangiopathy, autoimmune pancreatitis, hepatic inflammatory pseudotumor, eosinophilic cholangitis, portal biliopathy, and ischemic cholangiopathy (9). Although percutaneous biopsy specimens may demonstrate findings that are suggestive of PSC, such as numerous eosinophils in the periportal parenchyma, periductal fibrosis, and ductopenia, there is no histologic feature that is pathognomonic of PSC (10). Likewise, the results of biochemical analysis are nonspecific; they reveal elevated alkaline phosphatase and/or bilirubin levels, which can be seen in a variety of cholestatic processes in addition to PSC (11). The diagnosis of PSC is usually established with endoscopic retrograde cholangiopancreatography (ERCP) and less often with percutaneous transhepatic cholangiography; these studies demonstrate multiple segmental strictures, mural irregularities, and diverticula that are characteristic of PSC. Although ERCP and percutaneous transhepatic cholangiography provide highquality images of the biliary tract, both are invasive procedures that are associated with risks of sepsis and hemorrhage. ERCP is also associated with risks of pancreatitis and bowel perforation and has been shown to result in progression of cholestasis in patients with advanced PSC (12). Magnetic resonance cholangiopancreatography (MRCP) is a relatively new, noninvasive cholangiographic technique that is comparable with invasive endoscopic retrograde cholangiopancreatography (ERCP) in the detection and characterization of extrahepatic bile duct abnormalities. The role of MRCP in evaluation of the intrahepatic bile ducts, especially in patients with primary or secondary sclerosing cholangitis, is under investigation (7). Although ERCP is still the standard of reference for imaging the pancreaticobiliary system, MRCP has some advantages over ERCP. Specifically, MRCP (a) is noninvasive; (b) is cheaper; (c) uses no ionizing radiation; (d) requires no anesthesia; (e) is less operator dependent; (f) better demonstrates ducts proximal to an obstruction or tight stenosis; and (g) when combined with conventional T1- and T2-weighted sequences, allows anatomic imaging of extraductal disease. However, MRCP provides less spatial resolution than ERCP, thereby decreasing the sensitivity to peripheral ductal abnormalities. In addition, the peripheral ducts may not be visualized because imaging is performed in the physiologic, nondistended state. The main criticism of MRCP is that appropriate care may be delayed in patients
M. Eid, K.A. Matrawy who need therapeutic endoscopic or percutaneous intervention of obstructing bile duct lesions (7). 1.1. Principles of MR cholangiopancreatography At MR cholangiopancreatography, the bile within the biliary tree is imaged with heavily T2-weighted sequences. The sequences are heavily T2 weighted with use of long echo times in the range of 300–1000 ms, such that only tissues or fluid with prolonged transverse relaxation time (T2) retain signal. These tissues and fluid are seen as hyperintense structures. The background soft tissues with shorter T2 do not retain significant signal long enough in a sequence with prolonged echo time and are, therefore, suppressed. Blood vessels are not seen, since flowing blood does not produce any signal on these images (13).
1.2. Types of sequences used 1.2.1. Fast spin-echo (turbo spin-echo) sequence With the fast spin-echo (FSE) (turbo spin-echo [TSE]) sequence, a 90° radiofrequency (RF) pulse is followed by a train of 180° RF pulses. The number of 180° pulses is called the echo train length (ETL) or turbo factor. The speed of acquisition increases with an increase in ETL. For the purposes of MR cholangiopancreatography, FSE imaging is performed with a long ETL, repetition time, and echo time (>250 ms) (14). A long ETL is well suited for the type of long echo-time acquisition required for MR cholangiopancreatography. FSE imaging can be performed with a breath hold or with free breathing with the use of respiratory gating or a navigator technique (13). It can be performed as a two-dimensional (2D) sequence with a slab thickness of 2–7 cm or as a three-dimensional (3D) sequence with thinner sections. The resultant data can then be reconstructed into cholangiographic images with a maximum-intensity-projection (MIP) technique (14). Fast recovery FSE (FRFSE; GE Medical Systems, Waukesha, Wis), RESTORE (Siemens Medical Solutions, Forchheim, Germany), and driven equilibrium FSE (DRIVE; Philips Medical Systems, Best, the Netherlands) sequences are modified FSE sequences in which a 90° RF pulse is used at the end of the ETL to get the magnetization immediately in longitudinal plane, thereby reducing repetition time (13). Single-shot FSE (TSE) sequence single-shot FSE (SSFSE, GE Medical Systems), half-Fourier single-shot TSE (HASTE, Siemens), and single-shot TSE (SSTSE, Philips) sequences are FSE sequences in which just more than one half of k-space is filled, thus reducing scanning time significantly. All of the required k-space lines (phase-encoding steps) are filled in a single repetition time; hence the name ‘‘single-shot.’’ Acquisition times are in seconds, with reasonably good spatial resolution (15). SSFSE imaging has a higher signal-to-noise ratio (SNR) than does FSE imaging as a result of less motion artifact producing noise (14). Limitations of SSFSE imaging include image blur induced by long ETLs, flow artifacts, and problems with saturation of adjacent sections. Echo times typically range between 300
Primary Sclerosing Cholangitis: Evaluation with MRCP and 1000 ms. These sequences can be performed with a breath hold or with respiratory triggering, and good-quality images can be obtained, even with quiet breathing (15). 1.2.2. Other sequences Fast gradient-echo sequences such as balanced fully refocused steady-state sequences (true fast imaging with steady-state precession, fast imaging employing steady-state acquisition, balanced fast field echo) show the biliary tree well, with excellent SNR and good spatial resolution. These sequences can be performed with a breath hold or with quiet breathing and may show ducts reasonably well when other sequences fail to do so because of motion artifacts. One limitation, however, is the fact that blood vessels are seen as bright structures, which may make it difficult to differentiate them from bile ducts (13). Diagnostic criteria for PSC include (a) typical cholangiographic abnormalities; (b) appropriate clinical, biochemical, and hepatic histologic findings; and (c) the exclusion of secondary causes of sclerosing cholangitis. Cholangiographic findings usually include multifocal, intrahepatic bile duct strictures alternating with normal-caliber ducts, which sometimes produce a beaded appearance (16). Although patients may be asymptomatic, 75% have progressive fatigue, pruritus, or jaundice (17). At biochemical analysis, levels of serum bilirubin and alkaline phosphatase are increased in most patients, with a mean increase in the alkaline phosphatase level to three times the upper limit of normal Because histologic examination of the liver shows nonspecific inflammatory fibrosis of the portal triads and a paucity of bile ducts, histologic analysis is used only for confirmation of a suspected diagnosis of PSC (17,18). Before the diagnosis of PSC is established, secondary sclerosing and nonsclerosing processes that mimic PSC at cholangiography must be excluded (16). The cholangiographic findings in PSC depend on the stage of the disease process. Early in the course of the disease, randomly distributed, short (1–2 mm), annular intrahepatic strictures alternating with normal or slightly dilated segments produce a beaded appearance. Strictures usually occur at the bifurcation of ducts and are out of proportion to upstream ductal dilatation. The peripheral ducts should extend to the periphery of the liver and form acute angles with the central ducts. As the fibrosing process worsens, strictures increase and the ducts become obliterated, and the peripheral ducts cannot be visualized to the periphery of the liver at ERCP, producing a ‘‘pruned tree’’ appearance (16). In addition, the acute angles formed with the central ducts become more obtuse. With further progression, strictures of the central ducts prevent peripheral ductal opacification at ERCP. The key cholangiographic features of PSC are randomly distributed annular strictures out of proportion to upstream dilatation, which probably reflect periductal inflammation and fibrosis that prevent the ducts from dilating (17,18). If the ducts in a case simulating PSC are dilated, one should consider other sclerosing ductal processes such as ascending cholangitis or PSC complicated by cholangiocarcinoma. Other cholangiographic findings include webs, diverticula, and stones. A web is a focal, 1–2-mm thick area of incomplete circumferential narrowing; a diverticulum is a focal, eccentric, saccular dilatation of the bile duct. These two findings may
353 represent manifestations of the same abnormality because a web may transform into a diverticulum with an increase in intraductal pressure during conventional cholangiography (19). Diverticula and webs are not pathognomonic for PSC and can be seen in other inflammatory and traumatic processes (19). Up to 27% of patients with PSC have diverticula. Primary pigmented stones occur in 30% of patients with PSC secondary to bile stasis (19). 2. Materials and methods Magnetic resonance cholangiopancreatography (MRCP) was done for the included patients using a 1.5-T closed MR unit (Avanto, Siemens) with a circularly polarized; phased-array body coil was used in all cases. Antiperistaltic agents and oral contrast material were not used, and the patients did not fast prior to the examination.
Figure 1 Coronal 3D-T2 MRI revealed characteristic segmental dilatation of the intrahepatic biliary radicles, separated by multiple strictures. Note the pancreatic duct dilatation resulting from associated autoimmune pancreatitis.
Figure 2 Coronal 3D-T2 MRI revealed characteristic segmental dilatation of the intrahepatic biliary radicles, separated by multiple strictures (arrows). Note the stricture (asterisk) affecting the CBD.
354
M. Eid, K.A. Matrawy
All the patients were examined by using half-Fourier rapid acquisition with relaxation enhancement (RARE) MR cholangiographic sequences.
3.1. Case 1 (PSC)
3. Results
Fig. 1: Coronal 3D-T2 MRI revealed characteristic segmental dilatation of the intrahepatic biliary radicles, separated by multiple strictures. Note the pancreatic duct dilatation resulting from associated autoimmune pancreatitis.
The study included 20 patients (12 women and 8 men) age ranged from 29 to 70 years. All the patients presented with obstructive jaundice and abdominal pain. In 3 patients cholangiocarcinoma was seen superadded on primary sclerosing cholangitis (PSC). Two patients were diagnosed as ulcerative colitis.
A 23 years old female, suffering from ulcerative colitis presented with obstructive jaundice and abdominal pain.
3.2. Case 2 (PSC) A 58 years old female, suffering from obstructive jaundice.
Figure 3 (A) Axial T2W image shows a hepatic hyperintense mass with segmental biliary dilatation. (B) MRCP shows the segmental strictures and dilatations of the intrahepatic biliary radicles, away from the mass.
Figure 4 (A) Axial T2W image shows scattered periportal patches of hyperintensity. (B) MRCP shows the segmental strictures and dilatations of the intrahepatic biliary radicles, as well as the CBD. (C) Sonography reveals mild diffuse GB wall thickening, a feature associated with PSC.
Primary Sclerosing Cholangitis: Evaluation with MRCP Fig. 2: Coronal 3D-T2 MRI revealed characteristic segmental dilatation of the intrahepatic biliary radicles, separated by multiple strictures (arrows). Note the stricture (asterisk) affecting the CBD. 3.3. Case 3 (PSC and CCA) A 60 years old female, suffering from obstructive jaundice. Fig. 3(A): Axial T2W image shows a hepatic hyperintense mass with segmental biliary dilatation. Fig. 3(B): MRCP shows the segmental strictures and dilatations of the intrahepatic biliary radicles, away from the mass.
355 highest incidence in the first 2 years after diagnosis of PSC. Patients with PSC develop CCA approximately 2–3 decades earlier than patients without PSC (6). In our work we concluded that MRCP is a noninvasive technique that is comparable with ERCP in the detection and localization of bile duct obstruction and choledocholithiasis. MRCP has some advantages over ERCP. Specifically, MRCP is non invasive, cheaper; uses no ionizing radiation; requires no anesthesia; less operator dependent; better demonstrating ducts proximal to an obstruction or tight stenosis; and when combined with conventional T1- and T2-weighted sequences, allows anatomic imaging of extraductal disease. However, MRCP provides less spatial resolution than ERCP, thereby decreasing the sensitivity to peripheral ductal abnormalities.
3.4. Case 4 (PSC patches) A 60 years old female, suffering from obstructive jaundice. Fig. 4(A): Axial T2W image shows scattered periportal patches of hyperintensity. Fig. 4(B): MRCP shows the segmental strictures and dilatations of the intrahepatic biliary radicles, as well as the CBD. Fig. 4(C): Sonography reveals mild diffuse GB wall thickening, a feature associated with PSC. 4. Discussion MRCP performed with the single-shot fast spine echo technique is a promising, noninvasive alternative to more invasive direct cholangiography for evaluating the intrahepatic and extrahepatic bile ducts in patients with sclerosing cholangitis (7). MRCP has high sensitivity and very high specificity for the diagnosis of PSC. In many cases of suspected PSC, MRCP is sufficient for diagnosis, and, thus, the risks associated with ERCP can be avoided (21). MRCP enabled confirmation of PSC; in patients with low pretest probabilities, MRCP enabled exclusion of PSC (21). High-quality magnetic resonance (MR) cholangiopancreatographic images are difficult to obtain in children due to the small caliber of the pediatric bile ducts and motion artifacts. However, there has been ongoing improvement in image quality, thanks to better coil technology, increased speed of acquisition, refinement in respiratory compensation techniques, and newer sequences. Heavily T2-weighted fast spin-echo (FSE) and single-shot FSE MR imaging sequences with long echotimes are used to image the biliary and pancreatic ducts (13). MR cholangiography was found to be accurate in detecting PSC and in defining the extent of disease. In the detection of PSC, the sensitivities were 88% and 85%; specificities, 97% and 92% (20). Sixty percent to 80% of patients with PSC have associated inflammatory bowel disease, especially ulcerative colitis (1). Cholangiocarcinoma is the second most common primary malignant hepatobiliary neoplasm, accounting for approximately 15% of liver cancers. Diagnosis of cholangiocarcinoma is challenging and the prognosis is uniformly poor, with recurrence rates of 60–90% after surgical resection (8). The chronic inflammation of PSC predisposes to the development of CCA, the most dreaded complication of PSC (1). CCA develops in 10% of patients with PSC. The incidence of CCA in patients with PSC is 0.6–1.5% per year, with the
Grant support None. References (1) LaRusso NF, Shneider BL, Black D, et al. Primary sclerosing cholangitis: summary of a workshop. Hepatology 2006;44:746–64. (2) Vitellas KM, Keogan MT, Freed KS, et al. Radiologic manifestations of sclerosing cholangitis with emphasis on MR cholangiopancreatography. RadioGraphics 2000;20:959–75. (3) Elsayes KM, Oliveira EP, Narra VR, et al. MR and MRCP in the evaluation of primary sclerosing cholangitis: current applications and imaging findings. J Comput Assist Tomogr 2006;30:398–404. (4) Wiesner RH, LaRusso NF. Clinicopathologic features of the syndrome of primary sclerosing cholangitis. Gastroenterology 1980;79:200–6. (5) Wiesner RH, Grambsch PM, Dickson ER, et al. Primary sclerosing cholangitis: natural history, prognostic factors, and survival analysis. Hepatology 1989;10:430–6. (6) Burak K, Angulo P, Pasha TM, Egan K, Petz J, Lindor KD. Incidence and risk factors for cholangiocarcinoma in primary sclerosing cholangitis. Am J Gastroenterol 2004;99:523–6. (7) Kenneth M, Mary T, Freed Kelly S. Radiologic manifestations of sclerosing cholangitis with emphasis on MR cholangiopancreatography. RadioGraphics 2000;20:959–75. (8) Christine O, Venkateswar R, Srinivasa R. Mimics of cholangiocarcinoma: spectrum of disease. RadioGraphics 2008;28:1115–29. (9) Abdalian R, Heathcote EJ. Sclerosing cholangitis: a focus on secondary causes. Hepatology 2006;44:1063–74. (10) Snover DC. Non-neoplastic biliary tract disease. In: Snover DC, editor. Biopsy diagnosis of liver disease. Baltimore, MD: Williams &Wilkins; 1992. p. 92–111. (11) Lee YM, Kaplan MM. Primary sclerosing cholangitis. N Engl J Med 1995;332:924–33. (12) Beuers U, Spengler U, Sackmann M, Paumgartner G, Sauerbruch T. Deterioration of cholestasis after endoscopic retrograde cholangiography in advanced primary sclerosing cholangitis. J Hepatol 1992;15:140–3. (13) Govind B, Paul S, David M. Pediatric MR cholangiopancreatography: principles, technique, and clinical applications. RadioGraphics 2008;28:1951–62. (14) Vitellas KM, Keogan MT, Spritzer CE, Nelson RC. MR cholangiography of bile and pancreatic duct abnormalities with emphasis on single-shot FSE technique. RadioGraphics 2000;20:939–57. (15) Glockner JF. Hepatobiliary MRI: current concepts and controversies. J Magn Reson Imaging 2007;25:681–95.
356 (16) MacCarty RL, LaRusso NF, Wiesner RH, Ludwig J. Primary sclerosing cholangitis: findings on cholangiography and pancreatography. Radiology 1983;149:39–44. (17) Ueno Y, LaRusso NF. Primary sclerosing cholangitis. J Gastroenterol 1994;29:531–43. (18) Lindor KD, Wiesner RH, MacCarty RL, Ludwig J, LaRusso NF. Advances in primary sclerosing cholangitis. Am J Med 1990;89:73–80. (19) Gulliver DJ, Baker ME, Putman W, Baillie J, Rice R, Cotton PB. Bile duct diverticula and webs: nonspecific cholangiographic
M. Eid, K.A. Matrawy features of primary sclerosing cholangitis. AJR Am J Roentgenol 1991;157:281–5. (20) Ann S, Mary A. Primary sclerosing cholangitis: evaluation with MR cholangiography a case-control study. Radiology 2000;215:71–80. (21) Dave M. Primary sclerosing cholangitis: meta-analysis of diagnostic performance of MR cholangiopancreatography. Radiology 2010;256(2):387–96.
Egyptian Society of Radiology and Nuclear Medicine
The Egyptian Journal of Radiology and Nuclear Medicine www.elsevier.com/locate/ejrnm www.sciencedirect.com
ORIGINAL ARTICLE
Primary sclerosing cholangitis: Evaluation with MR cholangiopancreatography (MRCP) Mohamed Eid a, Khaled Aly Matrawy a b
b,*
Department of Radiodiagnosis, Faculty of Medicine, Alexandria University, Egypt Department of Radiodiagnosis, Medical Research Institute, Alexandria University, Egypt
Received 5 September 2011; accepted 30 September 2011 Available online 16 November 2011
KEYWORDS Magnetic resonance cholangiopancreatography; Primary sclerosing cholangitis
Abstract Objective: To highlight the diagnostic features of PSC on MRCP studies in patients with biochemical cholestasis. Conclusion: MRCP enables accurate detection and localization of PSC and in defining the extent of disease. Ó 2011 Egyptian Society of Radiology and Nuclear Medicine. Production and hosting by Elsevier B.V. All rights reserved.
1. Introduction Primary sclerosing cholangitis (PSC) is an idiopathic, chronic cholestatic disease of possible autoimmune origin that is characterized by diffuse cholangitis and progressive fibrosis of the extra- and intrahepatic bile ducts. PSC typically manifests in Abbreviations: MRCP, magnetic resonance cholangiopancreatography; PSC, primary sclerosing cholangitis * Corresponding author. Tel.: +20 123377159; fax: +20 32466656. E-mail address: [email protected] (K.A. Matrawy). 0378-603X Ó 2011 Egyptian Society of Radiology and Nuclear Medicine. Production and hosting by Elsevier B.V. All rights reserved. Peer review under responsibility of Egyptian Society of Radiology and Nuclear Medicine. doi:10.1016/j.ejrnm.2011.09.007
Production and hosting by Elsevier
the fourth or fifth decade. There is a distinct male preponderance (1). The classic imaging findings of PSC include multifocal strictures, ectasias, ductal wall thickening, and irregular beading of the intra- and extrahepatic bile ducts (2,3). A strong association with the inflammatory bowel disease, especially ulcerative colitis, is noted (70% of cases) (4). The rate of progression is unpredictable, with up to 49% of symptomatic patients eventually developing biliary cirrhosis and liver failure. Treatment is usually palliative and includes medical therapy with orally administered agents such as ursodiol (ursodeoxycholic acid) or endoscopic or percutaneous mechanical dilation of dominant strictures. Currently, orthotopic liver transplantation is the only curative therapy for PSC (5). The chronic inflammation of PSC predisposes to the development of cholangiocarcinoma (CCA), the most dreaded complication of PSC (1). CCA develops in 10% of patients with PSC. The incidence of CCA in patients with PSC is 0.6–1.5% per year, with the highest incidence in the first 2 years after diagnosis of PSC. Patients with PSC develop CCA approximately 2–3 decades earlier than patients without PSC (6).
352 Cholangiographic features that suggest cholangiocarcinoma include irregular high grade ductal narrowing with shouldered margins, rapid progression of strictures, marked ductal dilatation proximal to strictures, and polypoid lesions. Secondary sclerosing and nonsclerosing processes can mimic primary sclerosing cholangitis at cholangiography (7). In a small percentage of patients, focal segmental involvement of PSC manifesting as a focal short-segment stricture without the classic imaging findings makes it difficult to distinguish from the periductal-infiltrating type of CCA (8). Secondary sclerosing cholangitis syndromes are a heterogeneous group of chronic cholestatic disorders that are morphologically similar to PSC but result from distinct pathologic processes. The wide spectrum of secondary sclerosing cholangitis entities includes recurrent pyogenic cholangitis, acquired immunodeficiency syndrome (AIDS) cholangiopathy, autoimmune pancreatitis, hepatic inflammatory pseudotumor, eosinophilic cholangitis, portal biliopathy, and ischemic cholangiopathy (9). Although percutaneous biopsy specimens may demonstrate findings that are suggestive of PSC, such as numerous eosinophils in the periportal parenchyma, periductal fibrosis, and ductopenia, there is no histologic feature that is pathognomonic of PSC (10). Likewise, the results of biochemical analysis are nonspecific; they reveal elevated alkaline phosphatase and/or bilirubin levels, which can be seen in a variety of cholestatic processes in addition to PSC (11). The diagnosis of PSC is usually established with endoscopic retrograde cholangiopancreatography (ERCP) and less often with percutaneous transhepatic cholangiography; these studies demonstrate multiple segmental strictures, mural irregularities, and diverticula that are characteristic of PSC. Although ERCP and percutaneous transhepatic cholangiography provide highquality images of the biliary tract, both are invasive procedures that are associated with risks of sepsis and hemorrhage. ERCP is also associated with risks of pancreatitis and bowel perforation and has been shown to result in progression of cholestasis in patients with advanced PSC (12). Magnetic resonance cholangiopancreatography (MRCP) is a relatively new, noninvasive cholangiographic technique that is comparable with invasive endoscopic retrograde cholangiopancreatography (ERCP) in the detection and characterization of extrahepatic bile duct abnormalities. The role of MRCP in evaluation of the intrahepatic bile ducts, especially in patients with primary or secondary sclerosing cholangitis, is under investigation (7). Although ERCP is still the standard of reference for imaging the pancreaticobiliary system, MRCP has some advantages over ERCP. Specifically, MRCP (a) is noninvasive; (b) is cheaper; (c) uses no ionizing radiation; (d) requires no anesthesia; (e) is less operator dependent; (f) better demonstrates ducts proximal to an obstruction or tight stenosis; and (g) when combined with conventional T1- and T2-weighted sequences, allows anatomic imaging of extraductal disease. However, MRCP provides less spatial resolution than ERCP, thereby decreasing the sensitivity to peripheral ductal abnormalities. In addition, the peripheral ducts may not be visualized because imaging is performed in the physiologic, nondistended state. The main criticism of MRCP is that appropriate care may be delayed in patients
M. Eid, K.A. Matrawy who need therapeutic endoscopic or percutaneous intervention of obstructing bile duct lesions (7). 1.1. Principles of MR cholangiopancreatography At MR cholangiopancreatography, the bile within the biliary tree is imaged with heavily T2-weighted sequences. The sequences are heavily T2 weighted with use of long echo times in the range of 300–1000 ms, such that only tissues or fluid with prolonged transverse relaxation time (T2) retain signal. These tissues and fluid are seen as hyperintense structures. The background soft tissues with shorter T2 do not retain significant signal long enough in a sequence with prolonged echo time and are, therefore, suppressed. Blood vessels are not seen, since flowing blood does not produce any signal on these images (13).
1.2. Types of sequences used 1.2.1. Fast spin-echo (turbo spin-echo) sequence With the fast spin-echo (FSE) (turbo spin-echo [TSE]) sequence, a 90° radiofrequency (RF) pulse is followed by a train of 180° RF pulses. The number of 180° pulses is called the echo train length (ETL) or turbo factor. The speed of acquisition increases with an increase in ETL. For the purposes of MR cholangiopancreatography, FSE imaging is performed with a long ETL, repetition time, and echo time (>250 ms) (14). A long ETL is well suited for the type of long echo-time acquisition required for MR cholangiopancreatography. FSE imaging can be performed with a breath hold or with free breathing with the use of respiratory gating or a navigator technique (13). It can be performed as a two-dimensional (2D) sequence with a slab thickness of 2–7 cm or as a three-dimensional (3D) sequence with thinner sections. The resultant data can then be reconstructed into cholangiographic images with a maximum-intensity-projection (MIP) technique (14). Fast recovery FSE (FRFSE; GE Medical Systems, Waukesha, Wis), RESTORE (Siemens Medical Solutions, Forchheim, Germany), and driven equilibrium FSE (DRIVE; Philips Medical Systems, Best, the Netherlands) sequences are modified FSE sequences in which a 90° RF pulse is used at the end of the ETL to get the magnetization immediately in longitudinal plane, thereby reducing repetition time (13). Single-shot FSE (TSE) sequence single-shot FSE (SSFSE, GE Medical Systems), half-Fourier single-shot TSE (HASTE, Siemens), and single-shot TSE (SSTSE, Philips) sequences are FSE sequences in which just more than one half of k-space is filled, thus reducing scanning time significantly. All of the required k-space lines (phase-encoding steps) are filled in a single repetition time; hence the name ‘‘single-shot.’’ Acquisition times are in seconds, with reasonably good spatial resolution (15). SSFSE imaging has a higher signal-to-noise ratio (SNR) than does FSE imaging as a result of less motion artifact producing noise (14). Limitations of SSFSE imaging include image blur induced by long ETLs, flow artifacts, and problems with saturation of adjacent sections. Echo times typically range between 300
Primary Sclerosing Cholangitis: Evaluation with MRCP and 1000 ms. These sequences can be performed with a breath hold or with respiratory triggering, and good-quality images can be obtained, even with quiet breathing (15). 1.2.2. Other sequences Fast gradient-echo sequences such as balanced fully refocused steady-state sequences (true fast imaging with steady-state precession, fast imaging employing steady-state acquisition, balanced fast field echo) show the biliary tree well, with excellent SNR and good spatial resolution. These sequences can be performed with a breath hold or with quiet breathing and may show ducts reasonably well when other sequences fail to do so because of motion artifacts. One limitation, however, is the fact that blood vessels are seen as bright structures, which may make it difficult to differentiate them from bile ducts (13). Diagnostic criteria for PSC include (a) typical cholangiographic abnormalities; (b) appropriate clinical, biochemical, and hepatic histologic findings; and (c) the exclusion of secondary causes of sclerosing cholangitis. Cholangiographic findings usually include multifocal, intrahepatic bile duct strictures alternating with normal-caliber ducts, which sometimes produce a beaded appearance (16). Although patients may be asymptomatic, 75% have progressive fatigue, pruritus, or jaundice (17). At biochemical analysis, levels of serum bilirubin and alkaline phosphatase are increased in most patients, with a mean increase in the alkaline phosphatase level to three times the upper limit of normal Because histologic examination of the liver shows nonspecific inflammatory fibrosis of the portal triads and a paucity of bile ducts, histologic analysis is used only for confirmation of a suspected diagnosis of PSC (17,18). Before the diagnosis of PSC is established, secondary sclerosing and nonsclerosing processes that mimic PSC at cholangiography must be excluded (16). The cholangiographic findings in PSC depend on the stage of the disease process. Early in the course of the disease, randomly distributed, short (1–2 mm), annular intrahepatic strictures alternating with normal or slightly dilated segments produce a beaded appearance. Strictures usually occur at the bifurcation of ducts and are out of proportion to upstream ductal dilatation. The peripheral ducts should extend to the periphery of the liver and form acute angles with the central ducts. As the fibrosing process worsens, strictures increase and the ducts become obliterated, and the peripheral ducts cannot be visualized to the periphery of the liver at ERCP, producing a ‘‘pruned tree’’ appearance (16). In addition, the acute angles formed with the central ducts become more obtuse. With further progression, strictures of the central ducts prevent peripheral ductal opacification at ERCP. The key cholangiographic features of PSC are randomly distributed annular strictures out of proportion to upstream dilatation, which probably reflect periductal inflammation and fibrosis that prevent the ducts from dilating (17,18). If the ducts in a case simulating PSC are dilated, one should consider other sclerosing ductal processes such as ascending cholangitis or PSC complicated by cholangiocarcinoma. Other cholangiographic findings include webs, diverticula, and stones. A web is a focal, 1–2-mm thick area of incomplete circumferential narrowing; a diverticulum is a focal, eccentric, saccular dilatation of the bile duct. These two findings may
353 represent manifestations of the same abnormality because a web may transform into a diverticulum with an increase in intraductal pressure during conventional cholangiography (19). Diverticula and webs are not pathognomonic for PSC and can be seen in other inflammatory and traumatic processes (19). Up to 27% of patients with PSC have diverticula. Primary pigmented stones occur in 30% of patients with PSC secondary to bile stasis (19). 2. Materials and methods Magnetic resonance cholangiopancreatography (MRCP) was done for the included patients using a 1.5-T closed MR unit (Avanto, Siemens) with a circularly polarized; phased-array body coil was used in all cases. Antiperistaltic agents and oral contrast material were not used, and the patients did not fast prior to the examination.
Figure 1 Coronal 3D-T2 MRI revealed characteristic segmental dilatation of the intrahepatic biliary radicles, separated by multiple strictures. Note the pancreatic duct dilatation resulting from associated autoimmune pancreatitis.
Figure 2 Coronal 3D-T2 MRI revealed characteristic segmental dilatation of the intrahepatic biliary radicles, separated by multiple strictures (arrows). Note the stricture (asterisk) affecting the CBD.
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All the patients were examined by using half-Fourier rapid acquisition with relaxation enhancement (RARE) MR cholangiographic sequences.
3.1. Case 1 (PSC)
3. Results
Fig. 1: Coronal 3D-T2 MRI revealed characteristic segmental dilatation of the intrahepatic biliary radicles, separated by multiple strictures. Note the pancreatic duct dilatation resulting from associated autoimmune pancreatitis.
The study included 20 patients (12 women and 8 men) age ranged from 29 to 70 years. All the patients presented with obstructive jaundice and abdominal pain. In 3 patients cholangiocarcinoma was seen superadded on primary sclerosing cholangitis (PSC). Two patients were diagnosed as ulcerative colitis.
A 23 years old female, suffering from ulcerative colitis presented with obstructive jaundice and abdominal pain.
3.2. Case 2 (PSC) A 58 years old female, suffering from obstructive jaundice.
Figure 3 (A) Axial T2W image shows a hepatic hyperintense mass with segmental biliary dilatation. (B) MRCP shows the segmental strictures and dilatations of the intrahepatic biliary radicles, away from the mass.
Figure 4 (A) Axial T2W image shows scattered periportal patches of hyperintensity. (B) MRCP shows the segmental strictures and dilatations of the intrahepatic biliary radicles, as well as the CBD. (C) Sonography reveals mild diffuse GB wall thickening, a feature associated with PSC.
Primary Sclerosing Cholangitis: Evaluation with MRCP Fig. 2: Coronal 3D-T2 MRI revealed characteristic segmental dilatation of the intrahepatic biliary radicles, separated by multiple strictures (arrows). Note the stricture (asterisk) affecting the CBD. 3.3. Case 3 (PSC and CCA) A 60 years old female, suffering from obstructive jaundice. Fig. 3(A): Axial T2W image shows a hepatic hyperintense mass with segmental biliary dilatation. Fig. 3(B): MRCP shows the segmental strictures and dilatations of the intrahepatic biliary radicles, away from the mass.
355 highest incidence in the first 2 years after diagnosis of PSC. Patients with PSC develop CCA approximately 2–3 decades earlier than patients without PSC (6). In our work we concluded that MRCP is a noninvasive technique that is comparable with ERCP in the detection and localization of bile duct obstruction and choledocholithiasis. MRCP has some advantages over ERCP. Specifically, MRCP is non invasive, cheaper; uses no ionizing radiation; requires no anesthesia; less operator dependent; better demonstrating ducts proximal to an obstruction or tight stenosis; and when combined with conventional T1- and T2-weighted sequences, allows anatomic imaging of extraductal disease. However, MRCP provides less spatial resolution than ERCP, thereby decreasing the sensitivity to peripheral ductal abnormalities.
3.4. Case 4 (PSC patches) A 60 years old female, suffering from obstructive jaundice. Fig. 4(A): Axial T2W image shows scattered periportal patches of hyperintensity. Fig. 4(B): MRCP shows the segmental strictures and dilatations of the intrahepatic biliary radicles, as well as the CBD. Fig. 4(C): Sonography reveals mild diffuse GB wall thickening, a feature associated with PSC. 4. Discussion MRCP performed with the single-shot fast spine echo technique is a promising, noninvasive alternative to more invasive direct cholangiography for evaluating the intrahepatic and extrahepatic bile ducts in patients with sclerosing cholangitis (7). MRCP has high sensitivity and very high specificity for the diagnosis of PSC. In many cases of suspected PSC, MRCP is sufficient for diagnosis, and, thus, the risks associated with ERCP can be avoided (21). MRCP enabled confirmation of PSC; in patients with low pretest probabilities, MRCP enabled exclusion of PSC (21). High-quality magnetic resonance (MR) cholangiopancreatographic images are difficult to obtain in children due to the small caliber of the pediatric bile ducts and motion artifacts. However, there has been ongoing improvement in image quality, thanks to better coil technology, increased speed of acquisition, refinement in respiratory compensation techniques, and newer sequences. Heavily T2-weighted fast spin-echo (FSE) and single-shot FSE MR imaging sequences with long echotimes are used to image the biliary and pancreatic ducts (13). MR cholangiography was found to be accurate in detecting PSC and in defining the extent of disease. In the detection of PSC, the sensitivities were 88% and 85%; specificities, 97% and 92% (20). Sixty percent to 80% of patients with PSC have associated inflammatory bowel disease, especially ulcerative colitis (1). Cholangiocarcinoma is the second most common primary malignant hepatobiliary neoplasm, accounting for approximately 15% of liver cancers. Diagnosis of cholangiocarcinoma is challenging and the prognosis is uniformly poor, with recurrence rates of 60–90% after surgical resection (8). The chronic inflammation of PSC predisposes to the development of CCA, the most dreaded complication of PSC (1). CCA develops in 10% of patients with PSC. The incidence of CCA in patients with PSC is 0.6–1.5% per year, with the
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