Abdominal Imaging
ª Springer Science+Business Media, LLC 2011 Published online: 17 June 2011
Abdom Imaging (2012) 37:83–90 DOI: 10.1007/s00261-011-9765-2
Portal biliopathy: a multitechnique imaging approach Cecilia Besa, Juan Pablo Cruz, Alvaro Huete, Francisco Cruz Department of Radiology, Pontificia Universidad Catolica de Chile, Marcoleta 367, 8330024 Santiago, Chile
Abstract Portal biliopathy (PB) is a disorder characterized by biliary ductal and gallbladder wall abnormalities seen in patients with extrahepatic portal vein obstruction. These abnormalities consist mainly of bile duct compression and tethering, stenoses, fibrotic strictures and dilatation of both extrahepatic and intrahepatic bile ducts, as well as gallbladder varices. In this pictorial essay, we describe the imaging findings of PB, which allow differentiation of this entity from other diseases that may have similar imaging findings including cholangiocarcinoma, extrinsic compression of the bile duct caused by metastatic adenopathy or sclerosing cholangitis. Key words: Portal biliopathy—Portal vein thrombosis—Common bile duct—Stenosis—MRCP
Portal biliopathy (PB) is the term used to define the biliary obstruction and morphologic changes occurring in the biliary tree and gallbladder in patients with portal hypertension [1–3]. Extrahepatic obstruction of the portal vein (EHOPV) accounts for approximately 40% of portal hypertension cases worldwide [3], but it is almost always the culprit when PB is present [1]. Causes of EHOPV are myriad and include neonatal umbilical vein catheterization, clotting disorders, abdominal postoperative complications, dehydration and shock, intraabdominal inflammatory diseases, and direct invasion or extrinsic compression by tumors among others [4, 5]. In response to chronic occlusion of the portal vein and superior mesenteric vein (SMV), which occurs more commonly in the setting of hypercoagulability than in that of cirrhosis, several new venous collaterals are recruited in the porta hepatitis to compensate the diminished hepatopetal portal flow. These collateral veins
Correspondence to: Alvaro Huete; email:
[email protected]
dilate forming huge varices that completely surround the biliary tree producing a ‘‘portal cavernoma’’, thus providing an alternate route for portal-mesenteric blood flow to enter the hepatic parenchyma [6]. There are two main portal collateral pathways that anatomically relate directly to the biliary tract (Fig. 1): the peribiliary venous plexus of Saint and the parabiliary venous plexus of Petren. The former is a mesh of vessels, not greater than 1 mm in diameter, which are on the surface of the common bile duct (CBD) and hepatic ducts. The parabiliary plexus runs parallel to the bile duct in the hepatoduodenal ligament and is supplied by gastric and pancreaticoduodenal veins, which connect to portal vein branches around the hepatic hilum. Hypertrophy of both collateral plexuses produces scalloped or smooth indentations in the ductal lumen of the bile ducts, which can progress to more dramatic narrowing, stenosis, and kinking. Development of varices in the gallbladder wall as a collateral pathway via the cystic vein is also a characteristic feature of PB [1, 2, 6]. Biliopathy (symptomatic or not) has been reported in 70%–100% of patients with EHOPV and is far less common in the setting of cirrhosis [1]. The mechanisms suggested for these biliary abnormalities are two: (a) Mechanical extrinsic compression by collaterals; this hypothesis is supported by the fact that some of the changes revert once portal hypertension is relieved with a portosystemic surgical shunt. (b) Biliary ischemic injury due to venous thrombosis or maintained extrinsic pressure on the bile duct wall leading to inflammation and fibrosis [7]. The majority of the patients are asymptomatic and biliary changes are an incidental imaging finding (80%) [1, 2]. An increase in total bilirubin and alkaline phosphatase levels can be detected in up to 40%–80% of cases [8]. Symptoms may occur if partial or high-grade obstruction of the bile ducts develops and include right upper quadrant pain, cholestasis, cholangitis and, rarely, obstructive jaundice in cases of duct stones or development of a high grade stricture [1–3, 9]. Choledocholithiasis and hepatolithiasis are present in 5%–20% of
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Fig. 1. Diagram showing the anatomic relationships of the peri and parabiliary plexuses with the bile duct. GDV gastrodudodenal vein, PDV pancreaticoduodenal vein.
patients with PB and are probably related to stasis because it generally occurs independently of cholelithiasis [10, 11]. Secondary biliary cirrhosis can occur in patients with late diagnosis. Findings of PB are most prominent in the CBD. They include mural irregularities, localized saccular dilatations, strictures, and filling defects suggestive of calculi [8, 10, 12]. Some of these changes are similar to those seen in sclerosing cholangitis, lymphoplasmocytic cholangiopathy (associated with autoimmune pancreatitis), cholangiocarcinoma, invasive gallbladder carcinoma or extrinsic compression of the bile duct by metastatic adenopathies. At present, strategies for the management of PB are selective and directed to symptomatic patients only. Asymptomatic patients do not need any treatment, especially if the liver function tests are normal [13]. In this pictorial essay, we describe the imaging findings of PB and emphasize noninvasive imaging modalities such as ultrasound (US), computed tomography (CT), and magnetic resonance imaging (MRI) in its diagnosis and follow up. Since this is a chronic, slowly progressive pathology, accurate serial and, whenever possible, noninvasive imaging is mandatory, reserving endoscopic retrograde cholangiopancreatography (ERCP) for treatment and diagnosis of misleading cases.
Imaging findings Color Doppler ultrasound (CDU) The main utility of US is to distinguish gallbladder and bile duct inflammatory or neoplastic wall thickening from mural varices. Doppler sonography demonstrates the portoportal collaterals in the hepatoduodenal ligament and porta hepatitis as a network of serpentine vessels with hepatopetal flow. US is also capable of
detecting luminal narrowing of the CBD as well as biliary duct dilatation proximal to the focal area of stenosis due to compressing pericholedochal venous collaterals [14, 15]. A potential pitfall is to mistake the portoportal collateral veins in the hepatic hilium as a solid mass on gray scale images. This error can be easily avoided using CDU that clearly identifies the vascular nature of this abnormality (Fig. 2). Gallbladder varices appear as tortuous dilated vessels in or around the wall of the gallbladder, or in the gallbladder fossa when prior cholecystectomy has been performed. As these collaterals develop in response to thrombosis of the extrahepatic portal vein, CDU images can demonstrate a direct connection between the gallbladder varices and the intrahepatic portal vein branches, with a low velocity continuous wave in pulsed Doppler, typical of venous flow in the portal system [16]. Although detailed CDU imaging assessment can show biliary and gallbladder abnormalities associated with EHOPV, cholangiographic images remain essential to confirm the diagnosis of PB in the majority of the cases.
Multidetector computed tomography (MDCT) MDCT imaging shows similar vascular findings in the porta hepatitis. CT clearly depicts cavernous transformation of the portal vein, marked dilatation of the intra and extrahepatic portions of the parabiliary and peribiliary plexuses, and gallbladder varices [17] (Fig. 3). Postprocessing tools, such as isotropic multiplanar reformation (MPR), maximum intensity projection (MIP), and volume rendering techniques (VR), can demonstrate the profuse network of collateral veins and its anatomic relationship with the bile ducts (Fig. 4). Minimum intensity projection (MinIP) images can provide cholangiographic-like images and detect dominant stenoses.
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Fig. 2. CDU (A) shows dilated bile ducts with a cavernomatous transformation of the portal vein. B, C Large varices producing gallbladder wall thickening.
MDCT can show secondary biliary ductal dilatation caused by the portal collaterals thus excluding a cholangiocarcinoma or extrinsic compression by metastatic adenopathies as the cause of obstruction. MDCT is also useful for evaluating portal vein obstruction excluding neoplastic causes such as tumoral thrombosis, and showing ancillary vascular findings related with portal hypertension such as splenorenal shunts, gastric or esophageal varices.
Fig. 3. A, B Contrast-enhanced CT in porto venous phase. Cavernomatous transformation of the portal vein (arrows) with grossly dilated veins in intimate contact with the bile duct (arrowhead). Note the dumbbell shape of the extrahepatic bile duct due to extrinsic compression by peribiliary varices.
Magnetic resonance imaging (MRI) Currently MRI has replaced direct cholangiography (DC) as the diagnostic procedure of choice for numerous conditions involving the biliary tract, including PB. Ultrafast 3D gadolinium-enhanced magnetic resonance angiography and portography depict the vascular abnormalities in the upper abdomen and their relationship with the biliary tract [18]. MRI is also helpful in
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Contrast-enhanced CT in porto venous phase. A, B Dilatation of the para and peribiliary venous plexuses which are in intimate contact with the common bile duct (arrowheads). Development of gallbladder wall varices (short arrows), mesenteric collateral circulation (long arrows), and splenomegaly. C Non invasive portography (coronal oblique MIP) showing the profuse mesh of variceal veins (short arrows) and its relationship with the common bile duct.
bFig. 4.
clarifying the cause of bile duct obstruction, allowing distinction between ductal wall ischemic fibrosis and cholangiocarcinoma. The major advantage of MRI, besides the lack of ionizing radiation, is the capability to
perform non-invasive magnetic resonance cholangiography (MRC). MRC identifies all the morphologic changes of the biliary tree in a panoramic fashion, resembling the images obtained with a DC. Chandra et al. [1] proposed a classification system for PB based on the location of cholangiographic abnormalities in DC that can also be applied to MRC images. Type I: involvement of extrahepatic ducts; type II: involvement of intrahepatic bile ducts only; type III a: extrahepatic bile duct and unilateral intrahepatic bile duct involvement; and type III b: extrahepatic bile duct and bilateral intrahepatic bile duct involvement. Recent reports of MRC imaging in PB show that either type I or type III biliary changes are the most frequent, with the extrahepatic bile ducts being the most common location of a dominant stenosis [17]. MRC abnormalities of the biliary system include a wavy appearance of the bile ducts, biliary ducts and gallbladder wall thickening, focal biliary stenosis, proximal dilatation, CBD angulation and lithiasis [17–20] (Figs. 5, 6). Three characteristic patterns of biliary involvement in PB have been described with MRI on the basis of the pathogenesis and the presence or absence of strictures: a varicoid type, a fibrotic type and a mixed pattern [20]. In the varicoid type the bile ducts show an irregular contour secondary to multiple smooth extrinsic compressions of dilated collateral veins (Fig. 7). This type may produce a ‘‘pseudocholangiocarcinoma sign’’, thus described because it mimics a cholangiocarcinoma spreading along the bile duct (Fig. 8). The fibrotic biliary abnormality is characterized by a dominant localized bile duct stricture with proximal dilatation of variable degree, the CBD being the most common segment involved (Fig. 9). MRC depicts biliary wall thickening with delayed progressive enhancement in the late phase of dynamic gadoliniumenhanced 3D gradient-echo images. The associated vascular abnormalities help differentiate this lesion from a bile duct tumor. In the mixed type, MRC shows irregular contours with multiple areas of narrowing and dilatation, with or without a dominant stricture (Fig. 10). MRC is also useful in determining the sites of stenosis due to PB, guiding therapeutic interventions and allowing noninvasive follow up of these patients. It is important to note that MRC can overestimate bile duct stenosis compared to DC. Biliary stasis proximal to dominant strictures predisposes to lithiasis. Stones are
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A Axial 3D GRE breath-hold sequence with gadolinium in porto venous phase. B Coronal true FISP. Cavernomatous transformation of the portal vein (arrowheads) with marked dilation of the bile ducts (white asterisk) due to a focal stenosis of the common bile duct. Note the gallbladder wall varices (black asterisk). C MRC shows a focal stenosis in the common bile duct (arrow) secondary to fibrosis, with marked dilatation of the proximal biliary tree.
bFig. 5.
Fig. 6. A MRC shows a smooth stricture (arrowheads) in the proximal common bile duct with dilatation of the main bile ducts. B Coronal true FISP sequence shows the dilated vascular structures surrounding the common bile duct with an extrinsic compression (black asterisk).
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Fig. 8. A MRC showing multiple indentations and smooth strictures involving the common bile duct and extending into the bile duct confluence (arrowheads) resembling the appearance of a cholangiocarcinoma. B Dynamic 3D GRE sequence with gadolinium in the portal phase shows the vascular pathology responsible for the cholangiographic abnormalities (arrow).
Fig. 7. A Diagram and B MRC showing multiple sites of smooth stenosis due to extrinsic compression (arrowheads) in the common and main bile ducts with mild dilatation of the biliary tree.
seen as hypointense round or ovoid filling defects within dilated ducts on T2-weighted images (Fig. 11). They can occasionally be hyperintense on T1-weighted sequences. Care must be taken when reviewing images in patients with prior ERCP as pneumobilia may also cause intraluminal filling defects on MRC [21].
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Fig. 10. MRC showing multiple sites of smooth strictures due to extrinsic compression (arrowheads) with a dominant focus (asterisk) secondary to wall fibrosis.
MRC seems to be the most accurate tool allowing a comprehensive noninvasive evaluation of patients with PB. Findings, however, must be always be interpreted in the light of clinical history and laboratory results as most patients with PB will be asymptomatic.
Conclusion
Fig. 9. A Diagram and B MRC showing a stenotic focus (arrowhead) with marked dilatation of the proximal biliary tree (asterisk).
PB is mainly secondary to obstruction of both the portal vein and adjacent SMV and most commonly occurs in noncirrhotic patients with hypercoagulable states. This chronic occlusion leads to cavernous transformation of the portal vein with marked dilatation of the venous plexuses surrounding the biliary tree to compensate for the diminished portal flow, causing extrinsic compression of the bile duct and/or ischemic biliary changes with secondary focal stenosis. Imaging findings include occlusion of the extrahepatic portal vein, cavernous transformation, gallbladder varices, bile duct wall irregularities secondary to extrinsic compression, stenotic foci of the biliary tree, variable upstream dilatation, and stone formation. Therefore, an understanding of the clinical and imaging findings in PB may improve the differentiation of this entity from other causes of bile duct and gallbladder wall thickening, as cholangiocarcinoma, and thus avoid unnecessary and dangerous biliary biopsies.
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References
Fig. 11. A MRC showing marked dilatation of the intrahepatic ducts and CBD with multiple intraluminal filling defects (arrow). Axial HASTE (not shown) clearly depicted stones within dilated ducts on T2-weighted images (arrow). B Coronal Dynamic 3D GRE sequence with gadolinium in the portal phase shows cavernomatous transformation of the portal vein that explains the wavy appearance of the CBD in the MRC (arrowheads).
Noninvasive diagnostic imaging modalities such as CDU, MDCT, and MRI can provide an accurate diagnosis of this entity, with MRC replacing DC for evaluation and follow up of the majority of cases.
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