DOI: 10.1148/rg.281075037
RadioGraphics 2008;28:171-183
© RSNA, 2008
Abdominal Findings in Hereditary Hemorrhagic Telangiectasia: Pictorial Essay on 2D and 3D Findings with Isotropic Multiphase CT1
Hassan Siddiki, MD,
Michael G. Doherty, MD,
Joel G. Fletcher, MD,
Anthony W. Stanson, MD,
Terri J. Vrtiska, MD,
David M. Hough, MD,
Jeff L. Fidler, MD,
Cynthia H. McCollough, PhD, and
Karen L. Swanson, DO
1 From the Departments of Radiology (H.S., M.G.D., J.G.F., A.W.S., T.J.V., D.M.H., J.L.F., C.H.M.) and Pulmonary and Critical Care Medicine (K.L.S.), Mayo Clinic, 200 First St SW, Rochester, MN 55905. Presented as an education exhibit at the 2005 RSNA Annual Meeting. Received March 5, 2007; revision requested May 9 and received July 16; accepted July 27. J.G.F. receives grant support from Siemens and E-Z-Em and has a license agreement with General Electric; J.L.F. receives grant support from E-Z-Em; C.H.M. receives grant support from Siemens and RTI Electronics; all other authors have no financial relationships to disclose.
Address correspondence to J.G.F. (e-mail: fletcher.joel{at}mayo.edu).
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Abstract
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The rapid evolution in multidetector computed tomographic (CT) technology has produced improvements in temporal and spatial resolution, leading to greater recognition of the spectrum of abdominal findings in hereditary hemorrhagic telangiectasia (HHT). In this multisystem vascular disorder, the abdominal findings are predominantly within the liver. Hepatic vascular lesions in HHT range from tiny telangiectases to transient perfusion abnormalities and large confluent vascular masses. Focal hepatic lesions are often associated with arteriovenous, arterioportal, or portovenous shunts. Pancreatic, splenic, and other vascular abnormalities are also observed because they are included in the field of view. By taking advantage of the increased z-axis spatial resolution and faster scanning times, and by using a bolus tracking technique, multiphase CT can be used to identify hepatic and extrahepatic lesions in HHT and to characterize the associated vascular shunts. Coronal maximum intensity projection images are particularly helpful in depiction of small hepatic vascular lesions.
© RSNA, 2008
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LEARNING OBJECTIVES
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After reading this article and taking the test, the reader will be able to:- Identify the well-defined spectrum of abdominal findings in patients with HHT.
- Discuss use of multiphase multidetector CT to increase detection of hepatic lesions in HHT and acquisition techniques to improve visualization of these lesions.
- Describe the common clinical findings and complications that can occur secondary to hepatic involvement in HHT.
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Introduction
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Hereditary hemorrhagic telangiectasia (HHT) is a rare autosomal dominant, multisystem vascular disorder affecting many organ systems and occurring in approximately 10–20 individuals per 100,000 (1,2). It is characterized by angiodysplastic lesions, in which there is direct communication between arteries and veins of varying sizes without an intervening capillary network (3). These communications may either cause bleeding (eg, epistaxis or hemoptysis) or result in shunting, which (depending on their location) may cause hypoxemia, stroke, seizures, brain abscesses, or high-output cardiac failure (4). At present, the pathogenesis of HHT is known with little certainty, but mutations in proteins in the transforming growth factor beta pathway have been implicated (5) and are thought to be important for vascular remodeling and angiogenesis (6).
Classically, the most commonly involved organs are the skin, lungs, and mucous membranes, but any organ system may be involved (3). With the advent of multidetector computed tomography (CT), hepatic involvement with HHT is recognized more commonly now than previously (7). Retrospective studies that used single-detector CT previously estimated the prevalence of hepatic involvement in HHT to be 8%–31% (4,8,9); however, more recent studies with multi-detector CT of consecutive patients have estimated it to be much higher, on the order of 74%–79% (7,10). In a prospective study of a large family with 40 members with HHT, hepatic involvement was detected in 13 with Doppler sonographic screening, and only two were symptomatic (11).
According to a review of the literature since 1978, only about just over half of patients with known hepatic HHT involvement were symptomatic (12), and when symptoms occur, the clinical features vary widely (8). Therefore, staging hepatic disease burden with CT can provide important information relating to disease prognosis and treatment. The purpose of this article is to describe our method of using bolus-tracking multiphase CT to detect vascular lesions and shunts and to illustrate the spectrum of abdominal findings in HHT.
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CT Technique
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The transitory enhancement of the vascular masses and shunts in HHT requires multiphase multidetector hepatic CT to optimize the timing of the contrast material bolus, permit high-temporal-resolution scanning (ie, minimize scan duration), and maximize the z-axis spatial resolution.
Optimization of the Contrast Material Bolus
The temporal appearance of the vascular masses and shunts in HHT requires dedicated scanning of the liver only. The time it takes to perform CT angiography of the chest (prior to liver imaging) can result in portal vein filling, precluding accurate assessment of arterioportal shunts (Fig 1). 
Furthermore, pulmonary arteriovenous malformations (AVMs) are clearly delineated at unenhanced chest CT owing to the surrounding lung parenchyma, so contrast material timing should be based on optimal hepatic imaging in order to display hepatic lesions and shunts, which may be seen only transiently. Consequently, when chest CT is being performed in addition to abdominal imaging, we perform the thoracic portion without intravenous contrast material (Fig 2a).
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Figure 1a. CT angiography of the chest and abdomen in a 76-year-old woman with HHT. (a) Axial image shows a small telangiectasis (arrow). (b) Coronal image shows physiologic filling of the portal vein (arrow). Although small telangiectases can be seen with routine acquisition protocols that include traditional intravenous contrast material, filling of the portal vein precludes detection of arterioportal shunts if the chest is scanned before the liver. Such routine CT angiograms lack temporal information because of the time delay.
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Figure 1b. CT angiography of the chest and abdomen in a 76-year-old woman with HHT. (a) Axial image shows a small telangiectasis (arrow). (b) Coronal image shows physiologic filling of the portal vein (arrow). Although small telangiectases can be seen with routine acquisition protocols that include traditional intravenous contrast material, filling of the portal vein precludes detection of arterioportal shunts if the chest is scanned before the liver. Such routine CT angiograms lack temporal information because of the time delay.
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Figure 2a. Unenhanced CT of the chest followed by CT angiography of the upper abdomen in a 62-year-old woman with HHT. (a) Coronal reformatted image (lung window) obtained without intravenous contrast material clearly shows a pulmonary AVM (arrow). (An axial image obtained with a soft-tissue window is not shown.) (b) Coronal maximum intensity projection (MIP) image (5-mm-thick section), obtained in the early arterial phase, shows diffuse punctate telangiectases (within braces) in the right hepatic lobe and arteriovenous shunting to the right hepatic vein (arrows). (c) Axial image shows the small telangiectases (white arrows) and right hepatic vein (black arrow). However, both the hepatic vein and the telangiectases are more conspicuous on the coronal MIP image owing to the vertical orientation of the hepatic vein and the use of MIP. Thus, coronal MIP images are helpful for both detection of lesions and characterization of liver involvement. (d) Hepatic phase image does not show the diffuse tiny telangiectases or other focal vascular lesions.
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Figure 2b. Unenhanced CT of the chest followed by CT angiography of the upper abdomen in a 62-year-old woman with HHT. (a) Coronal reformatted image (lung window) obtained without intravenous contrast material clearly shows a pulmonary AVM (arrow). (An axial image obtained with a soft-tissue window is not shown.) (b) Coronal maximum intensity projection (MIP) image (5-mm-thick section), obtained in the early arterial phase, shows diffuse punctate telangiectases (within braces) in the right hepatic lobe and arteriovenous shunting to the right hepatic vein (arrows). (c) Axial image shows the small telangiectases (white arrows) and right hepatic vein (black arrow). However, both the hepatic vein and the telangiectases are more conspicuous on the coronal MIP image owing to the vertical orientation of the hepatic vein and the use of MIP. Thus, coronal MIP images are helpful for both detection of lesions and characterization of liver involvement. (d) Hepatic phase image does not show the diffuse tiny telangiectases or other focal vascular lesions.
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Figure 2c. Unenhanced CT of the chest followed by CT angiography of the upper abdomen in a 62-year-old woman with HHT. (a) Coronal reformatted image (lung window) obtained without intravenous contrast material clearly shows a pulmonary AVM (arrow). (An axial image obtained with a soft-tissue window is not shown.) (b) Coronal maximum intensity projection (MIP) image (5-mm-thick section), obtained in the early arterial phase, shows diffuse punctate telangiectases (within braces) in the right hepatic lobe and arteriovenous shunting to the right hepatic vein (arrows). (c) Axial image shows the small telangiectases (white arrows) and right hepatic vein (black arrow). However, both the hepatic vein and the telangiectases are more conspicuous on the coronal MIP image owing to the vertical orientation of the hepatic vein and the use of MIP. Thus, coronal MIP images are helpful for both detection of lesions and characterization of liver involvement. (d) Hepatic phase image does not show the diffuse tiny telangiectases or other focal vascular lesions.
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Figure 2d. Unenhanced CT of the chest followed by CT angiography of the upper abdomen in a 62-year-old woman with HHT. (a) Coronal reformatted image (lung window) obtained without intravenous contrast material clearly shows a pulmonary AVM (arrow). (An axial image obtained with a soft-tissue window is not shown.) (b) Coronal maximum intensity projection (MIP) image (5-mm-thick section), obtained in the early arterial phase, shows diffuse punctate telangiectases (within braces) in the right hepatic lobe and arteriovenous shunting to the right hepatic vein (arrows). (c) Axial image shows the small telangiectases (white arrows) and right hepatic vein (black arrow). However, both the hepatic vein and the telangiectases are more conspicuous on the coronal MIP image owing to the vertical orientation of the hepatic vein and the use of MIP. Thus, coronal MIP images are helpful for both detection of lesions and characterization of liver involvement. (d) Hepatic phase image does not show the diffuse tiny telangiectases or other focal vascular lesions.
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To initiate arterial phase scanning, we perform low-dose monitoring over the aorta, 2 cm above the diaphragm, beginning at 5 seconds after initiation of contrast material injection and sampling every 2 seconds until a threshold of 150 HU is achieved. Early arterial phase scanning is performed after a 4-second delay after the threshold is achieved, with the late arterial and hepatic phases initiated 20 and 40 seconds after initiation of the early arterial phase, respectively. The early arterial phase is necessary to visualize arterioportal and arteriovenous shunting. Telangiectases are best seen in the early or late arterial phase, while the hepatic phase demonstrates lesion washout, parenchymal normalization, and portovenous shunting. To minimize the radiation dose, we do not routinely image the pelvis. The bolus tracking for the arterial phase imaging maximizes the likelihood of detecting arterioportal or arteriovenous shunting. This is clinically important because its presence even in an asymptomatic patient may portend development of future complications, such as high-output heart failure.
Multiphasic Imaging with High Temporal Resolution
For multiphasic organ imaging, we seek to minimize the time it takes to image an entire organ (in this case the liver). We use a 64-section CT scanner (Sensation 64; Siemens Medical Solutions, Malvern, Pa) with a quality reference milliampere-seconds value of 350 mAs, a table feed of 15.36 mm/sec, and a tube rotation time of 0.5 seconds. The tube rotation of 0.5 seconds is selected to permit an adequate speed while requiring little change of technique among patients with variable body habitus. Assuming 15 cm of coverage, each phase is completed in 9.8 seconds. As opposed to our routine abdominal CT practice, we increase the quality reference milliampere-seconds value to 350 mAs (from 240 mAs) to reduce image noise, such that detection of small vascular masses in solid organs can be optimized.
The volume-averaged CT dose index value used in the HHT liver protocol is 25 mGy. The nominal total effective dose for the three-phase HHT liver protocol is approximately 38 mSv. However, milliamperage-modulation dose reduction technologies used in the protocol can significantly lower the delivered dose. Reducing the prescribed milliampere-seconds value would also reduce the dose, but image noise would increase. Achieving the appropriate balance between patient dose and image noise is currently being investigated.
Maximizing Z-Axis Spatial Resolution and Lesion Conspicuity
Unlike earlier generations of multidetector CT, most 64-section CT scanners permit isotropic spatial resolution. We use a 64-section CT scanner with a default detector configuration of 32 x 0.6 mm (employing a z flying focal point in the x-ray tube, which produces overlapping) to yield 64 sections with isotropic spatial resolution (ie, z-axis resolution of 0.4 mm). Rather than creating hundreds of noisy submillimeter sections, we take advantage of the isotropic spatial resolution of the scanner and increase the conspicuity of hypervascular masses by reconstructing 5-mm coronal MIP images directly from the CT console for the early and late arterial phases, using a 3-mm reconstruction interval. This practice increases the conspicuity of small hypervascular masses adjacent to vessels (Fig 2). Optimal spatial resolution for coronal images is achieved by using the narrowest collimation available (0.6 mm for our scanner). For all three phases, we also reconstruct axial 2-mm sections (1.5-mm intervals); 0.6-mm axial sections (0.5-mm intervals) are sent to the workstation for review but not archived.
Multidetector CT Findings in HHT
Hepatic vascular lesions in HHT range from tiny telangiectases to transient perfusion abnormalities and large confluent vascular masses (8,12). Focal hepatic lesions are often associated with arteriovenous, arterioportal, or portovenous shunts. Pancreatic, splenic, and other vascular abnormalities are also observed because they are included in the scanning field of view.
Hepatic Lesions
Telangiectases.—
Telangiectases are the most commonly seen hepatic lesion and can be focal or diffuse (Figs 2, 3). They are hypervascular rounded masses, usually measuring only a few millimeters in size, but may be as large as 9 mm in diameter, usually resembling an asterisk in appearance (8,12). Coronal MIP images are helpful in appreciating telangiectases, especially when they exist in proximity to the large vertically oriented vessels, which makes them difficult to appreciate on transverse images (Figs 2, 4). Axial MIP images can be generated at the workstation at the time of review. The reconstructed multiplanar reformation and MIP images maximize the conspicuity of the attenuation differences between the hepatic parenchyma, small vascular lesions, and vascular structures (8,12) (Figs 2, 4). Telangiectases appear as focal hyperattenuating lesions in the arterial and late arterial phases, often becoming isointense with the hepatic parenchyma in the hepatic parenchymal phase (13).
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Figure 3a. Telangiectasis in a 36-year-old man with HHT. Axial early arterial (a), late arterial (b), and hepatic (c) phase images show a focal telangiectasis (arrow) in the posterolateral right hepatic lobe. The lesion is hyperattenuating in the early and late arterial phases and isoattenuating in the hepatic phase.
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Figure 3b. Telangiectasis in a 36-year-old man with HHT. Axial early arterial (a), late arterial (b), and hepatic (c) phase images show a focal telangiectasis (arrow) in the posterolateral right hepatic lobe. The lesion is hyperattenuating in the early and late arterial phases and isoattenuating in the hepatic phase.
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Figure 3c. Telangiectasis in a 36-year-old man with HHT. Axial early arterial (a), late arterial (b), and hepatic (c) phase images show a focal telangiectasis (arrow) in the posterolateral right hepatic lobe. The lesion is hyperattenuating in the early and late arterial phases and isoattenuating in the hepatic phase.
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Figure 4a. Telangiectases and large confluent vascular masses in a 43-year-old woman with HHT. (a, b) Axial (a) and coronal oblique MIP (b) images of the upper abdomen, obtained in the early arterial phase, show innumerable tiny telangiectases (arrows in a, arrowheads in b). Note that the telangiectases are displayed apart from the vessels on the coronal oblique MIP image, whereas it can be difficult to distinguish between the telangiectases and vessels on the axial image. Also seen is early filling of the adjacent hepatic veins, a finding indicative of arteriovenous shunting and enlargement of the common hepatic artery. (c, d) Axial late arterial (c) and hepatic (d) phase images show large confluent vascular masses (arrows). The masses demonstrate delayed and persistent enhancement but have different imaging characteristics than a cavernous hemangioma (ie, they are not isoattenuating relative to the blood pool and they lack peripheral or globular enhancement). A coronal view (inset in d) can be particularly helpful in imaging HHT, specifically for masses near the hepatic dome (arrows in inset).
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Figure 4b. Telangiectases and large confluent vascular masses in a 43-year-old woman with HHT. (a, b) Axial (a) and coronal oblique MIP (b) images of the upper abdomen, obtained in the early arterial phase, show innumerable tiny telangiectases (arrows in a, arrowheads in b). Note that the telangiectases are displayed apart from the vessels on the coronal oblique MIP image, whereas it can be difficult to distinguish between the telangiectases and vessels on the axial image. Also seen is early filling of the adjacent hepatic veins, a finding indicative of arteriovenous shunting and enlargement of the common hepatic artery. (c, d) Axial late arterial (c) and hepatic (d) phase images show large confluent vascular masses (arrows). The masses demonstrate delayed and persistent enhancement but have different imaging characteristics than a cavernous hemangioma (ie, they are not isoattenuating relative to the blood pool and they lack peripheral or globular enhancement). A coronal view (inset in d) can be particularly helpful in imaging HHT, specifically for masses near the hepatic dome (arrows in inset).
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Figure 4c. Telangiectases and large confluent vascular masses in a 43-year-old woman with HHT. (a, b) Axial (a) and coronal oblique MIP (b) images of the upper abdomen, obtained in the early arterial phase, show innumerable tiny telangiectases (arrows in a, arrowheads in b). Note that the telangiectases are displayed apart from the vessels on the coronal oblique MIP image, whereas it can be difficult to distinguish between the telangiectases and vessels on the axial image. Also seen is early filling of the adjacent hepatic veins, a finding indicative of arteriovenous shunting and enlargement of the common hepatic artery. (c, d) Axial late arterial (c) and hepatic (d) phase images show large confluent vascular masses (arrows). The masses demonstrate delayed and persistent enhancement but have different imaging characteristics than a cavernous hemangioma (ie, they are not isoattenuating relative to the blood pool and they lack peripheral or globular enhancement). A coronal view (inset in d) can be particularly helpful in imaging HHT, specifically for masses near the hepatic dome (arrows in inset).
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Figure 4d. Telangiectases and large confluent vascular masses in a 43-year-old woman with HHT. (a, b) Axial (a) and coronal oblique MIP (b) images of the upper abdomen, obtained in the early arterial phase, show innumerable tiny telangiectases (arrows in a, arrowheads in b). Note that the telangiectases are displayed apart from the vessels on the coronal oblique MIP image, whereas it can be difficult to distinguish between the telangiectases and vessels on the axial image. Also seen is early filling of the adjacent hepatic veins, a finding indicative of arteriovenous shunting and enlargement of the common hepatic artery. (c, d) Axial late arterial (c) and hepatic (d) phase images show large confluent vascular masses (arrows). The masses demonstrate delayed and persistent enhancement but have different imaging characteristics than a cavernous hemangioma (ie, they are not isoattenuating relative to the blood pool and they lack peripheral or globular enhancement). A coronal view (inset in d) can be particularly helpful in imaging HHT, specifically for masses near the hepatic dome (arrows in inset).
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Large Confluent Vascular Masses.—
The Bari group (10) has proposed the term large confluent vascular masses, which they define as "large areas of multiple telangiectases that coalesce or large shunts that are directly visible." Any enhancing lesion with a diameter more than 10 mm is called a large confluent vascular mass (10). These larger vascular pools usually demonstrate early enhancement that is seen during both arterial phases, with enhancement persisting in the hepatic phase. The CT appearance of large vascular masses differs from that of cavernous hemangiomas. Large vascular masses have a heterogeneous or homogeneous enhancement pattern, but without the characteristic globular enhancement pattern seen in cavernous hemangiomas, which is isoattenuating with respect to the blood pool at multiphasic imaging. Large vascular masses often appear least conspicuous during hepatic phase imaging (Figs 4c, 4d, 5).
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Figure 5a. Confluent vascular mass in a 65-year-old woman with HHT. Axial early arterial (a), late arterial (b), and hepatic (c) phase images and coronal early arterial phase MIP image (d) show a confluent vascular mass (arrow) with early and delayed persistent enhancement. Note the AVM in the falciform ligament (braces in d).
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Figure 5b. Confluent vascular mass in a 65-year-old woman with HHT. Axial early arterial (a), late arterial (b), and hepatic (c) phase images and coronal early arterial phase MIP image (d) show a confluent vascular mass (arrow) with early and delayed persistent enhancement. Note the AVM in the falciform ligament (braces in d).
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Figure 5c. Confluent vascular mass in a 65-year-old woman with HHT. Axial early arterial (a), late arterial (b), and hepatic (c) phase images and coronal early arterial phase MIP image (d) show a confluent vascular mass (arrow) with early and delayed persistent enhancement. Note the AVM in the falciform ligament (braces in d).
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Figure 5d. Confluent vascular mass in a 65-year-old woman with HHT. Axial early arterial (a), late arterial (b), and hepatic (c) phase images and coronal early arterial phase MIP image (d) show a confluent vascular mass (arrow) with early and delayed persistent enhancement. Note the AVM in the falciform ligament (braces in d).
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Hepatic Perfusion Abnormalities.—
Nonfocal hepatic perfusion abnormalities are identified as an inhomogeneous attenuating pattern within the liver parenchyma (Fig 6). Like telangiectases and large confluent vascular masses, these abnormalities are best seen during the early arterial and late arterial phases, almost always disappearing in the hepatic phase as the hepatic parenchyma becomes homogeneous.
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Figure 6a. Hepatic perfusion abnormality in a 30-year-old patient with HHT. Axial early arterial (a) and late arterial (b) phase images show diffuse heterogeneity of attenuation throughout the hepatic parenchyma, an appearance that normalizes on the hepatic phase image (c).
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Figure 6b. Hepatic perfusion abnormality in a 30-year-old patient with HHT. Axial early arterial (a) and late arterial (b) phase images show diffuse heterogeneity of attenuation throughout the hepatic parenchyma, an appearance that normalizes on the hepatic phase image (c).
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Figure 6c. Hepatic perfusion abnormality in a 30-year-old patient with HHT. Axial early arterial (a) and late arterial (b) phase images show diffuse heterogeneity of attenuation throughout the hepatic parenchyma, an appearance that normalizes on the hepatic phase image (c).
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In contrast to the perfusion abnormalities of HHT, perfusion abnormalities that are seen in the setting of cirrhosis usually are more focal and can be related to focal areas of occlusion of small hepatic venules, small arterioportal shunts, hepatocellular carcinoma, or idiopathic causes (14). Frequently, the focal abnormalities in cirrhosis are seen more peripherally near the liver surface. These cirrhotic peripheral perfusion abnormalities may have a characteristic wedge-shaped con-figuration on either coronal or axial projections. With HHT, the perfusion abnormalities are frequently more diffuse (nonfocal) and inhomogeneous or ill-defined (15,16). The more diffuse appearance seen with HHT likely relates to the more extensive widespread underlying vascular lesions. Other cirrhotic findings such as a nodular liver surface and lobar atrophy are not seen in HHT. Moreover, hepatic diseases associated with increased blood flow (such as cirrhosis or hepatocellular carcinoma) do not have the enlarged hepatic artery observed in many HHT patients with diffuse hepatic involvement and arteriovenous shunting (17).
Focal perfusion defects resembling transient hepatic attenuation defects ("THAD" lesions) can be seen alone with peripheral location, triangular shape, and straight margins. Such defects may be an indirect sign of other abnormalities, such as an arterioportal shunt, a tiny telangiectasis, or serosal venous drainage.
An association between HHT and focal nodular hyperplasia (FNH) of the liver has been reported (Fig 7) (18). As a practical matter, small FNH lesions are difficult to distinguish from vascular lesions in HHT when diffuse hepatic abnormalities are present.
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Figure 7. FNH in a 46-year-old man with HHT. Axial early arterial phase image shows an incidentally discovered mass with an appearance consistent with FNH. The inset image shows the lesion in the hepatic phase. Others have reported an increased prevalence of FNH in HHT patients.
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Hepatic Shunts
Three types of hepatic vascular shunts exist in HHT: arteriovenous, arterioportal, and portovenous. Arteriovenous and arterioportal shunts are artery-to-vein shunts with the early draining vein connecting to the hepatic vein or portal vein, respectively. Both are detected during the early arterial phase, with later phases being less diagnostic.
- Arteriovenous (hepatic artery to hepatic vein) shunts are the most frequently observed vascular shunt in our HHT practice. Arteriovenous shunts are most conspicuous in the early arterial phase and are usually seen with coexistent telangiectases or large vascular masses, through which shunting is occurring (Fig 8). Direct arteriovenous fistulas can also be seen in isolation or in combination with focal hepatic vascular masses (Figs 9–11). Because hepatic veins normally fill with contrast material during the hepatic phase, early opacification of the hepatic veins (ie, simultaneously with intra- and extrahepatic arteries) during the early arterial phase indicates arteriovenous shunting (10). As a result of high-output shunting, both hepatic arteries and hepatic veins may become enlarged (Figs 4b, 8, 9).
- Arterioportal (hepatic artery to portal vein) shunts demonstrate early enhancement of the portal vein during the early arterial phase. Early opacification of the portal vein as a result of the shunt leads to visualization of the paired hepatic artery and portal vein branches in the early arterial phase (Fig 12). As mentioned earlier, arterioportal shunts can result in wedge-shaped hyperattenuating areas of disordered perfusion, which at times may be the only clue to their presence.
- Portovenous (portal vein to hepatic vein) shunts are rarely seen in HHT. These shunts are seen in the hepatic phase (10), with a dilated portal vein branch (during the portal venous phase) communicating with the large hepatic vein, usually through a focal hepatic mass (Fig 13). Portovenous shunts are occult at angiography.
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Figure 8a. Arteriovenous shunt in a 43-year-old woman with HHT (same patient as in Fig 4). Lateral (a) and oblique (b) three-dimensional (3D) volume-rendered arterial phase images show early opacification of the hepatic veins (white arrows) secondary to arteriovenous shunting. Note the small telangiectases (arrowheads). Also evident are splenic artery aneurysms (yellow arrows in b).
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Figure 8b. Arteriovenous shunt in a 43-year-old woman with HHT (same patient as in Fig 4). Lateral (a) and oblique (b) three-dimensional (3D) volume-rendered arterial phase images show early opacification of the hepatic veins (white arrows) secondary to arteriovenous shunting. Note the small telangiectases (arrowheads). Also evident are splenic artery aneurysms (yellow arrows in b).
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Figure 9a. Arteriovenous shunt in a 33-year-old woman with HHT. Late arterial phase coronal MIP (a) and early arterial phase 3D volume-rendered (b) images show enlargement of the hepatic arteries and early opacification of the hepatic veins (white arrows) secondary to arteriovenous shunting. The shunting was secondary to diffuse hepatic telangiectases (yellow arrow in b) and arteriovenous fistulas.
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Figure 9b. Arteriovenous shunt in a 33-year-old woman with HHT. Late arterial phase coronal MIP (a) and early arterial phase 3D volume-rendered (b) images show enlargement of the hepatic arteries and early opacification of the hepatic veins (white arrows) secondary to arteriovenous shunting. The shunting was secondary to diffuse hepatic telangiectases (yellow arrow in b) and arteriovenous fistulas.
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Figure 10a. Arteriovenous shunt in a 65-year-old woman with HHT and hepatic involvement. (a) Three-dimensional volume-rendered image shows markedly enlarged left (white arrow) and right (yellow arrow) hepatic arteries secondary to arteriovenous shunting. (b) Corresponding 3D volume-rendered image shows the hepatic veins (arrows), which are rendered blue to distinguish them from the arteries. (c) CT image shows that the arteriovenous shunting is likely due to a combination of telangiectases, large vascular masses, and arteriovenous fistulas (arrow).
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Figure 10b. Arteriovenous shunt in a 65-year-old woman with HHT and hepatic involvement. (a) Three-dimensional volume-rendered image shows markedly enlarged left (white arrow) and right (yellow arrow) hepatic arteries secondary to arteriovenous shunting. (b) Corresponding 3D volume-rendered image shows the hepatic veins (arrows), which are rendered blue to distinguish them from the arteries. (c) CT image shows that the arteriovenous shunting is likely due to a combination of telangiectases, large vascular masses, and arteriovenous fistulas (arrow).
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Figure 10c. Arteriovenous shunt in a 65-year-old woman with HHT and hepatic involvement. (a) Three-dimensional volume-rendered image shows markedly enlarged left (white arrow) and right (yellow arrow) hepatic arteries secondary to arteriovenous shunting. (b) Corresponding 3D volume-rendered image shows the hepatic veins (arrows), which are rendered blue to distinguish them from the arteries. (c) CT image shows that the arteriovenous shunting is likely due to a combination of telangiectases, large vascular masses, and arteriovenous fistulas (arrow).
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Figure 11. Arteriovenous shunts in a 68-year-old woman with HHT. Arterial phase coronal MIP image shows a large AVM with arteriovenous shunting in the right hepatic lobe near the dome (arrow) with early opacification and enlargement of the right hepatic vein. Note another arteriovenous shunt at the lower margin of the liver (arrowhead).
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Figure 12a. Arterioportal shunt in a 67-year-old woman with HHT. (a, b) Axial images show myriad findings associated with an arterioportal shunt, including an arterioportal fistula in the left hepatic lobe (arrow in a), an enlarged portal vein with a thrombus (arrowhead in b), paraesophageal varices (arrowhead in inset in b), ascites, and mild splenomegaly secondary to portal hypertension (seen in b). (c, d) Oblique MIP (c) and 3D volume-rendered (d) images obtained in the early arterial phase show the paired hepatic artery and portal vein branches supplying and draining the arterioportal shunt (arrow).
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Figure 12b. Arterioportal shunt in a 67-year-old woman with HHT. (a, b) Axial images show myriad findings associated with an arterioportal shunt, including an arterioportal fistula in the left hepatic lobe (arrow in a), an enlarged portal vein with a thrombus (arrowhead in b), paraesophageal varices (arrowhead in inset in b), ascites, and mild splenomegaly secondary to portal hypertension (seen in b). (c, d) Oblique MIP (c) and 3D volume-rendered (d) images obtained in the early arterial phase show the paired hepatic artery and portal vein branches supplying and draining the arterioportal shunt (arrow).
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Figure 12c. Arterioportal shunt in a 67-year-old woman with HHT. (a, b) Axial images show myriad findings associated with an arterioportal shunt, including an arterioportal fistula in the left hepatic lobe (arrow in a), an enlarged portal vein with a thrombus (arrowhead in b), paraesophageal varices (arrowhead in inset in b), ascites, and mild splenomegaly secondary to portal hypertension (seen in b). (c, d) Oblique MIP (c) and 3D volume-rendered (d) images obtained in the early arterial phase show the paired hepatic artery and portal vein branches supplying and draining the arterioportal shunt (arrow).
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Figure 12d. Arterioportal shunt in a 67-year-old woman with HHT. (a, b) Axial images show myriad findings associated with an arterioportal shunt, including an arterioportal fistula in the left hepatic lobe (arrow in a), an enlarged portal vein with a thrombus (arrowhead in b), paraesophageal varices (arrowhead in inset in b), ascites, and mild splenomegaly secondary to portal hypertension (seen in b). (c, d) Oblique MIP (c) and 3D volume-rendered (d) images obtained in the early arterial phase show the paired hepatic artery and portal vein branches supplying and draining the arterioportal shunt (arrow).
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Figure 13. Portovenous shunt in a 58-year-old woman with HHT. Axial MIP image obtained in the hepatic phase shows portohepatic venous shunting, with the dilated portal vein communicating with the left hepatic vein through a focal vascular mass (arrow).
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Although vascular shunting is a prominent feature of HHT, other pathologic conditions such as invasive and hypervascular tumors and traumatic or iatrogenic intrahepatic arteriovenous fistulas can cause intrahepatic vascular shunts.
Other Lesions
AVMs may potentially occur in the vascular system of any organ as part of HHT. Extrahepatic lesions in HHT occur within a predefined spectrum of appearances and locations, with pancreatic AVMs being the most common. Approximately 10%–15% of patients in our practice demonstrated a pancreatic AVM (Fig 14). Pancreatic AVMs appear as focal hypervascular lesions measuring over 5–10 mm in size, usually with arteriovenous shunting to mesenteric veins, such as the superior mesenteric vein or splenic vein. These lesions were small and incidentally detected and did not result in clinical sequelae. A variety of splenic lesions were seen in about 10% of HHT patients at our clinic, including small hypervascular lesions and splenic artery aneurysms (Fig 8). We have also observed extrahepatic vascular lesions of HHT within the bowel and stomach (Figs 15, 16).
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Figure 14. Pancreatic AVMs in a 55-year-old man with HHT. Arterial phase coronal MIP image of the upper abdomen shows arteriovenous fistulas in the pancreatic head (arrowhead). Note the draining vein (arrow) associated with the pancreatic head AVM. The inset axial image shows another vascular lesion in the pancreatic tail (arrow in inset).
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Figure 15a. Cecal AVM in a 53-year-old man with HHT. (a) Oblique coronal image shows the feeding artery (arrow) and draining vein (arrowhead) of a cecal AVM. (b) Axial image shows the entire course of the feeding artery (arrow) and the AVM nidus in the cecal wall (arrowhead). The cecal lesion could be an isolated finding unrelated to HHT.
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Figure 15b. Cecal AVM in a 53-year-old man with HHT. (a) Oblique coronal image shows the feeding artery (arrow) and draining vein (arrowhead) of a cecal AVM. (b) Axial image shows the entire course of the feeding artery (arrow) and the AVM nidus in the cecal wall (arrowhead). The cecal lesion could be an isolated finding unrelated to HHT.
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Figure 16. Extrahepatic vascular lesions in a 53-year-old man with HHT. Axial image shows a gastric AVM (arrowhead) and its feeding artery in the greater curvature of the stomach (white arrow). There is also a coexistent pancreatic AVM (black arrow). The inset coronal image shows a different view of the gastric AVM (arrow in inset).
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Clinical Features and Complications
There is more than one clinical subtype of HHT liver disease. The particular clinical manifestation of liver involvement in patients with HHT may depend on the predominant type and size of the shunt as well as on the effects of an abnormal hepatic blood supply. The majority of such patients have a hyperdynamic circulation resulting from arteriovenous shunting, portovenous shunting, or both (17), which may contribute to high-output cardiac failure from shunting within the liver (Fig 17). Other factors related to diastolic dysfunction, such as older age, hypertension, and coronary artery disease, may play a part in precipitating heart failure.
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Figure 17a. Arteriovenous shunt in a 58-year-old woman with HHT. (a) Axial nonen-hanced image of the lower chest (lung window) shows marked cardiac enlargement. The patient did not have overt signs of congestive heart failure. (b) Sagittal arterial phase image of the abdomen shows high-grade stenosis of the celiac artery (black arrow) incidental to compression by the arcuate ligament. Arteriovenous shunting to the hepatic veins is seen (white arrows).
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Figure 17b. Arteriovenous shunt in a 58-year-old woman with HHT. (a) Axial nonen-hanced image of the lower chest (lung window) shows marked cardiac enlargement. The patient did not have overt signs of congestive heart failure. (b) Sagittal arterial phase image of the abdomen shows high-grade stenosis of the celiac artery (black arrow) incidental to compression by the arcuate ligament. Arteriovenous shunting to the hepatic veins is seen (white arrows).
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In contrast, arterioportal shunts can infrequently cause life-threatening portal hypertension (17). A dilated portal vein (diameter > 13 mm), often associated with collateral venous drainage (such as a recanalized umbilical vein or esophageal varices) and splenomegaly, indicates portal hypertension resulting from an arterioportal shunt (10). As an isolated finding, however, a dilated portal vein can reflect increased flow without portal hypertension, particularly in the absence of correlative imaging and clinical findings.
Wu et al (17) studied a series of 24 HHT patients, all with symptomatic liver disease. Although every patient had diffuse liver telangiectases that led to a markedly heterogeneous hepatic enhancement pattern, the type of vascular shunt (eg, arteriovenous or arterioportal) did not always correspond to the clinical presentation (ie, high-output heart failure or portal hypertension, respectively). Thus, arterioportal and arteriovenous shunts are frequently seen with symptomatic liver disease but correlate poorly with the clinical presentation. Wu et al (17) also reported a high prevalence of biliary abnormalities in their series. In our practice, where we screen for hepatic involvement in asymptomatic patients with known HHT, we often detect vascular shunts but rarely see biliary complications. Similarly, atypical cirrhosis is described as a rare complication but has not been observed at our institute (3).
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Future Directions
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Imaging may play a larger role in the future for HHT patients, especially for those who have symptomatic liver disease and a less favorable course, ultimately requiring a liver transplant. In such patients, multidetector CT may have a potential to be used in preoperative assessment because it can provide critical details about the characteristics of liver involvement as well as any variant vascular anatomy. It has already been suggested that biliary abnormalities (strictures, dilatation, cysts, etc) are more common in symptomatic than in asymptomatic patients and may be indicative of more advanced disease (17).
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Conclusions
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HHT is a multisystem disease with abdominal findings mainly but not exclusively limited to the liver. Hepatic vascular abnormalities in HHT range from tiny telangiectases to heterogeneous vascular masses. Abdominal involvement by HHT is increasingly recognized with multidetector CT. Vascular hepatic and pancreatic lesions in HHT have a well-defined spectrum of appearances. Coronal MIP images are particularly helpful for depiction of small hepatic vascular lesions. Multiphasic scanning with bolus tracking combined with faster scanning times and improved z-axis spatial resolution permits increased recognition and characterization of transient vascular lesions within and outside the liver, along with associated vascular shunts.
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Footnotes
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Abbreviations: AVM = arteriovenous malformation, FNH = focal nodular hyperplasia, HHT = hereditary hemorrhagic telangiectasia, MIP = maximum intensity projection, 3D = three-dimensional
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References
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Abstract
LEARNING OBJECTIVES
