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(Radiographics. 2002;22:1041-1051.)
© RSNA, 2002

EDUCATION EXHIBIT

CT during Hepatic Arteriography and Portography: An Illustrative Review1

Hyun Cheol Kim, MD, Tae Kyoung Kim, MD, Kyu-Bo Sung, MD, Hyun-Ki Yoon, MD, Pyo Nyun Kim, MD, Hyun Kwon Ha, MD, Ah Young Kim, MD, Hyun Jin Kim, MD and Moon-Gyu Lee, MD

1 From the Department of Radiology, Asan Medical Center, University of Ulsan College of Medicine, 388-1 Poongnap-Dong, Songpa-Ku, Seoul 138-736, Korea. Presented as an education exhibit at the 2001 RSNA scientific assembly. Received February 15, 2002; revision requested April 5 and received May 7; accepted May 9. Address correspondence to T.K.K. (e-mail: tkkim@amc.seoul.kr).


   Abstract
Top
 Abstract
LEARNING OBJECTIVES
 Introduction
 Imaging Techniques
 Focal Liver Lesions
 Nontumorous Hemodynamic Changes
 Conclusions
 References
 
The combination of computed tomography (CT) during arterial portography (CTAP) and CT during hepatic arteriography (CTHA) has been used for evaluation of hepatic neoplasms before partial hepatic resection. Focal hepatic lesions that can be demonstrated with CTAP and CTHA include regenerative nodules, dysplastic nodules, dysplastic nodules with malignant foci, hepatocellular carcinoma, cholangiocarcinoma, hemangioma, and metastases. CTAP is considered the most sensitive modality for detection of small hepatic lesions, particularly small hepatic tumors such as hepatocellular carcinoma and metastatic tumors. CTHA can demonstrate not only hypervascular tumors but also hypovascular tumors and can help differentiate malignant from benign lesions. However, various types of nontumorous hemodynamic changes are frequently encountered at CTAP or CTHA and appear as focal lesions that mimic true hepatic lesions. Such hemodynamic changes include several types of arterioportal shunts, liver cirrhosis, Budd-Chiari syndrome, inflammatory changes, pseudolesions due to an aberrant blood supply, and laminar flow in the portal vein. Familiarity with the CTAP and CTHA appearances of various hepatic lesions and nontumorous hemodynamic changes allows the radiologist to improve the diagnostic accuracy.

© RSNA, 2002

Index Terms: Budd-Chiari syndrome, 761.659 • Computed tomography (CT), angiography, 761.12116 • Liver, abscess, 761.21 • Liver, cirrhosis, 761.794 • Liver, nodules, 761.3198 • Liver neoplasms, diagnosis, 761.30, 761.3194 • Shunts, arterioportal, 95.717


   LEARNING OBJECTIVES
Top
 Abstract
 LEARNING OBJECTIVES
Introduction
 Imaging Techniques
 Focal Liver Lesions
 Nontumorous Hemodynamic Changes
 Conclusions
 References
 
After reading this article and taking the test, the reader will be able to:


   Introduction
Top
 Abstract
 LEARNING OBJECTIVES
 Introduction
Imaging Techniques
 Focal Liver Lesions
 Nontumorous Hemodynamic Changes
 Conclusions
 References
 
Computed tomography (CT) during arterial portography (CTAP) and CT during hepatic arteriography (CTHA) have been used for preoperative evaluation of candidates for hepatic resection (1). Although CTAP is considered the most sensitive imaging modality for detecting focal liver lesions, use of this technique is limited by its invasiveness and high false-positive rate. Combined use of CTAP and CTHA can improve diagnostic accuracy by reducing the false-positive results (1–3). However, we frequently encounter various types of perfusion disorders at CTAP and CTHA, caused mainly by altered hemodynamics of the liver, that frequently mimic true hepatic lesions and evoke diagnostic uncertainty (4–10).

During our recent 3-year experience with CTAP and CTHA examinations, we found various focal liver lesions and nontumorous hemodynamic changes. Focal liver lesions include regenerative nodules, dysplastic nodules, dysplastic nodules with malignant foci, hepatocellular carcinoma, cholangiocarcinoma, hemangioma, and metastases. Nontumorous hemodynamic changes include several types of arterioportal shunts, liver cirrhosis, Budd-Chiari syndrome, inflammatory changes, pseudolesions due to aberrant blood supply, and laminar flow in the portal vein.

In this article, we present the imaging spectra of various hepatic lesions and nontumorous hemodynamic changes at CTAP and CTHA.


   Imaging Techniques
Top
 Abstract
 LEARNING OBJECTIVES
 Introduction
 Imaging Techniques
Focal Liver Lesions
 Nontumorous Hemodynamic Changes
 Conclusions
 References
 
For CTAP and CTHA, arterial vascular access was obtained with two unilateral femoral artery punctures by using the Seldinger technique. Two catheters were selectively placed, one in the superior mesenteric artery and the other in the common hepatic artery. Before CTAP and CTHA, celiac and superior mesenteric angiographic examinations were performed to evaluate tumor vascularity and the vascular anatomy.

For CTAP, 80 mL of nonionic contrast material (iodine, 370 mg/mL) was injected through the superior mesenteric artery at a rate of 2.5 mL/sec with a power injector, and CT scanning was performed 35 seconds after the start of the injection. For CTHA, 36 mL of contrast material was injected through the common hepatic artery at a rate of 1.8 mL/sec, and CT scanning was performed 6 seconds after the start of the injection. The images were obtained in a craniocaudal direction with 7–8-mm collimation, 10-mm/sec table speed during a single breath-hold helical acquisition of 20–30 seconds depending on the liver size, and a 7–8-mm reconstruction interval.


   Focal Liver Lesions
Top
 Abstract
 LEARNING OBJECTIVES
 Introduction
 Imaging Techniques
 Focal Liver Lesions
Nontumorous Hemodynamic Changes
 Conclusions
 References
 
Regenerative Nodules
In micronodular cirrhosis, regenerative nodules are not visible at all or are seen only as heterogeneity of the liver parenchyma at CTAP and CTHA. The appearance of regenerative nodules at CTAP and CTHA mainly depends on the size of the nodules and the degree of fibrosis. Generally, the larger the nodules and the thicker the fibrosis, the better the nodules are visualized. Regenerative nodules are seen as innumerable enhancing nodules surrounded by low-attenuation septa at CTAP and as nonenhancing nodules surrounded by enhancing septa at CTHA (11) (Fig 1). An individual regenerative nodule contains a normal portal venous supply and is enhanced similarly to the surrounding liver parenchyma at CTAP, whereas fibrous septa have low attenuation. However, some regenerative nodules show low attenuation at CTAP and high attenuation at CTHA compared with surrounding liver parenchyma.



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  		Figure 1a.  Multiple regenerative nodules in a 49-year-old man with liver cirrhosis. (a) CTAP image shows heterogeneous enhancement of the liver. Poorly defined nodules with slightly increased attenuation (arrowheads) are seen in the liver. (b) CTHA image shows that the nodules (arrowheads) are hypoattenuating and outlined by thin enhancing septa.

 


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  		Figure 1b.  Multiple regenerative nodules in a 49-year-old man with liver cirrhosis. (a) CTAP image shows heterogeneous enhancement of the liver. Poorly defined nodules with slightly increased attenuation (arrowheads) are seen in the liver. (b) CTHA image shows that the nodules (arrowheads) are hypoattenuating and outlined by thin enhancing septa.

 
Dysplastic Nodules with and without Malignant Foci
Dysplastic nodules in the liver are nodular hepatocellular proliferations at least 1 mm in diameter and lacking the definite histopathologic criteria of malignancy. Although low-grade dysplastic nodules have a tendency to have more portal blood supply than high-grade dysplastic nodules, the portal and arterial supplies to low- and high-grade dysplastic nodules are variable and inconsistent (12) (Fig 2). Thus, it is difficult to detect and characterize dysplastic nodules at CTAP and CTHA (12). The relationship between the portal and arterial blood supplies to hepatic nodules in a cirrhotic liver is considered reciprocal (13). Intranodular portal blood flow tends to decrease and arterial blood flow tends to decrease initially and then increase as the grade of malignancy increases from regenerative nodules through the intermediate steps of dysplastic nodules to hepatocellular carcinoma (14). Thus, if a focal enhancing portion within a hypoattenuating nodule is visible at CTHA, a high-grade dysplastic nodule with malignant foci is suggested (Fig 3).



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  		Figure 2a.  Dysplastic nodules in a 58-year-old man. (a) CTAP image shows a slightly hypoattenuating nodule (arrows) with a central hyperattenuating area in the right lobe of the liver. (b) CTHA image shows that the nodule (arrows) is slightly hypoattenuating. Histopathologic analysis of a percutaneous needle biopsy specimen showed that the lesion was a low-grade dysplastic nodule. (c) CTAP image obtained at a lower level shows another mass (arrows), which is isoattenuating relative to adjacent liver tissue. (d) CTHA image shows that the lesion (arrows) is hypoattenuating. Histopathologic analysis of a percutaneous needle biopsy specimen showed that the lesion was a high-grade dysplastic nodule.

 


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  		Figure 2b.  Dysplastic nodules in a 58-year-old man. (a) CTAP image shows a slightly hypoattenuating nodule (arrows) with a central hyperattenuating area in the right lobe of the liver. (b) CTHA image shows that the nodule (arrows) is slightly hypoattenuating. Histopathologic analysis of a percutaneous needle biopsy specimen showed that the lesion was a low-grade dysplastic nodule. (c) CTAP image obtained at a lower level shows another mass (arrows), which is isoattenuating relative to adjacent liver tissue. (d) CTHA image shows that the lesion (arrows) is hypoattenuating. Histopathologic analysis of a percutaneous needle biopsy specimen showed that the lesion was a high-grade dysplastic nodule.

 


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  		Figure 2c.  Dysplastic nodules in a 58-year-old man. (a) CTAP image shows a slightly hypoattenuating nodule (arrows) with a central hyperattenuating area in the right lobe of the liver. (b) CTHA image shows that the nodule (arrows) is slightly hypoattenuating. Histopathologic analysis of a percutaneous needle biopsy specimen showed that the lesion was a low-grade dysplastic nodule. (c) CTAP image obtained at a lower level shows another mass (arrows), which is isoattenuating relative to adjacent liver tissue. (d) CTHA image shows that the lesion (arrows) is hypoattenuating. Histopathologic analysis of a percutaneous needle biopsy specimen showed that the lesion was a high-grade dysplastic nodule.

 


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  		Figure 2d.  Dysplastic nodules in a 58-year-old man. (a) CTAP image shows a slightly hypoattenuating nodule (arrows) with a central hyperattenuating area in the right lobe of the liver. (b) CTHA image shows that the nodule (arrows) is slightly hypoattenuating. Histopathologic analysis of a percutaneous needle biopsy specimen showed that the lesion was a low-grade dysplastic nodule. (c) CTAP image obtained at a lower level shows another mass (arrows), which is isoattenuating relative to adjacent liver tissue. (d) CTHA image shows that the lesion (arrows) is hypoattenuating. Histopathologic analysis of a percutaneous needle biopsy specimen showed that the lesion was a high-grade dysplastic nodule.

 


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  		Figure 3a.  High-grade dysplastic nodule with foci of hepatocellular carcinoma in a 52-year-old woman. (a) CTAP image shows a slightly hypoattenuating nodule with a tiny perfusion defect (arrow) in the left lobe of the liver. (b) CTHA image shows that the nodule is hypoattenuating with a tiny enhancing spot (arrow). Histopathologic analysis of a surgical specimen showed that the lesion was a high-grade dysplastic nodule with microscopic foci of well-differentiated hepatocellular carcinoma.

 


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  		Figure 3b.  High-grade dysplastic nodule with foci of hepatocellular carcinoma in a 52-year-old woman. (a) CTAP image shows a slightly hypoattenuating nodule with a tiny perfusion defect (arrow) in the left lobe of the liver. (b) CTHA image shows that the nodule is hypoattenuating with a tiny enhancing spot (arrow). Histopathologic analysis of a surgical specimen showed that the lesion was a high-grade dysplastic nodule with microscopic foci of well-differentiated hepatocellular carcinoma.

 
Hepatocellular Carcinoma
Hepatocellular carcinoma replaces the dual supply provided by the arterial and portal blood flows with an arterial blood supply alone; as a result, hepatocellular carcinomas usually do not receive portal blood flow (15). Thus, hepatocellular carcinomas are seen as hypoattenuating lesions at CTAP and as hyperattenuating lesions at CTHA (Fig 4). However, these typical findings are not commonly seen in early hepatocellular carcinomas, possibly due to the combination of normal hepatic artery degeneration and preserved portal veins (16).



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  		Figure 4a.  Typical hepatocellular carcinoma in a 72-year-old man. (a) CTAP image shows a well-defined, round perfusion defect in the right lobe of the liver. (b) CTHA image shows marked enhancement of the mass. Histopathologic analysis of a surgical specimen showed that the lesion was a hepatocellular carcinoma.

 


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  		Figure 4b.  Typical hepatocellular carcinoma in a 72-year-old man. (a) CTAP image shows a well-defined, round perfusion defect in the right lobe of the liver. (b) CTHA image shows marked enhancement of the mass. Histopathologic analysis of a surgical specimen showed that the lesion was a hepatocellular carcinoma.

 
Peripheral Cholangiocarcinoma
Peripheral cholangiocarcinoma usually appears as a purely intrahepatic mass. Typical contrast material–enhanced CT findings include markedly low intratumoral attenuation with thin enhancement at the tumor periphery and focal intrahepatic bile duct dilatation around the tumor (17). Peripheral cholangiocarcinomas are generally seen as hypoattenuating lesions at CTAP and as hypoattenuating lesions with a peripheral, irregular hyperattenuating rim at CTHA (1) (Fig 5).



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  		Figure 5a.  Peripheral cholangiocarcinoma in a 61-year-old man. (a) CTAP image shows an irregular perfusion defect (arrows) in the right lobe of the liver. The peripheral bile ducts (arrowhead) are dilated in the subcapsular area of the liver. (b) CTHA image shows an irregular hyperattenuating rim (arrows) surrounding the lesion. Histopathologic analysis of a surgical specimen showed that the lesion was a cholangiocarcinoma.

 


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  		Figure 5b.  Peripheral cholangiocarcinoma in a 61-year-old man. (a) CTAP image shows an irregular perfusion defect (arrows) in the right lobe of the liver. The peripheral bile ducts (arrowhead) are dilated in the subcapsular area of the liver. (b) CTHA image shows an irregular hyperattenuating rim (arrows) surrounding the lesion. Histopathologic analysis of a surgical specimen showed that the lesion was a cholangiocarcinoma.

 
Hemangioma
At contrast-enhanced CT, hepatic hemangioma is typically seen as a hypoattenuating lesion with peripheral globular enhancement that progresses centrally (18). However, hepatic hemangiomas are seen as nonspecific perfusion defects at CTAP. Findings at CTHA are variable according to the rapidity of the enhancement of the hemangiomas; the most common finding is peripheral globular enhancement (Fig 6). CTHA is more useful than CTAP in characterization of hemangiomas; however, combined CTAP and CTHA is not considered a specific imaging method for diagnosing hemangiomas.



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  		Figure 6a.  Hemangioma in a 40-year-old man. (a) CTAP image shows an ovoid perfusion defect (arrows) in the left lobe of the liver. (b) CTHA image shows peripheral globular enhancement (arrow) of the mass.

 


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  		Figure 6b.  Hemangioma in a 40-year-old man. (a) CTAP image shows an ovoid perfusion defect (arrows) in the left lobe of the liver. (b) CTHA image shows peripheral globular enhancement (arrow) of the mass.

 
Metastases
In the past, because of its high sensitivity, CTAP alone was recommended for detection of metastases in the preoperative evaluation of surgical candidates with metastatic liver tumor (19). However, combined CTAP and CTHA significantly raises the detectability of hepatic metastases (1). A metastatic liver tumor is generally seen as a perfusion defect at CTAP and with rimlike enhancement at CTHA (Fig 7).



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  		Figure 7a.  Metastasis from colon cancer in a 53-year-old man. (a) CTAP image shows a large perfusion defect (arrows) in the right lobe of the liver. (b) CTHA image shows irregular rimlike enhancement of the mass (white arrows). An adjacent wedge-shaped enhanced area is noted (black arrows), which is possibly due to arterial hyperperfusion resulting from compression of the portal vein by the tumor. Pathologic analysis of a biopsy specimen showed that the lesion was a metastatic adenocarcinoma from colon cancer.

 


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  		Figure 7b.  Metastasis from colon cancer in a 53-year-old man. (a) CTAP image shows a large perfusion defect (arrows) in the right lobe of the liver. (b) CTHA image shows irregular rimlike enhancement of the mass (white arrows). An adjacent wedge-shaped enhanced area is noted (black arrows), which is possibly due to arterial hyperperfusion resulting from compression of the portal vein by the tumor. Pathologic analysis of a biopsy specimen showed that the lesion was a metastatic adenocarcinoma from colon cancer.

 

   Nontumorous Hemodynamic Changes
Top
 Abstract
 LEARNING OBJECTIVES
 Introduction
 Imaging Techniques
 Focal Liver Lesions
 Nontumorous Hemodynamic Changes
Conclusions
 References
 
Arterioportal Shunt
An arterioportal shunt is an organic or functional communication between a hepatic arterial branch and the portal venous system; it results in redistribution of the arterial flow into a focal region of the portal venous flow (20). Arterioportal shunts are a common cause of pseudolesions at CTAP and CTHA. Causes of arterioportal shunts include hepatic neoplasms, iatrogenic trauma such as biopsy or biliary drainage, liver cirrhosis (nontumorous arterioportal shunt), and portal vein obstruction or compression (functional arterioportal shunt) (4). At two-phase helical CT, an arterioportal shunt appears as an area of wedge-shaped high attenuation with or without internal branching structures during the hepatic arterial phase and as slightly high attenuation or isoattenuation with the liver during the portal venous phase (21). Similarly, common findings of arterioportal shunts are peripheral wedge-shaped enhancement with or without early enhancement of the peripheral portal vein branches at CTHA and a peripheral wedge-shaped perfusion defect at CTAP. The peripheral portal vein branches are more clearly delineated with a wide window setting (400–500 HU) at CTHA (Fig 8).



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  		Figure 8a.  Wedge-shaped pseudolesion due to an arterioportal shunt in a 64-year-old woman with liver cirrhosis. (a) CTAP image shows a wedge-shaped hypoattenuating lesion (arrows) in the subcapsular area of the liver. (b) CTHA image shows that the lesion is hyperattenuating (arrows). (c) CTHA image obtained with a wide window setting (480 HU) clearly shows enhancement of the portal vein branches (arrows) within the lesion. (d) Contrast-enhanced CT scan obtained at 24 months follow-up no longer shows the lesion.

 


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  		Figure 8b.  Wedge-shaped pseudolesion due to an arterioportal shunt in a 64-year-old woman with liver cirrhosis. (a) CTAP image shows a wedge-shaped hypoattenuating lesion (arrows) in the subcapsular area of the liver. (b) CTHA image shows that the lesion is hyperattenuating (arrows). (c) CTHA image obtained with a wide window setting (480 HU) clearly shows enhancement of the portal vein branches (arrows) within the lesion. (d) Contrast-enhanced CT scan obtained at 24 months follow-up no longer shows the lesion.

 


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  		Figure 8c.  Wedge-shaped pseudolesion due to an arterioportal shunt in a 64-year-old woman with liver cirrhosis. (a) CTAP image shows a wedge-shaped hypoattenuating lesion (arrows) in the subcapsular area of the liver. (b) CTHA image shows that the lesion is hyperattenuating (arrows). (c) CTHA image obtained with a wide window setting (480 HU) clearly shows enhancement of the portal vein branches (arrows) within the lesion. (d) Contrast-enhanced CT scan obtained at 24 months follow-up no longer shows the lesion.

 


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  		Figure 8d.  Wedge-shaped pseudolesion due to an arterioportal shunt in a 64-year-old woman with liver cirrhosis. (a) CTAP image shows a wedge-shaped hypoattenuating lesion (arrows) in the subcapsular area of the liver. (b) CTHA image shows that the lesion is hyperattenuating (arrows). (c) CTHA image obtained with a wide window setting (480 HU) clearly shows enhancement of the portal vein branches (arrows) within the lesion. (d) Contrast-enhanced CT scan obtained at 24 months follow-up no longer shows the lesion.

 
Liver Cirrhosis
Liver cirrhosis is known to alter normal hepatic blood flow dynamics, resulting in increased arterial flow and decreased portal vein flow to the liver. Therefore, patients with advanced cirrhosis often have inadequate hepatic parenchymal enhancement during CTAP (22). Areas of diffuse nontumorous mottling or zones of poor parenchymal enhancement can be seen at CTAP (Fig 9). Therefore, it is likely that CTAP has limited usefulness for detection or characterization of hepatic neoplasms in patients with advanced cirrhosis.



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  		Figure 9a.  Liver cirrhosis in a 43-year-old man. (a) CTAP image shows poor, heterogeneous enhancement of the liver with diffuse nontumorous mottling. (b) CTHA image shows slightly heterogeneous enhancement of the liver with multiple small hypoattenuating nodules (arrows), which represent regenerative nodules.

 


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  		Figure 9b.  Liver cirrhosis in a 43-year-old man. (a) CTAP image shows poor, heterogeneous enhancement of the liver with diffuse nontumorous mottling. (b) CTHA image shows slightly heterogeneous enhancement of the liver with multiple small hypoattenuating nodules (arrows), which represent regenerative nodules.

 
Budd-Chiari Syndrome
In Budd-Chiari syndrome, hepatic vein outflow obstruction resulting from obstruction of the inferior vena cava produces changes in the attenuation and morphology of the liver depending on the acuteness, severity, and location of the obstruction. Obstruction of the hepatic vein results in increased sinusoidal pressure. During the acute phase of hepatic venous obstruction, the portal vein becomes a draining vein and there is an increase in hepatic arterial flow (4). In the chronic stage, necrotic areas resulting from hepatic vein congestion are replaced by fibrotic tissue and reestablishment of hepatic venous drainage occurs through intrahepatic collateral vessels (23). In this stage, heterogeneous enhancement with a reticular pattern, especially at the periphery of the liver, is frequently seen at CTAP and CTHA (Fig 10).



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  		Figure 10a.  Budd-Chiari syndrome in a 54-year-old woman with hepatocellular carcinoma. (a) CTAP image shows heterogeneous enhancement of the liver with linear and wedge-shaped hypoattenuating lesions (open arrows) in the periphery. An ovoid perfusion defect (solid arrows) is noted in the left lobe of the liver. (b) CTHA image shows enhancement of the linear and wedge-shaped areas in the periphery of the liver. The mass in the left lobe is hyperattenuating (arrows). The mass was diagnosed as a hepatocellular carcinoma on the basis of the clinical and radiologic findings and treated with transcatheter arterial chemoembolization.

 


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  		Figure 10b.  Budd-Chiari syndrome in a 54-year-old woman with hepatocellular carcinoma. (a) CTAP image shows heterogeneous enhancement of the liver with linear and wedge-shaped hypoattenuating lesions (open arrows) in the periphery. An ovoid perfusion defect (solid arrows) is noted in the left lobe of the liver. (b) CTHA image shows enhancement of the linear and wedge-shaped areas in the periphery of the liver. The mass in the left lobe is hyperattenuating (arrows). The mass was diagnosed as a hepatocellular carcinoma on the basis of the clinical and radiologic findings and treated with transcatheter arterial chemoembolization.

 
Inflammatory Changes
Eosinophilic abscesses manifest as local inflammation. An eosinophilic liver abscess appears as marked eosinophilic infiltrates at pathologic analysis due to some parasitic infestations, such as fascioliasis or toxocariasis (24). At CT, the appearance of an eosinophil-related lesion is nonspecific; however, the eosinophil-related lesion is usually located adjacent to the portal vein or is traversed by the portal vein (24). At CTAP and CTHA, the imaging findings of an eosinophilic abscess are nonspecific and it may therefore be difficult to differentiate from a malignant hepatic neoplasm (Fig 11). Local liver inflammation can cause hyperemia of the hepatic artery and portal venous flow stoppage (4). At biphasic helical CT, inflammation is seen as a high-attenuation area on hepatic arterial phase images that returns to normal attenuation on portal venous phase images (25). Similarly, enhancement adjacent to the inflamed area can be seen at CTHA, although the involved area usually returns to isoattenuation with the surrounding liver parenchyma at CTAP (Fig 11).



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  		Figure 11a.  Inflammatory changes in a 53-year-old man with an eosinophilic abscess. (a) CTAP image shows an ill-defined portal venous perfusion defect (solid arrows) in the right lobe of the liver. Peripheral portal vein branches (open arrow) are seen within the lesion. (b) CTHA image shows heterogeneous enhancement of the lesion (arrows). Histopathologic analysis of a surgical specimen showed that the lesion was an eosinophilic abscess. (c) CTHA image obtained at a lower level shows enhancement (arrows) below the inflamed lesion. (d) CTAP image shows that the area of enhancement has become nearly isoattenuating relative to the surrounding liver parenchyma.

 


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  		Figure 11b.  Inflammatory changes in a 53-year-old man with an eosinophilic abscess. (a) CTAP image shows an ill-defined portal venous perfusion defect (solid arrows) in the right lobe of the liver. Peripheral portal vein branches (open arrow) are seen within the lesion. (b) CTHA image shows heterogeneous enhancement of the lesion (arrows). Histopathologic analysis of a surgical specimen showed that the lesion was an eosinophilic abscess. (c) CTHA image obtained at a lower level shows enhancement (arrows) below the inflamed lesion. (d) CTAP image shows that the area of enhancement has become nearly isoattenuating relative to the surrounding liver parenchyma.

 


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  		Figure 11c.  Inflammatory changes in a 53-year-old man with an eosinophilic abscess. (a) CTAP image shows an ill-defined portal venous perfusion defect (solid arrows) in the right lobe of the liver. Peripheral portal vein branches (open arrow) are seen within the lesion. (b) CTHA image shows heterogeneous enhancement of the lesion (arrows). Histopathologic analysis of a surgical specimen showed that the lesion was an eosinophilic abscess. (c) CTHA image obtained at a lower level shows enhancement (arrows) below the inflamed lesion. (d) CTAP image shows that the area of enhancement has become nearly isoattenuating relative to the surrounding liver parenchyma.

 


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  		Figure 11d.  Inflammatory changes in a 53-year-old man with an eosinophilic abscess. (a) CTAP image shows an ill-defined portal venous perfusion defect (solid arrows) in the right lobe of the liver. Peripheral portal vein branches (open arrow) are seen within the lesion. (b) CTHA image shows heterogeneous enhancement of the lesion (arrows). Histopathologic analysis of a surgical specimen showed that the lesion was an eosinophilic abscess. (c) CTHA image obtained at a lower level shows enhancement (arrows) below the inflamed lesion. (d) CTAP image shows that the area of enhancement has become nearly isoattenuating relative to the surrounding liver parenchyma.

 
Aberrant Portal Venous Supply
When third hepatic inflow tracts (capsular veins, accessory cystic vein, or an aberrant right gastric vein) are present, systemic venous blood directly enters the liver independently of the portal venous system (26). Such veins communicate with intrahepatic portal branches to variable degrees, thereby decreasing portal perfusion from the mesenteric vein. Common locations of the aberrant portal venous supply include the pericholecystic area, anterior to the porta hepatis, adjacent to the falciform ligament, and the subcapsular area (4). These areas are seen as wedge-shaped portal perfusion defects at CTAP and as hyperattenuating or isoattenuating compared with the surrounding liver parenchyma at CTHA (Fig 12), thereby potentially mimicking liver tumors. However, their typical locations and shapes usually lead to the correct diagnosis.



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  		Figure 12a.  Drainage via an aberrant gastric vein in a 50-year-old man with cholangiocarcinoma. (a) CTAP image shows a rectangular portal venous perfusion defect (black arrows) in the dorsum of the medial segment of the left lobe. An irregular portal venous perfusion defect (white arrows) is also seen in the right lobe. (b) CTHA image shows that the lesion in the left lobe (solid black arrows) is slightly hyperattenuating and contains a linear enhancing vascular structure (open black arrow), which represents drainage via an aberrant right gastric vein. The lesion in the right lobe (white arrows) appears as an ill-defined enhancing mass. At surgery, the mass in the right lobe was proved to be a cholangiocarcinoma.

 


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  		Figure 12b.  Drainage via an aberrant gastric vein in a 50-year-old man with cholangiocarcinoma. (a) CTAP image shows a rectangular portal venous perfusion defect (black arrows) in the dorsum of the medial segment of the left lobe. An irregular portal venous perfusion defect (white arrows) is also seen in the right lobe. (b) CTHA image shows that the lesion in the left lobe (solid black arrows) is slightly hyperattenuating and contains a linear enhancing vascular structure (open black arrow), which represents drainage via an aberrant right gastric vein. The lesion in the right lobe (white arrows) appears as an ill-defined enhancing mass. At surgery, the mass in the right lobe was proved to be a cholangiocarcinoma.

 
Laminar Flow
Occasionally, intense enhancement in the dependent portion of the liver associated with laminar flow in the portal vein is seen at CTAP. This phenomenon is due to rapid venous return with high contrast material concentration from a selective injection into the proximal branch vessels of the superior mesenteric artery (27). When the contrast medium reaches the liver, it is more likely to cause preferential enhancement of the segments receiving flow from dependent branches of the portal vein. No abnormality is seen in this area at CTHA (Fig 13).



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  		Figure 13a.  Laminar flow in a 51-year-old man. (a) CTAP image shows predominant enhancement in the dependent area of the liver (arrows). (b) CTHA image shows no abnormal findings in this area.

 


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  		Figure 13b.  Laminar flow in a 51-year-old man. (a) CTAP image shows predominant enhancement in the dependent area of the liver (arrows). (b) CTHA image shows no abnormal findings in this area.

 

   Conclusions
Top
 Abstract
 LEARNING OBJECTIVES
 Introduction
 Imaging Techniques
 Focal Liver Lesions
 Nontumorous Hemodynamic Changes
 Conclusions
References
 
Although the combined use of CTAP and CTHA is considered the most sensitive imaging technique to detect focal hepatic lesions, pseudolesions caused by hemodynamic changes are problematic. Familiarity with the CTAP and CTHA findings of various focal hepatic lesions and a better understanding of nontumorous hemodynamic changes can improve diagnostic accuracy.


   Acknowledgments
 
The authors thank Bonnie Hami, MA, for editorial assistance in preparing the manuscript.


   Footnotes
 
Abbreviations: CTAP = CT during arterial portography, CTHA = CT during hepatic arteriography

See also the article by Hussain et al (pp 1023–1039 ) in this issue.


   References
Top
 Abstract
 LEARNING OBJECTIVES
 Introduction
 Imaging Techniques
 Focal Liver Lesions
 Nontumorous Hemodynamic Changes
 Conclusions
 References
 

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