CT and MRI of Hepatic Contour Abnormalities

Transcription

1 Hepatobiliary Imaging Pictorial Essay CT and MRI of Jafi A. Lipson 1, Aliya Qayyum 1, David E. Avrin 2, Antonio Westphalen 1, Benjamin M. Yeh 1, Fergus V. Coakley 1 Fig year-old woman imaged for abdominal pain. Contrast-enhanced CT scan shows prominent diaphragmatic slip (arrowhead) indenting right lobe of liver. Received November 25, 2003; accepted after revision June 30, epatic contour abnormalities are H seen commonly on CT or MRI but have received relatively little attention in the radiology literature compared with parenchymal hepatic disease. The objective of this pictorial essay is to provide a concise pictorial review of the causes and appearances of hepatic contour abnormalities on CT and MRI with an emphasis on clini- Lipson JA, Qayyum A, Avrin DE, Westphalen A, Yeh BM, Coakley FV cal and imaging features that facilitate a correct diagnosis. Such a review is timely because new causes of liver contour abnormalities have been described recently [1], and the interpretation of such findings remains controversial. Intrinsic disorders of the liver that may cause contour abnormalities consist of hepatic tumors, cirrhosis, infarction, and vascular occlusion; treatment change also may cause contour abnormalities. Perihepatic diseases also may cause extrinsic alteration of the liver contour. Depending on the nature and extent of these disorders, the contour abnormality may be unifocal, multifocal, or diffuse. The mechanism of contour change also varies and may reflect focal expansion of the liver, capsular retraction, parenchymal distortion, capsular indentation, or some combination of these factors. All of 1 Department of Radiology, University of California San Francisco, 505 Parnassus Ave., Rm. M-372, San Francisco, CA Address correspondence to A. Qayyum. 2 Department of Radiology, University of Utah, 30 N 1900, E #1A71, Salt Lake City, UT AJR 2005;184: X/05/ American Roentgen Ray Society AJR:184, January

2 Fig year-old woman with cholangiocarcinoma. Contrast-enhanced CT scan shows ill-defined hypoattenuating mass (arrow) in left lobe of liver with associated retraction of liver surface (arrowhead) and intrahepatic biliary dilatation. these abnormalities should be distinguished from physiologic irregularity of the hepatic contour, particularly indentation related to diaphragmatic slips (Fig. 1). Hepatic Tumors Although hepatic parenchymal tumors generally are associated with mass effect resulting in contour bulge, some tumors may result in only capsular retraction. Cholangiocarcinoma may cause hepatic atrophy and capsular retraction [2] (Fig. 2), probably due to combined venous and biliary occlusion of the atrophic part of the liver. However, these findings are not specific, and other characteristics such as a visible mass with delayed enhancement and biliary dilatation should be sought. Hepatocellular carcinoma may be variably exophytic [2], causing bulging of the hepatic contour (Fig. 3). Fig year-old man with hepatocellular carcinoma. Contrast-enhanced CT scan shows exophytic heterogeneously enhancing mass (arrow) bulging from inferior right lobe of liver. Mass has central hypoattenuating scar (arrowhead). Fig year-old woman with hepatic epithelioid hemangioendothelioma. A, Contrast-enhanced CT scan shows multiple peripheral liver masses (arrows). B, Contrast-enhanced CT scan shows characteristic retraction of liver capsule in association with one of the masses (arrowhead). A The tumor typically is hypervascular [3] and is associated with cirrhosis. Hepatic hemangioendothelioma can be considered an intermediate between hemangioma and angiosarcoma. Such tumors include infantile, spindle cell, and epithelioid hemangioendothelioma. Infantile hemangioendothelioma is a benign lesion typically presenting as a liver mass, cardiac failure secondary to arteriovenous shunting, and con- B 76 AJR:184, January 2005

3 Fig year-old woman with epithelioid hemangioendothelioma. Fat-suppressed T2-weighted fast spin-echo image shows high-signal-intensity mass with slight retraction of liver surface (arrow) at liver dome with central higher signal intensity or target sign (arrowhead). Fig year-old woman with large hemangioma. Contrast-enhanced CT scan shows bulging of liver contour (arrow) due to hypoattenuating mass with interrupted peripheral nodular enhancement. Fig year-old man with metastatic islet cell tumor. Contrast-enhanced CT scan shows multiple hypervascular liver metastases (arrowheads) causing bulging of liver contour. AJR:184, January

4 A Fig year-old man with untreated metastatic colon cancer. Contrast-enhanced CT scan shows hypoattenuating liver masses. There is focal retraction (arrowhead) of liver surface adjacent to one of the metastases. Bland thrombus is present incidentally within inferior vena cava (arrow). Fig year-old man with cirrhosis. Fat-suppressed T1-weighted gradient-echo image with gadolinium enhancement shows shrunken liver with diffusely nodular contour and recanalized paraumbilical vein (arrowhead). Fig year-old man with cirrhosis. A, Fat-suppressed T1-weighted gradient-echo image with early gadolinium enhancement shows diffusely nodular liver contour with associated retraction (arrowhead) of liver surface involving medial segment of left lobe and anterior segment of right lobe. B, Fat-suppressed T2-weighted fast spin-echo image shows wedge-shaped region of slightly increased signal intensity (arrowhead) involving medial segment of left lobe and anterior segment of right lobe with associated retraction of liver surface. B 78 AJR:184, January 2005

5 Fig year-old woman with liver infarct after having undergone liver transplantation. A, Fat-suppressed T1-weighted gradient-echo image with gadolinium enhancement shows small geographic area of low signal intensity (arrow). B, Contrast-enhanced CT scan obtained 4 months after A shows interval development of focal liver retraction at site of infarction (arrowhead). sumptive coagulopathy and is seen most frequently in patients before the age of 6 months. Spindle cell hemangioendothelioma is a low-grade malignant tumor with a propensity for local recurrence. Epithelioid hemangioendothelioma is a low-grade slowly progressive malignant vascular tumor that was described first in 1982 and typically occurs in the liver, bone, skin, or soft tissues of children and young adults. At imaging, the enhancement pattern of a hemangioendothelioma may mimic that of a hemangioma. Hepatic epithelioid hemangioendothelioma usually is multifocal (but may coalesce to become diffuse or infiltrative) and subcapsular. Capsular retraction has been reported in 25 69% of cases (Fig. 4). A target sign of Fig year-old woman with antiphospholipid antibody and Budd-Chiari syndrome. Fat-suppressed T1-weighted gradient-echo image with gadolinium enhancement shows lobulated liver contour (arrowheads), heterogeneous reduced signal intensity in liver periphery, and caudate enlargement. A concentric zones may be seen on MRI [4] (Fig. 5). Hemangiomas may be exophytic, causing a focal bulge of the hepatic contour (Fig. 6). Large hemangiomas may develop central thrombosis, leading to fibrotic retraction of the adjacent capsule [2]. Metastatic neuroendocrine tumor is one of the few secondary cancers that commonly causes contour abnormality (Fig. 7), possibly because the indolent nature of the tumor allows the slow development of hepatic enlargement and surface expansion. Rarely, untreated metastases from adenocarcinoma of the colon, stomach, breast, lung, pancreas, and gallbladder cause focal capsular retraction, probably due to internal necrosis and desmoplasia [2] (Fig. 8). Cirrhosis and Confluent Hepatic Fibrosis Cirrhosis is a diffuse progressive process of ongoing hepatic necrosis resulting in nodular regenerative hyperplasia and fibrosis [1]. Imaging characteristics include surface nodularity, atrophy of the right lobe and medial segment of the left lobe, enlargement of the caudate lobe and lateral segment of the left lobe, increased porta hepatis fat, and expansion of the gallbladder fossa [3] (Fig. 9). Liver surface nodularity has been attributed to regenerative nodules [3]. Confluent hepatic fibrosis is a masslike atrophic region occasionally seen in cirrhosis, and it typically affects the anterior and medial segments (Fig. 10). On CT, confluent hepatic B AJR:184, January

6 Fig year-old woman with pseudocirrhosis secondary to chemotherapy treatment for breast cancer metastatic to liver. Contrast-enhanced CT scan shows diffusely lobulated liver contour and ascites. Fig year-old woman with metastatic ovarian cancer. Contrast-enhanced CT scan shows biconvex perihepatic implants (arrowheads) that indent hepatic contour. Metastatic involvement of spleen also is depicted. Fig year-old woman with pseudomyxoma peritonei. Contrast-enhanced CT scan shows low-attenuation masslike nodular material causing scalloping of liver contour (arrowheads). 80 AJR:184, January 2005

7 fibrosis appears as a wedge-shaped region of iso- or hypoattenuation with associated atrophy and capsular retraction [2]. On MRI, focal confluent hepatic fibrosis is hypointense on T1-weighted images and usually is hyperintense on T2-weighted images [3]. Possible explanations for the observed hyperintense signal of confluent fibrosis on T2-weighted imaging may be a relative reduction in the signal of the remaining liver parenchyma due to increased iron deposition or edema associated with areas of confluent fibrosis due to venous thrombosis in this region; however, these explanations are speculative. Infarction and Vascular Occlusion Hepatic infarction is uncommon due to the dual vascular supply of the liver, but recognized causes include liver transplantation, laparoscopic cholecystectomy, profound shock, sepsis, arterial embolism, vasculitis, preeclampsia, and oral contraceptives. Infarcts appear as peripheral nonenhancing geographic regions that may change in shape over time and that may be associated with necrosis, bile lakes, and atrophic capsular retraction [5] (Fig. 11). Hepatic vein thrombosis (Budd-Chiari syndrome) may be spontaneous secondary to prothrombotic conditions (e.g., myeloproliferative disorders, paroxysmal nocturnal hemoglobinuria, coagulation disorders, and oral contraceptives) or may be caused by malignant venous occlusion [1] (Fig. 12). Portal vein thrombosis may be due to pancreatitis, cholangitis, peritonitis, lymphadenopathy, pancreatic cancer, or cirrhosis. Both chronic Budd-Chiari syndrome and chronic portal vein thrombosis may result in venous collateral formation and hepatic atrophy with lobulated capsular irregularity [1, 3]. Treatment Change Resection, chemoembolization, radiofrequency ablation, and chemotherapy may cause cystic change, focal atrophy, and capsular retraction within and adjacent to treated tumors [2]. An increasingly recognized entity is the phenomenon known as pseudocirrhosis, the development of diffuse hepatic nodularity, segmental volume loss, and enlargement of the caudate lobe in patients receiving chemotherapy for breast cancer metastatic to the liver [1, 3] (Fig. 13). This condition actually may be a type of true cirrhosis, because changes of portal hypertension can be seen in these patients. The pathologic basis of this process has not been well established [6]. Perihepatic Disease Peritoneal spread of tumor may result in biconvex perihepatic implants that indent the hepatic contour, particularly in the intersegmental fissure, the superior recess of the lesser sac, subphrenic space, and Morison s pouch. Tumors that commonly spread within the peritoneal cavity are cancer of the ovary, colon, stomach, pancreas, and breast (Fig. 14). Pseudomyxoma peritonei is a type of peritoneal neoplasia characterized by the progressive accumulation of mucinous ascites ( jelly belly ) that usually is caused by rupture of an ovarian or appendiceal mucinous adenoma or adenocarcinoma [7]. In practice, the primary site is often unclear. On CT or MRI, the condition is distinguished from simple ascites by the masslike nodular nature of the gelatinous material that results in suggestive findings such as hepatic, splenic, and mesenteric scalloping and visible septations or locules [7] (Fig. 15). Perihepatic hematoma is another condition that may indent the hepatic contour and can be recognized by the typical imaging characteristics of blood on CT and MRI. Causes include trauma; bleeding disorders; and rupture of a hepatic tumor, cyst, or abscess. Preeclampsia and the HELLP syndrome (hemolysis, elevated liver enzymes, and low platelet count) appear to have a particular predilection to cause perihepatic hematoma [8]. Summary Hepatic contour abnormalities commonly are seen on CT and MRI; although these findings are not specific, awareness of the possible causes and their imaging appearances may facilitate recognition of the underlying diagnosis. References 1. Ros PR, Mortele KF. Diffuse liver disease. Clin Liver Dis 2002;6: Yang DM, Kim HS, Cho SW. Various causes of hepatic capsular retraction: CT and MR findings. Br J Radiol 2002;75: Danet IM, Semelka RC, Braga L. MR imaging of diffuse liver disease. Radiol Clin North Am 2003;41: Lyburn ID, Torreggiani WC, Harris AC, et al. Hepatic epithelioid hemangioendothelioma: sonographic, CT, and MR imaging appearances. AJR 2003;180: Tzakis A, Gordon R, Shaw B Jr, et al. Clinical presentation of hepatic artery thrombosis after liver transplantation in the cyclosporine era. Transplantation 1985;40: Shirkhoda A, Baird S. Morphologic changes of the liver following chemotherapy for metastatic breast carcinoma: CT findings. Abdom Imaging 1994;19: Coakley FV. Staging ovarian cancer: role of imaging. Radiol Clin North Am 2002;40: Barton JR, Sibai BM. Hepatic imaging in HELLP syndrome (hemolysis, elevated liver enzymes, and low platelet count). Am J Obstet Gynecol 1996;174: AJR:184, January