Benign versus malignant hepatic nodules: MR imaging findings with pathologic correlation.

According to the currently used nomenclature, there are only two types of hepatocellular nodular lesions: regenerative lesions and dysplastic or neoplastic lesions. Regenerative nodules include monoacinar regenerative nodules, multiacinar regenerative nodules, cirrhotic nodules, segmental or lobar hyperplasia, and focal nodular hyperplasia. Dysplastic or neoplastic nodules include hepatocellular adenoma, dysplastic foci, dysplastic nodules, and hepatocellular carcinoma (HCC). Many of these types of hepatic nodules play a role in the de novo and stepwise carcinogenesis of HCC, which comprises the following steps: regenerative nodule, low-grade dysplastic nodule, high-grade dysplastic nodule, small HCC, and large HCC. State-of-the-art magnetic resonance (MR) imaging facilitates detection and characterization in most cases of hepatic nodules. State-of-the-art MR imaging includes single-shot fast spin-echo imaging, in-phase and opposed-phase T1-weighted gradient-echo imaging, T2-weighted fast spin-echo imaging with fat saturation, and two-dimensional or three-dimensional dynamic multiphase contrast material-enhanced imaging.     

Focal manifestations of diffuse liver disease at MR imaging.

Detection and exclusion of focal liver lesions is especially difficult in patients with diffuse liver disease. Magnetic resonance (MR) imaging may be particularly valuable in these patients. By judicious comparison of appropriate pulse sequences, normal and hypertrophic liver may be distinguished from atrophic, neoplastic, or otherwise abnormal hepatic parenchyma. Chemical shift (lipid-sensitive) techniques allow definitive identification of fatty liver, including focal fatty infiltration or focal sparing. T2-weighted and T2*-weighted images allow identification of iron overload, depicting malignancies as focal masses without iron. Analysis of signal intensity and internal morphology allows confident distinction between regenerative nodules and hepatocellular carcinoma in most instances, and allows diagnosis of early carcinoma within regenerative nodules. MR imaging provides capabilities for noninvasive characterization of liver tissue beyond those available with other noninvasive modalities.     

Large regenerative nodules in Budd-Chiari syndrome and other vascular disorders of the liver: CT and MR imaging findings with clinicopathologic correlation

OBJECTIVE: The purpose of this study was to determine the CT and MR imaging appearance of large regenerative nodules arising in livers with vascular disorders and to correlate these findings with the clinical and pathologic findings. CONCLUSION: Large regenerative nodules are a characteristic feature of Budd-Chiari syndrome and other hepatic vascular disorders. CT and MR imaging show consistent features of the nodules and the surrounding liver that may allow distinction of Budd-Chiari nodules from other types of hypervascular hyperplastic or dysplastic nodules.     

Differentiation of hepatocellular carcinomas from hyperplastic nodules induced in rat liver with ferrite-enhanced MR imaging.

The potential of superparamagnetic ferrite particles in magnetic resonance (MR) imaging to help differentiate between hyperplastic nodular lesions in the liver and hepatocellular carcinomas was evaluated with chemically induced liver tumors in cirrhotic rats. Ferrite particles decreased the signal intensity of hyperplastic nodules but not that of hepatocellular carcinomas, and stainable iron was found in the former but not in the latter with Prussian blue iron stain. T1-weighted spin-echo images made little contribution to the differentiation between these two lesions, while T2-weighted spin-echo images were effective for this purpose, since ferrite particles cause T2 shortening. Ferrite-enhanced MR imaging may be useful in differentiating these two lesion types according to their signal intensity changes on images, because Kupffer cells are present in hyperplastic nodular lesions but rarely in hepatocellular carcinomas.     

CT during hepatic arteriography and portography: an illustrative review.

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.     

Dynamic contrast-enhanced ultrasound with carbon dioxide microbubbles as adjunct to arteriography of liver tumors

Purpose The goal of the study is to evaluate utility of contrast enhanced ultrasound (US) with carbon dioxide microbubbles in evaluation of hepatic lesions.Methods Twenty eight patients with single or multiple t hepatic lesions (11 hepatocellular carcinoma, 8 hemangiomas, 5 metastases, 1 adenoma, 1 focal nodular hyperplasia, 2 regenerative nodules) were examined. US exam was performed during intraarterial injection of 10 ml of CO₂ through the same catheter employed for liver arteriography. The US exam was videotaped in its salient phases. Characteristics of enhancement were evaluated and correlated with histological findings or patient follow up.Results Sonographic angiography clearly demonstrated vascularization of the lesions. Hepatocellular carcinoma, hemangioma, metastases, focal nodular hyperplasia, and regenerative nodules had very characteristic patterns. The injection of CO₂ allowed detection of small additional nodules.Conclusion Sonographic angiography can improve characterization and staging of hepatic tumors. Low cost and the simplicity of the technique should encourage further experimentation.     

Imaging nodules within cirrhotic liver: how do I do it?

Cirrhosis is a chronic liver disease characterized by the presence of diffuse parenchymal necrosis, reactive fibrosis and nodular regeneration. These regenerative nodules may evolve into dysplastic nodules and finally nodules of hepatocellular carcinoma (HCC). Improved survival of cirrhotic patients with HCC depends on eligibility to liver transplantation. The purpose of this paper is to review the imaging features of liver nodules within cirrhotic liver and to propose the imaging strategies when considering the possibility of liver transplantation.     

Fat-containing lesions of the liver: cross-sectional imaging findings with emphasis on MRI

OBJECTIVE: The purpose of this pictorial essay is to identify different types of liver lesions that contain fat. Cross-sectional imaging findings of fat- or lipid-containing lesions can help in characterizing focal liver lesions. We searched our archive retrospectively and reviewed the literature for fat-containing liver lesions and identified 16 different types. CONCLUSION: These lesions can contain macroscopic fat (i.e., angiomyolipoma, lipoma, liposarcoma, hydatid cyst, lipopeliosis, adrenal rest tumor, pseudolipoma, hepatic teratoma, pericaval fat, extramedullary hematopoiesis, and metastases) or intracellular lipid (i.e., focal steatosis, adenoma, focal nodular hyperplasia, regenerative nodules, and hepatocellular carcinoma). CT, MRI, and sonographic findings of these lesions can help in characterization by allowing specific diagnosis or narrowing the differential diagnosis of liver lesions.     

Congenital absence of portal vein with nodular regenerative hyperplasia of the liver

Congenital absence of the portal vein is a very rare anomaly. The intestinal and splenic venous drainage bypasses the liver and drain into the inferior vena cava (IVC). Two cases of such anomaly are described. Both cases were investigated by US coupled with echo-colour Doppler examination, CT and MR imaging, followed by digital subtraction angiography (DSA) and liver biopsy. In the first case the splenic and superior mesenteric vein formed a venous trunk which emptied directly into the IVC; in the second case, the splanchnic blood flowed into a dilated hepatofugal inferior mesenteric vein which connected to the left internal iliac vein. In both cases nodular regenerative hyperplasia of the liver was present, presumably due to an abnormal hepatic cell response to the absent portal flow. The particular contribution of MR imaging to the diagnosis of both vascular abnormalities and liver parenchyma derangement and its advantages over the other diagnostic techniques is emphasized. The clinical and radiological features of 17 previously reported cases are reviewed. Received: 22 September 1998; Revised: 21 January 1999; Accepted: 22 April 1999     

Sonography with intraarterial infusion of carbon dioxide microbubbles (sonographic angiography): value in differential diagnosis of hepatic tumors.

Differential diagnosis of small liver tumors is important, but is not always possible, even with angiography. To solve this problem, we introduced sonographic angiography, which combines sonography and angiography. The vascular pattern of a variety of hepatic nodules was evaluated with sonographic angiography, and the results were compared with those of conventional angiography. Sonographic angiography (sonography performed during intraarterial infusion of carbon dioxide microbubbles) was performed in 184 patients with a total of 222 hepatic nodules: 139 hepatocellular carcinomas, nine adenomatous hyperplasias, seven regenerative nodules, 21 hemangiomas, 33 metastases, seven lymphomas, one granuloma, and five focal nodular hyperplasias. Sonographic angiography detected a hypervascular pattern with peripheral blood supply in cases of hepatocellular carcinoma (sensitivity, 90%; specificity, 89%). Typical vascular patterns of adenomatous hyperplasia, hemangioma, metastasis, and focal nodular hyperplasia on sonographic angiography were hypovascularity (sensitivity, 100%; specificity, 91%), spotty pooling (sensitivity, 100%; specificity, 100%), peripheral hypervascularity (sensitivity, 64%; specificity, 100%), respectively. The detectability of hypervascularity was greater with sonographic angiography than with conventional angiography in hepatocellular carcinoma, metastasis, and hemangioma. Our experience indicates that sonographic angiography depicts characteristic vascular features that reflect the vascular anatomy of specific types of hepatic tumors, and thus is useful in the differential diagnosis of these lesions.     

肝脏不典型腺瘤样增生结节的综合影像诊断

研究肝脏不典型腺瘤样增生结节的ＵＳ、ＣＴ和ＭＲＩ表现与诊断。方法回顾性分析经病理证实的７例（手术切除３例,ＵＳ引导下肝穿刺活检４例）肝脏不典型腺瘤样增生结节的ＵＳ、ＣＴ和ＭＲＩ表现,以及术前或穿刺前诊断情况,并与病理对照。结果５例诊断为癌前病变,２例误诊为小肝癌。ＵＳ显示稍低或等回声６例,稍强回声１例。     

Unveiling the unreal: Comprehensive imaging review of hepatic pseudolesions

Hepatic pseudolesions are defined as non-neoplastic focal abnormalities of the liver which can mimic or conceal true liver lesions. It is particularly common in liver due to its unique dual blood supply and the existence of multilevel anastomosis between them. Because of the recent advances in CT and MRI technology, they are being increasingly encountered in daily practice. Broadly they can be categorised in to (1) Focal parenchymal abnormalities like focal fatty change, focal fat sparing, focal confluent fibrosis, segmental hypertrophy and regenerative nodules, (2) Perfusion abnormalities which include transient hepatic parenchymal enhancement in portal vein obstruction, third inflow, intrahepatic shunts, hepatic arterial occlusion and hepatic venous obstruction, (3) Imaging pitfalls like parenchymal compression, unenhanced vessels and pseudolipoma. It is essential for the radiologists to be familiar with the typical and atypical imaging features of pseudolesions to avoid mistaking them for sinister pathologies and also to avoid overlooking underlying hidden pathologies.     

Cirrhosis: CT and MR imaging evaluation

In this article, we present the CT and MR imaging characteristics of the cirrhotic liver. We describe the altered liver morphology in different forms of viral, alcoholic and autoimmune end-stage liver disease. We present the spectrum of imaging findings in portal hypertension, such as splenomegaly, ascites and varices. We describe the patchy and lacelike patterns of fibrosis, along with the focal confluent form. The process of hepatocarcinogenesis is detailed, from regenerative to dysplastic nodules to overt hepatocellular carcinoma. Different types of non-neoplastic focal liver lesions occurring in the cirrhotic liver are discussed, including arterially enhancing nodules, hemangiomas and peribiliary cysts. We show different conditions causing liver morphology changes that can mimic cirrhosis, such as congenital hepatic fibrosis, "pseudo-cirrhosis" due to breast metastases treated with chemotherapy, Budd-Chiari syndrome, sarcoidosis and cavernous transformation of the portal vein.     

微小肝细胞结节性病变CTHA及CTAP的诊断价值

目的:分析肝细胞结节性病变在CTHA 和CTAP 上的不同表现,评价其对早期肝细胞癌的诊断价值。方法:对32例肝细胞结节性病变患者行CTHA、CTAP和组织学检查。结果:18 个中、低分化型肝细胞癌结节均显示为CTHA高密度、CTAP低密度;7个再生性结节和腺瘤样增生中有4个结节CTHA和CTAP均呈等密度;其余21 个结节根据恶性程度的不同,显示为由高分化到低分化不同类型的CTHA和CTAP表现。结论:CTHA和CTAP可提高早期肝细胞癌的检出率,且可用以推测肝细胞结节性病变的恶性程度,指导临床治疗。     

Benign regenerative nodules in Budd-Chiari syndrome and other vascular disorders of the liver: radiologic-pathologic and clinical correlation.

Large regenerative nodules are benign liver lesions that are frequently seen in Budd-Chiari syndrome and less commonly in other vascular disorders of the liver or systemic conditions such as autoimmune disease, myeloproliferative disorders, and lymphoproliferative disorders. They are usually multiple, with a typical diameter of 0.5-4 cm. At pathologic analysis, large regenerative nodules are well-circumscribed, round lesions that may distort the contour of the liver. Only a minority of these nodules are detected at cross-sectional imaging. At multiphasic helical computed tomography, large regenerative nodules are markedly and homogeneously hyperattenuating on arterial dominant phase images and remain slightly hyperattenuating on portal venous phase images. Large regenerative nodules are bright on T1-weighted magnetic resonance images and show the same enhancement characteristics after intravenous bolus administration of gadolinium contrast material. They are predominantly isointense or hypointense relative to the liver on T2-weighted images. There is no evidence that large regenerative nodules degenerate into malignancy. If these nodules are misdiagnosed as multifocal hepatocellular carcinoma, patients might be denied transplantation or offered inappropriately aggressive therapy such as transcatheter arterial chemoembolization. Understanding the clinical setting and imaging appearance of large regenerative nodules can help avoid misdiagnosis as other hypervascular masses.     

Focal nodular hyperplasia inducing hepatic vein obstruction

OBJECTIVE: The records of 10 patients with focal nodular hyperplasia inducing intrahepatic vein obstruction were reviewed. The purpose of this study was to describe and emphasize the imaging features of these findings. CONCLUSION: Focal nodular hyperplasia may be responsible for hepatic vein obstruction with hepatic vein collaterals. The relatively large size and central location of the lesions seem to play important roles in the obstruction of the hepatic veins.     

Hepatic nodular regenerative lesions in patients with hereditary haemorrhagic telangiectasia: computed tomography and magnetic resonance findings

Purpose

This study was done to evaluate the prevalence of regenerative hepatic nodules in patients with hereditary haemorrhagic telangiectasia (HHT).

Materials and methods

Between February 2001 and December 2010, 171 consecutive HHT patients (95 men and 76 women) were studied with triphasic multidetector computed tomography (MDCT) in 91 cases, magnetic resonance imaging (MRI) in 34 cases and both in the remaining 46 cases. The presence of diffuse vascular abnormalities and focal liver lesions were recorded.

Results

Hepatic arteriovenous malformations (HAVMs) were found in 126/171 (74%) patients. Arteriovenous shunts were found in 24/171 (14%) cases, arterioportal shunts in 52/171 (30%), mixed shunts in 26/171 (15%), telangiectases in 84/171 (49%) and transient hepatic attenuation differences (THADs) in 70/171 (41%). Hepatic nodular lesions were found in 6/171 (3.5%) patients (three men; three women). In 5/6 cases, vascular abnormalities were also evident. Two patients had a single lesion; four had multiple lesions. No lesion showed a central scar.

Conclusions

Hyperenhancing hepatic regenerative lesions have a high prevalence in HHT patients, representing the response of liver parenchyma to hypoperfusion caused by HAVMs. These lesions are often multiple and may lead to nodular regenerative hyperplasia.     

肝硬化结节与小肝癌的CT、MRI诊断

在肝硬化结节及小肝癌的早期诊断方面,CT、MRI仍是目前临床工作中最重要的方法,本文阐述肝硬化结节演变为肝癌过程中的几个重要环节的CT、MRI表现及国内、外对此的研究现状,这几个环节包括肝硬化再生结节、发育不良性结节(低、中、高级)、小肝癌及肝癌,它们在CT、MRI表现上各有特征,但相互间也有影像学表现上的重叠,故多数较典型者可以通过CT密度值、MRI信号值及增强表现判断其性质,少部分诊断有困难的病灶可以通过双动脉期扫描、MR菲立磁增强及灌注成像等方法提供更多的诊断信息。     

Enhancement patterns and signal-intensity characteristics of small hepatocellular carcinoma in cirrhosis: pathologic basis and diagnostic challenges

Recent pathologic studies of hepatic resection and transplantation specimens have elucidated the morphologic features of the precancerous lesions and small hepatocellular carcinomas (HCCs) arising in cirrhotic livers. Small HCCs measuring less than 2 cm in diameter are of two types: vaguely nodular, well-differentiated tumors, also known as "early" HCCs, and distinctly nodular tumors, with histologic features of "classic" HCC. The precancerous lesions include dysplastic foci and dysplastic nodules. "Classic" small HCCs are supplied by nontriadal arteries, whereas early HCCs and dysplastic nodules may receive blood supply from both portal tracts and nontriadal arteries. The similarities in blood supply of these three types of nodular lesions result in significant overlap of findings on dynamic imaging. Nevertheless, small HCCs sometimes display characteristic radiologic features, such as "nodule-in-nodule" configuration and "corona enhancement" pattern. Moreover, various histologic features of these nodular lesions may also be related to a variety of signal intensities and attenuation coefficients, while the presence of cirrhosis is known to limit the sensitivity and specificity of any imaging modality, due to liver inhomogeneity. Because of these reasons, imaging findings of nodular lesions in cirrhotic livers are often inconclusive, emphasizing the need for a better understanding of these imaging features.     

Hypervascular hepatic focal lesions: spectrum of imaging features

Detection and characterization of liver lesions often present a diagnostic challenge to the radiologists. Liver lesions may be classified as hypovascular and hypervascular based on degree of hepatic arterial blood supply. Common hypervascular liver lesions include hemangioma, focal nodular hyperplasia, hepatocellular adenoma, hepatocellular carcinoma, fibrolamellar carcinoma, and metastases from primary tumors such as islet cell tumor, carcinoid, renal cell carcinoma, melanoma, and thyroid carcinoma. In this review article, we discuss the spectrum of imaging features of hypervascular liver lesions.