Hepatocellular nodules in liver cirrhosis: MR evaluation

Liver cirrhosis is a major public health problem worldwide. Common causes of cirrhosis include hepatitis C virus, hepatitis B virus, alcohol consumption, and nonalcoholic steatohepatitis. Cirrhotic livers are characterized by advanced hepatic fibrosis and the development of hepatocellular nodules such as regenerative nodules, dysplastic or neoplastic nodules. Cirrhosis is the strongest predisposing factor for hepatocellular carcinoma (HCC). For example, viral hepatitis is the main risk factor for cirrhosis and is associated with the increased incidence (1%–4% per year) of HCC after development of cirrhosis. Currently, a variety of imaging modalities, including ultrasound (US), computed tomography (CT), magnetic resonance imaging (MRI), and positron-emission tomography (PET) are used in noninvasive evaluation of patients with chronic liver disease and suspected HCC. With technological development of MR scanners, MR imaging has emerged as an important imaging modality for assessing cirrhosis and its complications such as HCC. The recent advance in MR is the introduction of faster sequences which have allowed high-quality imaging of the entire liver with high intrinsic soft-tissue contrast, and also multiphasic dynamic MRI that is essential for the detection and characterization of HCC. In addition, functional MRI including diffusion-weighted MRI, MR elastography, and new MR contrast agent with dual function have been investigated for the clinical utility of detection and characterization of HCCs. In this article, we provide an overview of the state-of-the-art MR imaging techniques being used for noninvasive assessment of hepatocellular nodules including conventional dynamic imaging, liver-specific contrast-enhanced MR imaging, diffusion-weighted imaging, MR spectroscopy, and MR elastography.     

Magnetic resonance of focal liver lesions in hepatic cirrhosis and chronic hepatitis.

Detection of focal liver nodules in patients with cirrhosis continues to be a radiologic challenge despite progressive advances in liver imaging in the past 2 decades. Patients with hepatic cirrhosis have a high predisposition to develop hepatocellular carcinoma (HCC), and the early detection and diagnosis of this tumor is very important because the most effective treatment is surgical resection, transplantation, or local ablation therapy when the tumor is small. Cirrhotic livers are mainly composed of fibrosis, together with a broad spectrum of focal nodular lesions ranging from regenerative nodules to premalignant dysplastic nodules to overt HCC. Awareness of such lesions and interpretation of imaging studies in these patients requires a critical review to detect subtle tumors, and a thorough understanding of the imaging appearance of the malignant and benign masses that can occur in the cirrhotic liver. Although the recent advances in liver imaging techniques, especially computed tomography (CT) and magnetic resonance (MR), have facilitated the detection and characterization of focal liver nodules in cirrhotic patients, discriminating between HCC and precancerous nodules remains problematic with all available imaging techniques. Nevertheless, MR imaging appears to have more potential than other imaging techniques in the study of cirrhotic patients and MR may be more appropriate than the other imaging modalities for the detection of small HCCs. In this article we review the imaging characteristics of nodular focal lesions that arise in cirrhotic livers, with special attention to MR imaging features.     

Cirrhosis: MR imaging features

The intent of this article is to provide a comprehensive review of MR imaging findings of cirrhosis and discusses clinical implications. Areas of focus include: (1) Morphologic changes of the liver in advanced cirrhosis and in early cirrhosis, (2) the frequency and imaging spectrum of intra- and extrahepatic changes in cirrhosis such as regenerative nodules, nodular liver surface, hepatic iron deposition, fibrosis, dilation of right inferior phrenic artery, gastrointestinal wall thickening, and portal hypertension, (3) serial MR findings of clinically progressive cirrhosis, (4) newly described MR sign of cirrhosis (an expanded gallbladder fossa sign), and (5) complications after liver transplantation. Understanding these MR features related to cirrhosis is helpful in clinical MR practice.     

Imaging diagnosis of cirrhosis and chronic hepatitis

Cirrhosis is an end stage of chronic diffuse liver disease, characterized by irreversible hepatic fibrosis. Cirrhosis slowly progresses from chronic hepatitis to early cirrhosis and finally to advanced cirrhosis with the increasing risk of complications, and causes regional morphologic changes of the liver during the course of the disease, according to disease severity. MR imaging is better able to provide comprehensive information about cirrhosis or chronic hepatitis and their complications than any other imaging modality currently available. In this article, we reviewed the spectrum of imaging findings of cirrhosis and chronic hepatitis, including regional changes of hepatic morphology, several signs of early and advanced cirrhosis, nodular liver surface, hepatic iron deposition, regenerative nodules, and varices and portosystemic collaterals.     

MR imaging features of focal liver lesions in Wilson disease

Hepatic involvement in Wilson disease (WD) manifests as a diffuse chronic disease in the majority of patients. However, in a subset of patients focal liver lesions may develop, presenting with a wide range of imaging features. The majority of focal liver lesions in patients with WD are benign nodules, but there are reports that have described malignant liver tumors or dysplastic nodules in these patients. Because of the possibility of malignant transformation of liver nodules, major concerns have been raised with respect to the management and follow-up of patients with WD in whom focal liver lesions have been identified. The assessment of liver involvement in patients with WD is generally performed with ultrasonography. However, ultrasonography conveys limited specificity so that magnetic resonance (MR) imaging is often performed to improve lesion characterization. This review was performed to illustrate the spectrum of MR imaging features of focal liver lesions that develop in patients with WD. It is assumed that familiarity with the MR imaging presentation of focal liver lesions in WD may help clarify the actual nature of hepatic nodules in patients with this condition.     

Ultrasound of focal liver masses

Detecting and characterizing focal liver lesions is one of the most difficult challenges in imaging today. All standard noninvasive imaging modalities are less sensitive than generally perceived, and characterization is imperfect. Liver sonography's main strengths are its ability to definitively characterize common benign lesions (eg, cysts and hemangiomas), safety, low cost, and its ability to guide biopsy. Sonography's weaknesses include its inability to image the entire liver in many patients and its inferiority to CT as a means of detecting extrahepatic malignant disease. Sonography is less sensitive than CT or MRI in detecting focal lesions. Ultrasound contrast agents will certainly improve liver lesion detection and characterization, but their impact is not yet clear.Typical findings in common focal liver lesions are discussed, and some hints to improve sonographic diagnosis are presented. Increased color Doppler flow should bring the possibility of hepatocellular carcinoma and focal nodular hyperplasia to mind, but Doppler diagnosis is ultimately not highly specific. Sonography, including Doppler analysis, is useful to assess the resectability of malignant masses. Intraoperative ultrasound is the most sensitive imaging modality in detecting focal liver lesions.     

Chronic hepatitis and cirrhosis on MR imaging

This article focuses on the current role of magnetic resonance imaging in the detection and characterization of chronic hepatitis and cirrhosis. In particular, the characteristic MR imaging features of morphologic changes and focal manifestations of chronic liver disease are highlighted.     

Cirrhosis: spectrum of findings on unenhanced and dynamic gadolinium-enhanced MR imaging

The appearance of the cirrhotic liver on computed tomography can be difficult to evaluate and can frustrate the radiologist distinguishing benign from malignant lesions. Hepatic edema, fibrosis, atrophy, and vascular abnormalities are common in the cirrhotic liver and produce derangements in morphology, attenuation, and perfusion, limiting the accurate characterization of hepatic masses. With the development of fast magnetic resonance (MR) sequences and dynamic postgadolinium-enhanced imaging, most hepatic lesions with uncertain etiology on computed tomography can be accurately characterized on MR imaging. We describe MR imaging techniques useful for imaging cirrhosis and its complications. We also illustrate the spectrum of findings in the cirrhotic liver on dynamic gadolinium-enhanced MR imaging, including reticular and confluent fibrosis, fatty infiltration, hemochromatosis, regenerating nodules, dysplastic nodules, hepatocellular carcinoma, and sequela of portal hypertension. Received: 16 November 2000/Revision accepted: 7 February 2001     

Detection and characterization of focal hepatic lesions with diffusion-weighted MR imaging: a pictorial review

The purpose of this pictorial review is to discuss the usefulness and limitations of diffusion-weighted (DW) MR imaging of the liver, demonstrating DW images of a variety of focal hepatic diseases. We include hepatocellular carcinoma, borderline-lesions in cirrhosis, metastasis, cavernous hemangioma, cyst, focal nodular hyperplasia, hepatic adenoma, abscess, and hematoma. DW imaging is an important supplementary sequence of routine MR imaging protocols of the liver. Radiologists need to understand its usefulness and limitations in the detection and characterization of benign and malignant focal hepatic diseases.     

MR imaging of benign focal liver lesions

MRI has become the most important imaging modality for detecting and characterizing focal liver lesions. The introduction of high-field-strengths, such as 3 Tesla MR imaging, in combination with the parallel imaging technique, has led to significant improvements in spatial and temporal resolution and has established this technique as a valuable asset in daily clinical practice. New techniques, such as diffusion-weighted imaging, may improve MR imaging sensitivity and specificity in the diagnostic workup of focal liver lesions. The tailored administration of various nonspecific and liver-specific contrast agents enables clinicians to increase the detection rate and improve the characterization of the different focal liver lesions. This article describes the usefulness of these imaging techniques in detecting and characterizing the most common benign focal liver lesions.     

肝硬变的MRI诊断

笔者复习了我院９４年３～１１月经临床及ＭＲＩ诊断为肝硬变５０例，其中３７例伴有肝癌（７４％），提出肝硬变的ＭＲＩ特点：①肝内弥漫性结节，按结节大小分为小结节型．大结节型及大小结节混合型；②肝普遍增大；③肝表面凸凹不整．各叶比例失调；④肝内静脉细，稀少；⑤脾静脉扩张，胃底及脾门静脉曲张；⑥脾肿大；⑦腹水。文中着重分析肝内再生结节、脉瘤性增生结节及小肝癌三者的ＭＲＩ信号特点及其演变过程。提出ＭＲＩ诊断肝硬变的价值。     

Pediatric liver: focal masses

Imaging is a standard part of the evaluation of pediatric liver disease. Advances in MR imaging have improved detection, characterization, and staging of hepatic lesions. This article addresses the MR imaging appearances of various focal hepatic lesions that can present in children. Techniques for performing hepatic MR imaging also are reviewed.     

Imaging features of nodular regenerative hyperplasia of the liver mimicking hepatic metastases

We described the sonographic, computed tomographic (CT), and magnetic resonance (MR) imaging features of one atypical case of nodular regenerative hyperplasia of the liver. The presence of multiple hepatic nodules suggested the diagnosis of metastatic disease to the liver because of a peripheral rim of enhancement on CT obtained after intravenous administration of contrast material and a halo sign on T2-weighted spin-echo MR imaging. Examination of the pathologic specimen obtained after surgical biopsy showed that the nodules were made of hepatocytes, with a nodular arrangement surrounded by peliosis, without fibrosis or cirrhosis. These findings suggested that peliosis may cause peripheral rim of enhancement on CT and halo sign on MR imaging. In light of this case, nodular regenerative hyperplasia of the liver should be considered in the differential diagnosis of hepatic metastases.     

肝移植术前MRI评价

目的 应用MRI扫描成像技术和血管成像方法对肝移植进行术前综合评价，为肝移植手术方案的制定提供依据。方法 对拟行肝移植的29例患者进行MRI成像．肝胰胆管水成像．肝脏体积测量和动态3D血管成像，处理和分析成像结果，以明确肝脏病变性质与范围，病肝体积以及肝脏动静脉及门静脉情况。结果 29例肝移植患者中肝硬化10例．肝恶性肿瘤15例，慢性活动性肝炎2例，布加综合征1例，多囊肝1例。出现肝动脉变异5例，其中2例肝动脉起自肠系膜上动脉，2例起自腹腔干，1例起自胃左动脉。门静脉栓子6例，其中癌栓5例，门静脉海绵样变性1例，1支或2支肝静脉栓塞7例，肝体积明显缩小5例。结论 应用正确的MRI扫描方法可充分显示肝脏病变的范围与性质，明确肝脏体积，采用动态3D血管成像方法可明确显示肝动脉起源，门静脉有无栓子，肝静脉是否通畅，为肝移植术前手术方案的制定提供依据。     

A Pictorial Review of the MRI Appearances of Focal Liver Lesions

The role of magnetic resonance imaging (MRI) in evaluating benign and malignant liver lesions has undergone significant expansion in recent years with the evolution and optimization of imaging sequences and contrast enhanced techniques. The aim of this article is first to summarize the various imaging sequences employed in the evaluation of liver pathology, with reference to the recent literature on the subject and second, to illustrate through pictorial review, the MRI characteristics of a number of benign and malignant lesions both in the normal liver and in those with chronic liver disease. We highlight the importance of availability of adequate clinical history in the interpretation of focal liver lesions on MRI, including the presence or absence of chronic liver disease, known history of primary malignancy and if applicable, serum alpha fetoprotein levels. In conclusion, MRI is the optimum imaging modality in the evaluation of focal liver lesions. Pattern recognition and knowledge of patient history enables characterization of the majority of liver lesions without the use of ionizing radiation.     

Assessment of the Hallmarks of Wilson Disease in CT Scan Imaging

IntroductionOwing to nonspecific clinical symptoms, Wilson disease (WD) diagnosis is often missed or delayed; hence, many patients reach end-stage liver disease. When cirrhosis takes place, it is difficult to distinguish between WD and other causes of cirrhosis by imaging alone. This study outlines abdominal computed tomography (CT) imaging findings that occur more frequently in patients with WD cirrhosis.Material and MethodsFifty-seven patients with WD who had referred for liver transplantation took part in this study and underwent dynamic liver CT examination before transplantation. Qualitative and quantitative parameters including liver density, contour irregularity, dysmorphia, hypertrophy of caudate lobe, presence of focal parenchymal lesion, thickness of perihepatic fat layer, periportal thickness, lymphadenopathy, and other associated findings were recorded and evaluated.ResultsAmong these patients, 85.9% had contour irregularity, 28% had hepatic dysmorphia, and periportal thickening and cholelithiasis were found in 25.5% and 12.3% of patients, respectively. Splenomegaly, lymphadenopathy, and portosystemic shunting were observed in all patients. Also, hyperdense nodules (>20 mm) and honeycomb pattern were detected in 65.2% and 15.2% of patients, respectively, in the arterial phase. In the portal phase, these findings were detected only in 13% and 4.3% of patients. Hypertrophy of caudate lobe was seen only in 12.2% of patients.ConclusionWD-associated cirrhosis has many CT imaging findings, although most of them are nonspecific. Some findings, such as hyperdense nodules and honeycomb pattern in non–contrast-enhanced CT scan and arterial phase of triphasic CT scan with lack of hypertrophy of caudate lobes, are hallmarks of WD.     

肝移植术前影像学表现

目的研究肝移植术前的影像学表现,为外科肝移植术前病人选择,手术计划制定,预后评估及合理选择影像学检查方法提供帮助。方法肝移植患者37例中,术前行超声检查15例,CT检查20例,MRI检查17例。结果结节性肝硬化18例;肝细胞癌5例;肝硬化合并肝细胞癌8例;胆管细胞癌2例;胆囊癌1例;重症肝炎1例;包虫病并结节性肝硬化和肝脏恶性间质瘤各1例,术前未作出诊断。结论各种影像学检查各有优势,合理地运用,不仅可以作出疾病的定性诊断,为外科医生术前提供全面的影像信息,还有助于手术计划的制定,预后的评估,为我国肝移植标准的制定提供帮助。     

胆囊窝扩大的MRI征象对肝硬化诊断的价值

目的：评价胆囊窝扩大MRI征象对肝硬化诊断的敏感性和特异性。方法;本文收集临床证实的肝硬化患者61例;同时收集同期无肝硬化病史病例80例作为对照组,将病变组和对照组的病例随机混合,不提供临床病史分别由两位有多年MR诊断经验和医师独立阅片,确定有无胆囊窝扩大征;计算胆囊窝扩大的MRI征象对肝硬化诊断的准确性、敏感性、特异 性、阳性预检值和阴性预检值。结果：（1）医师Ⅰ阅片结果显示：胆囊窝扩大的MRI征象对肝硬化诊断的准确性为86％、敏感性为70％、特异性为98％、阳性预检值为96％;（2）医师Ⅱ阅片结果显示：胆囊窝扩大的MRI征象对肝硬化诊断的准确性为84％、敏感性为74％、特异性为93％、阳性预检值为88％。结论：胆囊窝扩大MRI征象在肝硬化中较常见,可以作为肝硬化诊断的特异征象。     

Portal blood flow in the presence or absence of diffuse liver disease: measurement by phase contrast MR imaging

Background: In patients with diffuse liver disease, the portal flow dynamics change markedly in accordance with disease progression and would provide a useful index of progression of stage. Methods: Portal blood flow (PBF) was measured by phase contrast magnetic resonance imaging (MRI) in 21 patients with diffuse liver disease and 20 healthy volunteers. The MRI method was validated by a flow phantom study. The mean PBF could be measured in 6.8 min without breath-holding. Results: Doppler ultrasound measurements of PBF volume were obtained reproducibly in all the healthy volunteers and were shown to correlate with the MRI values (Doppler: 12.5 ±3.2 cm³/s, MRI: 12.0 ± 3.3 cm³/s; mean ± SD). The PBF volume of patients with chronic hepatitis showed no significant difference from that of the healthy volunteers. In patients with liver cirrhosis, the PBF volume ranged from 5.01 to 32.3 cm³/s. A significant increase in PBF volume was caused in one patient by massive intrahepatic shunting and a significant decrease was caused in two patients by massive extrahepatic shunting. Conclusions: The measurement of PBF by phase contrast MRI is clinically useful in predicting intrahepatic or extrahepatic shunting in patients with liver cirrhosis, and may be of value in detecting the progression of stage in diffuse liver diseases.     

MR imaging in the evaluation of hepatic metastases

Optimal detection of focal hepatic lesions in patients with metastases can alter patient management and result in significant cost savings by reducing the number of unnecessary laparotomies for unresectable disease. Liver-specific MR imaging contrast agents (reticuloendothelial and hepatobiliary agents) offer greater lesion-to-liver contrast than the conventional extracellular fluid space MR imaging contrast agents (gadolinium chelates), which have a nonspecific distribution. For the detection of hepatic metastases, although the work of Seneterre et al suggests that the accuracy of ferumoxide-enhanced MR imaging is equivalent to that of CTAP, other studies find CTAP to be superior. Comparisons of reticuloendothelial agents and hepatobiliary agents for imaging liver metastases are lacking in the literature. Further studies comparing MR imaging enhanced with liver-specific contrast agents to CTAP are needed to determine if hepatic MR imaging can replace CTAP for the preoperative evaluation of hepatic metastases. For the characterization of focal liver lesions, MnDPDP and ferumoxides have been added to the small list of FDA-approved contrast agents, and both can help to increase diagnostic specificity. Two of the hepatobiliary agents which are not yet approved, Gd-BOPTA and Gd-EOB-DTPA, have the potential of characterizing liver lesions during dynamic contrast enhancement (similar to Gd-DTPA) and during the hepatocyte phase (similar to MnDPDP), and may increase the detection of focal liver lesions.