Nondiffuse fatty change of the liver: discerning pseudotumor on MR images enhanced with ferumoxides-initial observations

PURPOSE: To clarify the findings of nondiffuse fatty change of the liver on ferumoxides-enhanced magnetic resonance (MR) images. MATERIALS AND METHODS: Of 202 patients who underwent ferumoxides-enhanced MR imaging, eight who had nondiffuse fatty change of the liver at computed tomography (CT) were examined as study subjects. MR imaging findings before and 1 hour after ferumoxides administration were compared with CT findings. RESULTS: Focal fatty areas of the liver showing low attenuation on CT images were depicted as areas of relatively high intensity on the ferumoxides-enhanced T1-weighted images in all patients. On enhanced T2-weighted images, focal fatty change showed relatively high intensity in three and isointensity in one of the four patients. Focal spared areas appearing as areas of relatively high attenuation on CT images were depicted as areas of relatively low intensity on the ferumoxides-enhanced T1- and T2-weighted images in all patients. CONCLUSION: Although prior reports of hepatic MR imaging with ferumoxides indicated that there is accumulation of ferumoxides within focal fatty areas that are no longer seen after the administration of contrast medium, this study revealed that focal fatty change and focal spared areas of fatty liver may be pseudotumors because of the relatively high intensity of fatty areas of the liver. Radiologists can distinguish these conditions from hepatic tumors by using the opposed-phase gradient-echo sequence or the fat-saturation technique.     

Detection of hepatic metastases in diffuse fatty infiltration by CT: the complementary role of imaging

Six patients undergoing computed tomographic (CT) evaluation for possible abdominal and pelvic metastases were shown to have diffuse fatty infiltration of the liver and findings indeterminate for hepatic metastases. In two patients with diffuse fatty infiltration and no focal hepatic lesions on CT, technetium-99m sulfur colloid imaging demonstrated focal hepatic defects confirmed to represent metastases. In four patients with diffuse fatty infiltration and hyperdense liver foci on CT, radionuclide imaging demonstrated normal uptake in the hyperdense foci confirmed to represent areas of normal liver spared by fatty infiltration. In each of the six patients, clinical management was altered by the radionuclide findings.     

Focal fatty infiltration of the liver: analysis of prevalence and CT findings in children and young adults

OBJECTIVE: Focal fatty infiltration of the liver, a benign entity that can be confused with a malignant lesion, is well characterized in adults but not in children. The goal of this study was to determine by CT the prevalence and characteristics of focal fatty infiltration in children and young adults. MATERIALS AND METHODS: We retrospectively analyzed 305 consecutive contrast-enhanced abdominal CT examinations of 218 children and young adults with no known liver disease, performed during 2 years at our institution, to identify focal fatty infiltration of the liver. The imaging criterion for focal fatty infiltration of the liver on helical CT was a geometric or ovoid low-attenuation area adjacent to the falciform ligament, gallbladder fossa, or porta hepatis. If a patient's findings met the CT criterion for focal fatty infiltration of the liver, all previous abdominal CT and MR imaging examinations performed for that patient were reviewed to assess the evolution of focal fatty infiltration of the liver. RESULTS: Of 218 children and young adults, 20 (9.2%) met the CT criterion for focal fatty infiltration of the liver. In our population, focal fatty infiltration of the liver was identified only adjacent to the falciform ligament. The prevalence of focal fatty infiltration of the liver increased significantly with advancing age: 0% for ages 1 month-4 years; 7.3% for 5-9 years; 10.2% for 10-14 years, and 25.6% for 15-19 years (p < 0.0001). CONCLUSION: Focal fatty infiltration of the liver was identified in 9.2% of patients in our population, and occurrence of this lesion in children increases significantly with advancing age. However, focal fatty infiltration of the liver is uncommon in infants and young children and should be a diagnosis of exclusion.     

Value of MR imaging in evaluating focal fatty infiltration of the liver: preliminary study.

Focal fatty infiltration of the liver is a well-known entity that occasionally mimics metastatic disease on ultrasonographic (US) and computed tomographic (CT) scans and requires biopsy for diagnosis. To determine if high-field-strength magnetic resonance (MR) imaging might be useful in the differential diagnosis of the lesions, the authors compared US, CT, and MR findings in three patients with biopsy-proved fatty hepatic lesions. Areas of focal fatty infiltration were hyperechoic on US scans and had low attenuation on CT scans. No mass effect of the lesions on vascular structures or liver contours was observed, particularly on contrast material-enhanced CT scans. For all three patients, MR findings suggested the correct diagnosis by demonstrating focal high signal intensity on spin-echo T1- and T2-weighted images. On the basis of these preliminary findings, it appears that focal fatty infiltration of the liver may be differentiated from metastatic disease by means of high-field-strength MR imaging.     

Focal sparing around the gallbladder in fatty liver: an useful sign in the diagnosis of borderline cases by CT

The role of CT in the diagnosis of fatty liver is well established. CT has been proved to be a useful noninvasive tool for the demonstration of fatty infiltration of the liver. The characteristic finding is a diffuse decrease in the attenuation within the liver compared with that of the spleen. Commonly, fatty infiltration of the liver is generalized and both CT scans and sonograms can easily demonstrate changes related to this condition. Sometimes, fatty infiltration of the liver is focal and occasionally, it is generalized with focal sparing of the normal liver tissue creating some problems in the diagnosis. Recently, some reports have mentioned the appearance of a focal sparing area in the generalized fatty liver. We often found a high attenuation region around the gallbladder bed in the fatty liver patients on CT examination. There appears to be some relationship between the high density around the gallbladder area and the fatty liver. A retrospective study was undertaken to evaluate the relationship. In this paper, we presented the CT scans of 57 fatty liver cases and compared them with the CT scans of 50 normal patients to discuss the possible cause of the phenomenon and its usage in the diagnosis of the fatty liver.     

Visceral CT findings associated with Thorotrast

Plain radiography and CT of the abdomen were reviewed in four patients who had undergone angiography with thorium dioxide (Thorotrast). In three patients CT showed irregularly scattered focal punctate collections of Thorotrast in the liver parenchyma, predominantly in the subcapsular zone, associated with areas of low or nonhomogeneous attenuation. These areas of low attenuation were identified on microscopic studies as sites of hepatic fibrosis or neoplasia. Computed tomography identified intrahepatic Thorotrast deposits more definitively than plain radiography.     

脂肪肝内正常肝岛及正常肝内局灶脂肪变性的CT与MR诊断

目的：探讨脂肪肝内正常肝岛及正常肝内局灶脂肪变性的ＣＴ与ＭＲ征象。方法：６例脂肪肝内正常肝组织岛（Ａ组）与７例正常肝内局灶性脂肪变性（Ｂ组）病人,ＣＴ与常规ＳＥＴ１ 及Ｔ２ 加权及梯度回波Ｔ１ 加权ｉｎ－ ｐｈａｓｅ及ｏｕｔ－ ｐｈａｓｅ ＭＲ成像。结果：增强前、后ＣＴ显示正常肝组织岛保持正常肝组织与脾脏密度关系;肝组织局灶脂肪变性呈相对低密度。ＭＲＩＳＥＴ１、Ｔ２ 加权成像及梯度回波ｉｎ－ ｐｈａｓｅＴ１ 加权成像显示正常肝组织岛相对低信号区;局灶脂肪变性区呈稍高信号。梯度回波ｏｕｔ－ ｐｈａｓｅ Ｔ１ 加权成像正常肝组织岛呈高信号;局灶脂肪变性区呈低信号。脂肪抑制Ｔ２ 加权成像均呈等信号。结论：采用ＭＲ的梯度回波ｏｕｔ－ ｐｈａｓｅＴ１ 加权及ＴＳＥＴ２ 加权脂肪抑制成像可以诊断正常肝岛及正常肝内的局灶脂肪变性。     

弥漫型脂肪肝内局灶性病变的CT诊断

目的 研究在弥漫型脂肪肝背景下肝局灶性病变的CT特征,以提高对其诊断的准确率.资料与方法 回顾性分析40例弥漫型脂肪肝合并局灶性病变(35例)或残存肝岛(5例)患者的CT资料,观察脂肪肝对肝局灶性病变CT表现的影响.结果 40例弥漫型脂肪肝中,26例合并多发局灶性肝病变,9例合并单发病变,5例残存肝岛. 35例肝局灶性病变中,转移瘤18例 ,肝细胞癌(HCC)术后复发2例,血管瘤8例,多发囊肿5例,多发腺瘤及单发局灶性结节增生(FNH)各1例.CT平扫肝局灶性病变相对密度随脂肪肝程度而异,边界多不清,增强后强化方式则与无脂肪肝背景的肝内病变相似.结论 弥漫型脂肪肝内局灶性病变,其CT表现与正常背景下有所差异,增强检查尤其是动态增强对病变的诊断与鉴别具有重要意义;对不典型病例,随访对比有助于正确诊断.     

Computed tomographic and ultrasound appearances of focal spared areas in fatty infiltration of the liver

Computed tomography (CT) and ultrasound (US) appearances of diffuse and focal fatty infiltration of the liver (FIL) are well recognized. We have recently seen 10 cases with "fat spared" areas in FIL presenting as pseudo tumours of the liver. Characteristic appearances of fat free areas in FIL which help differentiate these areas from other focal liver lesions include (i) location in the medial segment of the left lobe of the liver, (ii) absence of mass effect on surrounding vessels and liver tissue, and (iii) presence of typical changes of FIL elsewhere in the liver on CT or US examination.     

Hepatosplenic fungal infection: CT and pathologic evaluation after treatment with liposomal amphotericin B

Disseminated fungal disease, predominantly involving liver and spleen, developed in eight patients with hematologic malignancies. Because the patients failed to respond to standard antifungal drugs, they were treated with liposomal amphotericin B (L AmpB). Before therapy began, the diagnosis was confirmed histologically and the patients underwent abdominal computed tomography (CT), which indicated hepatosplenomegaly with or without multiple microabscesses in the liver and spleen. After each course of treatment with L AmpB, patients underwent CT, followed by either open or CT-guided percutaneous aspiration biopsy of the liver. Post-treatment CT showed partial regression of lesions in six patients and persistence in two. In all patients a liver biopsy confirmed that the lesions noted after treatment were due to granulomas or focal areas of fibrosis compatible with healing. Thus, the persistence of multiple defects on enhanced scans in two patients was not an indication of persistent abscesses. Clinical response was an additional important factor. Close clinical and pathologic correlation in addition to CT scanning are required in the follow-up of hepatosplenic fungal infections.     

Contrast-enhanced ultrasonography in the characterization of benign focal liver lesions: activity-based cost analysis

PURPOSE: The aim of this study was to perform a cost analysis of contrast-enhanced ultrasonography (CEUS) in the study of benign focal liver lesions (BFLL) with indeterminate appearance on ultrasonography (US). MATERIALS AND METHODS: A decision model of patients with suspected BFLL on baseline US who subsequently underwent CEUS between 2002 and 2005 was constructed. We analysed the cost effectiveness of CEUS, considering whether or not computed tomography (CT) was necessary for the diagnosis. There were 398 patients with 213 angiomas, 41 focal nodular hyperplasias (FNH) and 154 pseudolesions (focal fatty sparing, focal fatty areas). Each patient underwent CEUS, and 98 of them were also studied by CT. All lesions were followed up. RESULTS: The cost of a single CEUS examination was 101.51 euros, and that of a single CT scan was 211.48 euros. For diagnosis of haemangiomas, we saved 1,406.97 euros in 2002, 5,315.22 euros in 2003, 10,317.78 euros in 2004 and 9,536.13 euros in 2005. For diagnosis of focal nodular hyperplasias, we saved 781.65 euros in 2003, 781.65 euros in 2004 and 1,406.97 euros in 2005. For diagnosis of pseudolesions, we saved 2,813.94 euros in 2002, 5,158.89 euros in 2003, 5,158.89 euros in 2004 and 4,220.91 euros in 2005. In the period 2002-2005, the introduction of CEUS allowed us to save a total of 47,055.33 euros in the diagnosis of benign focal hepatic liver lesions. CONCLUSIONS: This cost analysis shows that CEUS is the least expensive second-line modality after baseline US for the diagnosis of BFLL.     

CT and MR imaging of fatty tumors of the liver

The presence of fat in hepatic masses narrows the range of differential diagnoses down to hepatic angiomyolipoma, lipoma, adenoma, hepatoma, metastatic fatty tumors of the liver, focal fatty infiltration of the liver, and extrahepatic fatty masses such as intraperitoneal implants from malignant teratomas, and packed omentum. We report six hepatic tumors containing fat (lipoma, hepatocellular carcinoma, and calcified mass with fat-fluid level) with CT and magnetic resonance (MR) imaging. The distribution of fat was diffuse in the lipomas and some hepatocellular carcinomas and localized in other hepatocellular carcinomas and fat-fluid masses. The density ranged from - 100 to 0 HU. High intensity areas on both T1- and T2-weighted MR images corresponded to the hypodense areas on CT.     

Value of dual-energy CT in differentiating focal fatty infiltration of the liver from low-density masses

Focal (irregular, partial) fatty infiltration of the liver may simulate neoplastic or other hypodense masses on CT. On the basis of previous observations of the phenomenon that differences in X-ray attenuation diminish with increasing energy of X-rays used, we performed a preliminary study to determine if dual-energy CT could be used to discriminate between fatty infiltration and hypodense liver masses. Dual-energy CT at 140 and 80 kVp was performed in 14 patients undergoing liver biopsy and in seven control subjects with presumedly normal liver. Attenuation measurements were taken, and the changes in attenuation between 140 and 80 kVp were calculated. The mean changes in attenuation were 3.5 H for normal liver (n = 7), 2.5 H for hypodense liver masses (n = 6), 13 H for fatty liver (n = 5), 0.3 H for fatty liver combined with hemochromatosis or hemosiderosis (n = 3), and 2 H for the spleen (n = 18). The change in attenuation increased as the fat content in the liver increased. Analysis of variance showed a statistically significant difference (p less than .001) between fatty liver and the other groups. A difference greater than 10 H was unique to fatty infiltration. These results suggest that dual-energy CT may help to differentiate focal fatty infiltration of the liver from low-density neoplastic or other lesions, but only if the iron content of the liver is not increased.     

Frequency of benign hepatic lesions incidentally detected with contrast-enhanced thin-section portal venous phase spiral CT

PURPOSE: To evaluate the frequency of benign focal hepatic lesions incidentally detected at contrast-enhanced thin-section portal venous phase spiral CT. MATERIAL AND METHODS: Between January 1998 and February 1999, contrast-enhanced hepatic spiral CT examinations were performed in 1,892 patients. Out of these, only 100 patients fulfilled the following inclusion criteria: No underlying malignant disease, no liver cirrhosis, no suspected or known focal liver lesions. Standardized spiral CT parameters were applied. All CT studies were reviewed retrospectively by one radiologist. Any focal lesion was recorded and classified. Lesion size and number were noted. RESULTS: A total of 108 hepatic lesions were reported in 33 out of 100 patients (80 cysts; 18 hemangiomas; 3 focal fatty infiltrations; 2 focal non-tumorous perfusion defects; 1 calcification; and 4 non-classified lesions). The average lesion size was 9.4 mm (< or =5 mm: n=40; 6-10 mm: n=30; 11-15 mm: n=28; >15 mm: n=10). CONCLUSION: Benign liver lesions are probably a frequent incidental finding at abdominal spiral CT.     

高原地区脂肪肝CT表现与缺氧等关系探讨

目的:分析高海拔地区CT诊断为脂肪肝的50例病例,探讨慢性缺氧、酒精与 CT表现的关系。方法:50 例均为普通门诊病例或体检发现,男40例,女10例。均行CT平扫,其中1例行增强CT扫描。结果:50例饮酒史中超过10年以上34例,CT表现分型为弥漫型24例、节段型10例;少于10年16例:弥漫型 10 例、节段型 3 例、局灶型 3 例。脂肪肝受累肝叶分布以肝右叶与左叶内侧段受累为主、肝左叶外侧段与肝尾叶受累相对较少。海拔高度及饮酒史与脂肪肝CT表现及分型有关。结论:高原环境中肝脏处于相对乏氧状态,如持续长时间饮酒将会进一步加重肝脏缺氧性改变及形成肝脂肪变性,同时高原地区独有的高脂肪高能量饮食、肥胖与脂肪肝形成有关。     

放射治疗相关肝损伤的CT影像及其影响因素

放射治疗致肝损伤的病理表现为典型的肝静脉闭塞性疾病。正常肝脏、肝硬化肝脏放射性肝损伤CT平扫显示为照射区低密度改变,而脂肪肝放射性肝损伤显示为照射区高密度改变。正常肝脏、肝硬化肝脏动态CT增强扫描表现不同。放射性肝损伤的不同表现与肝脏基础相关。放射性肝损伤的发生与照射剂量、肝脏基础、放射性肝炎的关系需进一步研究。     

Characteristic sonographic signs of hepatic fatty infiltration

Hepatic fatty infiltration sonographically appears as an area of increased echogenicity. When focal areas of fat are present in otherwise normal liver parenchyma, the fatty area may be masslike in appearance, leading to further imaging evaluation and sometimes even biopsy. This article discusses seven patients with focal fatty infiltration, who had sonographic signs that were highly suggestive of the fatty nature of the masses. These signs included angulated, geometric margins between normal and fatty tissue and interdigitating margins with slender fingers of normal or fatty tissue. These signs may be useful in diagnosing masslike areas of focal fatty infiltration and distinguishing these sonographically from other hepatic mass lesions.     

Hepatic steatosis: combined echography-computerized tomography imaging

The authors report their experience with the combined use of US and CT in the study of diffuse and subtotal fatty infiltration of the liver. An apparent disagreement was initially found between the two examinations in the study of fatty infiltration. Fifty-five patients were studied with US and CT of the upper abdomen, as suggested by clinics. US showed normal liver echogenicity in 30 patients and diffuse increased echogenicity (bright liver) in 25 cases. In 5 patients with bright liver, US demonstrated a solitary hypoechoic area, appearing as a "skip area", in the quadrate lobe. In 2 patients with bright liver, the hypoechoic area was seen in the right lobe and exhibited no typical US features of "skip area". Bright liver was quantified by measuring CT density of both liver and spleen. The relative attenuation values of spleen and liver were compared on plain and enhanced CT scans. In 5 cases with a hypoechoic area in the right lobe, CT findings were suggestive of hemangioma. A good correlation was found between bright liver and CT attenuation values, which decrease with increasing fat content of the liver. Moreover, CT attenuation values confirmed US findings in the study of typical "skip areas", by demonstrating normal density--which suggests that CT can characterize normal tissue in atypical "skip areas".     

CT evaluation of atypical hepatic fatty metamorphosis

Focal fatty metamorphosis of the liver is a well-recognized entity characteristically demonstrated by a nonspherical, low-density area without mass effect. We present a case of focal fatty metamorphosis of the liver that shows multiple areas of low attenuation within the liver with mass effect. Radionuclide liver-spleen scan shows multiple focal defects corresponding to the areas of fatty metamorphosis.     

Pitfalls in liver imaging

Localized, abnormal attenuation/intensity areas on unenhanced and/or enhanced study of CT/MR imaging do not necessarily correspond to tumors themselves or real tumor size. Pitfalls in the diagnosis of liver tumor are described dividing into enhanced study (vascular variants, vascular abnormalities, hyperplastic nodules, around the tumor, and miscellaneous) and unenhanced study (fatty change, focal spared area of diffuse fatty liver, and miscellaneous).