Multifocal nodular fatty infiltration of the liver mimicking metastatic disease on CT: imaging findings and diagnosis using MR imaging

The aim of this study was to describe the MR appearance of multifocal nodular fatty infiltration of the liver (MNFIL) using T1-weighted in-phase (IP) and opposed-phase (OP) gradient-echo as well as T2-weighted turbo-spin-echo sequences with fat suppression (FSTSE) and without (HASTE). Magnetic resonance imaging examinations at 1.5 T using T1-weighted IP and OP-GRE with fast low angle shot (FLASH) technique, and T2-weighted FSTSE, T2-weighted HASTE of 137 patients undergoing evaluation for focal liver lesions were reviewed. Five patients were identified in whom CT indicated metastatic disease; however, no liver malignancy was finally proven. Diagnosis was confirmed by biopsy (n = 3), additional wedge resection (n = 1) or follow-up MRI 6–12 months later (n = 5). Regarding the identified five patients, the number of focal liver lesions was 2 (n = 2) and more than 20 (n = 3). The MR imaging characteristics were as follows: OP-image: markedly hypointense (n = 5); IP image: isointense (n = 2) or slightly hyperintense (n = 3); T2-weighted FSTSE-image: isointense (n = 5); T2-weighted HASTE image isointense (n = 1); slightly hyperintense (n = 4). On OP images all lesions were sharply demarcated and of almost spherical configuration (n = 5). Further evaluation by histology or follow-up MR imaging did not give evidence of malignancy in any case. Histology revealed fatty infiltration of the liver parenchyma in three patients. Magnetic resonance follow-up showed complete resolution in two patients and no change in three patients. Multifocal nodular fatty infiltration can simulate metastatic disease on both CT and MR imaging. The combination of in-phase (IP) and opposed-phase (OP) gradient-echo imaging can reliably differentiate MNFIL from metastatic disease. Received: 15 September 1999 Revised: 3 February 2000; Accepted: 7 February 2000     

Multifocal fatty infiltration of the liver: report of six cases

Images of computed tomography (CT), ultrasonography (US), angiography and radionuclide imaging were analyzed in six cases of multifocal fatty infiltration of the liver. Histologic confirmation of fatty infiltration was obtained in one patient by percutaneous biopsy. In the remaining patients, presumptive confirmation of the diagnosis was based on the CT number in one patient and partial or complete resolution of the lesions on repeat CT scans or US in 4 patients. CT and US were performed in all six patients. CT scans demonstrated multiple round areas of low attenuation within both lobes of the liver in all cases. US studies showed hyperechoic foci in three cases and diffuse inhomogeneous hyperechogenicity in three cases. Hepatic arteriograms in five cases and liver scintigrams in four cases showed no evidence of space-occupying lesions. In all cases, the lesions completely or partially resolved in follow-up CT and US, and in four cases the lesions disappeared within two months, so follow-up examinations within about 2 months are necessary to differentiate these from liver neoplasms.     

Nuclear medicine evaluation of focal fatty infiltration of the liver

Focal fatty infiltration of the liver (FFIL) occasionally may be mistaken as metastatic disease, primary liver malignancy, or other space-occupying lesions on CT or ultrasound studies, especially if there is significant mass effect. In these confusing cases, Xe-133 liver imaging has been advocated for confirmation of FFIL, since such studies have been reported to be sensitive and specific. The authors present results of four Xe-133 and four Tc-99m sulfur colloid scans in six patients with FFIL. Xe-133 imaging was found useful for diagnostic confirmation in only one patient and was misleading in the other three. Routine liver-spleen imaging was a more reliable method of confirmation, since no focal defects were found in any of the patients.     

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.     

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.     

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.     

Focal fatty infiltration of the liver simulating metastatic disease

Two cases are reported in which multiple, well-defined lesions of the liver, as seen on computed tomographic (CT) scans and sonograms, were thought to represent metastatic malignancy. Results from radionuclide scans and biopsies (and surgery in one case) indicated the correct diagnosis was fatty infiltration of the liver. Focal fatty infiltration should be considered in cases of multiple discrete hepatic lesions, especially in patients with a predisposing condition. Radionuclide studies and biopsies may be needed to confirm the diagnosis by CT.     

Eosinophilic hepatic necrosis: magnetic resonance imaging and computed tomography comparison

OBJECTIVE: To compare the findings of magnetic resonance (MR) imaging with those of computed tomography (CT) of focal liver lesions related to peripheral eosinophilia. METHODS: For 12 patients with peripheral eosinophilia (>7%) examined with hepatic MR imaging and CT, 52 focal hepatic lesions larger than 0.5 cm, including 31 lesions simultaneously found on the 2 imaging modalities, were subjected to a comparative analysis of their imaging features. RESULTS: The total number of lesions distinguished from background liver was 39 (75%) on MR imaging and 44 (85%) on CT scans. On arterial phase images of 10 patients with comparable data, homogeneously hyperintense lesions were demonstrated more frequently (P = 0.006) on MR imaging (16 [50%] of 32 lesions) than on CT scans (4 [13%] of 32 lesions). Only 7 (22%) of the 32 hypoattenuating lesions on portal phase CT were depicted as hypointense lesions on portal phase MR images in 12 patients. On delayed phase images in 8 patients, the number of hyperintense lesions on MR images (9 [56%] of 16) was greater (P = 0.077) than that seen on the CT scans (4 [25%] of 16). CONCLUSIONS: For many focal hepatic lesions related to peripheral eosinophilia, dynamic MR imaging more easily demonstrates lesional enhancement on arterial and delayed phases than CT scans. Because of the higher degree of lesional enhancement of MR imaging compared with CT, the lesion-to-liver contrast may not be sufficient to distinguish the lesion from the background liver, resulting in decreased sensitivity of portal phase dynamic MR imaging.     

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.     

Diagnosis of small hepatocellular carcinoma: correlation of MR imaging and tumor histologic studies

Magnetic resonance (MR) images of the liver were used to study 43 patients with relatively small hepatocellular carcinomas (HCCs) and 36 with other hepatic mass lesions. In 27 HCC patients, histologic findings were available. All focal lesions detectable by CT without contrast media were delineated with greater contrast by MR imaging. The rate of detection depended on tumor size, being 97.5% for HCCs greater than 2 cm in the longest axis and 33.3% for those less than 2 cm. MR imaging demonstrated the ring sign characteristic of encapsulated HCC twice as frequently as CT scans. Inversion recovery (IR) images depicted the internal structure of the HCC better than T2-weighted spin-echo images. Lesions were classified into four patterns of intensity: low, iso, high, and mixed. The latter three were relatively characteristic of HCC and related closely with steatosis of cancer tissue. HCCs with fibrosis tended to have long T1 values; those with steatosis had short T1 values. T1 and T2 relaxation times were useful in the differential diagnosis.     

Leptomeningeal metastasis: MR imaging

Seven patients with central nervous system neoplasia and leptomeningeal metastases, proved either at initial diagnosis or on follow-up with contrast material-enhanced computed tomography (CT), were evaluated with magnetic resonance (MR) imaging. In two patients, diffuse sulcal enhancement on CT scans was inapparent on T1- or T2-weighted MR images. Likewise, in four patients diffuse cisternal enhancement on CT scans was not identifiable with MR. Nodular or focal cisternal masses were identified with both CT and MR imaging in three patients; in two, however, MR imaging provided less information. Ependymal and subependymal metastases identified with CT (two patients) were indistinguishable on MR images from periventricular abnormalities of radiation therapy and/or hydrocephalus. These findings suggest that leptomeningeal metastasis may be so subtle or inapparent as to be overlooked with MR imaging alone. Thus, CT and MR imaging should be considered complementary techniques for initial diagnosis and follow-up of tumors with a propensity for leptomeningeal metastasis.     

Hepatic bile duct hamartomas (von Meyenburg Complexes): MR and MR cholangiography findings

Multiple bile duct hamartomas (MBDHs) of the liver, also known as von Meyenburg complexes, are easily confused with diffuse metastatic disease of the liver on US and CT. At present, histologic examination after tissue preevaluation is usually necessary for definite diagnosis. We report four cases in which the MR features, and especially the MR cholangiographic (MRC) findings, were highly suggestive for MBDH. Characteristic findings include multiple markedly hyperintense nodules on T2-weighted imaging, typically measuring <1.5 cm; no communication with the biliary tree; and irregular delineation of the lesions with no or slight rim enhancement following gadolinium administration.     

Imaging features of perivascular fatty infiltration of the liver: initial observations

PURPOSE: To retrospectively identify and describe the imaging features that represent perivascular fatty infiltration of the liver. MATERIALS AND METHODS: The institutional review board approved the study and waived informed consent. The study complied with the Health Insurance Portability and Accountability Act. Ten patients (seven women, three men; mean age, 78 years; range, 31-78 years) with fatty infiltration surrounding hepatic veins and/or portal tracts were retrospectively identified by searching the abdominal imaging teaching file of an academic hospital. The patients' medical records were reviewed by one author. Computed tomographic (CT), magnetic resonance (MR), and ultrasonographic (US) imaging studies were reviewed by three radiologists in consensus. Fatty infiltration of the liver on CT images was defined as absolute attenuation less than 40 HU without mass effect and, if unenhanced images were available, as relative attenuation at least 10 HU less than that of the spleen; on gradient-echo MR images, it was defined as signal loss on opposed-phase images compared with in-phase images; and on US images, it was defined as hyperechogenicity of liver relative to kidney, ultrasound beam attenuation, and poor visualization of intrahepatic structures. Perivascular fatty infiltration of the liver was defined as a clear predisposition to fat accumulation around hepatic veins and/or portal tracts. For multiphase CT images, the contrast-to-noise ratio was calculated for comparison of spared liver with fatty liver in each imaging phase. RESULTS: Fatty infiltration surrounded hepatic veins in three, portal tracts in five, and both hepatic veins and portal tracts in two patients. Six of the 10 patients had alcoholic cirrhosis, two reported regular alcohol consumption (one of whom had acquired immunodeficiency syndrome and hepatitis B), one was positive for human immunodeficiency virus, and one had no risk factors for fatty infiltration of the liver. In three of the 10 patients, fatty infiltration was misdiagnosed as vascular or neoplastic disease on initial CT images but was correctly diagnosed on MR images. CONCLUSION: Perivascular fatty infiltration of the liver has imaging features that allow its recognition.     

Hepatic metastases: randomized, controlled comparison of detection with MR imaging and CT

To determine the accuracy of magnetic resonance (MR) imaging relative to computed tomography (CT) in the diagnosis of liver metastases, a randomized, controlled study was conducted of 135 subjects, including 57 with cancer metastatic to the liver, 27 with benign cysts or hemangiomas, and 51 without focal liver disease. The sensitivity of MR imaging for detecting individual metastatic deposits was 64%, significantly greater than 51% for CT (P less than .001); the difference in sensitivity for identifying patients with one or more hepatic metastases was less (82% for MR imaging vs. 80% for CT). In patients without hepatic metastases, the specificity of MR imaging was 99% versus 94% for CT. Significant differences were found between individual MR pulse sequences in detection of individual lesions. The sensitivity of both T1-weighted spin-echo (SE) (64%) and inversion-recovery (IR) (65%) pulse sequences was significantly (P less than .001) greater than either the TE (echo time) 60 msec (43%) or TE 120 msec (43%) T2-weighted pulse sequences. Overall, the accuracy of a single T1-weighted (10-minute) pulse sequence was superior to that of contrast-enhanced CT.     

肝脏局灶性结节性增生2例报告及文献复习

目的通过分析肝脏局灶性结节增生的影像表现，提高其诊断准确性。方法2例经手术病理证实的肝脏局灶性结节增生患者均接受超声、CT和MRI检查，其影像表现结合文献复习进行了分析。结果超声显示了2例的肝右叶实性占位性病变。1例CT平扫肝右叶病灶显示不清，增强扫描后，肝右叶前段有一直径约3．1cm的类圆形病灶呈均匀强化。MR平扫见2例的肝内结节病灶均呈等T1、等T2信号，增强扫描动脉期病灶明显强化，门脉期和延迟期病灶的强化程度逐渐下降。结论腹部超声可提示本病的诊断，而CT和MRI，尤其是增强扫描，可清晰显示病灶的血供特点和强化特征，为定性诊断提供重要依据。     

Advanced carcinoma of the thoracic esophagus: CT, MR, and echo-endoscopy in the staging after chemotherapy]

Thirteen patients affected with advanced epidermoid carcinoma of the thoracic esophagus were examined by means of CT, MR and endoscopic US (EUS) before and after chemotherapy. Eleven patients underwent esophagectomy and esophagogastroplasty. An intraesophageal prosthesis was positioned in 2 patients since chemotherapy had not modified tumour stage. Post-chemotherapy CT, MR and EUS parameters were compared with the corresponding pathologic findings. As for MR imaging, post-chemotherapy signal intensity variations in T1 and T2 sequences were also evaluated. MR imaging was more accurate than CT in depicting the involvement of mediastinal fatty layers, the relationships between mass and cardiovascular structures, and the cellularity. CT and MR exhibited limitations in identifying metastatic mediastinal lymph nodes, in which case EUS proved to be the most accurate technique. Both CT and MR failed to satisfactorily assess the infiltration of tracheobronchial tree, which was best demonstrated by endoscopy.     

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.     

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.     

Telangiectatic focal nodular hyperplasia: US,CT, and MR imaging findings with histopathologic correlation in 13 cases

PURPOSE: To review the ultrasonographic (US), computed tomographic (CT), and magnetic resonance (MR) imaging findings in 13 patients with telangiectatic focal nodular hyperplasia (FNH) and to compare imaging features with histopathologic results from resected specimens. MATERIALS AND METHODS: US, helical multiphasic CT, and MR images in 13 patients with pathologically proven telangiectatic FNH were reviewed retrospectively. Two abdominal radiologists evaluated lesions for number, size, heterogeneity, surface characteristics, presence of a central scar, presence of a pseudocapsule, US appearance, attenuation at CT, signal intensity at MR imaging, and presence of associated lesions. Imaging and pathologic findings were compared. RESULTS: Sixty-one lesions (5-140 mm in diameter) were seen at imaging. Lesions were multiple in eight of 13 (62%) patients. Imaging characteristics were heterogeneity in 26 of 61 lesions (43%), well-defined margins in 43 of 61 (70%), lack of a central scar in 56 of 61 (92%), presence of a pseudocapsule in three of 61 (5%), hyperintensity on T1-weighted MR images in 17 of 32 (53%), strong hyperintensity on T2-weighted MR images in 24 of 54 (44%), and persistent enhancement on delayed contrast material-enhanced CT or T1-weighted MR images in 23 of 38 (61%). No specific US pattern was noted. Two patients had additional lesions: One had classic FNH, and the other had a cavernous hemangioma. Hyperintensity on T1-weighted MR images was due to sinusoidal dilatation. Hyperintensity on T2-weighted MR images correlated well with the presence of inflammation. CONCLUSION: Telangiectatic FNH differs from typical FNH at imaging: Atypical FNH features often observed with telangiectatic FNH are lack of a central scar, lesion heterogeneity, hyperintensity on T1-weighted MR images, strong hyperintensity on T2-weighted MR images, and persistent contrast enhancement on delayed contrast-enhanced CT or T1-weighted MR images.     

Large focal defect on liver/spleen scan caused by fatty liver and masquerading as neoplasm.

Focal fatty infiltration of the liver may be mistaken for metastatic disease, primary tumor or other space-occupying lesions on CT or ultrasound. Usually, a 99mTc-sulfur colloid scan is sensitive in documenting the presence of Kupffer's cell in such a process. We present a case that was suggestive of focal fatty infiltrate on a CT scan, nondiagnostic on ultrasound, and seen as a large focal defect on the 99mTc-sulfur colloid liver/spleen scan. A 133Xe inhalation study, however, did show uptake in the area of fatty infiltration. A needle biopsy confirmed the diagnosis.