Macrovesicular hepatic steatosis in living related liver donors: correlation between CT and histologic findings

[Liver resection for living-donor liver transplantation: anesthesia and intensive care aspects]

The living related donor mortality after liver donation could occur as a result of postoperative cardiovascular and thromboembolic complication; which could be minimized by detailed preoperative assessment of the living donor. The preoperative functional tests evaluate the physiological reserve or identify the living donors with limited response to the surgical stress. Based on the results of CT volumetry, MRI and liver functional reserve capacity test (indocyanine green retention ratio) the liver resection can be done safely. The preoperative cytochrome P enzymes tests of donors identify the drugs with abnormal metabolism. Balanced anesthesia combined with thoracic epidural anesthesia is done with liver safe, renal safe and ischemic preconditioning drugs. Normovolemic state is maintained with physiologic extrahepatic perfusion and oxygenation conditions. The central venous and hepatic artery pressure is reduced with the guarantee of optimal hepatic perfusion-oxygenation and better liver resection condition. Intraoperative thrombosis prophylaxis is performed with sequential compression device. After liver resection the donor morbidity can be reduced, effective analgesia, thrombosis prophylaxis, liver safe drug therapy and a tight monitoring. Before the first postoperative mobilization a deep vein Doppler ultrasound control is proposed.

[The role of imaging methods in the pre- and intra-operative evaluation, and in post-operative follow-up of living donors in liver transplantation in Hungary]

The evaluation protocol for liver donors can vary from centre to centre, but the main points are the same. Medical history, physical examination, common laboratory tests and psychosocial evaluation are followed by imaging, and specific haemostasis and viral serology tests. The first imaging examinations have the aim of excluding any disease; conventional chest radiography and abdominal ultrasound are performed. Liver volume, fat content, and vascular and biliary anatomy are then evaluated with contrast-enhanced, multiphase, multidetector row CT/CTA and MR cholangiography. Ultrasound guided liver biopsy, and in some cases digital subtraction angiography, should also be performed. During the first phase of the donor operation, intraoperative investigations are done: cholangiography for the final evaluation of the biliary tree and ultrasound of the hepatic and portal venous system to help draw the resection plane. Donors have regular imaging examinations in the early postoperative period for early detection of complications: mainly US or CT to check the remnant hepatic vascularisation and fluid collections in the operated area, or X-ray for thoracic disorders. It is recommended that regular checkups are performed in the late postoperative period. The paper describes the imaging protocol for donor evaluation applied at our institute at the beginning of our living related liver transplantation programme.

Preoperative radiographic assessment of hepatic steatosis with histologic correlation

BACKGROUND

The adverse impact of hepatic steatosis on perioperative outcomes after liver resection is gaining recognition. But the accuracy of preoperative radiologic assessment of fatty liver disease remains unclear. The objective of this study was to correlate preoperative radiologic estimation with postoperative histologic measurement of steatosis.

STUDY DESIGN

Patients who underwent partial hepatectomy between 1997 and 2001, with complete preoperative radiographic imaging and postoperative pathologic assessment of steatosis, were retrospectively analyzed. The presence of steatosis was assessed radiographically using noncontrast-enhanced CT (NCCT), contrast-enhanced CT (CCT), or MRI, using standard quantitative radiologic criteria. Repeat histologic analysis was used to quantify the extent of hepatic steatosis.

RESULTS

One hundred thirty-one patients were studied. The overall sensitivity and specificity for all imaging modalities in detecting pathologically confirmed hepatic steatosis were 56% and 82%, respectively. Sensitivity and specificity for NCCT, CCT, and MRI using standard quantitative criteria were 33% and 100%, 50% and 83%, and 88%, and 63%, respectively. Increasing body mass indices adversely affected the accuracy of NCCT (p=0.002). Preoperative chemotherapy did not notably affect radiologic accuracy.

CONCLUSIONS

The presence of a fatty-appearing liver on NCCT scans indicates clinically significant steatosis, but steatosis cannot be excluded based on a normal NCCT scan, particularly in obese patients. Conversely, normal MRI helps to exclude hepatic steatosis, but abnormal MRI is not a reliable indicator of fatty change. CCT is not an effective means of identifying steatosis. We conclude that, when used alone, conventional cross-sectional imaging does not consistently permit accurate identification of hepatic steatosis.

Unenhanced CT for assessment of macrovesicular hepatic steatosis in living liver donors: comparison of visual grading with liver attenuation index

PURPOSE

To retrospectively compare the accuracy of visual grading and the liver attenuation index in the computed tomographic (CT) diagnosis of 30% or higher macrovesicular steatosis in living hepatic donors, by using histologic analysis as the reference standard.

MATERIALS AND METHODS

Institutional review board approval was obtained with waiver of informed consent. Of 703 consecutive hepatic donor candidates, 24 patients (22 men and two women; mean age +/- standard deviation, 36.3 years +/- 9.7) who had 30% or higher macrovesicular steatosis at histologic analysis and same-day CT with subsequent needle biopsy in the right hepatic lobe (at least two samples per patient) were evaluated. An age- and sex-matched control group of 24 subjects included those who had less than 30% macrovesicular steatosis but otherwise met the same criteria as the patient group. A diagnostically difficult setting was made by selecting those with the highest degree of macrovesicular steatosis when there were multiple control subjects matched for a particular subject in the patient group. Two independent radiologists assessed steatosis of the right hepatic lobe by using two methods: a five-point visual grading system that used attenuation comparison between the liver and hepatic vessels and the liver attenuation index (CT(L-S)), defined as hepatic attenuation minus splenic attenuation and calculated with region of interest measurements of hepatic attenuation. Interobserver agreement was assessed. Accuracy in the diagnosis of 30% or higher macrovesicular steatosis was compared by using a multireader, multicase receiver operating characteristic (ROC) analysis.

RESULTS

For visual grading, kappa = 0.905 (95% confidence interval [CI]: 0.834, 0.976). Intraclass correlation coefficient for CT(L-S) was 0.962 (95% CI: 0.893, 0.983). The area under the ROC curve of visual grading and CT(L-S) were 0.927 (95% CI: 0.822, 1) and 0.929 (95% CI: 0.874, 0.983), respectively, indicating no statistically significant difference (P = .975).

CONCLUSION

Both visual grading and CT(L-S) are highly reliable and similarly accurate in the diagnosis of 30% or higher macrovesicular steatosis in living hepatic donor candidates.

Evaluation and management of obesity-related nonalcoholic fatty liver disease

The clinicopathologic spectrum of nonalcoholic fatty liver disease (NAFLD) ranges from simple steatosis to nonalcoholic steatohepatitis (NASH). Simple steatosis has a relatively benign clinical course, but NASH can progress to cirrhosis and hepatocellular carcinoma. NAFLD occurs in the absence of significant alcohol use and is considered to be the hepatic manifestation of metabolic syndrome. NAFLD affects approximately 30% of the US population and the incidence seems to be rising as the obesity epidemic continues. At present, the most accurate modality for the diagnosis of NASH is liver biopsy; however, many patients do not have a liver biopsy, and in the absence of more-accurate imaging technologies and serum markers, the diagnosis is frequently one of exclusion. As yet there is no convincingly effective treatment for NAFLD--a multimodal treatment plan that targets obesity, insulin resistance, hyperlipidemia and hypertension might be the best option for these patients.

Comparison of CT methods for determining the fat content of the liver

OBJECTIVE

The purpose of this study was to assess which of a number of methods of measuring attenuation on CT scans is best for prediction of hepatic fat content.

MATERIALS AND METHODS

This retrospective study was approved by our institutional review board. Consecutively registered patients who underwent liver resection for metastatic disease formed the study group. Attenuation measurements were obtained from 12 regions of interest in the liver and three in the spleen on both unenhanced and portal phase contrast-enhanced preoperative hepatic CT images. Hepatic attenuation measurements were analyzed both with and without normalization with the spleen. Normalization included both differences and ratios between hepatic and splenic attenuation values. Pathologic fat content was graded semiquantitatively as a percentage of the nonneoplastic liver parenchyma of the resected specimen. Average attenuation values of the liver were compared with pathologic fat content, as were the differences and ratios between hepatic and splenic attenuation values. Linear regression analysis was conducted on a log-log scale.

RESULTS

Data on 88 patients were analyzed. On unenhanced and contrast-enhanced CT images, all associations between pathologic fat content and attenuation measurements were significant (p < 0.0001). All series of R2 values for unenhanced CT scans were much higher than those for contrast-enhanced CT scans. The R2 values of liver-only measurement were higher than those of hepatic values normalized with splenic values on both unenhanced (0.646-0.649 > 0.523, 0.565) and contrast-enhanced (0.516 > 0.242, 0.344) CT.

CONCLUSION

Measurement of attenuation of liver only on unenhanced CT scans is best for prediction of pathologic fat content.

Technology Insight: advances in liver imaging

The role of diagnostic imaging in the assessment of liver disease continues to gain in importance. The classic techniques used for liver imaging are ultrasonography, CT and MRI. In the past decade, there have been significant advances in all three techniques. In this article, we discuss the advances in ultrasonography, CT and MRI that have improved assessment of focal and diffuse liver disease, including the development of hardware, software, processing algorithms and procedural innovations.

Role of radiologic modalities in the management of non-alcoholic steatohepatitis

During the last decade, the role of radiologic modalities in management of patients who have fatty liver disease has expanded. Ultrasonography has been used as a noninvasive alternative to biopsy for monitoring patients who have hepatic steatosis, but MRI is more appealing than ultrasonography to denote minor changes in hepatic fat content. Distinguishing patients who have non-alcoholic steatohepatitis from steatosis alone has become of clinical importance; however, the differences are not apparent with any radiologic modalities. Several modalities have been developed to noninvasively and accurately quantify hepatic fat content and diagnose steatohepatitis. In the future, radiologic modalities might be used to monitor the natural history of the disease or evaluate therapeutic interventions in patients who have non-alcoholic fatty liver disease.

Non-invasive quantification of hepatic fat fraction by fast 1.0, 1.5 and 3.0 T MR imaging

INTRODUCTION

Even mild hepatic steatosis in a split liver donor may cause general liver failure and death in the donor. So far, CT density measurements or percutaneous biopsy is used to determine the presence of hepatic steatosis. Magnetic resonance imaging (MRI) may be an elegant method of non-invasive and non-radiation quantification of hepatic fat content.

METHODS

Fast gradient echo (GRE) technique was used to discriminate between fat and water spins. Echo time (TE) was adjusted for field strength dependent in-phase and out-of-phase states at 1.0, 1.5 and 3.0 T. Continuous MR signal transition from 100% water to 100% fat was investigated using a wedge water-oil phantom, which was positioned in such a way, that no spatial resolution occurred, thereby combining water and fat in one slice.

RESULTS

Using the phantom, a significant difference for a 5% difference in fat content was demonstrated in the range from 20 to 80% fat content (p<0.05) for all tested field strengths. In 25 patients MRI data were correlated with the percentage of fat determined by histologic evaluation of a CT-guided liver biopsy. Using the linear correlation calculated from the MRI phantom data at 1.0 T, we determined the liver fat from each patient's MRI measurements. Comparison of these data with the histologic quantified fat fraction of liver tissue showed a strong correlation (r(2)=0.93 for TE 6 ms and r(2)=0.91 for TE 10 ms).

CONCLUSION

The described method can be used to determine the presence of hepatic steatosis of >10% with p<0.05.

Imaging of hepatic steatosis and fatty sparing

Radiology has gained importance in the non-invasive diagnosis of hepatic steatosis. Ultrasonography is usually the first imaging modality for the evaluation of hepatic steatosis. Unenhanced CT with or without dual kVp measurement and MRI with in and out of phase sequence can allow objective evaluation of hepatic steatosis. However, none of the imaging modalities can differentiate non-alcoholic steatohepatitis/fatty liver disease from simple steatosis. Evaluation of hepatic steatosis is important in donor evaluation before orthotopic liver transplantation and hepatic surgery. Recently, one-stop shop evaluation of potential liver donors has become possible by CT and MRI integrating vascular, parenchymal, volume and steatosis evaluation. Moreover hepatic steatosis (diffuse, multinodular, focal, subcortical, perilesional, intralesional, periportal and perivenular), hypersteatosis and sparing (geographic, nodular and perilesional or peritumoral) can cause diagnostic problems as a pseudotumor particularly in the evaluation of oncology patients. Liver MRI is used as a problem-solving tool in these patients. In this review, we discuss the current role of radiology in diagnosing, quantifying hepatic steatosis and solutions for diagnostic problems associated with fatty infiltration and sparing.

Fatty Liver: Imaging Patterns and Pitfalls

Fat accumulation is one of the most common abnormalities of the liver depicted on cross-sectional images. Common patterns include diffuse fat accumulation, diffuse fat accumulation with focal sparing, and focal fat accumulation in an otherwise normal liver. Unusual patterns that may cause diagnostic confusion by mimicking neoplastic, inflammatory, or vascular conditions include multinodular and perivascular accumulation. All of these patterns involve the heterogeneous or nonuniform distribution of fat. To help prevent diagnostic errors and guide appropriate work-up and management, radiologists should be aware of the different patterns of fat accumulation in the liver, especially as they are depicted at ultrasonography, computed tomography, and magnetic resonance imaging. In addition, knowledge of the risk factors and the pathophysiologic, histologic, and epidemiologic features of fat accumulation may be useful for avoiding diagnostic pitfalls and planning an appropriate work-up in difficult cases.

Living Donor Right Liver Lobes: Preoperative CT Volumetric Measurement for Calculation of Intraoperative Weight and Volume

PURPOSE

To prospectively develop equations for the calculation of expected intraoperative weight and volume of a living donor's right liver lobe by using preoperative computed tomography (CT) for volumetric measurement.

MATERIALS AND METHODS

After medical ethics committee and state medical board approval, informed consent was obtained from eight female and eight male living donors (age range, 18-63 years) for participation in preoperative CT volumetric measurement of the right liver lobes by using the summation-of-area method. Intraoperatively, the graft was weighed, and the volume of the graft was determined by means of water displacement. Distributions of pre- and intraoperative data were depicted as Tukey box-and-whisker diagrams. Then, linear regressions were calculated, and the results were depicted as scatterplots. On the basis of intraoperative data, physical density of the parenchyma was calculated by dividing weight by volume of the graft.

RESULTS

Preoperative measurement of grafts resulted in a mean volume of 929 mL +/- 176 (standard deviation); intraoperative mean weight and volume of the grafts were 774 g +/- 138 and 697 mL +/- 139, respectively. All corresponding pre- and intraoperative data correlated significantly (P < .001) with each other. Intraoperatively expected volume (V(intraop)) in millilliters and weight (W(intraop)) in grams can be calculated with the equations V(intra)(op) = (0.656 . V(preop)) + 87.629 mL and W(intra)(op) = (0.678 g/mL . V(preop)) + 143.704 g, respectively, where preoperative volume is V(preop) in milliliters. Physical density of transplanted liver lobes was 1.1172 g/mL +/- 0.1015.

CONCLUSION

By using two equations developed from the data obtained in this study, expected intraoperative weight and volume can properly be determined from CT volumetric measurements.

Hypoattenuation in unenhanced CT reflects histological graft dysfunction and predicts 1-year mortality after living donor liver transplantation

Early postoperative graft function assessments are essential after living donor liver transplantation (LDLT) to predict patient and graft outcome. Computed tomography (CT) is usually used to evaluate various complications and parenchymal abnormalities after LDLT. Here, we attempted to determine the prognostic values of CT attenuation changes of grafts for predicting 1-year patient survival. Liver attenuation indices (LAIs), derived from differences between hepatic and splenic attenuations, were calculated on unenhanced CT images obtained 10 days after LDLT in 62 adult LDLT recipients between September 2002 and August 2004. Patients were assigned to 1 of 2 groups according to LAI value on the 10th postoperative day, as follows: group L (LAI < or = 5, n = 14) or group H (LAI > 5, n = 48). Parenchymal dysfunction scores, summed parameters for histological dysfunction including both portal tract and centrilobular features, were also assessed on the 10th postoperative day using liver biopsy specimens. Histological parenchymal dysfunction, especially in the centrilobular area, in terms of cholestasis, centrilobular necroinflammation, central vein fibrosis, steatosis, mononuclear infiltrates, and hepatocyte ballooning, was more prominent in group L than in group H, while that in the portal area was similar between the 2 study groups. Significant negative linear correlations were observed between LAI and parenchymal dysfunction scores (r = 0.486, P < 0.001). Group L patients showed lower 1-year survival (69.7%) than group H patients (95.8%; P = 0.0002). Moreover, group H patients died with a functioning graft (n = 3), whereas group L patients died of graft failure (n = 6). After multivariate analysis, LAI alone remained independently associated with 1-year mortality (P = 0.014; odds ratio = 0.845; 95% confidence interval, 0.739-0.967). The sensitivity and specificity of LAI were 84.6% and 75%, respectively, and LAI outperformed MELD score as a predictor of 1-year mortality after LDLT by receiver operating characteristic curve analysis. In conclusion, LAI, as determined by unenhanced CT 10 days after LDLT, well predicts 1-year patient survival after LDLT.

Influence of hepatic steatosis (fatty liver) on severity and composition of dyslipidemia in type 2 diabetes

OBJECTIVE

The objective of this study was to examine the associations between the severity of hepatic steatosis and dyslipidemia in type 2 diabetes, including circulating apolipoprotein B100 (apoB) concentrations and lipoprotein particle size and numbers.

RESEARCH DESIGN AND METHODS

Computed tomography imaging was used to assess hepatic fat content and adipose tissue distribution in 67 men and women with type 2 diabetes, withdrawn from antidiabetic medications preceding the study. Fasting serum lipoprotein number and size was determined by nuclear magnetic resonance. Insulin sensitivity was measured with a glucose clamp and a [6,6-(2)H(2)]glucose isotope infusion.

RESULTS

Two-thirds of the cohort had fatty liver. Hepatic steatosis correlated with serum triglycerides (r = 0.40, P < 0.01) and lower HDL cholesterol (r = -0.31, P < 0.05). ApoB and LDL cholesterol did not, being virtually identical in those with or without steatosis. The association between serum triglycerides and hepatic steatosis was largely accounted for by greater triglyceride enrichment in VLDL particles, which were larger. Severe steatosis was also associated with 70% higher small, dense LDL concentrations. Visceral obesity did not fully explain these associations, and hepatic steatosis was better correlated with triglycerides than with hyperglycemia or hepatic insulin resistance (P > 0.05).

CONCLUSIONS

The presence of hepatic steatosis in type 2 diabetes does not appear to affect apoB levels, but potentially increases atherogenesis by increasing triglycerides, reducing HDL levels, and increasing small, dense LDL.

Mild hepatic steatosis is not a major risk factor for hepatectomy and regenerative power is not impaired

BACKGROUND

An understanding of the regeneration power and operative risk of steatotic livers after hepatectomy is still unclear. We evaluated the volume regeneration and outcome of steatotic livers after donor hepatectomy.

METHODS

Fifty-four, consecutive living liver donors from September 2002 to December 2003 were evaluated prospectively by volumetric analysis, liver-spleen ratio, and liver attenuation index; the latter has been shown by serial computed tomographic scanning to be correlated strongly with histologic steatosis. Donors were followed up completely for at least 1 year (460-915 days) and were allocated according to histologic degree of macrovesicular steatosis: group 1, <5% (n = 36); group 2, 5%-30% (n = 18).

RESULTS

No mortality or hepatic failure was observed, and no donor required reoperation or intraoperative transfusion. The results of serial liver function tests, and major and minor morbidities were comparable between groups. Liver-spleen ratio and liver attenuation index remained at a constant level above normal values postoperatively in group 1, but increased rapidly above normal values in group 2. No difference in the rate of liver regeneration at 10 days after hepatectomy was found between the groups (P = .487), but the liver regeneration rate at 3 months after hepatectomy in group 1 was slightly higher than that in group 2 (P < .044). However, no difference was observed between the 2 groups at 1 year after hepatectomy (P = .4).

CONCLUSIONS

Mild hepatic steatosis is cleared immediately after hepatectomy, and early regeneration power is impaired, but the long-term regenerative power is comparable. Hepatectomy in donors with mild steatosis can be performed with low morbidity.

Hepatic macrosteatosis: predicting appropriateness of liver donation by using MR imaging--correlation with histopathologic findings

PURPOSE

To retrospectively evaluate the diagnostic performance of magnetic resonance (MR) imaging in predicting the appropriateness of liver donation in potential living liver donors by using histopathologic results as the reference standard.

MATERIALS AND METHODS

This study was approved by institutional review board; all patients gave informed consent for the use of MR data for future research. Fifty-seven potential liver donors (40 male, 17 female; age range, 17-57 years; mean age, 32 years) underwent dual-echo 1.5-T MR imaging. Two radiologists qualitatively graded each MR image, with consensus for disagreements. Livers were assigned one of three degrees of hepatic steatosis on the basis of changes in hepatic signal intensity (SI) between in-phase and opposed-phase images. For quantitative analysis, a third radiologist calculated mean hepatic and mean splenic SI by averaging 25 hepatic regions of interest and three splenic regions of interest. Relative SI decrease (RSID) in the liver on opposed-phase images compared with in-phase images was calculated. Linear regression analysis was used to correlate RSID with the degree of total steatosis, macrosteatosis, and microsteatosis. Diagnostic performance for predicting the appropriateness of liver donation was analyzed.

RESULTS

Histologic findings of macrosteatosis resulted in 52 patients being categorized as appropriate donors, with the remaining five being categorized as inappropriate donors. RSID was correlated with total steatosis (r = 0.850). When the RSID criterion for inappropriateness of liver donation was set at 20%, the sensitivity, specificity, and accuracy were 100%, 92.3%, and 93%, respectively. When RSID was used, four livers that had been misclassified as inappropriate for transplantation were found to have microsteatosis of various degrees and a less than moderate degree of macrosteatosis at histologic analysis. Qualitative and quantitative analyses were comparably accurate.

CONCLUSION

When an RSID criterion of less than 20% was used, dual-echo MR imaging facilitated the correct prediction of appropriateness of liver donation in 53 of 57 patients.

Visceral fat accumulation and insulin resistance are important factors in nonalcoholic fatty liver disease

BACKGROUND

Nonalcoholic fatty liver diseases are often associated with obesity, insulin resistance, and excessive visceral fat accumulation. The aims of this study were (1) to evaluate the relationship between the severity of fatty liver and visceral fat accumulation in nonalcoholic fatty liver diseases, and (2) to investigate the relationships of fatty liver with biochemical data and insulin resistance.

METHODS

One hundred twenty-nine subjects (63 women) with fatty liver diagnosed by ultrasonography were enrolled. Subjects positive for hepatitis B virus, hepatitis C virus, or autoimmune antibodies and those whose alcohol intake was over 20 g/day were excluded. The visceral fat area at the umbilical level and the liver-spleen ratio were evaluated by computed tomography.

RESULTS

The severity of fatty liver evaluated by ultrasonography showed a significant positive relationship with the visceral fat area and waist circumstance (fatty liver severity: mild, 92.0 +/- 30.9 cm(2); moderate, 122.1 +/- 32.6 cm(2); severe, 161.0 +/- 48.4 cm(2); P < 0.0001). The visceral fat area and liver-spleen ratio were negatively correlated (r = -0.605, P < 0.0001). The severity of fatty liver showed strong positive relationships with serum aspartate aminotransferase, alanine aminotransferase, fasting plasma glucose, fasting plasma insulin, and insulin resistance. The severity of fatty liver was positively related to the visceral fat area in 49 nonobese subjects (body mass index <25).

CONCLUSIONS

The severity of fatty liver was positively correlated with visceral fat accumulation and insulin resistance in both obese and nonobese subjects, suggesting that hepatic fat infiltration in nonalcoholic fatty liver disease may be influenced by visceral fat accumulation regardless of body mass index.

Evaluation of Living Liver Donors with an All-inclusive 3D Multi–Detector Row CT Protocol

PURPOSE

To prospectively assess parenchymal, vascular, and biliary anatomy of potential living liver donors with an all-inclusive multi-detector row computed tomographic (CT) approach.

MATERIALS AND METHODS

A total of 250 potential living liver donors (112 women, 138 men; mean age, 37 years) underwent three-phase, dual-enhancement multi-detector row CT to delineate biliary, vascular, and parenchymal morphology according to an institutional review board-approved protocol. Informed consent was obtained from all subjects. For display of the biliary system, the first CT image set was collected after the infusion of a biliary contrast agent. CT angiography was subsequently performed, after automated injection of a conventional iodinated contrast agent, to display the arterial and portal-hepatic venous systems. All data sets were reconstructed in 1-mm sections. Data analysis was based on source images, multiplanar reconstructions, and three-dimensional postprocessing images; was performed in consensus by two radiologists; and was focused on the detection of biliary and vascular variants, exclusion of focal liver lesions, and determination of hepatic volumes. Preoperative findings were correlated with intraoperative findings (available in 62 subjects).

RESULTS

Technical failures were experienced in 10 of 250 examinations. Twenty-seven subjects had moderate adverse reactions related to the biliary contrast agent. Benign hepatic lesions were detected in 61 candidates; one candidate had a renal cell carcinoma. Underlying biliary and vascular anatomy was displayed at least to the second intrahepatic branch in all but seven patients. Detected anatomic variants involved the biliary (38.8%), arterial (40.0%), portal venous (21.4%), and hepatic venous (43.5%) systems. Correlation with intraoperative findings was excellent. Some biliary (n = 4), arterial (n = 5), portal venous (n = 1), and hepatic venous (n = 6) variants were missed or misinterpreted at initial reading of preoperative data; however, variants could be retrospectively depicted in all but one biliary case and one hepatic venous case.

CONCLUSION

The outlined three-phase, dual-enhancement multi-detector row CT protocol represents an all-inclusive approach to evaluate potential living liver donors in a single diagnostic step.

Macrovesicular hepatic steatosis in living liver donors: use of CT for quantitative and qualitative assessment

PURPOSE

To determine prospectively the diagnostic performance of unenhanced computed tomography (CT) in the assessment of macrovesicular steatosis in potential donors for living donor liver transplantation by using same-day biopsy as a reference standard.

MATERIALS AND METHODS

Institutional review board approval and informed consent were obtained. A total of 154 candidates, including 104 men (mean age, 30.2 years +/- 10.3 [standard deviation]) and 50 women (mean age, 31.8 years +/- 11.2), underwent same-day unenhanced CT and ultrasonography-guided liver biopsy. Histologic degree of macrovesicular steatosis was determined. Three liver attenuation indices were derived: liver-to-spleen attenuation ratio (CT(L)(/S)), difference between hepatic and splenic attenuation (CT(L)(-S)), and blood-free hepatic parenchymal attenuation (CT(LP)). Regression equations were used to quantitatively estimate the degree of macrovesicular steatosis. Limits of agreement between estimated macrovesicular steatosis and the reference standard were calculated. Receiver operating characteristic analyses were used to determine the performance of each index for qualitative diagnosis of macrovesicular steatosis of 30% or greater. The cutoff value that provided a balance between sensitivity and specificity and the highest cutoff value that yielded 100% specificity were determined.

RESULTS

Limits of agreement were -14% to 14% for CT(L)(/S) and CT(L)(-S) and -13% to 13% for CT(LP). Performance in diagnosing macrovesicular steatosis of 30% or greater was not significantly different among indices (P > .05). Cutoff values of 0.9, -7, and 58 were determined for CT(L)(/S), CT(L)(-S), and CT(LP), respectively, and provided a balance between sensitivity and specificity. Cutoff values of 0.8, -9, and 42 were determined for CT(L)(/S), CT(L)(-S), and CT(LP), respectively, and yielded 100% specificity for all indices, with corresponding sensitivities of 82%, 82%, and 73% for CT(L)(/S), CT(L)(-S), and CT(LP), respectively.

CONCLUSION

Diagnostic performance of unenhanced CT for quantitative assessment of macrovesicular steatosis is not clinically acceptable. Unenhanced CT, however, provides high performance in qualitative diagnosis of macrovesicular steatosis of 30% or greater.

Fat in the liver: diagnosis and characterization

The purpose of this article is to provide an update on imaging techniques useful for detection and characterization of fat in the liver. Imaging findings of liver steatosis, both diffuse steatosis and focal fatty change, as well as focal fatty sparing, are presented. In addition, we will review computed tomography (CT) and magnetic resonance (MR) findings of focal liver lesions with fatty metamorphosis, including hepatocellular carcinoma, hepatocellular adenoma, focal nodular hyperplasia, angiomyolipoma, lipoma, and metastases.

Accuracy of liver fat quantification at MR imaging: comparison of out-of-phase gradient-echo and fat-saturated fast spin-echo techniques--initial experience

PURPOSE

To retrospectively determine the relative accuracy of liver fat quantification with out-of-phase gradient-echo magnetic resonance (MR) imaging and fat-saturated fast spin-echo MR imaging in patients with and without cirrhosis, with histologic analysis as the reference standard.

MATERIALS AND METHODS

Committee on Human Research approval was obtained. Patient consent was not required. Data collection ended before HIPAA regulations were implemented, but patient anonymity was maintained. Twenty-seven patients, 16 with cirrhosis, were retrospectively identified who underwent MR imaging before histopathologic evaluation of liver fat at biopsy or surgery. The patient population consisted of 15 male and 12 female patients (mean age, 55 years; range, 16-75 years). One radiologist blinded to the histopathologic results recorded mean signal intensity derived from three regions of interest placed in the right and left lobes of the liver on three sections and signal intensity of the spleen from one region of interest within the same section. Liver fat was quantified with the relative loss of signal intensity on out-of-phase images compared with that on in-phase T1-weighted gradient-echo images and with relative loss of signal intensity on T2-weighted fast spin-echo MR images obtained with fat saturation compared with those obtained without fat saturation. Hotelling t test was used to compare correlation coefficients between relative signal intensity differences and histopathologically determined percentage of fat.

RESULTS

In patients without cirrhosis, liver fat quantification with fat-saturated fast spin-echo MR imaging was significantly better than it was with out-of-phase gradient-echo MR imaging (r = 0.92 vs 0.69, P < .01). In patients with cirrhosis, liver fat quantification was correlated only with fat-saturated fast spin-echo MR imaging (r = 0.76, P < .01); the relative signal intensity loss on out-of-phase gradient-echo MR images was not correlated with histopathologically determined percentage of fat (r = 0.25, P = .36).

CONCLUSION

Preliminary results suggest liver fat may be more accurately quantified with fat-saturated fast spin-echo MR imaging than with out-of-phase gradient-echo MR imaging, especially in patients with cirrhosis.

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.

Significance of CT attenuation value in liver grafts following right lobe living-donor liver transplantation

In adult living-donor liver transplantation (LDLT), the assessment of the allograft functional reserve is important for adequate graft regeneration. From March 2002 to December 2003, 30 adult recipients underwent right lobe LDLT. Mean CT attenuation values (CT-AVs) in the graft were measured on unenhanced CT for 6 months after LDLT. The histological features of the graft parenchyma were evaluated with post-operative liver biopsy specimens. Mean CT-AVs after LDLT were decreased significantly from the pre-operative values, recovered to over 60 HU within 6 months. There was a positive linear correlation between the CT-AVs and the receptor index (LHL15) in technetium-99m-diethylenetriaminepenta-acetic acid-galactosyl-human serum albumin ((99m)Tc-GSA) liver scintigraphy (r = 0.803, p = 0.005). The recipients were divided into two groups according to the CT-AV at one post-operative week (group H; > or =55HU, group L; <55HU). The low CT-AVs, under 55 HU, in group L were prolonged for 3 months compared with those in group H (p < 0.05). The 1-year cumulative survival rate was 94.7% and 45.5% in groups H and L, respectively (p = 0.014). Histological findings revealed that the parenchymal damage was severe in the grafts with low CT-AVs. The CT-AVs in the grafts may be a useful parameter for assessing the allograft functional reserve.

Evolution of donor morbidity in living related liver transplantation: a single-center analysis of 165 cases

OBJECTIVE

During the last 14 years, living donor liver transplantation (LDLT) has evolved to an indispensable surgical strategy to minimize mortality of adult and pediatric patients awaiting transplantation. The crucial prerequisite to performing this procedure is a minimal morbidity and mortality risk to the healthy living donor. Little is known about the learning curve involved with this type of surgery.

PATIENTS AND METHODS

From January 1991 to August 2003, a total of 165 LDLTs were performed in our center. Of these, 135 were donations of the left-lateral lobe (LL, segments II and III), 3 were of the left lobe (L, segments II-IV), 3 were full-left lobes (FL, segments I-IV), and 24 were of the full-right lobe (FR, segments V-VIII). We divided the procedures into 3 periods: period 1 included the years 1991 to 1995 (LL, n = 49; L, n = 2; FR, n = 1), period 2 covered 1996 to 2000 (LL, n = 47), and period 3 covered 2001 to August 2003 (LL, n = 39; FR, n = 23; FL, n = 3; L, n = 1). Perioperative mortality and morbidity were assessed using a standardized classification. Length of stay in intensive care unit, postoperative hospital stay, laboratory results (bilirubin, INR, and LFTs), morbidity, and the different types of grafts in the 3 different periods were compared.

RESULTS

One early donor death was observed in period 1 (03/07/93, case 30; total mortality, 0.61.%). Since 1991, the perioperative morbidity has continually declined (53.8% vs. 23.4% vs. 9.2%). In period 1, 28 patients had 40 complications. In period 2, 11 patients had 12 complications, and in period 3, 6 patients had 9 complications. Within the first period, 1 donor underwent relaparotomy because of bile leakage. Postoperative hospital stay was 10 days, 7 days, and 6 days, respectively. Donation of the full right lobe, in comparison with that of the left lateral lobe, resulted in a significantly diminished liver function (bilirubin and INR) during the first 5 days after donation but did not increase morbidity. One donor from period 1 experienced late death caused by amyotrophic lateral sclerosis.

CONCLUSIONS

In a single center, morbidity after living liver donation strongly correlates to center experience. Despite the additional risks associated with temporary reduction of liver function, this experience enabled the team to bypass part of the learning curve when starting right lobe donation. Specific training of the surgical team and coaching by an experienced center should be implemented for centers offering this procedure to avoid the learning curve.

The hepatic regeneration power of mild steatotic grafts is not impaired in living-donor liver transplantation

The aim of this study was to assess histologic changes in steatotic grafts, regenerative capacity, and the outcome of steatotic grafts in living-donor liver transplantation (LDLT). Between September 2002 and February 2004, 55 cases of LDLT with a liver biopsy performed on the 10th postoperative day were enrolled. Patients were grouped according to the intraoperative histologic degree of macrovesicular steatosis (MaS) as follows: Group 1, <5% (n = 24); Group 2, 5 to 15% (n = 24); and Group 3, 15 to 30% (n = 7). The intraoperative microscopic findings and the findings on the 10th postoperative day were compared. Immunohistochemistry was performed using antibody of proliferating cell nuclear antigen (PCNA) and Ki-67 to assess the regeneration power of grafts on the 10th postoperative day. The histologic degree of MaS on postoperative day 10 decreased from 5.22 +/- 1.04% (mean +/- standard deviation) to 2.17 +/- 1.90 in Group 2 (P < .001) and from 21.4 +/- 8.02 to 4.43 +/- 2.70 in Group 3 (P = .003). The number of positively stained hepatocytes in 10 high power fields was 48.0 +/- 17.1, 53.8 +/- 14.4, and 51.5 +/- 4.1 in each group by PCNA (P = .681), and 24.0 +/- 14.0, 25.5 +/- 11.8, and 21.6 +/- 6.8 by Ki-67 (P = .825), respectively. No primary graft nonfunction (PNF) or delayed graft function (DGF) occurred. Major complications were comparable among groups. In conclusion, in LDLT, steatosis disappeared immediately after transplantation and hepatic regeneration power was not impaired in grafts with less than 30% of MaS. Furthermore, a mildly steatotic graft did not increase the risk of graft dysfunction or morbidity in LDLT.

Appropriateness of a donor liver with respect to macrosteatosis: application of artificial neural networks to US images--initial experience

PURPOSE

To retrospectively compare performance of artificial neural networks (ANNs) applied to ultrasonographic (US) images with that of radiologists for prediction of appropriateness of a donor liver with respect to macrosteatosis before liver transplantation.

MATERIALS AND METHODS

Institutional ethics committee approved study; written informed consent was obtained. ANNs, constructed with three-layered 15-neuron back-propagation algorithm, were trained to predict appropriateness of a donor liver with respect to macrosteatosis by using statistically significant laboratory and US parameters derived from univariate analyses, together with correct diagnosis. Input variables for ANNs were alkaline phosphatase, glutamic oxaloacetic transaminase, glutamic pyruvate transaminase, gamma-glutamyltransferase, hepatorenal ratio of echogenicity, and tail area ratio and tail length of portal vein wall echogenicity. Three radiologists graded US images in 94 potential donors (71 men and 23 women) on the basis of four degrees of hepatic steatosis. After training and testing of ANNs, performance of ANNs and radiologists in predicting appropriateness of potential donors was evaluated with receiver operating characteristic (ROC) analysis and compared by means of univariate z score test.

RESULTS

Among 94 potential donor livers, 76 were normal or had mild steatosis, and 18 had moderate or severe macrosteatosis at histopathologic examination. Area under ROC curve (Az) of ANNs (Az=0.9673) was significantly greater than that of radiologists (faculty, Az=0.9106, P=.048; fellow, Az= 0.9038, P=.044; resident, Az=0.8931, P=.038). No statistically significant difference in sensitivity for predicting appropriateness as a liver donor with respect to macrosteatosis was found between ANNs (88.9%) and radiologists (P >.05). However, specificity of ANNs (96.1%) was significantly better than that of radiologists (P <.003).

CONCLUSION

ANNs might be a useful tool to categorize whether a donor liver is appropriate for transplantation with respect to macrosteatosis on the basis of multiple variables related to laboratory and US features. Further study is needed.