Hepatic Steatosis in Morbidly Obese Patients Undergoing Gastric Bypass Surgery: Assessment With Open-System H-1-MR Spectroscopy
ABSTRACT The purpose of this study was to assess, with histopathologic control, the use of open-system 1-T (1)H MR spectroscopy for the evaluation of hepatic steatosis in morbidly obese patients undergoing gastric bypass surgery.
Patients underwent (1)H MR spectroscopy (MRS) for the assessment of steatosis before and 3 months after surgery. Liver biopsy was performed during surgery. Hepatic steatosis was expressed as the ratio of fat peak area to cumulative water and fat peak areas. Histopathologic percentage of steatosis was graded as none (0-5%), mild (5-33%), moderate (33-66%), or severe (> 66%). The accuracy of (1)H-MRS and Spearman correlation coefficient were calculated. Differences between groups were assessed with the Wilcoxon signed rank and Mann-Whitney tests.
The study included 38 patients (median age, 45.5 years; median body mass index, 47.7). Before surgery, median steatosis measured with (1)H-MRS was 5.8%. The accuracy of (1)H-MRS was 89% (32/36), and the (1)H-MRS findings correlated with the histopathologic assessment of steatosis (r = 0.85, p < 0.001). With (1)H-MRS, no steatosis was discriminated from mild steatosis (p = 0.011), mild was discriminated from moderate steatosis (p < 0.001), and moderate was discriminated from severe steatosis (p = 0.021). Three months after surgery, steatosis had decreased to 3.1% (p < 0.001). The prevalence of hepatic steatosis measured with (1)H-MRS decreased from 53% to 32%.
In the care of morbidly obese patients undergoing assessment of hepatic steatosis and changes in steatosis after gastric bypass surgery, (1)H-MRS with an open 1-T MRI system is feasible. Measurements of hepatic fat with (1)H-MRS are accurate and correlate with clinical and histopathologic results.
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- "Weight loss agents had no significant effects compared with weight loss only . In obese patients undergoing bariatric surgery, hepatic steatosis is decreased from 53% to 32%, three months after surgery as overall mortality [49, 50]. Cross-sectional investigations have shown an independent association between physical fitness and hepatic triglyceride concentration . "
ABSTRACT: Nonalcoholic fatty liver disease (NAFLD) is the most common, chronic liver disease worldwide. Within this spectrum, steatosis alone is apparently benign, while nonalcoholic steatohepatitis may progress to cirrhosis and hepatocellular carcinoma. NAFLD is strongly associated with obesity, dyslipidemia, type 2 diabetes mellitus, and cardiovascular disease. The pathogenesis of hepatic steatosis is not clearly known, but its main characteristics are considered insulin resistance, mitochondrial dysfunction, increased free fatty acids reflux from adipose tissue to the liver, hepatocyte lipotoxicity, stimulation of chronic necroinflammation, and fibrogenic response. With recent advances in technology, advanced imaging techniques provide important information for diagnosis. There is a significant research effort in developing noninvasive monitoring of disease progression to fibrosis and response to therapy with potential novel biomarkers, in order to facilitate diagnosis for the detection of advanced cirrhosis and to minimize the need of liver biopsy. The identification of NAFLD should be sought as part of the routine assessment of type 2 diabetics, as sought the microvascular complications and cardiovascular disease, because it is essential for the early diagnosis and proper intervention. Diet, exercise training, and weight loss provide significant clinical benefits and must be considered of first line for treating NAFLD.International Journal of Endocrinology 04/2013; 2013:450639. DOI:10.1155/2013/450639 · 1.52 Impact Factor
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ABSTRACT: To evaluate the diagnostic accuracy of ultrasonography (US) for the assessment of hepatic steatosis in severely obese adolescents, with proton magnetic resonance (MR) spectroscopy as the reference standard, and to provide insight on the influence of prevalence on predictive values by calculating positive and negative posttest probabilities. This prospective study was institutional review board approved. All participants, and/or their legal representatives, gave written informed consent. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated for the overall presence of steatosis and for the presence of substantial (moderate to severe) steatosis. Positive and negative posttest probabilities were calculated and plotted against prevalence. A total of 104 children (47 male, 57 female) were prospectively included. Mean age was 14.5 years (range, 8.3-18.9 years) and mean age-adjusted standard deviation body mass index (BMI) score (BMI z score) was 3.3 (range, 2.6-4.1). The overall prevalence of hepatic steatosis was 46.2% (48 of 104). Sensitivity of US was 85.4% (41 of 48), specificity was 55.4% (31 of 56), PPV was 62.1% (41 of 66), and NPV was 81.6% (31 of 38). The prevalence of substantial steatosis was 15.4% (16 of 104), with US sensitivity of 75.0% (12 of 16) and specificity of 87.5% (77 of 88). PPV was 52.2% (12 of 23) and NPV was 95.1% (77 of 81). Plotting of posttest probabilities against prevalence for both disease degrees demonstrated how disease prevalence influences US accuracy. Positive US results in severely obese adolescents cannot be used to accurately predict the presence and severity of hepatic steatosis, and additional imaging is required. Negative US results exclude the presence of substantial steatosis with acceptable accuracy. Steatosis prevalence differs among specific populations, strongly influencing posttest probabilities.Radiology 11/2011; 262(1):327-34. DOI:10.1148/radiol.11111094 · 6.21 Impact Factor
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ABSTRACT: To investigate the utility of acoustic radiation force impulse (ARFI) imaging, with the determination of shear wave velocity (SWV), to differentiate non-alcoholic fatty liver disease (NAFLD) from non-alcoholic steatohepatitis (NASH) in patients with morbid obesity before bariatric surgery. Thirty-two patients with morbid obesity were evaluated with ARFI and conventional ultrasound before bariatric surgery. The ARFI and ultrasound results were compared with liver biopsy findings, which is the reference standard. The patients were classed according to their histological findings into three groups: group A, simple steatosis; group B, inflammation; and group C, fibrosis. The median SWV was 1.57 ± 0.79 m/s. Hepatic alterations were observed in the histopathological findings for all the patients in the study (100 %), with the results of the laboratory tests proving normal. Differences in SWV were also observed between groups A, B and C: 1.34 ± 0.90 m/s, 1.55 ± 0.79 m/s and 1.86 ± 0.75 m/s (P < 0.001), respectively. The Az for differentiating NAFLD from NASH or fibrosis was 0.899 (optimal cut-off value 1.3 m/s; sensitivity 85 %; specificity 83.3 %). The ARFI technique is a useful diagnostic tool for differentiating NAFLD from NASH in asymptomatic patients with morbid obesity. KEY POINTS : • Acoustic radiation force impulse imaging provides ultrasonic shear wave velocity measurements. • SWV measurements were higher in patients with inflammation or fibrosis than NAFLD. • ARFI differentiates NAFLD from NASH in patients with morbid obesity. • Results suggest that ARFI can detect NASH in asymptomatic morbidly obese patients.European Radiology 06/2012; 22(11):2525-32. DOI:10.1007/s00330-012-2505-3 · 4.34 Impact Factor