Department of Radiology, University of Wisconsin School of Medicine and Public Health, E3/311 Clinical Science Center, 600 Highland Ave., Madison, WI 53792-3252, USA.
AJR Am J Roentgenol. 2010 Mar;194(3):623-8. doi: 10.2214/AJR.09.2590.
The purpose of this study was to investigate the prevalence of hepatic steatosis in an asymptomatic U.S. adult population using attenuation values at unenhanced CT as the reference standard. We also assessed the utility of known clinical risk factors for diagnosis.
For 3,357 consecutive asymptomatic adults (1,865 women and 1,492 men; mean age, 57.0 years), hepatic and splenic CT attenuation values (Hounsfield units) were obtained by unenhanced CT using a low-dose colonography technique for colorectal cancer screening. Multiple attenuation criteria for steatosis were applied, including liver thresholds and comparison of liver and spleen attenuation. Relevant clinical risk factors were compared against a CT liver attenuation < or = 40 HU, which has been shown to exclude mild steatosis.
Mean liver attenuation was 58.8 +/- 10.8 (SD) HU. The prevalence of moderate-to-severe hepatic steatosis (defined by liver attenuation < or = 40 HU) was 6.2% (208/3,357). For CT attenuation criteria that include milder degrees of steatosis, prevalence increased to as high as 45.9% (1,542/3,357) for a liver-to-spleen attenuation ratio of < or = 1.1. Overweight status (body mass index > 25) was a sensitive indicator for moderate-to-severe steatosis (92.8%) but was highly nonspecific (37.5%). Other clinical risk factors, such as diabetes, dyslipidemia, hypertension, alcohol overuse, and hepatitis, were more specific (77.6-92.4%) but highly insensitive (1.9-37.5%). Combining clinical risk factors did not substantially increase the accuracy for screening.
Assessment of liver attenuation by use of unenhanced CT represents an objective and noninvasive means for detection of asymptomatic hepatic steatosis, whereas clinical risk factor assessment is unreliable. Further longitudinal investigation is needed to determine the most appropriate attenuation threshold and the risk for disease progression to steatohepatitis and cirrhosis.
本研究旨在使用未增强 CT 的衰减值作为参考标准，调查无症状美国成年人群中肝脂肪变性的流行率。我们还评估了已知临床危险因素对诊断的作用。
对 3357 例连续的无症状成年人（1865 名女性和 1492 名男性；平均年龄 57.0 岁），使用低剂量结肠癌筛查技术进行未增强 CT 扫描，以获得肝脏和脾脏 CT 衰减值（亨氏单位）。应用多种脂肪变性的衰减标准，包括肝脏阈值和肝脏与脾脏衰减的比较。将相关临床危险因素与 CT 肝脏衰减值<或=40 HU 进行比较，后者已被证明可以排除轻度脂肪变性。
平均肝脏衰减值为 58.8 +/- 10.8（标准差）HU。中重度肝脂肪变性（定义为肝脏衰减值<或=40 HU）的患病率为 6.2%（208/3357）。对于包含较轻程度脂肪变性的 CT 衰减标准，肝脏-脾脏衰减比值<或=1.1 的患病率高达 45.9%（1542/3357）。超重状态（体重指数>25）是中重度脂肪变性的敏感指标（92.8%），但特异性差（37.5%）。其他临床危险因素，如糖尿病、血脂异常、高血压、酗酒和肝炎，具有较高的特异性（77.6%-92.4%），但敏感性较低（1.9%-37.5%）。结合临床危险因素并不能显著提高筛查的准确性。
使用未增强 CT 评估肝脏衰减值是一种客观、非侵入性的方法，用于检测无症状性肝脂肪变性，而临床危险因素评估不可靠。需要进一步的纵向研究来确定最合适的衰减阈值以及向脂肪性肝炎和肝硬化进展的风险。
