编者按：“第七届全国脂肪性肝病学术会议暨2017 CSH-AASLD脂肪性肝病联合学术会议”召开期间，AASLD主席、美国密歇根大学卫生系统Anna S.F.LOK教授在“诊断”专题中发表了题为“NAFLD肥胖及内脏肥胖的评价”的报告。会后，本刊有幸采访到LOK教授，请她介绍肥胖和内脏肥胖的定义、内脏肥胖的诊断、非肥胖脂肪肝患者的鉴别诊断。

 

一、肥胖与内脏肥胖的定义？

 

Anna S.F.LOK教授在采访中指出，肥胖取决于体质量指数（BMI），有不同的截止值。对于高加索人，BMI>30被视为肥胖；对于亚洲人群，BMI为27～28通常被作为肥胖定义。然而，我们也认识到，肥胖症者的脂肪可能分布在全身不同部位，其中向心性肥胖更为重要。向心性肥胖通常依据腰围进行判断，亚洲人群的常规截止值为女性80cm、男性88～90cm；对于高加索人群，通常推荐更高的截止值。如果想进一步评估内脏肥胖，过程更为复杂，通常需要借助影像学检查，如DXA扫描、CT扫描或MRI。

 

Obesityis determined by body mass index (BMI). There are different cut-offs. In Caucasian patient populations, a BMI >30 is considered to be obese. In Asian patients, a BMI of 27-28 is often used as a definition of obesity. However, we recognize that people who are obese may carry fat in different parts of the body. It is central obesity that is more important. Central obesity is usually measured by waist circumference, and for Asians, the general cutoffs are 80cm for a woman and 88-90cm for a man. Higher cutoffs are generally recommended for Caucasians. If we want to measure visceral adiposity, it is more complicated and generally requires radiology, such as a DXA scan, a CT scan or MRI.

 

二、如何评估内脏性肥胖？

 

仅通过腰围诊断向心性肥胖显得更为容易，这可以在临床实践中完成。但是，如果我们真正想评估向心性肥胖，则需要确定内脏脂肪的分布情况，而这要求影像学的参与，但临床上我们并不一定能实现，因为我们不会常规地要求患者做DXA扫描、CT扫描或MRI检查。所以，在现阶段，这些影像学手段更多地用于临床研究，而不是作为临床诊断工具。

 

As I mentioned, it is easier to assess central obesity as defined by just a waist circumference, which can be done in clinical practice. But if we really want to assess visceral adiposity, which requires that we define the visceral compartment, then we require imaging. That is not always available clinically, as we do not normally do DXA scans or CT scans or MRI on our patients. These are more clinical research tools than clinical diagnostic tools at this stage.

 

三、非肥胖者的脂肪肝鉴别？

 

非肥胖者也可能存在脂肪肝，即使他们的BMI值正常，但可能存在内脏脂肪含量增加，这类患者我们称之为“瘦者NAFLD”。但肝脏脂肪堆积也可能是酒精引起，如过量饮酒者可存在脂肪肝。所以，脂肪性肝病并不仅仅包括NAFLD，也包括酒精性脂肪性肝病。此外，某些药物治疗也可能导致肝脏脂肪变。另外，存在遗传易感性的患者罹患脂肪性肝病的发生风险增加，这就意味着脂肪肝患者未必是肥胖人群。

 

If we have a patient with normal BMI yet they have fatty liver, it is possible that even though they have a normal BMI, they can have increased visceral adiposity. These are what we call the lean NAFLD patients. But fat in the liver can also be because of alcohol - people with excessive alcohol consumption can have fatty liver. So, fatty liver is not always NAFLD, because it can be because of alcohol as well. There are certain medications that can also cause fat in the liver. And there are also people with a genetic predisposition that increases the risk of fatty liver, which means they don’t necessarily have to be obese.