An attempt to assess visceral fat accumulation by measuring fat content in the hepato-renal gap on abdominal ultrasound

Abstract

Purpose: The overlap between lifestyle-related diseases and visceral obesity is said to increase the risk of developing atherosclerosis. The assessment of visceral fat accumulation is commonly carried out by computed tomography scan (fat scan). However, due to radiation exposure and the cost of the test, it is difficult to perform this test on a large number of people. On the other hand, abdominal ultrasonography is a simple method without the problem of radiation exposure, and various reports on visceral fat accumulation have been published. In the present study, we focused on the perirenal fat (PRF) of the hepato-renal gap on abdominal ultrasonography. Subjects and Methods: The subjects were 478 patients (male: 333, female: 145, mean age: 58.3 ± 11.7 years, mean BMI: 24.6 ± 3.2) who underwent physical examination in 2018 and underwent abdominal ultrasonography and fat scan. PRF was measured from hepatic and renal images of abdominal ultrasound and compared with fat scan. The relationship between PRF and visceral fat accumulation was also investigated using a health questionnaire. Results and Discussion: The mean PRF of all subjects was 5 ± 5.5 mm, and the mean visceral fat area (VFA) on fat scan was 110 ± 51 cm². The correlation coefficient between PRF and VFA was 0.66 (p-value < 0.001), indicating a positive correlation. ROC analysis with PRF showed a threshold of 3 mm. The area under the curve was 0.855 (95% confidence interval: 0.821-0.889), the sensitivity was 81%, the specificity was 81%, the positive predictive value was 80%, and the negative predictive value was 82%.We considered that a fat layer of more than 3 mm in the hepato-renal gap on abdominal ultrasonography could estimate a visceral fat area of more than 100 cm². In addition, when the influence of medications (blood pressure, blood glucose, lipid) was examined based on the questionnaire, there was no difference in body mass index and abdominal circumference, and the fat scan and PRF showed a large amount of visceral fat (accumulation). Conclusion: Measurement of the hepato-renal gap using abdominal ultrasonography can help to estimate and diagnose visceral fat accumulation in physical examinations and screening tests.