Accuracy, reproducibility and repeatability of ultrasonography in the assessment of abdominal adiposity

Rationale and objectives: Despite improvements in the methods used in body composition analysis, some goals remain far from clinical practice. Among them, the most important is the quantification of intra-abdominal adipose tissue. Fat distribution is a key point in the assessment of cardiovascular and metabolic risk status. The aim of this study was to define the accuracy, reproducibility, and repeatability of ultrasonography in the evaluation of abdominal adiposity.

Materials and methods: Twenty-six nonobese patients (group A) who underwent computed tomographic (CT) abdominal imaging and 29 obese patients (group B) were enrolled. Patients from both groups were independently evaluated using ultrasound by three radiologists; computed tomography-like conditions were reproduced, and six main parameters of subcutaneous and internal adiposity were measured (as well as three derived indexes) with both linear and convex probes. In group A, the same measurements were also obtained on CT images. Time spent for every ultrasound session was recorded. Results were analyzed using Lin's concordance correlation (ρ), intraclass correlation, and linear regression analysis (and analysis of variance).

Results: Three patients were excluded from group A after CT scans because of technical problems. Mesenteric fat thickness did not show significant correlations and reliability. Strong correlations between ultrasound and CT measurements were observed for all other visceral and subcutaneous parameters (ρ = 0.85-0.96). Intraobserver and interobserver agreement was excellent in both groups (repeatability: ρ = 0.83-0.99 for group A, ρ = 0.90-0.99 for group B; reproducibility: intraclass correlation coefficient = 0.90-0.99 for groups A and B). The mean time spent was 95 ± 21 seconds for group A (mean body mass index, 27.4 ± 2.4 kg/m(2)) and 129 ± 33 seconds for group B (mean body mass index, 37.3 ± 11.9 kg/m(2)).

Conclusions: Ultrasound is accurate, reproducible, and fast in the analysis of abdominal adiposity. It offers a regional, easy, and close-at-hand evaluation of subcutaneous and visceral fat compartments. This should be taken into consideration when clinical routine examinations are performed or to evaluate patients with specific metabolic diseases before and after treatment.