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BACKGROUND: Performing ultrasound shear wave elastography (SWE) in the liver may present difficulties in patients with obesity. The aim of the study was to investigate the impact of different body positions on acoustic radiation force impulse (ARFI) - SWE measurements, skin-to liver capsule distance (SCD) and ARFI-SWE reliability, also stratified for sex.

METHODS: In this prospective study, ten ARFI-SWE and ten SCD measurements were obtained from chronic liver disease patients in three body positions: supine, 30° and 90º left decubitus. The study group was stratified into subgroups; increased sagittal abdominal diameter (SAD) (≥ 23 cm) and advanced fibrosis (≥ 9 kPa). Less reliable ARFI-SWE exams were defined as inter-quartile range /median kPa > 30%. Analysis included Friedman's test, Spearman's ρ and binary logistic regression.

RESULTS: Analysis of 200 patients showed ARFI-SWE median results 5.5 kPa in supine, 5.8 kPa in 30º and 5.8 kPa in 90º left decubitus (p = 0.023). Patients with increased SAD showed no difference in ARFI-SWE results across body positions (n = 80; p = 0.182), which was seen among patients with no increased SAD (n = 120; p = 0.020). Among advanced fibrosis cases (n = 21), results decreased from 12.2 kPa (supine) to 9.6 kPa (90° left decubitus, p = 0.015). The amount of reliable ARFI-SWE exams increased from supine to left decubitus (84.7% -92.6%, p = 0.014). The SCD value varied across the supine, 30º and 90º left decubitus body positions (p < 0.001; 1.9 cm, 1.8 cm, 1.9 cm, respectively). Only SAD associated with less reliable ARFI-SWE exams (p = 0.011; odds ratio = 1.2), and SAD showed a positive correlation to ARFI-SWE result (Spearman's ρ = 0.515, p < 0.001).

CONCLUSIONS: SAD appears to influence ARFI-SWE examinations. Adjusting body positioning from supine to left decubitus in patients with higher SAD increases the number of reliable exams and decreases SCD, without increasing ARFI-SWE results, regardless of sex.