Body posture can modulate liver stiffness measured by transient elastography: a prospective observational study

Background: Non-invasive measurement of liver stiffness (LS), traditionally performed in the supine position, has been established to assess liver fibrosis. However, fibrosis degree is not the sole determinant of LS, necessitating the identification of relevant confounders. One often-overlooked factor is body posture, and it remains unclear whether normal daily postures interfere with LS irrespective of fibrosis. A prospective two-group comparison study was conducted to investigate the relationship between posture and LS. Methods: Sixty-two adults participated, divided into two groups: patients with chronic liver disease and healthy controls. Both groups were assessed using transient elastography (TE) under the supine, seated, and standing postures. Randomization was applied to the order of the two upright postures. A two-way mixed ANOVA was conducted to assess the posture-dependence of LS and its variations between two groups. Results: Results showed that posture differentially affected LS depending on the presence of liver fibrosis. In 31 healthy individuals (baseline LS range: 3.5–6.8 kPa), a transition from the supine (5.0 ± 1.0 kPa) to seated (5.7 ± 1.4 kPa; p = 0.036) or standing (6.2 ± 1.7 kPa; p = 0.002) positions increased LS, indicating liver stiffening. Conversely, in 31 patients with varying fibrosis stages (baseline LS range: 8.8–38.2 kPa), posture decreased LS from the supine (15.9 ± 7.3 kPa) to seated (13.8 ± 6.2 kPa; p < 0.001) or standing (13.9 ± 6.2 kPa; p = 0.001) positions. No significant difference in LS was observed between the seated and standing positions in both groups (control group: 5.7 vs. 6.2 kPa, p = 0.305; patient group: 13.8 vs. 13.9 kPa, p = 1). Additionally, different postures did not elicit significant changes in the success rate (supine, 98.6 ± 4%; seated, 97.6 ± 6%; standing, 99.1 ± 3%; p = 0.258) and IQR/median value (supine, 25 ± 8%; seated, 29 ± 15%; standing, 29 ± 12%; p = 0.117), implying no impact on both measurement feasibility and reliability. Conclusions: We demonstrated, for the first time, the feasibility of utilizing upright postures as an alternative measurement protocol for TE. We further unravel a previously unrecognized role of transitioning between different postures to assist the diagnosis of cirrhosis. The findings suggested that daily physiological activity of postural changes suffices to alter LS. Therefore, body positioning should be standardized and carefully considered when interpreting LS.