Reliability of acoustic radiation force impulse shear wave elastography in the evaluation of liver stiffness in morbidly obese patients

Purpose: To evaluate technical and patient-related factors that can affect the reliability of acoustic radiation force impulse shear wave elastography (ARFI-SWE) in morbidly obese patients. Methods: A prospective single-center study was performed on 41 patients (32 females, 78%) presenting for preoperative evaluation for bariatric surgery. ARFI-SWE was performed using a 6 to 1.5 MHz curved (6C1) transducer. Hepatic steatosis was mild, moderate, severe, and absent in 24.4%, 12.2%, 43.9%, and 19.5% of patients, respectively. Interquartile range/median (IQR/M) ranged from 0.05 to 2.07 (0.78 ± 0.56 m/s). Twenty patients (48.7%) had reliable measurements (IQR/M < 0.3). Shear wave velocity (SWV) values were >1.34 m/s (clinically significant fibrosis) in 25 of 41 patients (61%) and >2.2 m/s (advanced fibrosis) in 19 patients (46%). Results: Median SWV was correlated with body mass index (BMI; correlation coefficient [CC] =.37; 95% CI, 0.07-0.61; P-value =.03) and skin-to-liver capsule distance (SLD) (CC =.38; 95% CI, 0.09-0.62; P-value =.01). IQR/M was higher in patients with BMI > 40 (0.24 ± 0.11 vs 0.39 ± 0.25, P-value =.031) and SLD > 3 cm (0.46 ± 0.27 vs 0.23 ± 0.08, P-value =.001), and there was higher number of unreliable examinations among patient with SLD > 3 cm (16/23 vs 5/18, P-value =.01). Conclusion: ARFI-SWE is technically more challenging among patients with higher BMI and SLD, resulting in a higher number of unreliable studies, which highlights the need for further advancement of ARFI technology.