Liver stiffness in obese patients: First experience using the novel XL probe for vibration-controlled transient elastography

Aims: Measurement of liver stiffness (LS) by vibration-controlled transient elastography [VCTE/Fibroscan] is limited in patients with obesity and ascites. We here test and compare the recently developed more powerful XL probe versus the conventional M probe. Methods: LS was measured in 80 obese and non-obese patients (BMI range 17.2–72.4) using both the M and XL probe. In addition, BMI, waist to hip ratio, transaminases and basic liver ultrasound parameters were obtained. Results: LS was not measurable in 3 patients (3.7%) by the XL probe as compared to 23 patients (28.7%) by the M probe. At a BMI>33, hardly any patient could be measured using the M probe. Out of the 3 patients not measurable with the XL probe, two had a BMI>40 and one was non obese. LS measurement failure in non obese patients was in one case due to ascites but mainly to a specific type of subcutaneaous fat tissue with poor ultrasound propagation. LS by M and XL probe were highly correlated (r=0.98, P<0.01). The maximum difference between LS measured with M-probe compared to XL-probe was 30% in patients with an increased LS>8 kPa. Bilirubin and waist-to-hip ratio but not BMI correlated with LS in both probes (r=0.40 and r=0.47, P<0.01). Discussion and conclusion: The novel more powerful XL probe drastically improves the success rate of LS measurements in patients with obesity and ascites. Patients with a BMI above 40 and lean patients with a specific type of subcutaneous fat tissue with poor ultrasound penetration are still problematic despite the use of the XL-probe.