Feasibility of transient Elastography (Fibroscan®) for the measurement of liver stiffness in morbidly obese patients undergoing bariatric surger

Background: The prevalence of non-alcoholic fatty liver disease (NAFLD) exceeds 90% in severely obese patients undergoing bariatric surgery. A substantial number of these patients may have end-stage liver disease with liver cirrhosis. Fibroscan as a non-invasive diagnostic tool to measure liver stiffness has a good accuracy in various liver diseases. However, few data exist about technical feasibility and accuracy of liver stiffness measurement in these patients at highest risk.

Aims: To analyse non-invasive liver stiffness measurement by Fibroscan® in severly obese patients undergoing bariatric surgery compared to liver histology and sonographic parameters.

Methods: Prospective patient cohort with 149 morbidly obese NAFLD patients. Fibroscan® examinations were classified into successful, not valid and not successful. Successful were 10 valid measurements with success rate (SR) > 60% and interquartile range of measurements (IQR)/median (M) of liver stiffness ≤0.3 or IQR/M ≥0.3 with a median of liver stiffness (p < 7,1 kPa. Not valid were classified 10 valid measurements with a SR > 60% regardless IQR.

Results: In the cohort 149 NAFLD patients were included and 87 patients had liver biopsies (NAFL n = 59, NASH n = 28). The patients were morbidly obese with a mean BMI of 51.6 (± SD 8.5)kg/m². In 41% Fibroscan® measurement with XL-probe was successful, in 22% not valid and in 37% not successful. Not successful Fibroscan® measurement was significant more frequent in patients with a higher BMI and a higher weight (pnot successful measurement sonographic paramedian and intercostal distances were significant higher compared to successful measurements. NASH patients had significantly higher liver stiffness in comparison to NAFL regarding successful as well as not vaild measurements. All patients with high grade fibrosis (F4) could successfully be diffentiated by Fibroscan® measurement from patients with no fibrosis (p < 0.05). In patients with not successful measurement sonographic paramedian and intercostal distances were significant higher compared to successful measurements. NASH patients had significantly higher liver stiffness in comparison to NAFL regarding successful as well as not vaild measurements. All patients with high grade fibrosis (F4) could successfully be diffentiated by Fibroscan® measurement from patients with no fibrosis (p < 0.05).

Conclusions: Non-invasive liver stiffness measurement is feasible in severely obese patients. NASH patients could be differentiated from NAFL by successful measurements and not valid measurements (regardless IQR). Transient elastography is useful in clinical evaluation before bariatric surgery in the majority of patients.