Introduction Liver biopsy remains the gold standard for diagnosing non-alcoholic steatohepatitis (NASH). But with a variability of 10–20% and a mortality rate of 0.01%, non invasive techniques of monitoring change in liver morphology have been sought after. Acoustic radiation force impulse imaging (ARFI) is a promising innovation that combines ultrasound imaging and elastography to measure liver stiffness which correlates well with liver fibrosis. Morbidly obese patients are at a risk of developing NASH or Non Alcoholic Fatty Liver Disease (NAFLD) and weight loss helps improve liver steatosis. Very low calorie diets (VLCD) help in weight reduction and are known to shrink the liver. Our aim was to assess the role of ARFI in assessing and monitoring the change in liver architecture in a cohort of morbidly obese patients in response to VLCD.

Methods A cohort of non-diabetic morbidly obese patients at risk for NASH was selected for this study (clinical trial no: NCT01950052). Liver volume was estimated with the help of a standardised ultrasound protocol while liver fibrosis was analysed with ARFI. After randomisation, a very low calorie diet (800 kcal) was given to one group while the rest were controls. Four weeks later, ARFI was repeated and all patients underwent a laparoscopic roux-en-y gastric bypass. A liver biopsy was taken during surgery from the same liver segment as the ARFI measurements. The liver histology was evaluated according to the NASH Clinical Research Network Scoring System by two blinded pathologists. Steatosis, fibrosis and NAFLD activity scores were correlated with ARFI scores.

Results Liver volume shrank by 21.5% in the diet arm (n = 10) compared to 2% (p < 0.05) in the control arm (n = 14) in 4 weeks. The ARFI scores were similar in the diet and control group [median 2.92 (1.1–3.8) m/s vs. 3.22 (1.54–3.65) m/s, p = 0.7], p = 0.7] at recruitment and at the time of the biopsy 4 weeks later [2.16 (1.19–3.68) m/s vs. 2.83 (1.5–3.48) m/s, p = 0.3]. ARFI demonstrated a drop in values in the diet group (p = 0.1) but this was not significant. Similarly, liver biopsy at surgery confirmed a trend of lower levels of steatosis in the diet group (27 vs. 42%, p = 0.12). The ARFI scores did not correlate with the steatosis grade (p = 0.8), or NAFLD score (p = 0.48).

Conclusion Low calorie diets shrink liver volumes but ARFI could not detect any change in liver stiffness. ARFI does not appear to correlate with liver steatosis and may not be ideally suited for short term monitoring of successful treatment of NASH. However its role in long term monitoring needs further evaluation.

Disclosure of Interest None Declared.