Background:
Prevalence of non-alcoholic fatty liver disease is increasing due to the morbid obesity. In severely obese patients, NAFLD is a potentially important indication for bariatric surgery. Liver elastography is a validated diagnostic tool to measure liver stiffness in different liver disease.
 Objectives:
We aimed to determine the diagnostic performance of elastography as a non-invasive tool compared to liver biopsy in bariatric surgery candidates.
 Methods:
Prospectively, a total of 30 severely obese subjects underwent bariatric surgery with liver needle biopsy during the surgery. Diagnostic accuracy of elastography in determining liver stiffness was determined by ROC curve in SPSS v22. Fibrosis and NASH score were considered as a gold standard. F≥2 and NASH≥7 were addressed as an advanced fibrosis and severe activity.
 Results:
Their mean BMI of 45.49±5.67 kg/m2. When fibrosis was as a gold standard the Area Under the Curve (AUC)of [0.82±0.10 (95% CI:0.62-1.0)] resulted from the ROC curve of elastography for this prediction. For a value of 7.05 (optimal cutoff), elastography had a sensitivity and specificity of 80%.when NASH score was as gold standard following results were achieved: AUC of [0.97±0.04 (95% CI: 0.9-1.0)] for this prediction and for a value of 7.25(optimal cutoff),elastography had a sensitivity of 100% and specificity of 88.5%.
 Conclusion:
Non-invasive liver stiffness measurement is feasible in severely obese patients using shear wave elastography. Shear wave elastography is useful in clinical evaluation before bariatric surgery.