Objective: The hepatorenal index has been reported to be a sensitive and noninvasive test to quantify steatosis, but it is cumbersome and time-consuming and requires specialized software. The aim of this study was to improve and simplify the hepatorenal index calculation and determine whether it is an effective tool for differentiating patients with steatosis from those without steatosis, thereby eliminating the need for biopsy in a large number of patients.
Materials and methods: One hundred one patients who had undergone ultrasound-guided percutaneous liver biopsy at our institution were selected from a patient database. Patients with renal disease, patients with liver masses, and patients whose liver and right kidney were not included on the same image were excluded. Images were acquired with high-resolution ultrasound, and the hepatorenal index was calculated using freeware based on comparison of hepatic and renal brightness.
Results: Of the 101 patients, 63 had 5% or less steatosis and 38 had more than 5% steatosis. Using freeware available online from the National Institutes of Health, we calculated hepatorenal index values for all patients. Our data showed a strong correlation between the hepatorenal index and percentage of fat (r = 0.71, p < 0.0001). A hepatorenal index of 1.28 or greater had a 100% sensitivity for identifying more than 5% fat, 54% specificity, 0.57 positive predictive value, and 1.0 negative predictive value. If this method had been used prospectively to select patients for biopsy in our sample, 34% of biopsies could have been avoided.
Conclusion: The hepatorenal index is a simple, reliable, and cost-effective screening tool for identifying patients who should not undergo liver biopsy for evaluation of steatosis.