Validity of real time ultrasound in the diagnosis of hepatic steatosis: a prospective study

Abstract

Background/aims: Ultrasound is used to screen for hepatic steatosis, the most common liver disease in the United States. However, few studies have prospectively evaluated the accuracy of ultrasound to diagnose hepatic steatosis. Therefore, a double blinded prospective study was performed in consecutive patients undergoing liver biopsy to evaluate the accuracy of ultrasound to diagnose hepatic steatosis.

Methods: Real time ultrasound was performed just prior to the biopsy by a single investigator masked to the clinical diagnosis. The liver biopsy was reviewed by a pathologist masked to the clinical indication or sonographic findings.

Results: Of 73 consecutive patients studied, macrovesicular steatosis of any severity on biopsy was found in 46 (63%) and micro vesicular fat found in 51 (69.9%). The overall impression of the sonographer for the presence of macrovesicular hepatic steatosis of any degree had a sensitivity of 60.9% and a specificity of 100%. The sensitivity increased to 100% and the specificity to 90% when there was > or =20% of fat. The zonular distribution of the fat did not alter the diagnostic accuracy of ultrasound. Ultrasound had a poor yield in the diagnosis of microvesicular fat with an overall sensitivity of 43% and a specificity of 73%. The combination of increased echogenicity and portal vein blurring on ultrasound had the greatest sensitivity in the diagnosis of hepatic steatosis.

Conclusion: Real time ultrasound using a combination of sonographic findings has a high specificity but underestimates the prevalence of hepatic steatosis when there is<20% fat.

Figure 1.

Histological evidence of total hepatocyte area involved with macrovesicular fat and presence of fat detected on ultrasound based on the overall impression of the sonographer. The box-and-whisker plot is represented by the lower boundary of the box indicating the 25th percentile, the line within the box indicating the median value, the upper boundary of the box indicating the 75th percentile. The whiskers extend to the most extreme data point which is no more than 1.5 times the interquartile range from the box.

Figure 2.

Macrovesicular fat levels by ultrasound criteria: (A) increased echogenicity, (B) hepatic vein blurring, (C) portal vein blurring and (D) poor visualization of diaphragm. Macrovesicular fat levels by ultrasound criteria: (A) increased echogenicity, (B) hepatic vein blurring (C) portal vein blurring and (d) poor visualization of diaphragm. PV- portal vein; HV hepatic vein

Figure 3.

Receiver Operating Characteristics assessment of increased echogenicity and portal vein blurring to predict Macrovesicular fat levels ≥ 20%.