Hepatic steatosis: qualitative and quantitative sonographic assessment in comparison to histology

Hepatic steatosis: qualitative and quantitative sonographic assessment in comparison to histology

REVIEWED BY Emma Jardine | ASA SIG: General

REFERENCE | Authors: Tan Z, Mehta B, Kusel K, Seow J, Zelesco M, Abbott S, Simons R, Boardman G, Welman C & Ayonrinde O

WHY THE STUDY WAS PERFORMED

This retrospective study was performed to assess the correlation between qualitative liver ultrasound assessment (B-mode) and attenuation imaging (ATI) assessment for hepatic steatosis, using liver biopsy as a reference standard. The secondary aim was to investigate the interobserver variability of qualitative ultrasound B-mode feature for hepatic steatosis assessment.

Steatotic liver disease is the primary cause of liver mortality and morbidity. Patients who have steatotic livers also have an increased risk of developing cardiovascular disease and chronic kidney disease. Early diagnosis enables interventions to reverse and reduce hepatic steatosis. B-mode ultrasound allows subjective grading of hepatic steatosis as absent, mild, moderate or severe. This grading system involves comparing the liver’s echogenicity to the renal cortex, evaluating the visualisation of the hepatic vessel walls and assessing posterior beam attenuation. This compares to quantitative ultrasound assessment using ATI. ATI measures the attenuation of the ultrasound beam and can accurately discriminate mild from moderate steatosis.

HOW THE STUDY WAS PERFORMED

A retrospective study was conducted in Australia over a 4-year period. Patients with a hepatic steatosis grade on histopathology who had an ultrasound of the liver performed in conjunction with an ultrasound-guided biopsy were included. The liver biopsies were obtained from the right lobe of the liver (segment 6 or 7). Liver biopsy histology results were obtained from the laboratory database.

Three radiologists who were blinded to clinical data graded qualitative images of the liver. Retrospective analysis of ultrasound images recorded subjective ultrasound parameters. These parameters included large hepatic vein blurring, main and right portal vein blurring, liver-kidney contrast, posterior beam attenuation, diaphragm definition, focal fat sparing, liver echotexture and overall impression.

WHAT THE STUDY FOUND

Ninety patients were included in the study, 67% were female, the median age was 54 years, mean patient BMI was 30.8 kg/m2. Sixty per cent of patients demonstrated no to mild steatosis.

The radiologist’s overall impression had a strong correlation with the biopsy results for the grade of steatosis. There was high interobserver reliability noted, with most subjective parameters having moderate to near-perfect interobserver agreement.

Figure 1. These images demonstrate no steatosis, mild steatosis, moderate steatosis and severe steatosis based on the radiologist’s overall impression. The images in the top row demonstrate liver-kidney contrast. The middle row highlights vessel wall blurring, posterior beam attenuation and diaphragmatic definition. The bottom row demonstrates attenuation imaging (ATI).

This study found that there is an ongoing role for B-mode ultrasound in the primary diagnosis and grading of steatotic liver disease.

RELEVANCE TO CLINICAL PRACTICE

Qualitative ultrasound continues to play a significant role in the assessment of hepatic steatosis, especially considering its high availability and proficiency. An experienced radiologist’s overall impression is at least as good as quantitative parameters for the assessment of steatotic liver disease.