Role of ultrasound in the diagnosis and treatment of nonalcoholic fatty liver disease and its complications

Abstract

We review the role of liver ultrasonography (US) and related techniques as non-invasive tools in predicting metabolic derangements, liver histology, portal hypertension and cardiovascular risk as well as allowing early diagnosis and management of hepatocellular carcinoma in patients with nonalcoholic fatty liver disease. In this setting, US detects fatty changes as low as ≥20% and hepatic steatosis identified ultrasonographically, in its turn, closely mirrors coronary and carotid atherosclerosis burden. Semi-quantitative US indices (to exclude nonalcoholic steatohepatitis) and sonoelastography (to quantify fibrosis) help in predicting liver histology and selecting patients to submit to liver biopsy. Surveillance for hepatocellular carcinoma conducted through biannual US is mandatory and US has a role in guiding locoregional treatment and in evaluating the efficacy of treatment. High-intensity focused ultrasound can be delivered with precision resulting in coagulative necrosis of hepatocellular carcinoma without puncturing the liver. Costs and inconveniences have so far hampered its diffusion.

Keywords:

• cardiovascular risk
• cirrhosis
• elastography
• fatty liver
• hepatocellular carcinoma
• liver biopsy
• liver fibrosis
• metabolic syndrome
• NASH
• portal hypertension
• ultrasound

Acknowledgements

This article is dedicated to the memory of our Director and friend, the late Professor Paola Loria.

Financial & competing interests disclosure

The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending or royalties.

No writing assistance was utilized in the production of this manuscript.

Key issues

• Findings at standard hepatic ultrasonography are closely correlated with those cardiometabolic derangements belonging to the domain of the metabolic syndrome: hence, the concept of the liver as a ‘barometer of health’.

• Liver ultrasonography may have a role in differentiating steatosis from evolutive nonalcoholic steatohepatitis, which is key in deciding treatment options and follow-up schedules.

• While liver ultrasound findings closely mirror the entity of hepatic steatosis changes >20%, the diagnosis of nonalcoholic steatohepatitis and quantitation of liver fibrosis are less accurate with standard liver US scanning. Intra- and inter-observer agreement of sonographic findings appears to be not fully consistent across the various published studies.

• However, semi-quantitative indices such as Hamaguchi’s and Ballestri’s indices are more accurate in predicting some specific liver histology changes and may thus assist in identifying those nonalcoholic fatty liver disease patients to submit to liver biopsy.

• Presence and severity of ultrasonographic nonalcoholic fatty liver disease are independently associated with coronary and carotid atherosclerosis burden.

• Sonoelastography techniques represent a reliable tool for the non-invasive detection of severe fibrosis allowing the restriction of liver biopsy to selected cases.

• Liver stiffness values assessed by transient elastography can be widely used for screening and monitoring purposes given that they are directly correlated with portal hypertension, predict long-term prognosis and, conceivably, the risk of developing hepatocellular carcinoma.

• Surveillance for hepatocellular carcinoma in high-risk individuals, conducted with biannual ultrasonography, is not a clinical option but the standard of care.

• High-intensity focused ultrasound can be precisely directed to the targeted tissue at a selected depth, resulting in a coagulative necrosis of hepatocellular carcinoma without puncturing the liver. Several limitations, such as prolonged general anesthesia, multiple sessions, non-applicability to deep lesions and high costs have so far hampered its diffusion.

Notes

HCC: Hepatocellular carcinoma; NAFLD: Non-alcoholic fatty liver disease; NASH: Non-alcoholic steatohepatitis.