Gastroenterologists are being urged not to overlook the utility of liver ultrasound (FibroScan) for obese patients after a study showed it picks up high rates of underlying NAFLD and accurately stratifies disease severity, in patients undergoing bariatric surgery.
Patients who underwent the scans also went on to report substantial reduction in their NAFLD severity post-surgery compared to baseline, prompting investigators to supports it’s use in the subgroup of patients.
Speaking to the limbic lead investigator gastroenterologist Associate Professor David van der Poorten from the University of Sydney said FibroScan has been considered ‘difficult and unreliable’ in a morbidly obese population – a throwback to early studies that show scan failure rates in up to 50% of patients.
But despite several more recent studies demonstrating much higher success rates in obese patients the perception that obesity is a contraindication to the technology prevails, he said.
It’s a bias that has led to higher rates of liver biopsy in obese patients that may be unnecessary.
Conversely, it also means that many obese patients go without knowing the extent of their NAFLD and risk of severe liver disease if clinicians forgo testing.
“These days we’re doing very few liver biopsies because FibroScan can pretty accurately determine if there’s any substantial liver fibrosis or scarring. It also gives a good readout on whether there’s much in the way of fatty liver,” explains A/Professor van der Poorten.
The basis for doing the study, he adds, is that for a lot of centres being obese, particularly morbidly obese above BMI 35, is still considered ‘almost a relative contradiction’ to FibroScan.
“It’s anticipated that the failure rate will be up to 50% sometimes and there have been quite a number of publications prior to this one to show that actually that’s not the case if you’re using it with the XL Probe.”
Success rates
In their analysis of 190 patients undergoing bariatric surgery, A/Professor van der Poorten and colleagues showed FibroScan was successful in 167 patients (87.9%) at baseline, and 100% at follow-up at ≥ 6 months post-surgery, with 70 patients receiving a follow-up FibroScan.
Of particular note is the high success rate even with mean BMI in the groups being 40.2 and 28.7, respectively confirming the utility of transient elastography even in extreme obesity, he adds.
The majority of patients in the cohort had significant hepatic steatosis by FibroScan, with a third having severe steatosis and 4% advanced fibrosis or cirrhosis. As expected, increasing weight and BMI correlated with the presence of steatosis or fibrosis and hence a diagnosis of NAFLD.
A reassuring finding, notes A/Professor van der Poorten, was the low level of significant FibroScan or worsening of NAFLD found – a finding that may be explained by the relatively young age of the cohort (mean 42 years) and low incidence of diabetes mellitus (12%), even though mean BMI was 40.2 kg/m2, he suggests.
Another important message highlighted by the study is the substantial impact that bariatric surgery has on NAFLD.
“For people who are very overweight and who have failed other weigh loss measures there’s nothing that beats bariatric surgery to cause the amount of weight loss that can then have such drastic improvements in fatty liver,” A/Prof van der Poorten stated.
Among the 70 patients who had follow-up scans post surgery reductions in steatosis were seen in 90% and fibrosis in 67%. Meanwhile 64% had complete resolution of steatosis.
Acknowledging that FibroScan failure is ‘almost always caused by excess subcutaneous fat overlying the right chest wall’, A/Prof van der Poorten said there is a skill in positioning patients to find ‘the right spot’ including having patients place their hands behind their head when being scanned.
“One of the things I really like about FibroScan is that it’s a way of empowering the patient and giving them more information about their illness. A lot of people figure, once you’ve got fatty liver you’ve got fatty liver but there’s quite good data now that shows if you lose enough weight, whether it’s through surgery or a totally different way, that fatty liver can reverse and can even go away.
When patients see those numbers go down as they lose weight it becomes a very powerful tool. You won’t get it right all the time but in most cases you can and it should still remain in most cases the number one non-invasive way to investigate these people.”
The study was published in Scientific Reports.