Dr Simon Hew is a medical doctor from Melbourne, Australia. He has worked in Gastroenterology, Hepatology and Medical research. He is a regular reviewer and contributor to research involving tech in health practice, including the precision of app-based liver disease calculators. This week he shares his insights into the disturbing legacy of growing non-alcoholic steatohepatitis (NASH) and organ transplants that the global obesity epidemic is bequeathing the health system.
Foie gras has been an indulgent dish since Ancient Rome. Ducks, typically of the Mulard breed, are cherished for their glistening fatty livers, forming the backbone of a number of creamy French delicacies. The production of foie gras is however, somewhat unsavory, with gavage, or deliberate overfeeding, used to create the fatty livers. Similarly, with the sizeable wave of the global obesity epidemic breaking on our health systems, fatty liver disease – in humans – is also an unsavory topic, but one that is absolutely necessary for us to palate.
Non-alcoholic fatty liver disease (NAFLD) represents a spectrum of pathological conditions arising from fatty infiltration of the liver, in the absence of significant alcohol consumption. It is a diagnosis made under the microscope, where healthy hepatocytes, or liver cells, are replaced with fat. With time, this promotes inflammation which damages the hepatocytes – namely non-alcoholic steatohepatitis (NASH). If this process continues unabated, the liver starts to fibrose, or scar, and the cumulative effect of this is cirrhosis, largely a permanent, life-threatening result. Cirrhosis can lead to infections, gastrointestinal bleeding, unremitting confusion, liver failure or liver cancer.
NAFLD is on the rise. It is estimated that approximately one-third of the US population has NAFLD. 6 million of these individuals have progressed to NASH and 10 percent of them have cirrhosis. Similar figures have been suggested in European populations. Developing nations have not been spared either. NAFLD is projected to become the leading cause of liver disease in developed nations, overtaking traditional causes such as alcohol and viral hepatitis. Consequently, NAFLD will become the most common indication for liver transplantation.
NAFLD has another medical sting in its tail: usually, outside of hepatitis B, liver cirrhosis is a required precursor for the development of liver cancer. It is sobering then that liver cancer in NAFLD can develop at a much earlier stage before there is significant scaring. Given the increasing prevalence of NAFLD, the implications of this for our health care system is potentially staggering.
The growing problem of NAFLD has paralleled increasing rates of obesity, diabetes and the metabolic syndrome. In fact, NAFLD is really the liver manifestation of metabolic syndrome. Its risk factors are the same as these more familiar problems: a sedentary lifestyle with poor dietary choices or options, mechanistically leading to central apidosity (ironically developing a ‘beer belly’, without the beer) and perhaps more importantly, insulin resistance.
NAFLD is challenge for medicine as it is both difficult to define and also difficult to treat. The diagnosis has been traditionally clinched with a liver biopsy, a time consuming and resource heavy procedure, not without potential morbidity. Non-invasive tests for NAFLD are emerging but definition disagreements have made quantifying the problem difficult. Unlike other forms of liver disease like hepatitis B and C which have effective anti-viral treatments and conditions like diabetes which can be managed with insulin, an effective therapeutic agent for NAFLD is notably absent.
I have been fortunate enough to work in a liver transplant unit for the last twelve months. NAFLD is certainly on the increase and whilst it might lack the frightening stigmata of viral hepatitis or drug induced liver failure, it is no less serious or challenging to manage. Often however, when patients reach our centre, the damage has been done. Transplant is a life saving procedure but the scarcity of organs in our opt-in donation system mean that a number of patients with end-stage liver disease continue to die.
The treatment of NAFLD is through the management of obesity and the other components of the metabolic syndrome. This is not a straight forward task and a truly multidisciplinary biopsychosocial approach to the patient is required. The best treatment however lies in something that modern medicine struggles to do well: prevention.
Investing in changing our obesogenic environment and culture is inherent to regressing the rates of NAFLD. This requires foresight by our leaders, advocacy from our healthcare systems and awareness amongst our patients. Heavily refined, processed foods need to be replaced by locally sourced, fresh produce. An urban environment conducive to exercise and less reliance on the car needs to be developed. An understanding that liver disease is much more than alcohol needs to be embraced and that ‘keeping fit’ is just as much about the liver as any other body system.
NAFLD is a rising problem that so far has been largely absent from the obesity/metabolic consciousness. It is clear however that it needs to become a significant component of the global health conversation. Unlike our Mulard duck friends, we need to shift it realms of delicacy to the main course.
Dr Simon Hew is from Melbourne, Australia. He is a medical doctor specialising in Gastroenterology, Hepatology and Medical research. He is a regular reviewer and contributor to research involving tech in health practice, including the precision of app-based liver disease calculators and the effect of music on detecting bowl cancer by endoscope.