Top Tips: Non-alcoholic Fatty Liver Disease in Adults

Dr Jez Thompson Offers Seven Top Tips on Dealing With the Challenges Involved in the Diagnosis and Management of Non-alcoholic Fatty Liver Disease in Primary Care

Primary non-alcoholic fatty liver disease (NAFLD) is characterised by excessive fat deposition in the liver that is not secondary to another source of liver damage,^1,2 such as excessive alcohol use, chronic viral hepatitis, or some inherited and endocrine conditions.^3,4 NAFLD is increasingly prevalent, particularly in developed countries,⁵ and is now estimated to affect 20–30% of the general population.²

NAFLD ranges in clinical severity from uncomplicated fatty liver (steatosis) to cirrhosis,^1,2 which has the attendant risks of hepatocellular carcinoma (HCC) and decompensated liver disease.^6,7 Patients with NAFLD are usually asymptomatic,⁸ although the rate of disease progression varies depending on the presence of risk factors,² which include obesity and type 2 diabetes.^2,3

There are important opportunities for early diagnosis and risk factor management in primary care, with the twin goals of reversal of fatty infiltration through dietary and lifestyle changes, and monitoring patients for the development of cirrhosis and its complications.

1. Recognise Those Patients at High Risk of Developing NAFLD

The underlying cause of NAFLD, the pathological mechanisms of NAFLD progression, and the reasons why this progression occurs in some people but not others, are not fully understood.

Most factors that contribute to NAFLD risk are environmental. Risk factors for the development of NAFLD are shown in Box 1.³  

Extremes of Body Weight

It is estimated that NAFLD is present in 80–90% of people classed as obese.⁹ However, it is important to remember that not everyone who is overweight develops fatty liver, and not everyone who has fatty liver is overweight. NAFLD is also associated with the metabolic changes that occur during rapid weight loss and starvation, such as in anorexia nervosa.¹⁰

Genetic Predisposition

Genetic factors may explain why some individuals are predisposed to fat deposition in the liver, and why hepatic steatosis develops into more serious liver disease in certain patients. Studies have identified specific genes—including variants of PNPLA3, TM6SF2, and HSD17B13— that are associated with progression to severe disease, including cirrhosis and HCC, in people with NAFLD.¹¹ Genetic predisposition is thought to underlie 27–39% of cases of NAFLD.¹²

2. Understand How to Diagnose NAFLD in Adults

Diagnosing NAFLD in adults can be difficult. Challenges include:

• the high prevalence of risk factors
• the benign clinical course of NAFLD in most patients
• a lack of good-quality evidence for factors that can predict disease progression
• the absence of a simple, cost-effective, sensitive, and specific screening test.

NICE Guideline (NG) 49, Non-alcoholic fatty liver disease (NAFLD): assessment and management, does not make any recommendations on the screening of asymptomatic adults with risk factors for NAFLD.² Therefore, whether to investigate patients with multiple and severe risk factors for NAFLD remains an individual clinical decision. The Fatty Liver Index¹³ is one example of a simple algorithm-based assessment that brings together clinical examination findings—such as body mass index (BMI), waist measurement, and standard blood test results—to give an estimate of the risk of NAFLD.¹³ Some clinicians may find this approach useful; however, NICE found that these tests had limitations, and was unable to recommend their use.¹⁴

Pragmatically, NAFLD can be suspected in primary care in two circumstances. Firstly, fatty changes in the liver are a fairly common incidental finding on upper abdominal ultrasound; and secondly, the onward investigation of patients with persistently abnormal liver function test (LFT) results may point to a diagnosis of NAFLD. However, it should be noted that patients on any part of the NAFLD disease spectrum may have normal LFTs, and that a routine, standard LFT panel has no value in excluding NAFLD¹⁵ —in fact NICE does not recommend that routine liver blood tests be used to rule out NAFLD.²

A useful algorithm detailing the initial response to abnormal liver blood tests is shown in Figure 1.¹⁶

NAFLD is a clinical and pathological diagnosis that requires the exclusion of other primary causes of liver disease. When NAFLD is suspected, it is important to ask about alcohol consumption to rule out alcohol-related liver disease as the underlying cause of fatty changes;² a threshold for alcohol consumption of less than 20 g/day (2.5 units/day) for women and less than 30 g/day (3.75 units/day) for men has been adopted to exclude alcohol-related steatosis.¹⁷ Fatty liver changes are part of the pathological process of many liver diseases, and chronic viral hepatitis, drug-induced liver disease, haemochromatosis, Wilson’s disease, and autoimmune liver disease must all be excluded before NAFLD can be diagnosed.¹⁷ A standard panel of relevant blood tests is available in many areas, and is often termed a ‘secondary liver screen’, ‘liver aetiology screen’, or something similar, depending on the area. 

3. Be Aware of the Natural History and Disease Spectrum of NAFLD

NAFLD represents a spectrum of liver disease ranging from simple, benign fatty deposition to end-stage decompensated cirrhosis. The four main stages of NAFLD are described in the following sections.

Hepatic Steatosis

Hepatic steatosis, or simple fatty liver, is defined as abnormal fat deposition within liver cells.¹⁸ At this stage, there has not been a progression to inflammation or scarring.¹⁴ For most people, this fatty infiltration is harmless and asymptomatic.¹⁸ However, for some, it can result in the development of local inflammation and progression to more serious disease—the risk of developing cirrhosis is 4.7 times higher in patients with NAFLD than in the general population,¹⁹ but disease progression is typically slow.²⁰ Although the risk of progression to cirrhosis in NAFLD is lower than that in some other liver conditions, the high prevalence of NAFLD means it is an increasingly important cause of advanced liver disease.

Non-alcohol-related Steatohepatitis

Some patients with fatty liver develop non-alcohol-related steatohepatitis (NASH), a more aggressive condition characterised by liver inflammation.¹⁸ The prevalence of NASH in the general population is thought to be around 2–3%,² and the condition may progress to cirrhosis over time.²⁰

Fibrosis

Persistent inflammation of the liver in NASH may lead to fibrotic changes, such as scarring around the liver and nearby blood vessels.¹⁸ In early fibrosis, liver function is preserved,¹⁸ as liver cell death may be minimal and liver architecture is maintained.

Cirrhosis

Cirrhosis is a life-threatening, irreversible condition in which long-term inflammation has resulted in the liver shrinking and becoming scarred and lumpy,¹⁸ with extensive fibrosis surrounding nodules of regenerating liver tissue.⁶ Both the structure and function of the liver are significantly disrupted in cirrhosis.⁶ Cirrhosis is the most severe expression of NAFLD, and is associated with decompensated liver failure, portal hypertension, and HCC.^6,7,18

4. Establish Disease Severity in Adults Diagnosed with NAFLD

Once NAFLD has been diagnosed, the next steps in the clinical assessment are to evaluate disease severity and to establish whether fibrosis is present. The British Society of Gastroenterology (BSG) guidelines on the management of abnormal liver blood tests contain a helpful algorithm to determine the likelihood of fibrosis (see Figure 2).¹⁶

NG49 recommends using the Enhanced Liver Fibrosis (ELF™) Test^14,21 to identify advanced liver fibrosis in patients diagnosed with NAFLD.² The ELF Test is a proprietary blood test that combines a panel of three serum biomarkers—tissue inhibitor of matrix metalloproteinase 1, procollagen III amino-terminal peptide, and hyaluronic acid—to produce an ‘ELF Score’.^14,21 An ELF Score greater than 10.51 is associated with the presence of fibrosis in individuals with NAFLD.^2,14

However, the ELF Test may not be available in all areas. Alternative assessments of fibrosis include the Fibrosis 4 Score and the NAFLD Fibrosis Score, although these are not specifically recommended in NG49.¹⁷ These scoring systems use readily accessible patient data—such as age, BMI, and serum and other biomarkers—in simple algorithms to provide indirect estimates of fibrosis risk. Easy-to-use ‘calculators’ for these algorithms are readily available on the internet.^22,23

In secondary care, liver biopsy remains the diagnostic gold standard in the assessment of liver fibrosis and cirrhosis, but the procedure is invasive and expensive.^14,24 Although computed tomography can also be used to diagnose fatty liver, the imaging modality is a significant source of ionising radiation.¹⁴ Ultrasound scanning and magnetic resonance imaging (MRI) are alternative imaging techniques, but ultrasound findings can be normal in NAFLD; 30% steatosis is the accepted lower limit for reliable detection by ultrasound.¹⁴

5. Consider Delivery of Lifestyle and Other Interventions in Primary Care

Because of the risk factors and comorbidities associated with NAFLD, a high proportion of patients with NAFLD will already attend primary care services for regular monitoring and treatment of long-term conditions such as diabetes, obesity, and hypertension, and there is considerable overlap between the management of these conditions and the management of NAFLD.

Lifestyle Changes

Lifestyle changes are likely to be beneficial for all patients with or at risk of developing NAFLD by helping to reduce liver fat content and lower the risk of disease progression.²⁵ NG49 recommends that people with NAFLD should be given advice about the following lifestyle modifications,² which aim to reduce the risk of morbidity and mortality related to NAFLD and its comorbidities.²⁵

Physical Activity

NG49 states that there is some evidence that exercise can reduce liver fat content;^2,14 providing patients who have NAFLD with guidance on increasing their level of physical activity, such as that provided by NICE,^26,27 is therefore of value.

Diet and Weight Loss

Advice on diet and weight loss is appropriate for people with NAFLD who are overweight or obese,^2,14 and is summarised in NICE Clinical Guideline 189, Obesity: identification, assessment and management.²⁸ Weight reductions of 10% or greater can induce a near universal resolution of NASH and improvement of fibrosis by at least one stage.²⁹

Bariatric surgery may be considered for patients who fit the referral criteria,²⁸ and has been shown to reduce NAFLD pathogenesis in addition to improving metabolic parameters.³⁰

Alcohol Consumption

Alcohol use may be harmful to liver health in people who have NAFLD,³¹ and patients—particularly those with cirrhosis—should be encouraged to stay within national recommended limits.^2,14

Screening

Obesity, dyslipidaemia, and type 2 diabetes are known risk factors for NAFLD;³ conversely, NAFLD is a risk factor for type 2 diabetes, hypertension, and chronic kidney disease and, in people with type 2 diabetes, the condition is a risk factor for atrial fibrillation, myocardial infarction, ischaemic stroke, and death from cardiovascular causes.² Consideration should therefore be given to screening patients with NAFLD for other relevant conditions (see Box 2).

6. Know When to Refer an Adult Patient with NAFLD to Specialist Care

Although most advice on lifestyle changes and risk reduction measures for patients with NAFLD will be delivered in primary care, some patients will require referral to secondary or tertiary care. NICE recommends that adults with NAFLD diagnosed with advanced liver fibrosis (ELF Score greater than 10.51, or other score indicating fibrosis¹⁷) should be referred to a specialist in hepatology.² If a diagnosis of cirrhosis is established, the patient will be followed up and monitored in secondary care.³²

Referral is also covered in the British Society of Gastroenterology non-alcoholic fatty liver fibrosis algorithm (see Figure 2).¹⁶

7. Be Familiar with Pharmacological and Other Interventions for NAFLD

A number of medical treatments have been proposed for the management of NAFLD, including insulin-sensitising drugs, such as pioglitazone, and anti-inflammatory agents, such as vitamin E.¹⁴ Currently, neither pioglitazone nor vitamin E has a UK licence for use in NAFLD,² but there is some supportive clinical evidence for the use of some agents.

NICE states that, in secondary or tertiary care settings, pioglitazone or vitamin E can be considered for adults with NAFLD and advanced liver fibrosis, irrespective of whether they have diabetes.² In my opinion, it may be useful to consider the presence of NAFLD when choosing the most appropriate antidiabetic agent for type 2 diabetes in primary care, where pioglitazone may be considered.

Other approaches to the management of NAFLD have been investigated; however, NICE found no evidence to suggest that measures such as reduction in sucrose or fructose intake, omega-3 dietary supplements, or drinking caffeine in coffee protect against NAFLD progression.^2,14 There may be some evidence to support the use of antioxidants such as anthocyanins in NAFLD,³³ but these are not currently recommended by NICE.

Medical treatment may be considered for suitable patients with NAFLD to support weight loss after dietary, exercise, and behavioural approaches have been started and evaluated.²⁸

Summary

The prevalence of NAFLD is increasing, and it has become one of the most important liver diseases worldwide. Targeted diagnosis, lifestyle modification advice, and management of comorbidities are necessary to improve the clinical outcome in patients with NAFLD.

Dr Jez Thompson

GP, Leeds