Metabolic dysfunction-associated steatotic liver disease (MASLD), is the accumulation of excess fat in hepatocytes in individuals with at least one cardiometabolic risk factor (e.g., hypertension, impaired glucose tolerance) in the absence of an alternative cause (e.g., heavy alcohol use, drug-induced liver injury). MASLD was previously known as nonalcoholic fatty liver disease. It is highly prevalent in patients with type 2 diabetes mellitus (T2DM), obesity, and/or metabolic syndrome. MASLD is usually asymptomatic and is a diagnosis of exclusion. Diagnostic findings may include hepatic steatosis on imaging and elevated transaminases. Patients with MASLD should be assessed for advanced liver fibrosis using a combination of laboratory-based noninvasive testing, such as the FIB-4, and vibration-controlled transient elastography. Metabolic dysfunction-associated steatohepatitis (MASH) is a subtype of MASLD characterized by chronic hepatocyte inflammation and damage due to lipid accumulation and is associated with a higher risk of progression to liver fibrosis and cirrhosis. MASH was previously known as nonalcoholic steatohepatitis (NASH). Biopsy may be indicated if there is diagnostic uncertainty. Management focuses on the prevention and treatment of associated metabolic conditions.
- Metabolic dysfunction-associated steatotic liver disease (MASLD) 
- Metabolic dysfunction-associated steatohepatitis (MASH) 
MASLD is a multifactorial disease with metabolic and genetic components. 
- Cardiometabolic risk factors: any 
- Genetic factors: Individuals with a first-degree relative with MASH-related cirrhosis are at increased risk. 
- MASLD: excess energy supply → insulin resistance →; ↑ circulating dietary sugars and free fatty acids → ↑ hepatic free fatty acids → ↑ triglyceride synthesis → hepatic steatosis 
- MASH cirrhosis: oxidative stress, endoplasmic reticulum stress, and inflammasome activation → inflammation and hepatocyte stress and/or death → fibrogenesis → cirrhosis 
- MASLD is a diagnosis of exclusion.
- Consider MASLD in patients with any cardiometabolic risk factor and either:
- Rule out alternative causes of hepatic steatosis based on patient history (e.g., current or prior heavy alcohol use), laboratory studies, and imaging.
- Evaluate all patients for liver fibrosis, e.g., by calculating a FIB-4 score.
- Consider referral for liver biopsy if the diagnosis remains uncertain.
It is only possible to distinguish MASLD from patient history. using
- Liver chemistries
- CBC: normal or ↓ platelet count
Tests to rule out alternative diagnoses
- All patients: serology for hepatitis B and hepatitis C
- Additional studies based on clinical suspicion, e.g.: 
Abdominal ultrasound 
- May be used to confirm hepatic steatosis and/or exclude alternative diagnoses 
- Often nondiagnostic in patients with mild steatosis
- Supportive finding: ↑ liver echogenicity
- Noninvasive tests
- Liver stiffness measurement 
Liver biopsy 
- Indication: diagnostic uncertainty after noninvasive testing and imaging
- Supportive findings for MASLD: hepatocellular lipid accumulation, mostly macrovesicular
- Additional findings in MASH
- Currently, there are no curative treatments for MASLD.
- Management is focused on the prevention and treatment of associated metabolic conditions.
- Provide multidisciplinary care (e.g., involve the primary care physician, endocrinologist, hepatologist, and dietitian).
- Refer to hepatology for:
Nonpharmacological management 
- Lifestyle changes
- Management of associated metabolic conditions
Pharmacological management 
- Alcohol-associated liver disease
- Drug-induced liver injury due to:
- Viral hepatitis
- Inherited or autoimmune disorders
- Reye syndrome
- Pregnancy-related conditions
- Nutrition-related conditions
The differential diagnoses listed here are not exhaustive.