Metabolic dysfunction-associated steatohepatitis (MASH) is a disease that occurs when steatosis (a buildup of fat) in the liver causes liver inflammation and damage.
MASH is an advanced stage of metabolic dysfunction-associated steatotic liver disease (MASLD), formerly known as nonalcoholic fatty liver disease (NAFLD). MASH can progress to more severe conditions, such as liver cirrhosis (scarring), liver failure, and cancer.
A gastroenterologist (a doctor specializing in the digestive system) or a hepatologist (a doctor specializing in liver diseases) usually diagnoses MASH.
The first steps in diagnosis typically involve a physical exam and questions about your medical history.
To help rule out other possible conditions, your healthcare provider may ask about your alcohol use, medications, lifestyle habits, and symptoms. MASH doesn’t always cause symptoms in its early stages, but common signs can include fatigue, abdominal pain, loss of appetite, unintended weight loss, bloating, and thirst.
Healthcare providers also look for advanced MASH symptoms or complications, including:
- Nausea
- Vomiting
- Itchy skin
- Jaundice, yellowing of the skin or whites of your eyes
- Ascites, swelling in your abdomen
- Swelling in your legs or feet
- Confusion, drowsiness, and memory difficulties
Your healthcare provider may also screen you for common factors that increase the risk of MASH. These include:
- Obesity
- High cholesterol
- Hypertension (high blood pressure)
- Type 2 diabetes
- Metabolic syndrome
By testing blood samples, healthcare providers can identify signs of MASH. Your provider may run blood tests such as:
- Liver function tests: These tests look for certain enzymes (special proteins) in your blood that give more information about your liver health. Elevated levels of the liver enzymes alanine aminotransferase (ALT) and aspartate aminotransferase (AST) are common signs of MASH.
- Fibrosis tests: Fibrosis is the development of scar tissue. These blood tests detect markers of damage and scarring in your liver, sometimes using a specialized panel called FibroTest or FibroSure.
- Lipid panel: This set of tests measures the level of cholesterol and triglycerides in your blood. High levels may be a sign of MASH.
Several imaging tests can help healthcare providers screen for signs of MASH. These include:
- Abdominal ultrasound: This imaging technique uses sound waves to produce images of your liver that help your healthcare provider detect signs of inflammation or scarring.
- Computerized tomography (CT) scan: This type of X-ray creates 3D images of the liver for a more detailed assessment of the tissue.
- Acoustic radiation force impulses (ARFI) scan: This test uses directed sound waves to check the level of stiffness in your liver tissue. Stiffness can indicate scarring or damage.
- Transient elastography: Also called FibroScan, this liver stiffness test uses a specialized ultrasound technique that measures levels of fat and scarring in the liver.
- Magnetic resonance elastography (MRE) scan: MRE is a form of magnetic resonance imaging (MRI) and ultrasound imaging that creates highly detailed 3D images of liver tissue.
To confirm a MASH diagnosis suggested by the other tests, your healthcare provider will need to do a liver biopsy. A biopsy can also help your provider assess how much liver damage you have.
During a liver biopsy, your healthcare provider typically inserts a specialized needle into your liver through your abdomen to collect a small sample of tissue. They sometimes use a laparoscope—an adjustable tube with a camera—to collect the biopsy sample.
After collecting the sample, your provider sends it to a laboratory. Specialists called pathologists will examine the tissue under a microscope and perform other tests to measure the level of scarring and fibrosis.
After evaluating your tests and biopsy, your healthcare provider will likely stage the disease. MASH may occur in four stages:
- Stage 1: This is the mildest stage of MASH, with very little fibrosis or scarring
- Stage 2: This involves more moderate scarring
- Stage 3: In this stage, the fibrosis and scarring are severe
- Stage 4: The final stage of MASH is cirrhosis, which involves significant scarring and permanent damage to the liver
Your healthcare provider may want to rule out other potential causes of symptoms before confirming a MASH diagnosis. They may also screen for co-occurring conditions like heart disease or type 2 diabetes.
Other conditions that can cause liver fibrosis and scarring symptoms include:
- Alcoholic liver disease: This is a similar condition, but the liver damage is due to prolonged, excessive drinking. Blood tests, imaging tests, and biopsy—as well as an assessment of your drinking history—help healthcare providers detect alcoholic liver disease.
- Hepatitis C: This is a viral liver infection that causes inflammation. It spreads through sexual contact or needle sharing, or between parent and baby during pregnancy. Along with liver function tests, healthcare providers rely on RNA tests, biopsy, and other tests to diagnose hepatitis C.
- Medication side effects: Some medications may cause MASH-like liver problems as a side effect. These include the heart medication Nexterone (amiodarone), the cancer drugs Otrexup (methotrexate) and Soltamox (tamoxifen), steroid hormones called glucocorticoids, the antiseizure drug Depakote (valproate), and some medications for HIV/AIDS.
- Reye syndrome: This rare disease increases pressure in your brain and causes fat buildup in your liver following a viral infection such as the flu. It primarily occurs in children. A healthcare provider may use liver function tests, other blood tests, and a spinal tap (testing a sample of spinal fluid) to help detect this condition.
Metabolic dysfunction-associated steatohepatitis (MASH) is a disease in which fat and scar tissue develop in your liver.
It often causes no symptoms in its early stages, so healthcare providers look at liver abnormalities using blood tests, imaging methods, and biopsy.
They also may do testing to rule out alcoholic liver disease, hepatitis C, and other potential causes of your symptoms.
