Steatotic liver disease (SLD) is a common condition characterized by the accumulation of excess fat within liver cells. A liver is considered steatotic if more than 5% of its weight consists of fat. This condition affects a significant portion of the global population, with metabolic dysfunction-associated steatotic liver disease (MASLD) alone estimated to affect over 30% of people worldwide, making it one of the most widespread chronic diseases.
Primary Causes of Liver Fat Accumulation
The buildup of fat in the liver primarily stems from two distinct pathways. Metabolic dysfunction-associated steatotic liver disease (MASLD) accounts for the majority of cases. This condition is closely linked to factors such as obesity, type 2 diabetes, insulin resistance, and elevated cholesterol or triglycerides. MASLD was previously known as nonalcoholic fatty liver disease (NAFLD), with the name updated to reflect its metabolic origins.
Another significant cause is alcohol-associated liver disease (ALD), resulting from excessive and prolonged alcohol consumption. Alcohol processing can damage liver cells, and continuous heavy drinking impairs the liver’s ability to regenerate. A category called MetALD applies to individuals with MASLD risk factors who also consume alcohol beyond certain thresholds, representing an overlap between these two primary causes.
The Progression from Fat to Fibrosis
If left unmanaged, steatotic liver disease can advance through several stages. The initial stage is simple steatosis, where fat is present in liver cells without significant inflammation or cellular injury. The liver typically functions normally, with symptoms usually absent.
The disease may then progress to steatohepatitis, where fat accumulation is accompanied by inflammation and damage to liver cells. This inflammatory form is termed metabolic dysfunction-associated steatohepatitis (MASH) for MASLD, and alcoholic steatohepatitis (ASH) for ALD. Chronic inflammation in MASH or ASH can lead to the formation of scar tissue, a process known as fibrosis, as the liver attempts to repair damaged cells.
Over time, if inflammation and scarring continue, the liver can develop cirrhosis. This is characterized by widespread, irreversible scarring that severely impairs liver function. Cirrhosis can lead to serious complications such as liver failure and an increased risk of liver cancer. While the progression rate varies, studies suggest it can take approximately three years on average for the disease to advance from one stage to the next.
How Steatotic Liver Disease Is Diagnosed
Steatotic liver disease often presents without noticeable symptoms in its early stages, leading to incidental discovery during medical evaluations for other conditions. A first indication may arise from routine blood tests, such as liver function tests, which measure enzymes like alanine aminotransferase (ALT) and aspartate aminotransferase (AST). Elevated levels of these enzymes can signal liver injury, prompting further investigation.
Imaging techniques are commonly used to visualize fat in the liver. An abdominal ultrasound is a non-invasive method that can detect liver steatosis. Specialized non-invasive tests like transient elastography (FibroScan) assess liver stiffness, correlating with the amount of fibrosis present. This test helps determine the extent of scarring without requiring an invasive procedure.
In certain cases, a liver biopsy, which involves taking a small tissue sample for microscopic examination, may be performed. This procedure is considered the most definitive method for confirming diagnosis and precisely staging the disease, revealing the presence of fat, inflammation, and fibrosis. However, due to its invasive nature, a biopsy is not always necessary, especially with advancements in non-invasive assessment tools.
Managing Steatotic Liver Disease
Managing steatotic liver disease largely depends on its underlying cause, with lifestyle modifications forming the cornerstone of treatment. For metabolic dysfunction-associated steatotic liver disease (MASLD), gradual weight loss is a primary intervention; losing 7-10% of body weight can reduce liver fat and improve inflammation and scarring. Adopting a healthy eating pattern, such as the Mediterranean diet, which emphasizes fruits, vegetables, lean proteins, and healthy fats, is recommended.
Regular physical activity is another component of MASLD management, with at least 150 minutes of moderate-intensity exercise per week suggested. Controlling associated metabolic conditions like type 2 diabetes, high cholesterol, and high blood pressure is also important for managing MASLD.
For alcohol-associated liver disease (ALD), the primary treatment is complete and sustained abstinence from alcohol. Stopping alcohol consumption can significantly improve the liver’s condition and reduce the risk of further damage and complications. While lifestyle changes are the main approach, ongoing research explores potential medications for MASLD, as no specific drugs are currently approved to directly treat the condition.