Clinical manifestations, main causes, and the effects of alcohol, overnutrition, and obesity on fatty liver.

Fatty liver

Fatty liver disease refers to a condition caused by excessive fat accumulation in liver cells due to various reasons. Fatty liver disease is seriously threatening the health of Chinese people, becoming the second most common liver disease after viral hepatitis, and is widely recognized as a common cause of occult cirrhosis. Fatty liver is a common clinical phenomenon, not an independent disease. Its clinical manifestations range from asymptomatic in mild cases to rapidly progressing in severe cases. Generally speaking, fatty liver is a reversible disease; early diagnosis and timely treatment can often lead to recovery. In normal individuals, the total fat content in the liver accounts for about 5% of the liver weight, containing phospholipids, triglycerides, fatty acids, cholesterol, and cholesterol esters. A fat content exceeding 5% is considered mild fatty liver, exceeding 10% is moderate fatty liver, and exceeding 25% is severe fatty liver. When the total fat content in the liver exceeds 30%, it can only be detected by ultrasound, leading to a diagnosis of "fatty liver." In patients with fatty liver, the total fat content can reach 40%-50%, and in some cases, over 60%, mainly consisting of triglycerides and fatty acids, while phospholipids, cholesterol, and cholesterol esters only increase slightly.

Clinical manifestations of fatty liver

Fatty liver presents with diverse clinical manifestations. Mild fatty liver often has no clinical symptoms and is easily overlooked. Approximately 25% of fatty liver patients are asymptomatic. Some may only experience fatigue, and since most fatty liver patients are obese, it is even more difficult to detect mild symptoms. Therefore, fatty liver is often discovered incidentally during routine physical examinations. Moderate to severe fatty liver presents with symptoms similar to chronic hepatitis, such as loss of appetite, fatigue, nausea, vomiting, weight loss, and dull pain in the liver area or right upper quadrant. Mild hepatomegaly may be tender to the touch, with a slightly firm texture, blunt edges, and a smooth surface. A few patients may also have splenomegaly and palmar erythema. When excessive fat deposits in the liver, the liver capsule can expand, and the liver ligaments can be stretched, causing severe pain or tenderness in the right upper quadrant, fever, and leukocytosis, which can easily be misdiagnosed as an acute abdomen, leading to laparotomy. When fat vesicles rupture, fat particles can enter the bloodstream, causing fat embolism in the brain and lungs, resulting in sudden death. When fatty accumulation in hepatocytes compresses the hepatic sinusoids or small bile ducts, portal venous blood flow and bile excretion are obstructed, leading to portal hypertension and cholestasis. In cases of acute chemical or drug poisoning, the clinical manifestations often present as acute or subacute liver necrosis, easily confused with severe hepatitis. Furthermore, patients with fatty liver often exhibit peripheral neuritis changes such as glossitis, angular cheilitis, skin ecchymosis, numbness in the extremities, and paresthesia. A few patients may also experience gastrointestinal bleeding, gingival bleeding, and epistaxis. Severe fatty liver patients may present with ascites and lower extremity edema, electrolyte imbalances such as hyponatremia and hypokalemia. Due to the diverse presentation of fatty liver, liver biopsy is often performed for definitive diagnosis when diagnosis is difficult.

The main causes of fatty liver

Fatty liver is not a disease in itself, but a metabolic disorder caused by excessive fat accumulation in liver cells due to various factors or diseases. It is a transitional stage between liver fibrosis and cirrhosis. Long-term research has identified six main causes of fatty liver:

1. Alcohol

Alcohol is the most common cause of fatty liver disease. In Chinese culture, relationships are often fostered through drinking, and long-term alcohol consumption leads to alcohol poisoning, which has a direct toxic effect on the metabolism of triglycerides in the liver, reducing fat oxidation and causing excessive fat accumulation. Nearly 60% of chronic alcoholics develop fatty liver disease, and 20%–30% will eventually develop cirrhosis and liver cancer.

2. Overnutrition

A long-term diet high in meat, fried foods, and sweets leads to excessive fat synthesis in the liver. When the fat content of the diet is too high, it exceeds the liver's processing capacity, increasing the liver's burden, interfering with fat metabolism, disrupting the liver's input-output balance, and causing fat to accumulate in the liver, resulting in fatty liver disease.

3. Obesity

Data shows that among 80 patients with fatty liver, 27 were obese (33.8%); and among 109 obese patients with hyperlipidemia, 56 (51%) were diagnosed with fatty liver. Both groups were significantly higher than the control group (12.5% ​​and 20.6%), indicating a higher incidence of fatty liver in obese individuals or those with hyperlipidemia, which warrants attention. The underlying reason for obesity-related fatty liver is the transfer of fatty acids from the body to the liver. Studies suggest that a normal liver contains approximately 5% fat by wet weight. When there is excessive body fat, and the rate at which fat and fatty acids are introduced into the liver and the rate at which triglycerides are synthesized in the liver exceeds the rate at which very low-density lipoprotein (VLDL) is formed and secreted into the bloodstream, triglycerides accumulate in the liver. If this exceeds 10% of the liver's wet weight, fatty liver occurs. Similarly, hyperlipidemia can further promote fat accumulation in the liver, leading to fatty liver; the incidence of fatty liver is even higher in obese individuals with hyperlipidemia. The clinical manifestations of fatty liver disease are nonspecific and are often misdiagnosed as hepatitis or cholecystitis. Ultrasound examination can make a more accurate diagnosis and reduce the misdiagnosis rate. Therefore, anyone who is obese or obese with hyperlipidemia and presents with symptoms such as right upper quadrant discomfort, abdominal distension, poor appetite, nausea and vomiting, and whose physical examination reveals hepatomegaly, mild to moderate liver texture, regular margins, and abnormal liver function, should undergo an ultrasound examination promptly.

4. Diabetes

About half of type 2 diabetes patients also have fatty liver. This is because glucose and fatty acids in the body of diabetic patients cannot be used well, and lipoprotein synthesis is also impaired. Most of the glucose and fatty acids are converted into fat in the liver, which eventually leads to the accumulation of fat in the liver and causes fatty liver.

5. Hyperlipidemia

Fatty substances in the blood are collectively referred to as blood lipids. Lipids in blood plasma include cholesterol, triglycerides, and phospholipids, which exist in the blood bound to different proteins in the form of "lipoproteins." Hyperlipidemia refers to excessively high levels of cholesterol and triglycerides in the blood, or excessively low levels of high-density lipoprotein cholesterol. When the amount of lipids in the blood exceeds the liver's processing capacity, fat accumulates in the liver, leading to fatty liver disease.

6. Malnutrition

Some might wonder, if overnutrition causes fatty liver, why does malnutrition also cause it? The answer is quite simple. Overnutrition is like having too much raw material, while malnutrition is like having too little auxiliary material in the processing, both failing to produce a qualified product. When malnourished, protein deficiency leads to reduced synthesis of very low-density lipoprotein (VLDL), which impairs the liver's transport of triglycerides, causing fat to accumulate in the liver and resulting in fatty liver.

If you have any of the above-mentioned risk factors or unhealthy lifestyle habits that can lead to fatty liver, you must be vigilant, as fat may be quietly invading your liver cells!