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# Alcoholic liver disease (biochemistry)

Alcohol damages the liver in stages: fatty liver, alcoholic hepatitis and cirrhosis; excess NADH and acetaldehyde are the cause.

Updated 2026-11-01

## Structures involved

Tap one to see what it is and open it in 3D.

- [Liver](https://durgical.com/en/anatomy/liver/)
- [Hepatic veins](https://durgical.com/en/anatomy/hepatic-veins/)
- [Spleen](https://durgical.com/en/anatomy/spleen/)
- [Esophagus](https://durgical.com/en/anatomy/esophagus-abdominal-part/)
- [Pancreas](https://durgical.com/en/anatomy/pancreas/)
- [Stomach](https://durgical.com/en/anatomy/stomach/)

## In biochemistry

- [Alcohol dehydrogenase (ADH)](https://durgical.com/en/biochemistry/enzymes/alcohol-dehydrogenase/)
- [Aldehyde dehydrogenase 2 (ALDH2)](https://durgical.com/en/biochemistry/enzymes/aldehyde-dehydrogenase-2/)
- [Cytochrome P450 2E1 (CYP2E1, MEOS)](https://durgical.com/en/biochemistry/enzymes/cytochrome-p450-2e1/)
- [Ethanol](https://durgical.com/en/biochemistry/molecules/ethanol/)
- [Acetaldehyde](https://durgical.com/en/biochemistry/molecules/acetaldehyde/)
- [Acetaminophen metabolism and NAPQI](https://durgical.com/en/biochemistry/topics/acetaminophen-metabolism-and-napqi/)

## In physiology

- [Functions of the liver](https://durgical.com/en/physiology/functions-of-the-liver/)

## Why it happens

- [Alcohol: how it injures the liver, brain, heart and fetus](https://durgical.com/en/general-pathology/alcohol-how-it-injures-the-liver-brain-heart-and-fetus/)
- [Fatty change (steatosis)](https://durgical.com/en/general-pathology/fatty-change/)
- [Liver regeneration](https://durgical.com/en/general-pathology/liver-regeneration/)
- [Intracellular accumulations: cholesterol, proteins, hyaline, glycogen](https://durgical.com/en/general-pathology/intracellular-accumulations-cholesterol-proteins-hyaline-glycogen/)
- [Fibrosis in organs: TGF-β and the myofibroblast](https://durgical.com/en/general-pathology/fibrosis-in-organs-tgf-and-the-myofibroblast/)
- [Chemical (toxic) cell injury: direct and after metabolism](https://durgical.com/en/general-pathology/chemical-cell-injury-direct-and-after-metabolism/)

## What it is

A spectrum of liver injury from prolonged heavy drinking, from reversible fatty liver to alcoholic hepatitis and cirrhosis.

## Who gets it

WHO estimates that alcohol causes millions of deaths a year and that cirrhosis is one of its main consequences. In Colombia and Latin America heavy episodic drinking is common and alcoholic liver disease is an important cause of cirrhosis.

## Causes

- Prolonged heavy alcohol consumption
- Risk depends on the cumulative amount and pattern, not the type of drink

## Risk factors

- Female sex (more damage with less alcohol)
- Obesity and metabolic syndrome
- Hepatitis B or C
- Genetic variants such as PNPLA3
- Malnutrition
- Smoking

## Pathophysiology

Alcohol dehydrogenase and ALDH2 make a lot of NADH; the high NADH/NAD⁺ ratio slows β-oxidation and the Krebs cycle and supplies glycerol-3-phosphate, so fatty acids are esterified into triglycerides: fatty liver (macrovesicular steatosis). Export in VLDL cannot keep up. Acetaldehyde forms protein adducts (damaging microtubules and protein secretion, so the hepatocyte swells) and acts as a neoantigen. Induced CYP2E1 generates free radicals and lipid peroxidation, with less glutathione. Gut endotoxin activates Kupffer cells (TNF-α): neutrophilic inflammation and Mallory–Denk bodies (alcoholic hepatitis). Activated stellate cells lay down collagen, first around the central vein: fibrosis and finally cirrhosis.

## Classification

- Alcoholic fatty liver (reversible with abstinence)
- Alcoholic hepatitis (acute, can be severe)
- Alcoholic fibrosis and cirrhosis

## Symptoms and signs

- None in fatty liver, or an enlarged liver and right upper quadrant discomfort
- Jaundice, fever and a tender liver (alcoholic hepatitis)
- Fatigue, weight and muscle loss
- Ascites, spider naevi and palmar erythema
- Confusion (hepatic encephalopathy)

## Red flags

- Vomiting blood or black stools
- Confusion or drowsiness
- Rapid-onset jaundice with fever
- Distended, painful [abdomen](https://durgical.com/en/anatomy/region/abdomen/) with fever (spontaneous bacterial peritonitis)

## Diagnosis

**Clinical**
Drinking history (questionnaires such as AUDIT), signs of chronic [liver](https://durgical.com/en/anatomy/liver/) disease and exclusion of other causes.

**Tests**
Transaminases with AST/ALT above 2 and AST rarely above 300–400 (ALT needs pyridoxal phosphate, scarce in drinkers); high GGT; high MCV; bilirubin, albumin and INR for function; severity scores (Maddrey, MELD); viral hepatitis markers.

**Imaging**
Ultrasound shows a bright liver (steatosis), nodules, a large [spleen](https://durgical.com/en/anatomy/spleen/) or ascites; elastography measures stiffness (fibrosis); endoscopy looks for varices.

## Treatment

**Lifestyle**
Complete abstinence from alcohol: what most changes the outcome at every stage.

**Medical**
Nutritional support and replacement of thiamine, folate and other vitamins.

**Medical**
Severe alcoholic hepatitis: corticosteroids in selected cases.

**Medical**
Treatment of dependence: psychotherapy and drugs such as naltrexone, acamprosate or disulfiram.

**Surgical**
Liver transplantation for decompensated cirrhosis, after a period of abstinence and assessment.

## Complications

- Cirrhosis and portal hypertension
- Oesophageal varices and gastrointestinal bleeding
- Ascites and spontaneous bacterial peritonitis
- Hepatic encephalopathy
- Hepatocellular carcinoma
- Hepatorenal syndrome

## Prognosis

Fatty liver reverses within weeks without alcohol; severe alcoholic hepatitis has high short-term mortality; in cirrhosis, abstinence greatly improves survival.

## Prevention

- Public health alcohol policies (price, availability, advertising)
- Early detection of risky drinking
- Hepatitis B vaccination

## Test yourself

Think of the answer, then tap the question to see it.

## Why does alcohol cause fatty liver?

Excess NADH slows β-oxidation and supplies glycerol-3-phosphate: fatty acids pile up as triglycerides.

## Why is the AST/ALT ratio usually above 2 in alcoholic hepatitis?

Drinkers lack pyridoxal phosphate, which ALT needs more, and alcohol damages mitochondria, which are rich in AST.

## Which hepatocyte inclusions are typical of alcoholic hepatitis?

Mallory–Denk bodies: aggregated keratin filaments.

## Which measure most changes the outcome at every stage?

Complete abstinence from alcohol.

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## Related conditions

- [Acetaminophen toxicity](https://durgical.com/en/conditions/acetaminophen-toxicity/)
- [Disulfiram–ethanol reaction](https://durgical.com/en/conditions/disulfiram-ethanol-reaction/)
- [Cirrhosis](https://durgical.com/en/conditions/cirrhosis/)
- [Portal hypertension](https://durgical.com/en/conditions/portal-hypertension/)
- [Hepatocellular carcinoma](https://durgical.com/en/conditions/hepatocellular-carcinoma/)
- [Upper gastrointestinal bleeding](https://durgical.com/en/conditions/upper-gastrointestinal-bleeding/)
- [Acute pancreatitis](https://durgical.com/en/conditions/acute-pancreatitis/)
- [Chronic pancreatitis](https://durgical.com/en/conditions/chronic-pancreatitis/)
- [Wernicke encephalopathy (thiamine deficiency)](https://durgical.com/en/conditions/wernicke-encephalopathy/)
- [Lactic acidosis](https://durgical.com/en/conditions/lactic-acidosis/)

Educational information, not medical advice. For any symptom, see a health professional.

Sources: [Alcoholic liver disease: MedlinePlus Medical Encyclopedia](https://medlineplus.gov/ency/article/000281.htm) (MedlinePlus, US National Library of Medicine, 2026); [Alcohol](https://www.who.int/news-room/fact-sheets/detail/alcohol) (World Health Organization, 2026); Textbook of Biochemistry for Medical Students, 6th ed. (Jaypee Brothers Medical Publishers (Vasudevan DM, Sreekumari S, Vaidyanathan K), 2011).

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Source: https://durgical.com/en/conditions/alcoholic-liver-disease/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/conditions/alcoholic-liver-disease/