Necrosis is the death of living tissue after severe cell injury. It is usually linked to disease, loss of blood supply, infection, toxins, trauma, heat, cold, or other damage that overwhelms the cell's ability to recover.
Necrosis is different from apoptosis, which is a controlled form of cell death used in normal development and tissue maintenance. Necrotic cells lose membrane integrity, swell, break down, and release their contents into surrounding tissue. That release often triggers inflammation.
Mechanism
Cell injury can begin with oxygen shortage, chemical damage, physical injury, infection, immune injury, or failure of energy production. When the damage is severe enough, ion balance fails, water enters the cell, organelles swell, and enzymes begin breaking down cell structures.
The final appearance depends on the tissue, the cause, and whether infection is present. Pathologists use the pattern of necrosis as a clue to what happened in the tissue.
Main Patterns
Common patterns include:
- Coagulative necrosis: tissue structure remains visible for a time after cell death. It is often seen after loss of blood supply in organs such as the heart, kidney, or spleen.
- Liquefactive necrosis: dead tissue is digested into a liquid or soft mass. It is common in brain infarcts and many bacterial infections.
- Caseous necrosis: dead tissue has a soft, cheese-like appearance. It is classically linked with tuberculosis and granulomatous inflammation.
- Fat necrosis: damaged fat tissue breaks down, often after pancreatitis, trauma, or breast injury.
- Fibrinoid necrosis: immune-related injury affects blood vessel walls, producing a bright pink appearance under routine staining.
- Gangrenous necrosis: a clinical term usually used for necrotic limbs or digits, especially when poor blood supply is involved. Wet gangrene includes secondary infection.
Causes
Necrosis may be caused by:
- Ischaemia, where tissue does not receive enough blood and oxygen.
- Infection by bacteria, viruses, fungi, or parasites.
- Physical trauma, burns, freezing injury, pressure injury, radiation, or electric shock.
- Chemical injury, including some poisons and drug toxicities.
- Immune-mediated injury, including some vasculitic and autoimmune processes.
The same broad process can appear in very different settings. A heart attack, a brain infarct, severe frostbite, a deep infected wound, and acute pancreatitis can all involve necrosis, but the treatment and urgency differ.
Clinical Features
Visible necrosis may look black, grey, brown, yellow, pale, or wet depending on the tissue and cause. It may be painful, numb, swollen, malodorous, or associated with loss of function. Internal necrosis is usually detected through symptoms of the underlying disease, imaging, blood tests, surgery, or microscopic examination.
Infection can make necrotic tissue more dangerous because dead tissue has poor blood supply and can support bacterial growth. In some settings, prompt debridement or restoration of blood flow is needed to prevent spread of damage.
Diagnosis and Management
Diagnosis depends on location. Clinicians may use examination, blood tests, imaging, tissue biopsy, microbiology, and surgical assessment. Pathology can confirm the pattern of necrosis and may identify infection, vascular injury, tumour necrosis, or inflammatory disease.
Management is aimed at the cause. Examples include restoring blood flow after ischaemia, treating infection, removing dead tissue, draining abscesses, controlling diabetes or vascular disease, and supporting wound healing. Necrotic tissue itself cannot be restored to normal living tissue.
See Also
References
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