Clinico-anatomical types of necrosis: gangrene, decubitus, sequestration
Clinical forms of necrosis
Gangrene
Gangrene is the product of insufficient blood supply (ischemia) leading to hypoxia. It is highest risks in those with Diabetes and long-term smoking. There are four types of gangrene:
- Wet gangrene
- Liquefactive necrosis
- Thriving bacteria in tissue
- Has poor prognosis due to sepsis
- Develops as product of blocked venous drainage (or rarely blocked arterial supply)
- Skin appears soft, putrid, rotten and dark
- Dry gangrene
- Coagulative necrosis
- Often due to peripheral artery disease, but can be acute limb ischemia
- No infection
- Skin appears black, with sharp line of demarcation
- Noma (wet gangrene of exhausted children in cheeks and lips)
- Rapidly progressive, found in mouth or genitals of children
- Develops in the mucous membranes
- Product of bacterial pathogens (Fusobacterium necrophorum and Prevotella intermedia)
- High mortality
- Gas gangrene (caused by gas forming gram +ve anaerobes)
- Caused by bacterial infection that produces gas within tissue (e.g Clostridium)
- Infection spreads rapidly
- Can cause necrosis, gas production and sepsis, progression to toxemia and shock is rapid.
Dry gangrene of a toe: the dead tissue is black, dry and shrivelled (mummified), with a clear line of demarcation from the living foot.
Image: “Dry gangrene 4th toe” by unknown author, CC BY-SA 3.0, via Wikimedia Commons.
Examples: dry gangrene of the toes in a diabetic or a smoker with peripheral arterial disease; wet gangrene of a strangulated loop of small bowel, of the appendix or of a diabetic foot that becomes infected; gas gangrene of a contaminated deep wound (Clostridium perfringens), with crepitus under the skin.
Decubitus ulcer (pressure sore)
This is damage to the skin and/or tissue overlying a bony prominence as a result of consistent pressure and/or friction. Common sites include:
- Sacrum
- Coccyx
- Heels
- And hips
The consistent pressure to these sites restricts the blood flow to soft tissue, reducing tissue tolerance for skin pressure and increasing risk of ulceration.
Such ulcers are more common in the elderly and bedridden.