Dry gangrene

Localized tissue die-off or necrosis associated with inadequate blood supply causes a condition that is defined as dry gangrene, and most cases are dry gangrene of the lower extremities. [1]

Epidemiology

According to the CDC (Centers for Disease Control, USA), ischemic/dry gangrene is most commonly seen in advanced peripheral arterial disease, which occurs in 1% of Americans over 50 years of age and 2.5% of people over 70 years of age.

Dry and wet gangrene of the foot in patients with diabetes leads to amputation of part of the limb in more than 80% of cases. For example, from 2010 to 2019, the annual number of amputations in diabetics in Poland increased by one and a half times to almost 7.8 thousand cases.

Causes of the dry gangrene

The key causes leading to ischemic/dry gangrene are vascular diseases in which the soft tissues are starved of oxygen due to obstruction of distal peripheral vessels and poor blood circulation. Specialists include chronic peripheral arterial disease:

• Lower extremity vascular atherosclerosis;
• diabetic angiopathy;
• Lower extremity obliterative diseases, such as thrombangiitis - obliterative endarteritis or Buerger's disease;
• Systemic vasculitis in the form of polyarteritis nodosa;
• thromboembolic disease with blockage of peripheral small vessels by a detached thrombus.

Also, dry gangrene of the toes of the foot, heel, fingers of the hand can be the result of frostbite of the 3-4th degree.

In addition to dry gangrene, there are types gangrene, such as wet and gas gangrene, the development of which is mainly associated with infected wounds. [2]

See also - Gangrene of the leg

Risk factors

The highest risk of developing dry gangrene is with diabetes mellitus and atherosclerosis affecting the blood vessels in the legs. In diabetic patients, hyperglycemia (high blood sugar), which damages blood vessels, causes blood flow to the lower extremities to slow or block. And dry gangrene in atherosclerosis is provoked by narrowing of their lumen by cholesterol deposits with deterioration of peripheral blood circulation.

Other risk factors include smoking, which can lead to obliterative thrombangiitis (with blood clots forming in small and medium-sized vessels and progressive ischemia), and obesity, in which it is quite common to impair leg circulation.

Pathogenesis

If at gas and wet gangrene mechanism of tissue death is caused by the action of bacterial infection with rapid development of inflammatory process, the pathogenesis of dry gangrene is different.

Dry gangrene and necrosis in it have ischemic origin, associated with local cessation of blood circulation and tissue hypoxia - lack of oxygen. And destruction of oxygen-deprived tissue occurs not by proteolysis (protein cleavage) of damaged cells, but by irreversible denaturation of proteins and tissue lysosomal enzymes. That is, necrotic tissues in dry gangrene are the result of local dehydration of soft tissues and coagulation of protein molecules forming their cells.

Since local blood circulation in the foot or fingers is blocked and there is no oxygen supply with blood, pathogenic bacteria cannot survive, and the putrefaction provoked by them does not occur. For this reason, dry gangrene is most often aseptic. The practical absence of decay of dead tissue and absorption of its toxic products also explains that intoxication in dry gangrene, as a rule, is not observed.

Symptoms of the dry gangrene

In ischemic gangrene, the first signs may be localized intense aching pain. In addition, in the first stage of dry gangrene, the affected area is pale and the skin becomes cold and numb.

Over time, there is redness and lividity of the skin, which in the place of necrosis shrivels and shrivels, and the volume of subcutaneous tissue is significantly reduced.

In this case, the gangrenous area spreads slowly, covered with greenish-brown or black scab. Reaching the areas where blood can still flow through anastomoses, a line of demarcation between the damaged tissue and healthy tissue is formed - the demarcation line in dry gangrene.

Further, the limb loses sensation, but pain in dry gangrene may be more prolonged, because the endings of peripheral nerves in the damaged tissues die off not immediately.

In the later stages, dead tissue may flake off, non-healing ulcers may occur in dry gangrene, and if the affected tissue is not removed, eventually spontaneous rejection of non-viable tissue from viable tissue occurs as a result of so-called autoamputation. [3]

Dry gangrene in diabetes develops and manifests itself in the same way, more details in the publication - Dry and wet gangrene of the toes in diabetes mellitus.

Complications and consequences

If ischemic/dry gangrene is not treated, it can progress, causing negative consequences, but they are not as life-threatening as in other types of this pathology.

The main complication concerns the transformation of dry gangrene, and the main question (to which doctors give an affirmative answer) is whether dry gangrene can turn into wet gangrene? Indeed, such a complication is possible when the necrosis area is damaged, its bacterial contamination - infection occurs.

And sepsis in dry gangrene is possible only in cases of its infection during transformation into wet gangrene.

Diagnostics of the dry gangrene

How is dry gangrene diagnosed? Collect anamnesis and physical examination of the affected part; the examination data and description of the tissue condition are formalized in writing, determining the local status of dry gangrene.

Laboratory tests include blood tests: general, biochemical, for glucose and cholesterol levels, C-reactive protein, coagulation factors and dimer D.

Instrumental diagnostics is also performed: angiography and ultrasound of vessels, radioisotope scintigraphy, laser Doppler flowmetry and ultrasound Doppler sphygmomanometry (giving an idea of the state of blood flow in the vessels of the extremities). [4]

Differential diagnosis

Differential diagnosis excludes other types of gangrene, gangrenous pyoderma, and compartment syndrome.

Treatment of the dry gangrene

Tissues damaged by gangrene cannot be saved. But treatment should help prevent its complications and relieve patients' condition.

And to improve the quality of life of patients, early surgical intervention - surgery for dry gangrene - should be chosen.

The indications for surgery in dry gangrene - its type and volume - depend on the state of blood flow and perfusion of viable tissue around the focus of necrosis, the presence of occlusion or thrombus in blood vessels, as well as the levels of perfusion pressure and vascular resistance of the skin.

If the main blood flow in the distal parts of the limb is preserved, it can be treated without amputation: necrectomy, i.e. Excision of all dead tissue followed by reconstructive surgery (skin grafting) with restoration of blood flow by bypass or angioplasty (balloon stenting).

However, in cases of extensive and deeply penetrating necrosis with inability to restore blood flow with irreversible limb ischemia, amputation of dry gangrene is unavoidable. The level of amputation is determined by examination and clinical findings, and prior revascularization and reperfusion of the affected limb may be required to minimize its extent and improve healing.

More details on surgical treatment techniques in the publication - Gangrene of the foot

Sessions hyperbaric oxygenation. Can help increase oxygen levels in the blood and speed healing.

Antibiotics may be used for dry gangrene (Ciprofloxacin, Amoxicillin, Doxycycline, Meropenem, Vancomycin) - to prevent infection of remaining viable tissue; analgesics - analgesics; anticoagulants (Heparin, Fenindione); antiaggregants (Aspirin, Clopidogrel, Pentoxifylline). [5]

Prevention

Dry gangrene usually develops in the distal extremities in poorly controlled diabetes and peripheral arterial disease, so preventive measures should focus on normalizing blood sugar levels and controlling cholesterol levels.

You should also quit smoking and get rid of excess weight. [6]

Forecast

The prognosis of ischemic/dry gangrene depends on the extent of necrosis, the underlying cause and the appropriate treatment. If the loss of tissue due to necrectomy is negligible, patients recover with minimal loss of limb function.