Gangrene

Gangrene is the death of a part of the body inside a living organism. Tissue dies when blood, and with it oxygen, stops reaching it: with nothing to live on, cells last hours, at most a day. There are two causes and they often go hand in hand: a blocked vessel and an infection that destroys tissue in its own right. It usually begins furthest from the heart — the toes, the foot, less often the fingers — but it also happens inside: in a loop of bowel, in the gallbladder, in the appendix. Here delay is not measured in days: between being in time and being too late there can be a matter of hours.

What it looks like and what the person feels

The picture depends on the cause, but the shared features are recognisable:

• the skin changes colour: pale or red at first, then purple, blue, brown and finally black; on brown and black skin this is harder to spot, so swelling, pain and skin temperature are the guide;
• the area either loses sensation entirely or, on the contrary, hurts unbearably;
• swelling appears and the skin becomes tight and shiny;
• blisters and ulcers form, oozing a cloudy, foul-smelling fluid;
• the border between dead and living tissue grows sharper, and the dead part dries and shrivels;
• if gas has collected under the skin, the limb feels heavy and crackles under pressure, like squeezing snow.

When infection joins in, general signs follow: a temperature of 38 °C or above, shivering, weakness, confusion. Worth remembering as well is an early sign of a blocked artery: the pain comes at night, at rest, and the person hangs the leg out of bed because that eases it.

Not all gangrene is the same

• Dry. Blood is not getting through, but there are no microbes. The affected part slowly mummifies: it darkens, dries and becomes demarcated. It takes weeks and goes with diabetes and hardened arteries.
• Wet. Bacteria have joined the failing blood supply. The tissue does not dry out but spreads: swelling, blisters, a foul smell and rapid deterioration. It is many times more dangerous than the dry form.
• Gas gangrene. Bacteria that live without oxygen get into a deep wound and give off gas and toxins. Tissue is destroyed before your eyes, it crackles under the skin and the person goes downhill within hours.
• Necrotising fasciitis. The infection travels not through the skin but through the layers beneath it, and spreads faster than it looks from outside. Its main sign is pain out of all proportion to what can be seen.
• Internal. The blood supply to an organ in the abdomen is cut off. Nothing shows on the outside, but there is severe pain, vomiting and distension, and the person looks far worse than examining the abdomen would suggest.

Why the blood supply stops

The final push can be sudden, but the ground is prepared over years.

• Diabetes. High sugar damages nerves and vessels over the years: the first stop feeling pain, the second stop delivering blood, and a small wound on the foot that nobody noticed becomes the way in for infection.
• Hardened arteries in the legs. Plaque narrows the vessel: first the calves hurt on walking, then the pain comes at rest, then any scratch takes months to close.
• A clot that has broken free. It shuts an artery in an instant: the limb goes pale and cold, numbness sets in and the pulse disappears. It usually comes from the heart in atrial fibrillation, the same source as blockages of the gut vessels.
• Injuries. Crush injuries, deep dirty wounds, burns, frostbite, tight dressings or plaster casts pressing on a vessel.
• Raynaud's and inflamed blood vessels. The small arteries of the fingers go into spasm or become inflamed, and ulcers that will not heal appear on the tips.
• Weakened defences. Chemotherapy, HIV, medicines that suppress immunity, kidney failure, malnutrition, alcohol dependence, injected drugs, older age. An infection a healthy body puts out in a day travels inwards.
• Smoking. It narrows vessels and speeds up arterial disease: in smokers the leg arteries suffer earlier and harder.

The diabetic foot deserves its own section

Most amputations not caused by an accident begin with a small wound on the foot of somebody with diabetes. The chain is nearly always the same: lost sensation, an unnoticed rub from a new shoe or a crack between the toes, infection, then an ulcer that will not close because the blood supply is poor. Out of this come rules that sound humdrum and save feet: look at your feet every day, sole and the spaces between the toes included; wash them in warm rather than hot water and dry them thoroughly; never pare corns with a blade or stick on acid plasters, but see a chiropodist; buy shoes in the right size and break them in gradually; do not walk barefoot; check with your hand that no stone has fallen into the shoe. A doctor should look at the feet at least once a year, and more often after an ulcer or with reduced sensation. And the main thing: a wound on the foot in diabetes that has not healed within a few days means seeing a doctor.

When it is counted in hours

Call an ambulance — in Spain, Italy, Portugal, Poland and Ukraine the single number 112 is in service — if any one of these appears:

• the limb has suddenly gone pale or blue, cold and numb, and has stopped moving;
• the pain in the wound or the limb is out of proportion to what can be seen and is rising fast;
• redness and swelling spread within hours;
• there is crackling under the skin, the skin has gone black, dark blisters appear or there is a putrid smell;
• severe abdominal pain with vomiting, distension and no stool or wind;
• signs of sepsis: fever with shivering, a fast weak pulse, breathlessness, cold clammy skin, confusion, dizziness on standing, very little urine.

One rare but important variety deserves separate mention: fast-rising pain, swelling and blackening of the skin of the perineum and genitals. Gangrene in that area occurs mainly in diabetes and develops within a few hours; there is even less room here for waiting or embarrassment. The same day, though without an ambulance, see a doctor if a wound is closing unusually slowly, if an ulcer that will not heal has appeared on a toe or the foot, if the skin around it is red, or if a mild temperature persists.

What the doctor does

The diagnosis rests first of all on examination: skin colour and temperature, the borders of the affected area, smell, the pulse in the foot, sensation. Then blood is taken — it shows inflammation, kidney function and sugar — and a swab from the wound is cultured to find which bacteria are there and what will treat them; if sepsis is suspected, blood cultures are taken too. X-rays and scans show how deep the dead tissue reaches and whether bone is involved; ultrasound of the vessels and angiography say where the blood supply is cut and whether it can be restored. Culture results are not waited for: treatment starts at once and is adjusted later.

How it is treated

There are three tasks: remove the dead tissue, stop the infection, and get blood back to where it is missing.

• Removing dead tissue. The surgeon cuts away everything no longer viable; this debridement sometimes has to be repeated. In necrotising fasciitis the operation is an emergency: delay costs lives.
• Antibiotics. In severe infection they are given into a vein so the drug reliably reaches the site; a broad group is started first and narrowed once the culture is back. Fluids are run at the same time, blood pressure is supported and sugar is brought under control.
• Restoring blood flow. If the vessel can still be opened, angioplasty is done — the narrowed stretch is widened with a balloon and a stent is placed if needed — or a bypass is made around the blockage. Both help save the limb; the choice depends on where the blockage is and how long it is.
• Amputation. It comes when tissue is beyond saving and is threatening life. The level is chosen to take away everything lost and leave as much living tissue as possible. Outside an emergency the decision is made with the patient, having talked through the prosthesis and the recovery.
• Supporting methods. Fly larvae bred under sterile conditions eat dead tissue and leave healthy tissue alone: it sounds odd, but it works. Hyperbaric oxygen helps in gas gangrene and diabetic foot ulcers, is not available everywhere, and in other forms its value is debated. Once the wound is clean, the skin defect is covered with a graft if needed.

What can be done in advance

Gangrene almost never comes out of a clear sky, so preventing it is more achievable than it sounds. The steps are familiar and dull: stop smoking, the one thing that changes the fate of the leg arteries straight away; keep sugar, blood pressure and cholesterol at the targets you have been given and do not drop prescribed medicines; walk, because regular exercise makes the body grow vessels around a blockage, with about two and a half hours of moderate activity a week as the marker; eat less animal fat and fewer sweet things, more vegetables, fish and plant oils; keep alcohol down, since it raises blood pressure and blood fats. And the most concrete point: any wound on the leg of someone with diabetes or diseased arteries gets cleaned and shown to a doctor, not left until it turns black.

Online consultation

Gangrene is not treated through a screen, but a consultation at a distance fits very well here, simply at a different stage. From a photograph and your account the doctor will work out what that small wound on the foot is, whether it is urgent or can be watched, and explain where to go next; will help with sugar, blood pressure and medicines if you are at risk; will teach you how to look after your feet and choose footwear; will support you in giving up smoking and name the vascular tests worth having. And if what you are reading about is blackened skin, creeping redness, unbearable pain or fever with shivering, close this page and call an ambulance. Here everything turns on time.

This material is for information only and does not replace medical advice.