Gangrene

What is Gangrene?

Gangrene is a medical condition in which body tissue dies due to a lack of blood supply. It often affects fingers, toes, or limbs and is characterized by discolored or black tissue, typically forming a ring around the affected area. The natural tissue starts to erode or “slough off.”

There are three main forms of gangrene: wet, dry, and gas gangrene. Dry gangrene occurs when there’s an insufficient blood supply to a specific part of the body, often due to a blockage in the arteries, worsened by conditions like peripheral artery disease. Wet gangrene, on the other hand, is a more severe form where an infection is also present, causing swelling and redness, but without the production of gas.

Gas gangrene, the specific type of infection caused primarily by bacteria, leads to swelling, the production of gas (evident on X-rays), and a crackling sound or feeling when the affected area is touched. It should be noted that necrotizing soft tissue infections, which cause severe skin lesions that may reach into the layers beneath the skin and into the muscle, could also lead to gangrene.

Gangrene can have devastating effects on a person’s quality of life due to the associated pain, decrease in movement capabilities, and the high possibility of needing to stay in the hospital. When left unattended, it can lead to serious health complications, including death. In advanced stages, it can necessitate multiple surgical procedures to manage its progression.

What Causes Gangrene?

Dry or ischemic gangrene usually happens because of a blockage in the blood vessels leading to the outer part of your body. Very often, this is due to a disease called atherosclerosis, where the arteries become clogged with fatty substances. Risks for this kind of disease include factors like diabetes, smoking, high blood pressure and high lipid levels in the blood, which are also risks for heart disease. Other things that increase blood flow demand, like infections or injuries to that area, can actually make the disease worse. Dry gangrene typically doesn’t have bacteria because they cannot survive in the dry and shriveled-up tissue.

Sometimes, ischemic gangrene happens because of blockages in the vessels due to other diseases. These can be conditions like blood clot diseases, conditions that make your blood clot too much, injuries to the limb or the blood vessels, inflammation of blood vessels, cysts, or Buerger disease. These conditions can also result in a sudden decrease in blood flow to a limb, leading to gangrene if it’s bad enough. This sudden decrease in blood flow is known by typical symptoms like tingling, pain, pale skin, no pulse, problems with temperature regulation, and paralysis.

There can even be ischemic gangrene in limbs with normal blood pulses, because of a clot in the tiny blood vessels. Sometimes, gangrene occurs due to an infection where parts of your body that are prone to swelling such as the lower extremities or feet get infected. People with diabetes are more susceptible because they often have trouble healing wounds and their blood sugar levels are too high.

Another type of gangrene, called gas gangrene, often occurs due to an infection with bacteria like Clostridium perfringens and other similar species. These bacteria can cause rapid tissue death and signs of illness in the body due to their production of toxins. These bacteria also release gas that collects under the skin. Other bacterial infections, like Escherichia coli, Bacteroides, Staphylococcus epidermidis, and streptococcal infections can also produce gas, spreading infection rapidly. Another bacterial infection that can cause gas in tissue is type I necrotizing fasciitis, which is identified by easy-to-tear surface tissue, grey juice and no pus.

Risk Factors and Frequency for Gangrene

Ischemic or dry gangrene, which is when tissues die off, often happens because of advanced peripheral artery disease (PAD). This condition is most severe in the form of critical limb ischemia or chronic limb-threatening ischemia (CLI/CLTI). This condition affects about 1% of people over 50 years old in the US, and it becomes twice as common for those over 70 years old. Worldwide, over 200 million people are affected by lower extremity peripheral artery disease. Among these people, up to 10% have CLI/CLTI. In a five-year period, 5% to 10% of patients with PAD (even those with minimal symptoms) may find their condition has progressed to CLI/CLTI.

On the other hand, gas gangrene typically happens after an injury exposes tissue to anaerobic bacteria. This form of gangrene has been observed after car accidents, severe injuries, gunshot wounds, and complications after surgeries where infection has occurred. However, non-traumatic gas gangrene (which spreads through the bloodstream) has also been connected to metastatic gut malignancy. While gas gangrene is relatively rare, seeing about 1000 cases each year in the US.

• 50% of these instances are due to traumatic injuries,
• 30% are due to complications after surgery,
• 20% occur spontaneously out of the blue.

As with gas gangrene, other similar infections also usually have a clear entry point because of trauma or complications at a surgical site after surgery.

Signs and Symptoms of Gangrene

Critical limb ischemia or chronic limb-threatening ischemia (CLI/CLTI) can lead to gangrene. It begins with pain in the limb, which may worsen when the leg is elevated and improve when the leg is lowered due to decreased blood flow. Patients with this type of condition might not feel consistent pain if they also have nerve damage, often resulting from diabetes. Sometimes the first sign of ischemia is tissue loss.

When someone has ischemic gangrene, a physical exam would typically show reddening of the damaged limb when lowered, and a lack of color when raised. Other signs may include slow capillary refill, lack of hair above the affected area, and missing ankle pulses. The site of tissue loss can also provide clues about the cause:

• Ischemic tissue loss usually affects the toes and distant foot
• Veins often develop ulcers above the ankle bones
• Ulcers caused by nerve damage usually start on pressure areas of the sole

Alongside, the healthcare provider should look for any nerve damage and use a probe-to-bone test if there is any ulceration or tissue loss. This will tell how deep the tissue damage is and the risk of bone infection.

Wet gangrene could be the cause if there’s fluid and swelling, especially in a patient with a previous foot ulcer or tissue damage due to diabetes or decreased blood flow. Any pain on the sole of the foot should be thoroughly checked for a potential deep foot abscess.

Sudden severe limb ischemia can cause extreme lower limb pain, loss of sensation, and paralysis. The flow of blood in the arteries may not be heard initially and the flow in the veins may also become inaudible as the disease gets worse.

Gas gangrene can cause pain, swelling, bleeding blisters, and color changes from pale to bronze-purplish red. This is often found in patients with a history of injury or recent surgery.

Necrotizing soft tissue infections, specifically from group A streptococcus, can start from a red lesion and evolve to a dull skin color with overlying bleeding blisters within 24 to 72 hours of the injury. If the skin becomes gangrenous and starts shedding, there is a high risk of death. Patients with necrotizing infections often present with swelling, fever, malaise, and pain but these symptoms can be subtle and easily missed, which increases the risk of a delayed diagnosis. It’s essential to be highly sensitive to these symptoms for early detection of the disease.

Testing for Gangrene

For diagnosing ischemic gangrene, doctors primarily concentrate on spotting risk factors like kidney failure, high cholesterol, or diabetes because these can affect the treatment plan. They will also look for signs of an infection, even if there are no obvious symptoms like redness or swelling around the wound.

Additional tests are usually conducted to pinpoint exactly where and how severe the arterial disease is, and these results will guide decisions on treatment. Non-invasive tests, such as an ankle-brachial index (ABI), are helpful in spotting peripheral arterial disease (PAD) earlier. An ABI less than 1.0, or ankle pressure below 40-60 mmHg, is alarming and could indicate critical ischemia. If tissue loss is detected, an ankle pressure reading under 70 mmHg is considered abnormal. If the results of the ABI point towards an arterial disease, additional imaging techniques will be used, including Duplex ultrasound, digital subtraction angiography, CT angiography, or Magnetic Resonance Angiography (MRA). In cases where ABI results are not clear, other non-invasive tests may be used to measure ankle pressure or toe pressure, or transcutaneous oxygen pressure.

In order to stage and understand the severity of diseases like critical limb ischemia or chronic limb-threatening ischemia, doctors use classification systems. A recent system developed by the Society of Vascular Surgery called the WIfI (wound, ischemia, foot Infection) uses the classification of the wound, the severity of ischemia, and the presence of foot infections to provide a prognosis and suggest treatment options. This helps doctors understand the anticipated response to revascularization or restoring blood flow to the area.

When gas or wet gangrene is suspected, a Gram stain test and wound cultures might be used to determine the type of bacteria causing the problem and guide the choice of antibiotics. Normally, though, doctors can identify gas gangrene clinically. Even though surface wound swabs aren’t often used due to risk of outside skin bacteria contamination, samples obtained from deep within the wound or pus can be useful.

X-ray can be useful to spot the presence of gas under the skin, a sign of gas gangrene and type 1 necrotizing skin infections. CT scans and MRI can further confirm the diagnosis. However, if gas gangrene is suspected, doctors usually proceed to treatment without waiting for these results. If the diagnosis isn’t clear, doctors might resort to exploring the area under local anesthesia – if there is any return of ‘dishwater’ fluid or the fascial planes are easily dissected, this indicates presence of necrotizing infections and will be followed up by surgical treatment.

Treatment Options for Gangrene

The treatment of ischemic gangrene, a severe condition where tissue death occurs due to reduced blood supply, aims to restore the flow of blood and minimize tissue loss. Medication can be used for these goals, although the outcome might not improve much if the condition has advanced to a stage known as dry gangrene.

Common treatments include medicines such as aspirin or clopidogrel, which makes the blood less sticky and helps in preventing clot formation. Medications may be used to control high blood pressure, and cholesterol-lowering drugs, such as statins, could be prescribed if necessary. Controlling blood sugar levels is crucial for diabetic patients, ideally to a level known as ‘Hemoglobin A1C less than 7%’, which basically means keeping average blood glucose levels under control. Quitting smoking is critical in reducing the risk of diseases getting worse.

Surgical treatment is aimed at revascularization, a process to restore blood flow to prevent possible limb loss. In immediate severe cases, a catheter-based procedure called intravascular thrombolysis is used to remove blood clots. Other surgery types include endovascular intervention with balloon angioplasty, which involves inflating a tiny balloon to widen the narrow artery, sometimes along with a stent to keep the artery open. In cases of significant necrosis, extreme pain, severe infection, weakened muscles or short life expectancy, primary amputation is recommended.

Another surgical measure that could be performed, mainly if significant foot necrosis exists, is an above-ankle amputation. Here, the spontaneous separation of non-viable tissue may occur but is rare. If necrosis requires removal of multiple fingers, an approach called transmetatarsal amputation is considered to preserve the function of the foot.

Hyperbaric oxygen therapy, where patients breathe pure oxygen in a pressurized room, has been suggested as a treatment to increase oxygen supply to ischemic tissues, but it has no proven benefit for critical limb ischemia. Experimental treatments, currently limited to clinical trials, include the use of growth factors and stem cell therapy.

When an infection is suspected for wet gangrene that causes rapid tissue damage, urgent surgical drainage and removal of dead tissue is needed. Antibiotic treatment begins, depending on patient risk factors and local deprivation rates. If a severe type of gangrene known as ‘gas gangrene’ occurs, swift surgical action is needed as this infection can prove fatal if treatment is delayed. This infection may require multiple surgical procedures and a very rapid delivery of broad-spectrum antibiotics.

What else can Gangrene be?

Gangrene is usually quite distinct because it involves visibly dead or decaying tissue. However, pain in the limbs could also be due to several other conditions such as:

• Diabetic neuropathy (nerve damage due to high blood sugar)
• Complex regional pain syndrome (a chronic pain condition)
• Nerve root compression (pressure on the nerves)

Another range of factors might cause local poor blood flow (ischemia) which are not listed above. These include:

• Frostbite (skin damage caused by freezing)
• Ergotism (localized blood vessel tightening with clotting)
• Compartment syndrome (increased pressure within a muscle compartment)
• Calciphylaxis, a rare condition seen in patients with kidney failure

For gas gangrene (a serious bacterial infection that produces gas within tissues), the following conditions could be mistaken for it:

• Group A streptococcal infections (bacterial infections)
• Septic shock (a severe infection causing organ failure)
• Toxic shock syndrome (a severe disease caused by bacterial toxins)
• Abdominal abscess (a pocket of pus in the abdomen)
• Vibrio infections (bacterial infections, usually from contaminated water or seafood)

What to expect with Gangrene

When diagnosed with severe long-term blood flow issues in the limbs, known as critical limb ischemia (CLI) or chronic limb-threatening ischemia (CLTI), 40-50% of diabetic patients face amputation within a year, and 20-25% may tragically lose their lives. Looking at patients without diabetes who experience severe limb pain and blood flow related sores or gangrene, 19% undergo amputation within six months, and this figure rises to 23% by a year’s mark. In these cases, amputation is most often necessitated by infections that can’t be effectively treated.

After undergoing procedures to restore blood flow, known as revascularization, patients should be monitored for at least two years to ensure there isn’t a reoccurrence of severe limb blood flow issues.

An infection known as gas gangrene carries significant risk as well; 25% of trauma patients with this condition may lose their lives. Unfortunately, this number may increase to 100% if the treatment is delayed or not up to par. The risk of a poor outcome with gas gangrene is higher in the elderly, in those with multiple underlying health conditions, or when the infection is located on the torso.

Possible Complications When Diagnosed with Gangrene

The main goal of limb salvage treatment is to reduce the need for amputations, particularly major amputations which are above the ankle and require a prosthetic for walking. However, for some patients, amputation could be the best choice to enable them to fully participate in rehabilitation with a prosthesis. Past studies, however, have shown that only a portion of patients who undergo these amputations are able to walk at one-year post-procedure; 65% of those with below-the-knee amputations and 29% of those with above-the-knee amputations. Additionally, studies have shown that two years after a below-the-knee amputation, 15% of patients underwent an amputation of the other limb, another 15% progressed to an above-the-knee amputation, and 30% had passed away.

Here is a list of these statistics:

• 65% of patients with amputations below the knee can walk at one year post-procedure.
• 29% of patients with above-the-knee amputations can walk at one year post-procedure.
• Two years post-below-the-knee amputation, 15% of patients also had the other limb amputated.
• Again, after two years, another 15% of patients progressed from a below-the-knee to an above-the-knee amputation.
• 30% of these patients had died within this two-year period.

Preventing Gangrene

It’s important for patients to understand how to properly care for their foot and wounds to encourage healing and stop the problem from coming back. This means learning about the right kinds of shoes and shoe inserts to wear. It also includes recognizing early signs of swelling or infection. If patients notice any symptoms such as discomfort, redness, pain that seems too severe, or a fever, they should seek medical help right away.

For people who use intravenous drugs like heroin, they need to be aware of the serious, potentially deadly, complications that can arise from gas gangrene – a severe type of infection – if the drug they’re injecting is contaminated with certain chemicals.