Early Diagnosis Saves Life in Flesh-Eating Disease

Dear Dr. B: My son has developed serious infection in his leg. How do I know if this is flesh-eating disease?

The most famous case of flesh-eating disease (FED) in Canada is Loucien Bouchard, the former premier of Quebec. He luckily survived and had to have one leg amputated.

FED is a very serious kind of infection which spreads rapidly in the body. It is deep seated under the skin and progressively destroys fat, fascia and muscles. The condition is also known as necrotizing fasciitis.

FED was first described by Hippocrates around 500 B.C. The condition is not that common. In Canada, it is estimated that 90 to 200 cases of FED occur each year. In the US, approximately 1000 cases are seen in a year. Since the condition is not common, a physician would probably see one or two cases in his career.

The death rate in FED has not changed in the last 30 years and remains around 25 to 35 per cent. Death rate is directly related to early diagnosis and surgical intervention.

The most common sites of infection are perineal and groin areas and post surgical wounds. Infection around the umbilicus in a new born can be life-threatening. Among children the FED can be a serious complication of varicella infection. Infection can occur in the trunk and the limbs. Patient who are diabetic, intravenous drug abusers, immuno-compromised or have peripheral vascular disease are also prone to FED.

How to diagnose FED?

The diagnosis is clinical. It is not always easy to make a diagnosis. But the condition should be kept in mind in any kind of skin infection.

Initially, it is hard to differentiate from ordinary infection of the skin. But gradually patients get very sick. The pain is more severe than the clinical findings. There are only minor changes in the skin in early phases.

The factors that help distinguish FED from ordinary skin infection include a generalized rash, toxic appearance, fever and low platelet count. Plain x-ray can reveal gas under the skin or soft-tissue swelling but cannot show deeper gas under the fascia. CAT scan is more sensitive because it can show inflammatory changes like fascial swelling, thickening, abscesses and gas formation. MRI can add more information but ultrasound has poor sensitivity and specificity in this condition.

“The main diagnostic tool, however, is surgical exploration”, says an editorial in the British Medical Journal (BMJ). The characteristic finding at surgery is of grey, edematous fat, which strips off the underlying fascia with a sweep of the finger. Deeper changes are invariably more widespread than the skin changes. If FED is suspected then surgical exploration should be undertaken and can be life saving.

Intravenous antibiotic therapy has an important role in reducing generalized infection and spread of bacteria in the body. The BMJ editorial says that no evidence exists that antibiotics halt the infection in FED and their use may tempt the surgeon to perform less mutilating and less effective surgery. Nevertheless, broad spectrum antibiotic cover is routine and should specifically target anaerobes and streptococci.

Hyperbaric oxygen is strongly advocated by some. But there are no controlled studies to prove its usefulness. Using it would seem reasonable if it was readily available but not if the need for inter-hospital transfer delayed definitive surgery, says the editorial.

In summary, the diagnosis of FED is mainly clinical. Surgery is the mainstay of management. Patient should be taken to the operating room as soon as flesh-eating disease is suspected. Massive removal of dead and dying tissue is undertaken. Sometimes amputation becomes necessary. Patient may require surgery more than once.

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