Making the Diagnosis
Gangrene is a type of necrotizing (flesh-destroying) bacterial infection that a doctor can easily recognize. A doctor will take a tissue sample or perhaps some fluid from a skin bubble. The sample is grown in a laboratory culture to identify the bacteria. Treatment won't wait for the results to come back, however. A doctor will start a giving a "broad-spectrum" antibiotic immediately.
If the infection is serious, sometimes x-rays or MRI scans are used to locate gas deep under the skin. If surgery is needed, these scans tell the doctor exactly where the bacteria are, and what needs to be removed.