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Q1: What abnormality is seen on the computed tomogram in fig 1 (see p 438)?
The scan shows the characteristic appearance of widespread gas formation in the soft tissues of the thigh and pelvis.
Q2: What is the lethal abnormality present on the computed tomogram in fig 2 (see p 438)?
The striking appearance of gas is seen within the great vessels and the apex of the right ventricle.
Q3: What is the underlying diagnosis and what are the treatment options for this condition?
Postmortem examination confirmed the diagnosis of necrotising myositis with a Duke's C carcinoma of the caecum. Culture of tissue from the gluteal region grew Clostridium septicum.The main treatment is by early and widespread surgical excision of all affected tissue. Other treatment options are described below.
Gas gangrene is a rapidly developing, spreading infection of muscle by toxin producing clostridial species, which are anaerobic Gram positive spore forming bacilli found in soil and the gastrointestinal tract of humans and animals.1 Most cases are caused byC perfringens type A. Infection in man is usually secondary to trauma. Rarely a non-traumatic primary myonecrosis can occur. This is commonly due to infection with the relatively aerotolerant C septicum that allows infection of healthy tissue. Intestinal tract abnormalities are the major predisposing conditions. Colonic neoplasm is the most common of these and seen in up to 88% of patients with C septicum bacteraemia.2 Approximately one third of cases of spontaneous clostridial gangrene are caused byC septicum (59 cases reported in the literature between 1969 to 1977). The organism produces several toxins but the α-toxin is particularly important causing haemolysis and tissue necrosis. Sudden onset of severe pain at the site of infection is often associated with a marked tachycardia out of proportion to any pyrexia Prognosis is improved by prompt recognition of the condition. The diagnosis may be confirmed by Gram stain of wound discharge or needle biopsy and radiology for early detection of intramuscular gas. Medical treatment is supportive to combat dehydration, shock, and acute tubular necrosis. In vitro data suggest that C septicum is susceptible to a wide range of antibiotics and penicillin, clindamycin, or metronidazole should all be effective.3 Hyperbaric oxygen has a bacteriocidal effect on most clostridial species and can inhibit further toxin production. In vitro, C septicum is more resistant to the lethal effects of hyperoxia in cell free systems.4 The use of antitoxin antibodies raised against the α-toxin remains controversial. Early surgical excision of all affected muscle is the essential life saving management. The overall mortality for gas gangrene is between 11% and 31% but between 67% and 100% for C septicum infection.
The radiological imaging performed immediately before the cardiovascular collapse graphically illustrates the widespread gas formation both at the site of initial infection and beyond. It is striking that the patient was able to maintain her cardiac output in the face of the appearance on computed tomography. The subsequent electromechanical dissociation was in retrospect a predictable and irrevocable event.
Gas gangrene caused by C septicuminfection.