Gas gangrene, or clostridial myonecrosis, is a severe acute specific anaerobic bacterial infection caused by Clostridium perfringens [2, 5]. Clostridium infection may be secondary to a major trauma or occur either in the presence or absence of mucocutaneous damage [6, 8]. In this patient, severe pain was a warning sign of a serious infection. CT or MRI can usually reveal the presence of gas accumulation at the site of infection [9]. Imaging test of this case showed signs of pneumatosis in the right ventricle and the main pulmonary artery and occlusion of the right femoral artery. To our knowledge, this is the first report of gas gangrene case with these radiographic signs.
Inconformity between pain and trauma degree
Gas gangrene is likely to be misdiagnosed due to the unremarkable early wound reaction [10]. This rare gas gangrene case started with local pain and minor skin lesion in the absence of remarkable early redness and swelling. In his first two visits of hospital, diagnosis of gas gangrene was not confirmed, however, the infection rapidly spread along his right side of body within 48 h accompanied by shock and multiple organ dysfunction syndrome (MODS), indicating that severe gas gangrene may also arise from minor trauma. Therefore, special medical care must be taken to prevent against gas gangrene if the post-traumatic sharp pain is inconsistent with the wound surface reaction.
Imaging findings: circulatory pneumatosis and arterial occlusion
The exact origin of pneumatosis in right ventricle and the main pulmonary artery remains unknown. At the time of CT examination, the patient had only one indwelling needle in the peripheral vein, and the iatrogenic procedure-induced intravenous pneumatosis was less likely to occur. The negativity of bacteria in blood culture excluded the possibility of gas production by circulating bacteria. The gas might come from extravascular tissue. Infection with Clostridium septicum or other gas-producing bacteria may lead to tissue decomposition and overproduction of gas. Moreover, the vascular endothelial cell damage following infection may lead to increase in vascular permeability [11]. Due to the relatively low pressure in the venous system, gas is likely to enter into the right heart and accumulate there. When the patient assumes a supine position, the right ventricle and the main pulmonary aorta were in a relatively high position, allowing gas accumulation there. The gas entry into the pulmonary artery may lead to pulmonary artery embolism. The patient with gas gangrene is susceptible to gas embolism, and the extensive embolization may lead to sudden death [12]. However, debridement and reduction of tissue pressure may contribute to a lower risk of gas embolism.
The underlying mechanism of right femoral artery occlusion remains unclear as well. The patient denied discomfort in his right lower limb prior to onset of symptoms. CTA revealed a maximum arterial stenosis of 30% in the lower limb and multiple artery plaques. Evidently, the occlusion of the right femoral artery was caused by infection. The possible mechanisms of right femoral artery occlusion include the following: (1) Acute compartment syndrome: extensive myonecrosis and gas accumulation in subcutaneous soft tissue on the right side of the body resulted in acute compartment syndrome in the right lower limb; (2) Thrombosis: thrombus formation may be trigged by pathogenic bacteria and inflammatory mediators in the presence of sepsis through multiple pathways like up-regulation of procoagulant pathway, down-regulation of physiological anticoagulant production, and inhibition of fibrin decomposition, etc. [7]. During the course of disease, blood clotting was monitored closely, with d-dimer showing a significant increase, suggesting a high possibility of thrombosis; (3) Sepsis-induced impairment of vascular tone [13]; (4) Vascular diseases (e.g. multiple atherosclerosis). Gas gangrene-induced limb gangrene might be caused by the combined action of infection and vascular occlusion. In this case, the right femoral artery occlusion aggravated the gangrene of the right lower limb, justifying the need for a secondary amputation surgery. The artery occlusion may be a self-protective response of the body to prevent the infection from spreading throughout the body. The underlying mechanisms for artery occlusion remain explored further.
Reflections on the treatment of gas gangrene
Gas gangrene progresses rapidly, however, timely treatment is the key for an improved prognosis [14]. Once gas gangrene infection is suspected, MDT-Green Channel mode should be initiated for achieving rapid diagnosis and treatment plan through the collaboration of multidisplinary personnel [15, 16]. In our report, this patient turned for the better in overall condition due to the application of the MDT-green channel mode.
Some problems in the treatment of this patient warrant further discussion. First, how can an early diagnosis of gas gangrene be achieved prior to the presence of characteristic symptoms? The presence of severe pain in minor wound may be an important indicator. Early bacterial identification of the wound exudate by smear or by more rapid and sensitive gene-sequencing techniques may contribute to early confirmed diagnosis [17]. Second, regarding treatment of circulatory pneumatosis, given the patient's stability in respiration and circulation after treatment, preventative measures aiming at circulatory pneumatosis including cardiac puncture to withdraw air was not performed. However, it is too late if cardiac puncture performed after presence of pulmonary embolism. Hence, the timing of intervention remains to be further explored. Third, due to the severe myonecrosis, vascular intervention aiming at clarifying the cause of vascular occlusion and achieving recanalization was not attempted. In patients with confined myonecrosis, infection control, and stable circulation, interventional recanalization efforts may help reduce the risk of undergoing amputation surgery. Fourth, in this case, the lymphocyte count showed a significant reduction, excluding the possibility of presence of immunodeficiency diseases. Evidently, this is sepsis-induced immunosuppression [18]. The timing of immunoregulation administration remains to be explored further in future study.
