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Post-traumatic subcutaneous emphysema - Is it always a sign of alarm?

Catarina Ladeira, Aline Vaz-Silva, João Pascoal

Department of Pediatric Surgery, Hospital Dona Estefânia, Centro Hospitalar de Lisboa Central EPE. Lisboa, Portugal



Catarina Ladeira
Avenida do Brasil, nº30, 6ºD
1700-070 Lisboa, Portugal
E-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.



Benign subcutaneous emphysema is a rare condition that commonly occurs secondary to trauma. We present a case of a child with a post-traumatic subcutaneous emphysema of the lower limb wrongly diagnosed as a necrotizing fasciitis. It is important to differentiate benign subcutaneous emphysema from serious soft-tissue infections such as gas gangrene and necrotizing fasciitis as the management, treatment and prognosis differ significantly.

Keywords: benign subcutaneous emphysema, necrotizing fasciitis




Subcutaneous emphysema is defined as the presence of gas or air in the subcutaneous tissue plane [1]. It is usually associated with gas gangrene or necrotizing fasciitis, however not all subcutaneous emphysema signifies a life-threatening infection [2]. Benign subcutaneous emphysema is a rare condition that commonly occurs secondary to trauma [3].

Case report

We present the case of an 11-year-old female who was transferred to our hospital with a diagnosis of necrotizing fasciitis. She had suffered a puncture wound to the foot with a piece of glass. A few minutes later her mother noticed some crepitation on palpation of the leg and took her to the emergency room. On admission the doctor identified subcutaneous emphysema on palpation without any other signs of infection. Due to the presence of subcutaneous emphysema the diagnosis of necrotizing fasciitis was made. The girl was put on clindamycin, meropenem and vancomycin and transferred to our hospital.

On arrival she looked well, was hemodynamically stable and afebrile. Inspection of the left lower limb showed a puncture wound on the external malleolus, with discrete swelling and tenderness around it. Crepitation could be felt in the area and extending anteriorly and posteriorly all around the tibio-tarsal joint and superiorly to the lower third of the leg. The X-Ray showed air in the subcutaneous tissue, the ultrasound described air in the subcutaneous tissue without signs of necrotizing fasciitis and the laboratory work showed no alterations compatible with infection (Fig.1). The girl was discharged on the same day, medicated with oral flucloxacillin and was re-evaluated three days later showing no signs of complications.

Figure 1. X-Ray showing subcutaneous emphysema

11.2 8 1


Benign subcutaneous emphysema of the hand and upper limb of non-infectious aetiology has been documented in several case reports [2]. To the authors knowledge this is the first case in literatureregarding the lower limb and affecting children.

Subcutaneous emphysema can result from numerous benign causes, most of which are trauma related [4]. Reported causes to date include; high pressure injuries from power tools, blast injuries, air-gun injuries, dental extractions, hawthorn injuries, simple abrasive injuries (bike trauma, falls, etc.), insect bites and self-harm (factitious emphysema) [2,5–7]. Other rare causes include iatrogenic injuries (post-biopsy or insertion of peripheral vascular access) [3]. Speculation regarding mechanism of injury is that the trauma/puncture injury results in a one-way ball-valve effect causing accumulation of gas in the subcutaneous plane [2,8].

It is important to differentiate benign subcutaneous emphysema from serious soft-tissue infections such as gas gangrene (clostridial myonecrosis) and necrotizing fasciitis [9], especially in the early stages, as the management approaches vary significantly [1]. Benign subcutaneous emphysema is limited to the subcutaneous tissue, without systemic symptoms, and is more common in the upper extremities [1,2].

Some authors point out that infection from gas-forming organisms usually takes 12–18 h to develop and that gas in the subcutaneous tissue within 6–10 h of trauma is most likely to be indicative of a benign process [10,11]. Conservative treatment has been suggested for subcutaneous emphysema in patients who are systemically well, with minimal pain at the site of injury and in the absence of extensive cellulitis.In this cases it is acceptable to reassure the patient and discharge on oral antibiotics with an outpatient follow up appointment [2].


Benign causes of subcutaneous emphysema should be considered in patients presenting without any signs and symptoms of an infectious process or systemic illness. This will avoid the unnecessary aggressive treatment which is reserved for gas gangrene and necrotizing fasciitis.




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