NSTI can affect any part of the body. For simplicity, the body regions most commonly affected are usually categorized in order of decreasing incidence: extremities, perineum and buttocks, trunk, and head and neck. The body region affected varies according to the study patient population, for example, IV drug abusers are disproportionately affected in the extremities at the sites of injection [15–17, 20], while Fournier’s gangrene is seen most commonly in diabetics [20, 33]. Fournier’s gangrene, named after French dermatologist Jean Alfred Fournier described a series of five male patients in 1883, is the eponymous name used to describe NSTI of the perineum (Figs. 17.1 and 17.2). This form of NSTI affects men ten times more commonly than women. NSTI of the head and neck is most commonly preceded by a dental infection [46, 47].

NSTI can occur following insect bites and muscle strains. Non-recreational drug use needle injection-related NSTI has been reported after tattooing [18], acupuncture [30, 48], and insulin administration [30] (Figs. 17.3 and 17.4). Case reports of postsurgical NSTI have been reported for appendectomy, inguinal hernia, various gynecologic operations, orthopedic fixation, dental procedures, transanal procedures, urologic procedures (including circumcision), angiographic interventions, and laparoscopic procedures [6, 49, 50]. As a general rule, infections adjacent to mucous membranes (oral cavity, rectum, vagina) are caused by the normal resident flora of those mucous membranes, while infections in distant areas are usually caused by resident skin flora [51].

The distinction between NSTI and non-necrotizing infections is of prime importance, the latter being treated with antibiotics alone. The main differential diagnosis includes simple cellulitis, erysipelas, abscess, Clostridial and non-Clostridial myonecrosis, toxic epidermal necrolysis (TEN), staphylococcal scalded skin syndrome, and rarely, cutaneous anthrax (Table 17.2).

It cannot be overemphasized that wide surgical debridement is the only effective therapy for NSTI and that time is of the utmost essence. Delay in surgical therapy has been repeatedly demonstrated to be associated with increased mortality and increased number of required debridements [29]. Even with severe hemodynamic and metabolic derangement, surgical exploration and debridement must proceed; physiologic resuscitation and correction is futile in the continued presence of infected, necrotic tissue. Because of the difficulty in establishing the diagnosis non-invasively, several authors have described bedside tests, including aspiration with Gram-stain [57], frozen section biopsy [58], and “the finger test.” The “finger test” is performed by making a small incision (2 cm) through the skin down to the fascia and bluntly probing the wound with a finger. A positive test (indicating NSTI) results if one can dissect the subcutaneous tissue off the fascia with minimal resistance [22]. Because of the possibility of sample bias and the potential delay in diagnosis and therapy, these lesser diagnostic operations are not recommended; in most instances the morbidity associated with delayed treatment of NSTI outweighs the morbidity of an exploratory incision in superficial skin and soft tissue infection.

The surgical approach at the first debridement should resemble a “search-and-destroy” mission. All frankly necrotic and infected tissue should be excised irrespective of anatomic or functional boundaries (Fig. 17.11). As this disease pays no respect to anatomic planes, neither should the treating surgeon hesitate to remove tissue when the patient’s life is at stake. At operation, affected tissue is easily recognized by lack of bleeding and lack of normal resistance to blunt dissection. In elderly patients, however, ease of tissue separation alone may not be a reliable indicator of infection.

A clinical caveat: finger dissection should be utilized with care in injection drug abusers as broken needle tips may reside in the subcutaneous tissues (Fig. 17.12). Necrotic fascia is noted to be discolored (grayish) and sometimes surrounded by a thin, foul-smelling “dishwater” liquid distinct from the garden variety creamy thick pus encountered in simple abscesses. Intraoperative aerobic and anaerobic cultures should be taken to aid in future targeted antibiotic therapy; these cultures should be taken from subcutaneous tissues, not from the skin surface or blister fluid. Tissue biopsies should be taken from the interface between necrotic and alive tissue for optimal diagnostic yield [38]. Skin should be debrided until brisk capillary dermal bleeding without epidermal discoloration is encountered. Large skin flaps may impede wound drainage and it may be prudent to excise skin with extensive underlining to facilitate wound care. Muscle and fascia should be debrided to healthy tissue with normal contractile function (in response to electrocautery).