Home / Visual Diagnosis # 17 : Answers

Visual Diagnosis # 17 : Answers



  1. The arrow on the image shows soft-tissue gas within the deep fascia and subcutaneous tissues and extending into the gluteus musculature.
  2. With the identification of subcutaneous gas from a suspected infectious cause, the differential diagnosis should include: (1) crepitant anaerobic cellulitis, (2) necrotizing fasciitis, (3) nonclostridial myonecrosis, (4) clostridial myonecrosis, (5) fungal necrotizing cellulitis, and (6) miscellaneous necrotizing infections in the immunocompromised host. This patient was diagnosed with necrotizing fasciitis.
  3. Necrotizing fasciitis is a surgical emergency and may require a ‘team-based’ approach. Aggressive resuscitation and antibiotics should be initiated immediately to maintain hemodynamic stability and the patient should be admitted to a surgical intensive care unit as the patient will likely require extensive debridement and possibly reconstructive surgery.
  4. Mortality rates can range between 25 – 75%.




Necrotizing fasciitis is a rare, rapidly progressive, life-threatening inflammatory necrotizing soft-tissue infection (NSTI) of the fascia with secondary necrosis of the subcutaneous tissues. It can be associated with severe systemic toxicity and may rapidly lead to death unless promptly treated. Necrotizing fasciitis is just part of a spectrum of soft-tissue infections.

There are approximately 500-1,500 new cases of necrotizing fasciitis each year in the United States. The causative bacteria may be aerobic, anaerobic, or mixed flora.


NSTIs include:

  • Necrotizing Fasciitis
  • Fournier’s gangrene
  • Clostridial “gas” gangrene or myonecrosis


A few distinct necrotizing fasciitis syndromes should be recognized. The 2 most common are:

  • Type I, or polymicrobial ( 90% of cases )
  • Type II, or group A streptococcal only ( 10% of cases )



Risk factors include: 

  • Diabetes mellitus
  • Peripheral vascular disease
  • IV drug use
  • Alcoholism
  • Immunosuppressed patients
  • Old age/obesity/malnutrition



  • Can affect any part of body
  • 80% caused by bacteria that extend from contaminated disruptions in skin or localized skin infection
    • General: skin disruption (cut, abrasion, etc.), blunt/penetrating trauma, post-op complications, cutaneous infections/ulcers, illicit/SQ drug injections
    • Abdominal Wall: post-op complication of abdominal surgery
    • Extremity: trauma, illicit drug use, insect bite, scratch, or wound
    • Perineum: post-op complication, pilonidal abscess, neglected ischiorectal/perineal abscess
    • Vulva: Bartholin’s gland duct abscess, vulvar abscess, pudendal nerve block; post-op wound infection from C-section, episiotomy, hysterectomy, etc.
    • Fournier’s gangrene (NF of male genital organs): GU infections, traumatic instrumentation, urethral calculus, neoplasm, surgery, coital injury
    • Head and Neck
      • Scalp/Periorbital: trauma, eyelid infection/puritis
      • Face/Neck: progressive dental infections, peritonsillar abscess, salivary gland infections, cervical adenitis, otologic sources
    • Complication of percutaneous catheter placement: chest tube, PEG, and percutaneous drain of abdominal abscess
    • Idiopathic necrotizing fasciitis
      • cases that occur without an obvious portal of entry
      • occur in ~ 20% of cases
      • more likely to occur in healthy patients
      • typically caused by single organism (Strep pyogenes)
      • commonly involves lower extremities
      • result of infection from unrecognized breaks in skin or hematogenous spread


On exam, increase your suspicion if you find:

  • Pain out of proportion to clinical lesion
  • Tense edema
  • Edema extends beyond erythema
  • Purplish skin discoloration
  • Numbness/weakness in the affected area (possible edema-induced compartment-like syndrome or directly damaged cutaneous nerves)
  • WBC > 15
  • Serum Sodium < 135


Hard signs:

  • Bullae  16-24%
  • Necrotic skin  6-3%
  • Crepitance  0-36%
  • Hypotension  7-11%
  • Gas on plain x-ray 32-57%
  • Tense edema 23-38%



Here is a great review video from EM in 5



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  1. Zacharias N, Velmahos GC, Salama A et-al. Diagnosis of necrotizing soft tissue infections by computed tomography. Arch Surg. 2010;145 (5): 452-5.
  2. Misiakos EP, Bagias G, Patapis P, Sotiropoulos D, Kanavidis P, Machairas A. Current concepts in the management of necrotizing fasciitis. Front Surg. 2014. 1:36.
  3. Bisno AL, Cockerill FR 3rd, Bermudez CT. The initial outpatient-physician encounter in group A streptococcal necrotizing fasciitis. Clin Infect Dis. 2000 Aug. 31(2):607-8.
  4. Kihiczak GG, Schwartz RA, Kapila R. Necrotizing fasciitis: a deadly infection. J Eur Acad Dermatol Venereol. 2006 Apr. 20(4):365-9.
  5. Edlich RF, Cross CL, Dahlstrom JJ, Long WB 3rd. Modern concepts of the diagnosis and treatment of necrotizing fasciitis. J Emerg Med. 2010 Aug. 39(2):261-5.
  6. Vayvada H, Demirdover C, Menderes A, Karaca C. [Necrotizing fasciitis: diagnosis, treatment and review of the literature]. Ulus Travma Acil Cerrahi Derg. 2012 Nov. 18(6):507-13.
  7. Stevens DL, Bisno AL, Chambers HF, et al. Practice guidelines for the diagnosis and management of skin and soft tissue infections: 2014 update by the infectious diseases society of America. Clin Infect Dis. 2014 Jul 15. 59(2):147-59.