Myositis, Fasciitis and Muscle Abscesses

Necrotizing fasciitis, myositis, and muscle abscesses

Synonyms

For fasciitis and myositis: gangrene; gas gangrene; Fournier’s gangrene

For muscle abscess: pyomyositis

1. Description of the problem

What every clinician needs to know

Necrotizing fasciitis and myositis

The key feature of fasciitis and myositis, and, to a lesser degree, muscle abscess, is pain – pain out of proportion to a traumatic event or seeming to arise spontaneously.
Fasciitis and myositis are severe necrotizing infections that may cause loss of limb or of life. The two entities often occur concomitantly and it may be difficult to distinguish between them except at surgery or by MRI.
Predisposing factors: diabetes, alcoholic cirrhosis, immunosuppression, infection drug use, peripheral vascular disease.
Muscle abscess is usually a less serious condition than myositis or fasciitis. It can be difficult to diagnose clinically; imaging modalities such as ultrasound, CT or MRI usually can make the diagnosis.
All of these conditions can be mistaken for cellulitis with swelling, redness, warmth and tenderness of the overlying skin, but they are distinguished from simple cellulitis by the presence of severe pain and often by fever, elevated WBC and other signs of severe infection. Moreover, the lesions often appear in sites (trunk or proximal limbs) that would be unusual for ordinary cellulitis. In some instances, especially initially, the overlying skin may appear normal but there is nearly always severe pain.
As the deeper process progresses, the overlying skin may change from pink, swollen, painful and tender to purple, bullous and necrotic, to anesthetic. Occasionally, anesthesia precedes the evidence of skin necrosis.
These infections, especially fasciitis and myositis, constitute a surgical emergency.

Muscle Abscess

Muscle abscesses are usually less aggressive than necrotizing fasciitis and myositis but, like those entities, cause pain.
In the absence of trauma, the most common risk factors are HIV and diabetes mellitus.
The most common cause is S. aureus (often MRSA).
There may be overlying cellulitis: if so, the clue to deeper infection is often intense pain and a slow response of the “cellulitis.”
If the overlying skin appears normal, the clue will be the unexplained pain and possibly swelling of the soft tissues.
Imaging can help to distinguish muscle abscess from myositis or fasciitis.

Clinical features

Necrotizing fasciitis and myositis may arise:

around sites of trauma or deep decubitus ulcers (especially in the perineal area).
following surgery, mainly intraabdominal or gynecological surgery.
by hematogenous spread, often from an occult source.

Infections following trauma or by spread from a deep decubitus ulcer are usually caused by mixtures of species which act synergistically, whereas infections following intraabdominal surgery or by hematogenous spread from an occult source usually involve a single species (primarily Streptococcus pyogenes or a clostridial species).

Infection around sites of trauma or deep decubitus ulcers

The trauma is generally obvious and severe but occasionally is minor (e.g. an abrasion). The damaged tissues allow the entry of skin or environmental organisms such as Staphylococcus aureus, streptococci, gram-negative bacilli or anaerobes. Often, more than one species is present. Traumatic necrotizing fasciitis or myositis may arise at any site in the body but most commonly appears on an extremity or the trunk.

Fournier’s gangrene is an uncommon necrotizing infection of the perineal area, usually involving the penis and scrotum. The infection may extend along fascial planes from the perineum to the upper thighs and lower abdominal wall. The infection may arise from trauma to the perineum or penis (e.g. from a traumatic urethral catheterization) or by extension from a deep decubitus ulcer. The causative agents are often mixtures of species as noted above. Anaerobes are prominent in Fournier’s gangrene and may produce gas and a foul odor. The infection occurs mainly in men but has also been reported in the perineum of women and children.

Infection following intraabdominal surgery

These infections usually appear within hours after surgery, progress rapidly with pain and signs of sepsis, and often produce bacteremia. They usually are caused by a single species, mainly Streptococcus pyogenes or clostridia, but may be caused by mixtures of species. Similar infections may arise after obstetrical or gynecological procedures. The tissues initially involved are those around the site of surgery.

Infection by hematogenous spread from an occult source

Hematogenous infections usually involve a single species, namely, Streptococcus pyogenes, Clostridium septicum or perfringens, or rarely, Staphylococcus aureus (esp. MRSA). They are sometimes called “distant myonecrosis” because the myositis or fasciitis is remote from the portal of entry.

In patients with fasciitis or myositis due to clostridia, a colonic lesion such as a malignancy is often present; once the acute infections has resolved, a search for a colonic source is warranted. In patients with streptococcal infection, there may be evidence of minor skin trauma or of pharyngitis, but often the source remains unknown.

The source of S. aureus myositis or fasciitis may be from the skin or may be occult. The overlying skin may appear unremarkable initially. The infections may present on the extremities or the trunk.

Key management points

Severe pain in soft tissues, whether or not there is apparent “cellulitis,” should suggest necrotizing fasciitis or myositis, or muscle abscess. Time is of the essence in diagnosing and treating these infections.
Even if there is a history of trauma, suspect fasciitis, myositis or muscle abscess if the pain increases over time.
Obtain prompt surgical consultation if there is reasonable suspicion of fasciitis or myositis; these infections may progress rapidly.
The urgency of surgical consultation is less for muscle abscess (patients are less sick) and may allow time for imaging studies to be done for diagnosis.
Assess exposures and possible portals of entry for clues to likely organisms (see above).
If there is no evident portal of entry, suspect infection by clostridia (possibly from a colonic source), or Streptococcus pyogenes or S. aureus.
If there is evidence of gas formation in soft tissues (on imaging or because of crepitus), suspect infection by clostridia, other anaerobes or gram-negative enteric bacilli.

2. Emergency Management

Stabilizing the patient

If the level of suspicion of necrotizing fasciitis or myositis is high (e.g. severe pain, abnormal vital signs, elevated WBC), request prompt surgical consultation for debridement.
If the patient’s condition is relatively stable, consider imaging studies to distinguish muscle abscess from the more dangerous necrotizing fasciitis or myositis.
Obtain blood cultures.
Obtain gram stains and cultures of material from open skin lesions and from operative specimens.
Administer antibiotics (see Specific treatments below) depending on suspected infectious agents.
MRI or (less useful) CT scan may help in diagnosing myositis or fasciitis but surgical consultation should not be delayed in order to obtain imaging studies if the level of suspicion for these entities is high.
Watch carefully for a “compartment syndrome.”
The utility of hyperbaric oxygen treatment as an adjunct to surgical debridement and antibiotics is controversial (see references below).

3. Diagnosis

Diagnostic criteria and tests

A necrotizing fasciitis or myositis diagnosis is suspected on clinical grounds (severe pain, swelling of soft tissues, abnormal vital signs, elevated WBC). It can be supported by findings on MRI or CT or at surgery. The diagnosis is confirmed at surgery.

A muscle abscess diagnosis is is suspected on clinical grounds (findings similar to those of myositis or fasciitis but less severe and no or mild derangements of vital signs, WBC). It is supported by findings on imaging, such as ultrasound. The diagnosis is confirmed when the abscess is drained.

Other possible diagnoses

Necrotizing fasciitis, myositis or muscle abscess may be mistaken for simple cellulitis. The distinguishing features are:

moderate or severe pain; or increasing pain.
location of the lesions, which are often on proximal extremities or the trunk (unlike the more distal lesions of simple cellulitis).
significant abnormalities of vital signs or the WBC.

All these findings are unusual in simple cellulitis, which usually presents in a distal extremity with little pain and little derangement of vital signs. Apparent cellulitis overlying these more serious lesions will appear to respond poorly to antibiotics until the underlying lesions have been addressed surgically.

Confirmatory tests

See Key management points and Emergency management above.

4. Specific Treatment

Necrotizing fasciitis and myositis

General principles

The key to treatment is surgical debridement to remove dead and dying tissue and to relieve the pressure within muscle and fascia compartments.
Consider the addition of clindamycinto suppress toxin production if there is:

Evidence of infection by Streptococcus pyogenes or Clostridium septicum or perfringens or

Evidence of a toxic shock syndrome (diffuse rash, refractory hypotension) due to Streptococcus pyogenes or S. aureus.
Consider treatment with IVIG for the streptococcal toxic shock syndrome.

For initial, empiric antibiotic treatment of necrotizing fasciitis and myositis

Following trauma or around deep decubiti (e.g. for Fournier’s gangrene), to address S. aureus, enteric gram negative bacilli and anaerobes:

Vancomycin PLUS a broad-spectrum beta-lactam (ampicillin-sulbactam or piperacillin-tazobactam or meropenem), all IV

Consider adding clindamycin IV to suppress toxin synthesis by Streptococcus pyogenes or clostridia

Hyperbaric oxygen treatment as an adjunct to surgery and antibiotic treatment is of uncertain value (see references below)

Consider intravenous immune globulin if there is evidence of a streptococcal toxic shock syndrome.

Administer tetanus toxoid booster
Following intraabdominal or obstetrical/gynecological surgery, to address Streptococcus pyogenes or clostridia:

Broad-spectrum beta-lactam (ampicillin-sulbactam or piperacillin-tazobactam or meropenem) IV.

Add clindamycin IV to suppress toxin synthesis.
If there is suspected hematogenous spread from an occult source (to address Streptococcus pyogenes or clostridia or S. aureus):

Broad-spectrum beta-lactam (ampicillin-sulbactam or piperacillin-tazobactam or meropenem) IV plus vancomycin.

Add clindamycin IV to suppress toxin synthesis.

Consider IVIG if there is evidence of a streptococcal toxic shock syndrome.

Antibiotic treatments can be refined once gram-stains (from lesions) and cultures (of lesions and blood) have been obtained.

Muscle Abscess

The key modality is open or percutaneous drainage of the abscess.

For initial, empiric antibiotic treatment of muscle abscess, to address primarily S. aureus:

Vancomycin IV.
May add a beta-lactam (e.g. ceftriaxone) or a quinolone (e.g. ciprofloxacin) for possible gram-negatives pending gram-stain and culture results.

Refractory cases

If culture and sensitivity results indicate that the antibiotic choice is appropriate, the usual cause of refractory illness is insuffficient surgical debridement. Especially in cases of myositis and fasciitis, repeated surgical debridement is usually necessary.

5. Disease monitoring, follow-up and disposition

Expected response to treatment

Necrotizing fasciitis and myositis have high mortality rates. Streptococcal fasciitis is often accompanied by a toxic shock syndrome with a very high mortality rate. The infections may produce a compartment syndrome.

Extensive amputations and tissue debridement are often necessary and plastic surgery may be needed to repair defects.

The prognosis of necrotizing fasciitis and myositis varies widely with the extent and site of the tissues involved and the patient’s age and underlying state of health. The duration of treatment is difficult to specify: often, weeks of antibiotic treatment and repeated debridements are necessary.

Muscle abscess is usually a less invasive infection and, provided adequate drainage is obtained, the prognosis is usually good with minimal long-term sequelae.

Follow-up

For myositis and fasciitis, routine post-surgical followup is necessary, and plastic surgery and rehabilitation services usually are needed. If “distant myonecrosis” is caused by clostridia, evaluation for a colonic lesion, especially a malignancy, is recommended.

For muscle abscess, once the lesion has resolved, no special followup is needed. Depending on the circumstances, it may be worth testing for the possibility of predisposing diabetes mellitus or HIV infection.

Pathophysiology

These are described under “Description of the Problem” above.

A “compartment syndrome” arises when inflammation of muscle in a confined fascial compartment leads to increased pressure within the compartment. The rise in pressure blocks venous return, which further raises the pressure in the compartment. When the pressure rises to the point that arterial circulation is compromised, death of muscle and fascia occur.

Epidemiology

See “Description of the Problem” above.

Prognosis

See Section 5: Disease monitoring, followup and disposition

Special considerations for nursing and allied health professionals.

What's the evidence?

Description of the problem (clinical presentation)

Bisno, AL, Stevens, DL. “Streptococcal infections of skin and soft tissues”. New Engl J Med. vol. 334. 1996. pp. 240-5. (An excellent description of severe invasive infections by Streptococcus pyogenes. The article also reviews "compartment syndromes" and the use of IVIG.)

Stevens, DL, Bisno, AL, Chambers, HF. “Infectious Diseases Society of America. Practice Guidelines for the diagnosis and management of skin and soft tissue infections”. Clin Infect Dis. vol. 41. 2005. pp. 1373-406.. (A comprehensive review of the diagnosis and treatment of skin and soft tissue infections, including Fournier's gangrene.)

Stevens, DL, Tanner, MH, Winship, J. “Severe group A streptococcal infections associated with a toxic shock-like syndrome”. New Engl J Med. vol. 321. 1989. pp. 1-7. (This landmark article describes a relatively new entity, the conjunction of necrotizing fasciitis and myositis with the syndrome of streptococcal toxic shock. The authors attribute the occurrence of these aggressive infections to more virulent strains of streptococci which produce pyrogenic toxin A, the toxin of scarlet fever.)

Green, RJ, Dafoe, DC, Raffin, TA. “Necrotizing fasciitis”. Chest. vol. 110. 1996. pp. 219-29. (Reviews necrotizing fasciitis including Fournier's gangrene and includes a discussion of the possible utility of hyperbaric oxygen treatment.)

Casali, RE, Tucker, WE, Petrino, RA. “Postoperative necrotizing fasciitis of the abdominal wall”. Am J Surg. vol. 140. 1980. pp. 787-90. (An excellent review of postsurgical infections of the abdominal wall and pelvis.)

Eke, N. “Fournier's gangrene. A review of 1726 cases”. Br J Surg. vol. 87. 2000. pp. 718-28. (The author points out that there is some controversy over the definition of the syndrome and that it can occur in the perineum of women and children, though most cases are reported in men. The overall mortality rate in this large series was 16%. The utililty of hyperbaric oxygen and radical excision remains controversial.)

Diagnosis

Anaya, DA, Dellinger, EP. “Necrotizing soft-tissue infection: diagnosis and management”. Clin Infect Dis. vol. 44. 2007. pp. 705-10. (Reviews the diagnosis and treatment of necrotizing soft tissue infections. The utility of hyperbaric oxygen and IVIG remain controversial.)

Anaya, DA, McMahon, K, Nathens, AB. “Predictors of mortality and limb loss in necrotizing soft-tissue infections”. Arch Surg. vol. 140. 2005. pp. 151-57. (Reviews the outcomes in 166 patients. The overall mortality was 17%. Independent predictors of death included a white blood cell count greater than 30,000/ml3 and a serum creatinine concentration greater than 2 mg/dl. Shock at the time of admission [systolic BP <90 mm Hg] was an independent predictor of limb loss and clostridial infection was an independent predictor both of limb loss and mortality.)

Stamenkovic, I, Lew, PD. “Early recognition of potentially fatal necrotizing fasciitis: The use of frozen-section biopsy”. New Engl J Med. vol. 310. 1984. pp. 1689-93. (Early diagnosis by frozen section biopsy led to earlier diagnosis and a lower mortality rate.)

Schmid, MR, Kossmann, T, Duewell, S. “Differentiation of necrotizing fasciitis and cellulitis using MR imaging”. AJR Am J Roentgenol. vol. 170. 1998. pp. 615-20. (MR imaging is a highly sensitive technique for the detection of deep fascial involvement and is useful for exclusion of fasciitis; however, false-positives can occur.)

Fayad, LM, Carrino, JA, Fishman, EK. “Musculoskeletal infection: role of CT in the emergency department”. Radiographics. vol. 27. 2007. pp. 1723-36. (CT scans are useful for detecting deep complications of cellulitis and delineating the anatomy and extent of infection. CT can identify cases requiring emergency surgical debridement of necrotizing fasciitis and drainage of deep abscesses.)

Levenson, RB, Singh, AK, Novelline, RA. “Fournier gangrene: role of imaging”. Radiographics. vol. 28. 2008. pp. 519-28. (CT scans can lead to early diagnosis of Fournier's gangrene and can detect retroperitoneal infection. Subcutaneous emphysema is a "hallmark" of the infection but is not always present.)

Roth, D, Alarcon, FJ, Fernandez, JA. “Acute rhabdomyolysis associated with cocaine intoxication”. New Engl J Med. vol. 319. 1988. pp. 673-77. (Describes 39 patients seen over a period of 8 years with rhabdomyolysis after cocaine use. One third of the patients had renal failure, some had severe hepatic dysfunction and some had DIC.)

Cheng, NC, Su, YM, Kuo, YS. “Factors affecting the mortality of necrotizing fasciitis involving the upper extremities”. Surg Today. vol. 38. 2008. pp. 1108-13. (A review of prognostic factors in the outcome of necrotizing fasciitis. All 14 patients in this series had pain and swelling of the extremity but only half had fever.)

Sudarsky, LA, Laschinger, JC, Coppa, GF, Spencer, FC. “Improved results from a standardized approach in treating patients with necrotizing fasciitis”. Ann Surg. vol. 206. 1987. pp. 661-5. (The critical time period for surgical intervention was less than 12 hours or more than 48 hours after admission, the latter presumably reflecting less serious infection. All deaths and amputations among these 33 patients were in the group operated on in the 12-48 hour period after admission. This study further emphasizes the importance of early intervention.)

Wang, C, Schwaitzberg, S, Berliner, E. “Hyperbaric oxygen for treating wounds: a systematic review of the literature”. Arch Surg. vol. 138. 2003. pp. 272-9. (This systematic review found four retrospective comparison studies and 13 case series of HBO for the treatment of gas gangrene. Because of the lack of reliable comparison groups, the authors concluded it was difficult to determine the value of HBO. For necrotizing infections, the authors found six nonrandomized studies and 3 case series; they concluded that the results were inconclusive regarding the value of HBO.)

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