Necrotizing Fasciitis: What We Have Learned

By Jennifer A. Walker MD (EM/Critical Care Physician)

Edited by Alex Koyfman, MD (@EMHighAK) and Stephen Alerhand, MD

Soft tissue infections are a common diagnosis in the emergency department. The ability to quickly identify infections that are more profound and to intervene in a timely manner remains the responsibility of the emergency physician. Necrotizing fasciitis (NF) is a rare but deadly infection that is a surgical emergency. Unfortunately, due to the rarity of the disease as well as the fact that diagnosis is made in the operative theater, delay in diagnosis is common. This case describes the clinical characteristics of an 82-year-old woman who presented to the emergency department with a rapidly-progressing, necrotizing infection of her finger.

Case Report

An 82-year-old African American female with a medical history of significant tobacco abuse, alcohol abuse, and arthritis arrived at the Emergency Department with two days of worsening, right middle-finger swelling. The patient had possibly burned her finger on a cigarette approximately one month previously, and she commonly burned herself due to lack of sensation in her fingers. The swelling had progressed rapidly within the past 24 hours and now involved erythema to the forearm. The patient had subjective fevers and chills the evening before. The patient’s vitals were: temperature 37.3°C (99.2°F), heart rate 83 beats/min, respiratory rate 18 breaths/min, blood pressure 151/74 mm Hg, and pulse oximetry of 97% on room air. The patient was a thin, elderly lady who appeared to have chronic dementia. There was significant erythema and swelling noted to the right middle finger with a necrotic, distal fingertip. The rest of her exam was unremarkable. Labs showed elevated serum inflammatory markers (ESR 63, CRP 24.7) as well as mild leukocytosis (WBC 14.3). Due to the appearance of her hand, immediate, broad-spectrum antibiotic coverage was initiated. A radiograph was obtained which showed significant soft tissue swelling, with associated underlying gas.

The orthopedic service was called to take the patient urgently to the operating room for suspected necrotizing infection, where she underwent a right middle finger amputation at the proximal interphalangeal joint. Aspiration cultures sent from the operating room grew Staphylococcus aureus, Lactobacillus, and Alpha-hemolytic Streptococci that were susceptible to penicillins. She had an otherwise unremarkable hospital course and was discharged five days later on oral antibiotics.

Discussion

What Is Necrotizing Fasciitis?

Skin infections are classified based on anatomy, and NF represents one clinical syndrome on this anatomic spectrum 1. Erysipelas, impetigo, and folliculitis, for example, involve skin, while underlying fascia, subcutaneous structures (fat, nerves, arteries and veins) as well as deep fascia are affected in NF. Cellulitis actually affects the junction of skin and subcutaneous tissue, while myonecrosis affects the underlying muscle. Surgical visualization of dull, gray, necrotic tissue and avascular fascial tissue is the gold-standard of diagnosis along with the so-called “dishwater pus” that exudes from the area during dissection.

What Organisms Cause Necrotizing Fasciitis?

While diagnosis of NF is based on surgical findings, NF is sub-classified based on culture results.

Type I NF is polymicrobial involving a synergy between anaerobic, aerobic, and facultative anaerobes. This is the most common type of NF, involving up to 80% of cases 2. Risk factors for development of Type 1 NF include an impaired immune system – whether due to primary immune suppressed states or due to secondary factors leading to altered immune activity, such as in diabetes, peripheral vascular disease, etc.

Type 2 NF is monomicrobial and due to gram-positive organisms, most commonly caused by Group A beta-hemolytic streptococcus (GAS). These types of infections occur in previously healthy individuals and seem to involve more clear history of trauma or surgery. Methicillin-resistant staph aureus (MRSA) infections are emerging as a more common cause of NF as well.

Some references list Clostridium species as a separate Type 3 and fungal species as a Type 4.

What Is the Incidence of Necrotizing Fasciitis?

Because there are many synonyms for NF, the incidence is somewhat difficult to obtain 3. Also, the rate seems to have increased, but this is not clearly due to increased incidence versus an increased awareness due to recent media scares of “flesh-eating bacteria” 2. Some sources cite a rate of 500 to 1000 cases of NF per year in the United States 4,5, so that NF is clearly a rare entity, making diagnosis more challenging. The incidence of community-acquired MRSA NF is increasing with reports of incidence among all necrotizing infections at greater than 15% 6.

How Deadly Is Necrotizing Fasciitis?

The mortality is high with these infections, up to 35% to 50%, and mortality increases as time to the operating room increases 7. In fact, in one study, the average time from admission to operation was 90 hours in non-survivors versus 25 hours in survivors (p = 0.0002) 8. The most important variable affecting mortality, therefore, seems to be time to admission and debridement 9. In fact, Goh et al show that survival decreases from 93.2 to 75.2% with a delay from 24 to 48 hours 10.

So Why Are We Talking about This?

As clinicians, we are used to relying on a combination of patient history, physical exam, lab testing, and radiologic findings to secure most diagnoses. Unfortunately, the diagnosis of NF is a surgical one, and history, physical exam, and testing are not often reliable. Many patients present with very few, and sometimes vague symptoms, leading to the misdiagnosis in a large percentage of patients. A systematic review found a mean rate of misdiagnosis of 71.4%, ranging from 41 to 96% 10. NF is most frequently misdiagnosed early in the disease as cellulitis or abscess.

Paralleling the diagnostic difficulties with this disease, the significant increase in morbidity and mortality with delay in definitive treatment, offers further challenges. Definitive diagnosis and treatment is surgical debridement, which means the emergency physician is responsible for calling a surgical consult mostly based on gestalt. It is important, therefore, to discuss the clinical features that can both improve pre-surgical probability of NF as well as offer false reassurance and a missed diagnosis.

Patient Attributes, Risk Factors, Epidemiology

In a recent systematic review, trauma was identified as the most common etiology of NF 10. The most common co-morbidity is diabetes, with an incidence of up to 70% in some studies 11. As noted above, diabetes is strongly associated with Type 1 NF (polymicrobial infections). Other co-morbidities include peripheral vascular disease, smoking, alcoholism, intravenous drug abuse, immunosuppression, obesity, and age 2,11–13. As noted above, however, NF – especially type 2 NF – can occur in previously healthy individuals. Relying on risk factors alone to diagnose NF is not possible.

There is some discussion as to whether the use of non-steroidal anti-inflammatory medications increases the risk of development of NF 13,14. Regardless, the use of the medications may mask other symptoms such as pain or fever, leading to a delay in diagnosis.

Physical Exam

Findings on physical exam vary both by patient as well as extent of infection and where in the time-course of the disease process the exam occurs. The course of NF begins with “erythematous, tender swollen areas of hot cellulitis” and present with “pain out of proportion to physical exam” and complaints of a feeling of fullness in the affected area 1. Later in the course, the area can look edematous, smooth, shiny, and woody 1,7,8. The affected area may also have crepitus, however, this is a late and ominous finding 10. One paper reports the incidence of findings as follows: erythema (80%), induration (66%), tenderness (54%), fluctuance (35%), skin necrosis (23%) and bullae (11%) 15. Other, systemic symptoms can occur such as fevers (44%) and tachycardia (59%) 15. In other reports, fever is more common – 70% of patients 2. Septic shock is a late sign that is associated with increased mortality 10.

Importantly, such as in this case, patients with baseline neuropathy may have decreased sensation to begin with; therefore, it is important to continue to be vigilant and seek out other exam findings if suspicion is high that NF exists.

Lab Testing

Lab tests are not sensitive or specific, and therefore, not particularly helpful. Leukocytosis is commonly present and is the most common lab derangement 11,12. Other lab abnormalities can include abnormal liver and renal functions tests, coagulopathy, and elevated creatine kinase, presumably from organ dysfunction related to sepsis 6,12,16. Wong et al, developed a Laboratory Risk Indicator for Necrotizing Fasciitis (LRINEC) which attempts to differentiate between NF and other soft tissue infections using CRP, WBC, Hgb, blood sodium concentration, Creatinine, and Glucose levels 11. While a scoring system such as this would be helpful, there are subsequent reports illustrating the lack of usefulness, and in fact, illustrating cases of NF where the risk assessment score was zero 17.

Radiology

Plain XR of the affected area is most useful if soft-tissue gas is present; however, this is not an assured finding. Goh et al found a rate of gas on plain XR of 24.8% in their study 10. Wall et al, found 7 out of 22 patients with plain films had gas on the XR (only 32%), making plain XR a poorly sensitive test 18. CT scan is probably the most useful radiographic study to assess for NF. One article cited increased attenuation of the subcutaneous fat with stranding in 80% of cases 19. Another study showed sensitivity up to 100% but lower specificity with the use of non-contrast CT scans to diagnose all necrotizing infections 20. Similar to the LRINEC score for diagnosis of NF, however, reports do exist of negative tests with a positive diagnosis, including a negative CT with a diagnosis of NF 6. Meanwhile, MRI has a high sensitivity, it has a lower specificity 6,21 and is also time-consuming and less readily available in most emergency departments.

Treatment

The definitive treatment for NF is surgical debridement. This is the only way to decrease mortality 4,7,9. Antibiotic coverage is also an important treatment factor, but because fascial tissue is poorly vascularized and also degraded due to infection, antibiotic delivery to those sites is poor, making it a substandard solitary treatment option. When antibiotics are initiated in the emergency department, broad-spectrum coverage is key. Antibiotics should cover against gram-positive, gram-negative, and anaerobic organisms. Most regimens, therefore, include: beta-lactam-beta-lactamase inhibitor or carbapenem plus an agent that covers against MRSA. Clindamycin is added due to its antitoxin effect, and its addition has been shown to decrease mortality 3,22. If exposure to possible fresh- or seawater or fungal organisms is suspected, antibiotic coverage should be tailored to cover those as well.

Conclusion

The preceding case offers many points for discussion. This patient does not have the common risk factor of diabetes that often triggers a search for NF, but she does have significant alcohol and tobacco abuse, which presumably has caused peripheral vascular disease and neuropathy. Trauma, as is most commonly the case, did precede this patient’s infection. The patient had completely normal vital signs at presentation, which is also a common finding; therefore, it is worth repeating that a lack of fever or other systemic inflammatory response markers should not completely reassure the clinician. The patient did have gas on her radiographs, which ultimately clinched the diagnosis, but again, lack of gas on X-ray should not falsely reassure the clinician. Finally, as is most commonly found in patients with peripheral vascular disease, this patient’s infection was polymicrobial. Prompt initiation of broad-spectrum antibiotics was critical.

Ultimately, early operative intervention remains the cornerstone of diagnosis and treatment for NF, and morbidity and mortality both increase as time to debridement increases. Maintaining a high-index of suspicion in any patient with skin inflammation and a combination of physical exam findings, altered lab markers, and/or radiographic findings is key. These infections remain elusive, however, due to their relative rarity and similarity to other, more benign conditions. The emergency physician must accurately and quickly provide a diagnosis in order to rapidly provide the appropriate life-saving treatment.

References and Further Reading