Necrotizing fasciitis | |
---|---|
Other names | Flesh-eating bacteria, flesh-eating bacteria syndrome, [1] necrotizing soft tissue infection (NSTI), [2] fasciitis necroticans |
Person with necrotizing fasciitis. The left leg shows extensive redness and tissue death. | |
Pronunciation | |
Specialty | Infectious disease |
Symptoms | Severe pain, fever, purple colored skin in the affected area [3] |
Usual onset | Sudden, spreads rapidly [3] |
Causes | Multiple types of bacteria, [4] occasional fungus [5] |
Risk factors | Poor immune function such as from diabetes or cancer, obesity, alcoholism, intravenous drug use, peripheral artery disease [2] [3] |
Diagnostic method | Based on symptoms, medical imaging [4] |
Differential diagnosis | Cellulitis, pyomyositis, gas gangrene, toxic shock syndrome or toxic shock-like syndrome, pyoderma gangrenosum, deep vein thrombosis, Mucormycosis, brown recluse spider bite [6] |
Prevention | Wound care, handwashing [3] |
Treatment | Surgery to remove the infected tissue, intravenous antibiotics [2] [3] |
Prognosis | ~30% mortality with treatment, [2] ~100% mortality without treatment |
Frequency | 0.7 per 100,000 per year [4] |
Necrotizing fasciitis (NF), also known as flesh-eating disease, is a bacterial infection that results in the death of parts of the body's soft tissue. [3] It is a severe disease of sudden onset that spreads rapidly. [3] Symptoms usually include red or purple skin in the affected area, swelling, severe pain, fever, and vomiting. [3] The most commonly affected areas are the limbs and perineum. [2]
Bacterial infection is by far the most common cause of necrotizing fasciitis. Despite the term "flesh-eating disease," the organisms do not eat human tissue; rather, they release virulence factors and toxins that cause tissue death. Typically, the infection enters the body through a break in the skin such as a cut or burn. [3] Risk factors include recent trauma or surgery and poor immune function due to diabetes or cancer, obesity, alcoholism, intravenous drug use, and peripheral artery disease. [3] [2] It does not usually spread between people. [3] The disease is classified into four types, depending on the infecting organisms. [4] Medical imaging is often helpful to confirm the diagnosis. [4]
Necrotizing fasciitis is usually treated with surgery to remove the infected tissue, and intravenous antibiotics. [2] [3] It is considered a surgical emergency, and delays in surgery are associated with a much higher risk of death. [4] Despite high-quality treatment, the risk of death remains between 25 and 35%. [2]
Symptoms emerge very quickly, often within hours. [7] Manifestations include:
The initial skin changes are similar to cellulitis or abscess, thus making the diagnosis at early stages difficult. The redness and swelling usually blend into surrounding normal tissues. The overlying skin may appear shiny and tense as well. [8]
Later signs more suggestive of necrotizing changes (but only present in less than half of cases) are:
Rapid progression to shock despite antibiotic therapy is another indication of necrotizing fasciitis. However, those who are immunocompromised may not show typical symptoms. This includes but is not limited to patients with:
Immunocompromised persons are twice as likely to die from necrotizing infections compared to the greater population, so higher suspicion should be maintained in this group. [2]
Vulnerable populations are typically older with medical comorbidities such as diabetes mellitus, obesity, and immunodeficiency. [4] Other documented risk factors include:
For reasons that are unclear, it occasionally occurs in healthy individuals with no previous medical history or injury. [7] [9]
NSAIDs may increase the rates of necrotizing infections by reducing the immune response in the body. NSAIDs inhibit the cycloxygenase-1 and cycloxygenase-2 enzymes, which are important in producing prostaglandins responsible for fever, inflammation, and pain. In theory, this inhibition of prostaglandin E2 production impairs the inflammatory response and leukocyte adhesion, thus increasing the risk of soft-tissue infections. [2] [7]
Skin infections such as abscess and ulcers can also complicate NF. A small percentage of people can also get NF when bacteria from streptococcal pharyngitis spreads through the blood. [10] For infection of the perineum and genitals (Fournier gangrene), urinary tract infection, renal stones, and Bartholin gland abscess may also be implicated. [2]
The risk of developing necrotizing fasciitis from a wound can be reduced by good wound care and handwashing. [3] There is insufficient evidence as to whether immunocompromised individuals would benefit from taking antibiotics prophylactically after being exposed to a person with a necrotizing infection. Generally, such a regimen entails 250 mg penicillin four times daily for 10 days. [7]
Types of soft-tissue necrotizing infection can be divided into four classes according to the types of bacteria infecting the soft tissue. This classification system was first described by Giuliano and his colleagues in 1977. [4] [2]
Type I infection: This is the most common type of infection, and accounts for 70 to 80% of cases. It is caused by a mixture of bacterial types, usually in abdominal or groin areas. [4] These bacterial species include:
In such polymicrobial (mixed) infections, Group A Streptococcus (S. pyogenes) is the most commonly found bacterium, followed by S. aureus. [10] However, when the infection is caused solely by S. pyogenes and/or S. aureus, it is classified as a Type II infection.
Gram-negative bacteria and anaerobes like Clostridia are more often implicated in Fournier gangrene, a subtype of Type I infections affecting the groin and perianal areas. [10] Clostridia account for 10% of overall type I infections and typically cause a specific kind of necrotizing fasciitis known as gas gangrene or myonecrosis.
Type II infection: This infection accounts for 20 to 30% of cases, mainly involving the extremities. [4] [11] This involves Streptococcus pyogenes , alone or in combination with staphylococcal infections. Methicillin-resistant Staphylococcus aureus (MRSA) is involved in up to a third of Type II infections. [4] Infection by either type of bacteria can progress rapidly and manifest as toxic shock syndrome. Type II infection more commonly affects young, healthy adults with a history of injury. [2]
Type III infection: Vibrio vulnificus , a bacterium found in saltwater, rarely causes NF after it is introduced into the body through a break in the skin. [12] One in three patients with a V. vulnificus infection develop necrotizing fasciitis. [12] Disease progression is similar to type II but sometimes with few visible skin changes. [2]
Type IV infection: This type of NF accounts for less than 1% of cases and is mostly caused by the Candida albicans fungus. Risk factors include age and immunodeficiency. [4] [13]
Early diagnosis is difficult, as the disease often looks early on like a simple superficial skin infection. [4] While a number of laboratory and imaging modalities can raise the suspicion for necrotizing fasciitis, none can rule it out. [14] The gold standard for diagnosis is a surgical exploration and subsequent tissue biopsy in a setting of high suspicion. When in doubt, a 2-cm incision can be made into the affected tissue under local anesthesia. [2] [15] If a finger easily separates the tissue along the fascial plane, then the finger test is positive, the diagnosis is confirmed, and an extensive debridement should be performed. [2] [15]
Necrotizing fasciitis is ideally a clinical diagnosis based on symptoms. Due to the need for rapid surgical treatment for this condition, the time delay in performing imaging is a major concern. [15] Hence, imaging may have a limited role in diagnosis if the symptoms are clearly indicative of a necrotizing infection. However, due to the vague symptoms associated with the earlier stages of this disease, imaging is often useful in clarifying or confirming the diagnosis. [15]
Both CT scan and MRI are used to diagnose NF, but neither are sensitive enough to rule out necrotizing changes completely. [2]
If available, computed tomography (CT) is the most convenient tool in diagnosing NF due to its speed and resolution (detects about 80% of NF cases). [16] CT scan may show fascial thickening, edema, or abscess formation. [2] [15] CT is able to pick up on subcutaneous gas better than MRI, but it is not unusual for NF to present without gas on imaging, especially if the patient has diabetes or is presenting early in the disease process. [15] In addition, CT is helpful in evaluating complications due to NF and finding possible sources of infections. [15] Its use may be limited in pregnant patients and patients with renal issues. [15]
Magnetic resonance imaging (MRI) is considered superior to computed tomography (CT) in the visualization of soft tissues and is able to detect about 93% of NF cases. [15] It is especially useful in finding fluid in the deep fascia, which can be a distinguishing factor between NF and cellulitis. [15] When there is fluid collection with deep fascial involvement, or thickening or enhancement with contrast injection, necrotizing fasciitis should be strongly suspected. However, MRI is much slower than CT and not as widely available. [15] There may also be limitations on its use in patients with renal impairment (a common comorbidity in patients vulnerable to acquiring NF). [15]
Point-of-care ultrasound (POCUS) may be useful in the diagnosis of NF if MRI and CT are not available. [18] It can also help rule out diagnoses that mimic earlier stages of NF, including deep vein thrombosis (DVT), superficial abscesses, and venous stasis. [18] Linear probes are generally preferred for the assessment, especially in the extremities. [18]
Findings characteristic of NF include abnormal thickening, air, or fluid in the subcutaneous tissue. [18] This can be summarized as the mnemonic "STAFF" (Subcutaneous irregularity or Thickening, Air, and Fascial Fluid). [18] The official diagnosis of NF using ultrasound requires "the presence of BOTH diffuse subcutaneous thickening AND fascial fluid more than 2 mm." [18] Gas in the subcutaneous tissue may show "dirty acoustic shadowing." [15] However, similar to other imaging modalities, the absence of subcutaneous free air does not definitively rule out a diagnosis of NF, because this is a finding that often emerges later in the disease process. [18]
Of note, the quality and accuracy of POCUS is highly user-dependent. It may also be difficult to visualize NF over larger areas, or if there are many intervening layers of fat or muscle. It is still unclear whether POCUS improves the speed of diagnosis of NF, or if it reduces the time to surgical intervention as a whole. [18]
It is difficult to distinguish NF from cellulitis in earlier stages of the disease using plain radiography. [15] X-rays can detect subcutaneous emphysema (gas in the subcutaneous tissue), which is strongly suggestive of necrotizing changes. However, air is often a late-stage finding, and not all necrotizing skin infections create subcutaneous emphysema. Hence, radiography is not recommended for the initial diagnosis of NF. [15] However, it may be able to identify the source of infection, such as foreign bodies or fractures, and thus aid in subsequent treatment. [15]
Correlated with clinical findings, a white blood cell count greater than 15,000 cells/mm3 and serum sodium level less than 135 mmol/L are predictive of necrotizing fasciitis in 90% of cases. [3] If lab values do not meet those values, there is a 99% chance that the patient does not have NF. Various scoring systems are being developed to determine the likelihood of getting necrotizing fasciitis, but the LRINEC scoring system developed by Wong and their colleagues in 2004 is most commonly used. This is the laboratory risk indicator for necrotizing fasciitis (LRINEC) score, which can be used to stratify by risk those people having signs of severe cellulitis or abscess to determine the likelihood of necrotizing fasciitis being present.
LRINEC uses six laboratory values: C-reactive protein, total white blood cell count, hemoglobin, sodium, creatinine, and blood glucose. [2] A score of 6 or more indicates that there is a 50-75% probability of necrotizing fasciitis, and a score of 8 or more represents over 75% likelihood of NF. [15] [19] [20] Patients with a LRINEC score ≥6 may have a higher rate of both death and amputation as well. [21] The scoring criteria are: [19] [22]
Lab value | Criteria | Points* |
---|---|---|
CRP | ≥ 15 mg/dL (150 mg/L) | +4 |
WBC count (×103) | 15 - 25/mm3 | +1 |
> 25/mm3 | +2 | |
Hemoglobin | 11 - 13.5 g/dL | +1 |
< 11 g/dL | +2 | |
Sodium | < 135 mEq/L | +2 |
Creatinine | > 1.6 mg/dL (141 μmol/L) | +2 |
Glucose | > 180 mg/dL (10 mmol/L) | +1 |
*If the lab value does not meet the listed criteria, it is assigned 0 points. |
However, this scoring system is yet to be validated. [3] A LRINEC score ≥6 is only able to detect 70% of NF cases, and a LRINEC score ≥8 has shown even poorer sensitivity. [20] Moreover, these lab values may be falsely positive if any other inflammatory conditions are present. Therefore, this scoring system should be interpreted with caution. [2]
Necrotizing fasciitis is treated with surgical debridement (cutting away affected tissue). [3] Early medical treatment is often presumptive; thus, antibiotics should be started as soon as this condition is suspected. Tissue cultures (rather than wound swabs) are taken to determine appropriate antibiotic coverage, and antibiotics may be changed in light of results. Besides blood pressure control and hydration, support should be initiated for those with unstable vital signs and low urine output. [2]
Aggressive wound debridement should be performed early, usually as soon as the diagnosis of necrotizing soft tissue infection (NSTI) is made. The affected area may need to be debrided several times, usually once every 12–36 hours. [3] Large sections of tissue and muscle may need to be removed to prevent the infection from spreading, and amputation may be needed if the infection is too severe. [3]
En bloc debridement (EBd) is most commonly employed in treating NSTIs. [23] This involves cutting away the skin overlying all diseased areas at the cost of increased scar formation and potential decreased quality of life post-operatively. [23] More recently, skin-sparing debridement (SSd) has gained traction, as it resects the underlying tissue and sources of infection while preserving skin that is not overtly necrotic. [23] However, more studies are needed to examine whether SSd actually accelerates the healing process after surgery. [23]
After the wound debridement, adequate dressings should be applied to prevent exposure of bones, tendons, and cartilage so that such structures do not dry out and to promote wound healing. [2] Wounds are generally packed with wet-to-dry dressings and left open to heal. [3] In certain cases, it may be advantageous to use vacuum-sealing drainage (VSD) to help the wound heal, especially in Fournier gangrene.
For necrotizing infection of the perineal area (Fournier's gangrene), wound debridement and wound care in this area can be difficult because of the excretory products that often render this area dirty and affect the wound-healing process. Therefore, regular dressing changes with a fecal management system can help to keep the wound at the perineal area clean. Sometimes, colostomy may be necessary to divert the excretory products to keep the wound at the perineal area clean. [2]
Empiric antibiotics are usually initiated as soon as the diagnosis of NSTI has been made, and then later changed to culture-guided antibiotic therapy. In the case of NSTIs, empiric antibiotics are broad-spectrum, covering gram-positive (including MRSA), gram-negative, and anaerobic bacteria. [24] Often, a combination of antibiotics is used, such as clindamycin, daptomycin, IV vancomycin, and gentamicin. [2] Gram-negative coverage may entail the use of fluoroquinolones, piperacillin/tazobactam, or carbapenems. [3]
While studies have compared moxifloxacin (a fluoroquinolone) and amoxicillin-clavulanate (a penicillin) and evaluated appropriate duration of treatment (varying from 7 to 21 days), no definitive conclusions on the efficacy of treatment, ideal duration of treatment, or the adverse effects could be made due to poor-quality evidence. [24] Generally, antibiotics are administered until surgeons decide that no further debridement is needed, and the patient no longer shows any systemic signs of infection from a clinical and laboratory standpoint. [3]
Necrotizing fasciitis occurs in about 4 people per million per year in the U.S., and about 1 per 100,000 in Western Europe. [4] About 1,000 cases of necrotizing fasciitis occur per year in the United States, but the rates have been increasing. This could be due to increasing awareness of this condition and increased reporting, or increasing antibiotic resistance. [2] Both sexes are affected equally. [2] It is more common among older people and is rare in children. [4]
Necrotizing fasciitis can occur at any part of the body, but it is more commonly seen at the extremities, perineum, and genitals. A small fraction of cases arise in the head/neck, chest and abdomen. [2]
In the fifth century BCE, Hippocrates described necrotizing soft tissue infection as a disease where those affected would have "erysipelas all over the body while the cause was only a trivial accident. Bones, flesh, and sinew (cord, tendon, or nerve) would fall off from the body and there were many deaths". The first English description for necrotizing soft-tissue infection was by British surgeon Leonard Gillespie and British physicians Gilbert Blaine and Thomas Trotter in the 18th century. At that time, necrotizing soft-tissue infections were known variously as "phagedaenic ulcer" (ulceration that spreads and destroys surrounding tissue), "gangrenous phagedena", "gangrenous ulcer", "malignant ulcer", "putrid ulcer", "fulminating gangrene", "necrotizing erysipelas", "gangrenous erysipelas", "crepitant cellulitis", "gangrenous cellulitis", "Meleney cellulitis", "necrotizing synergistic cellulitis", "hemolytic streptococcal gangrene", "progressive bacterial synergistic gangrene", or "necrotizing abscess". [26] Later, "hospital gangrene" became more commonly used.
In 1871 Confederate States Army surgeon Joseph Jones reported 2,642 cases of hospital gangrene with a mortality rate of 46%. In 1883, Dr Jean-Alfred Fournier described the necrotizing infection of the perineum and scrotum, now called Fournier gangrene. The term "necrotizing fasciitis" was coined by Dr. Bob Wilson in 1952. [4] [27] Since then, its definition has broadened to include not only infection of fascia but also other soft-tissue infections. [2] Despite being disfavored by the medical community, the term "galloping gangrene" is frequently used in sensationalistic news media to refer to outbreaks of necrotizing fasciitis. [28]
An abscess is a collection of pus that has built up within the tissue of the body. Signs and symptoms of abscesses include redness, pain, warmth, and swelling. The swelling may feel fluid-filled when pressed. The area of redness often extends beyond the swelling. Carbuncles and boils are types of abscess that often involve hair follicles, with carbuncles being larger. A cyst is related to an abscess, but it contains a material other than pus, and a cyst has a clearly defined wall. Abscesses can also form internally on internal organs and after surgery.
Erysipelas is a relatively common bacterial infection of the superficial layer of the skin, extending to the superficial lymphatic vessels within the skin, characterized by a raised, well-defined, tender, bright red rash, typically on the face or legs, but which can occur anywhere on the skin. It is a form of cellulitis and is potentially serious.
Group A streptococcal infections are a number of infections with Streptococcus pyogenes, a group A streptococcus (GAS). S. pyogenes is a species of beta-hemolytic Gram-positive bacteria that is responsible for a wide range of infections that are mostly common and fairly mild. If the bacteria enters the bloodstream, the infection can become severe and life-threatening, and is called an invasive GAS (iGAS).
Gangrene is a type of tissue death caused by a lack of blood supply. Symptoms may include a change in skin color to red or black, numbness, swelling, pain, skin breakdown, and coolness. The feet and hands are most commonly affected. If the gangrene is caused by an infectious agent, it may present with a fever or sepsis.
Cellulitis is usually a bacterial infection involving the inner layers of the skin. It specifically affects the dermis and subcutaneous fat. Signs and symptoms include an area of redness which increases in size over a few days. The borders of the area of redness are generally not sharp and the skin may be swollen. While the redness often turns white when pressure is applied, this is not always the case. The area of infection is usually painful. Lymphatic vessels may occasionally be involved, and the person may have a fever and feel tired.
Nocardiosis is an infectious disease affecting either the lungs or the whole body. It is due to infection by a bacterium of the genus Nocardia, most commonly Nocardia asteroides or Nocardia brasiliensis.
Epiglottitis is the inflammation of the epiglottis—the flap at the base of the tongue that prevents food entering the trachea (windpipe). Symptoms are usually rapid in onset and include trouble swallowing which can result in drooling, changes to the voice, fever, and an increased breathing rate. As the epiglottis is in the upper airway, swelling can interfere with breathing. People may lean forward in an effort to open the airway. As the condition worsens, stridor and bluish skin may occur.
Gas gangrene is a bacterial infection that produces tissue gas in gangrene. This deadly form of gangrene usually is caused by Clostridium perfringens bacteria. About 1,000 cases of gas gangrene are reported yearly in the United States.
Lymphangitis is an inflammation or an infection of the lymphatic channels that occurs as a result of infection at a site distal to the channel. It may present as long red streaks spreading away from the site of infection. It is a possible medical emergency as involvement of the lymphatic system allows for an infection to spread rapidly. The most common cause of lymphangitis in humans is bacteria, in which case sepsis and death could result within hours if left untreated. The most commonly involved bacteria include Streptococcus pyogenes and hemolytic streptococci. In some cases, it can be caused by viruses such as mononucleosis or cytomegalovirus, as well as specific conditions such as tuberculosis or syphilis, and the fungus Sporothrix schenckii. Other causes of Lymphangitis could be from Arthropod bites and Iatrogenic causes. Lymphangitis is sometimes mistakenly called "blood poisoning". In reality, "blood poisoning" is synonymous with sepsis.
A skin infection is an infection of the skin in humans and other animals, that can also affect the associated soft tissues such as loose connective tissue and mucous membranes. They comprise a category of infections termed skin and skin structure infections (SSSIs), or skin and soft tissue infections (SSTIs), and acute bacterial SSSIs (ABSSSIs). They are distinguished from dermatitis, although skin infections can result in skin inflammation.
Orbital cellulitis is inflammation of eye tissues behind the orbital septum. It is most commonly caused by an acute spread of infection into the eye socket from either the adjacent sinuses or through the blood. It may also occur after trauma. When it affects the rear of the eye, it is known as retro-orbital cellulitis.
Fournier gangrene is a type of necrotizing fasciitis or gangrene affecting the external genitalia or perineum. It commonly occurs in older men, but it can also occur both in women and children and in people with diabetes or alcoholism or those who are immunocompromised.
An open fracture, also called a compound fracture, is a type of bone fracture that has an open wound in the skin near the fractured bone. The skin wound is usually caused by the bone breaking through the surface of the skin. An open fracture can be life threatening or limb-threatening due to the risk of a deep infection and/or bleeding. Open fractures are often caused by high energy trauma such as road traffic accidents and are associated with a high degree of damage to the bone and nearby soft tissue. Other potential complications include nerve damage or impaired bone healing, including malunion or nonunion. The severity of open fractures can vary. For diagnosing and classifying open fractures, Gustilo-Anderson open fracture classification is the most commonly used method. This classification system can also be used to guide treatment, and to predict clinical outcomes. Advanced trauma life support is the first line of action in dealing with open fractures and to rule out other life-threatening condition in cases of trauma. The person is also administered antibiotics for at least 24 hours to reduce the risk of an infection.
Ecthyma gangrenosum is a type of skin lesion characterized by vesicles or blisters which rapidly evolve into pustules and necrotic ulcers with undermined tender erythematous border. "Ecthyma" means a pus forming infection of the skin with an ulcer, "gangrenosum" refers to the accompanying gangrene or necrosis. It is classically associated with Pseudomonas aeruginosa bacteremia, but it is not pathognomonic. Pseudomonas aeruginosa is a gram negative, aerobic bacillus.
Aquarium granuloma is a rare skin condition caused by a non-tubercular mycobacterium known as Mycobacterium marinum. Skin infections with M. marinum in humans are relatively uncommon, and are usually acquired from contact with contaminated swimming pools, aquariums or infected fish.
Skin and skin structure infections (SSSIs), also referred to as skin and soft tissue infections (SSTIs), or acute bacterial skin and skin structure infections (ABSSSIs), are infections of skin and associated soft tissues. Historically, the pathogen involved has most frequently been a bacterial species—always, since redescription of SSSIs as ABSSSIs—and as such, these infections require treatment by antibiotics.
Perianal cellulitis, also known as perianitis or perianal streptococcal dermatitis, is a bacterial infection affecting the lower layers of the skin (cellulitis) around the anus. It presents as bright redness in the skin and can be accompanied by pain, difficulty defecating, itching, and bleeding. This disease is considered a complicated skin and soft tissue infection (cSSTI) because of the involvement of the deeper soft tissues.
Anaerobic infections are caused by anaerobic bacteria. Obligately anaerobic bacteria do not grow on solid media in room air ; facultatively anaerobic bacteria can grow in the presence or absence of air. Microaerophilic bacteria do not grow at all aerobically or grow poorly, but grow better under 10% carbon dioxide or anaerobically. Anaerobic bacteria can be divided into strict anaerobes that can not grow in the presence of more than 0.5% oxygen and moderate anaerobic bacteria that are able of growing between 2 and 8% oxygen. Anaerobic bacteria usually do not possess catalase, but some can generate superoxide dismutase which protects them from oxygen.
Clostridium tertium is an anaerobic, motile, gram-positive bacterium. Although it can be considered an uncommon pathogen in humans, there has been substantial evidence of septic episodes in human beings. C. tertium is easily decolorized in Gram-stained smears and can be mistaken for a Gram-negative organism. However, C.tertium does not grow on selective media for Gram-negative organisms.
Diabetic foot infection is any infection of the foot in a diabetic person. The most frequent cause of hospitalization for diabetic patients is due to foot infections. Symptoms may include pus from a wound, redness, swelling, pain, warmth, tachycardia, or tachypnea. Complications can include infection of the bone, tissue death, amputation, or sepsis. They are common and occur equally frequently in males and females. Older people are more commonly affected.