The virulence of any microorganism depends on its ability to cause damage to the host. Exotoxins, such as streptococcal hyaluronidase, are digestive enzymes released locally by some organisms that allow the spread of infection by breaking down host extracellular matrix proteins. Endotoxins, such as lipopolysaccharides, are components of gram-negative cell walls that are released only after bacterial cell death. Once systemically absorbed, endotoxins trigger a severe and rapid systemic inflammatory response by releasing various endogenous mediators such as cytokines, bradykinin, and prostaglandins. Surgical infections may be polymicrobial, involving various interactions among the microorganisms and toxins.

The size of the inoculum is the second important component of infection. The number of colonies of microorganisms per gram of tissue is the key determinant. Predictably, any decrease in host resistance decreases the absolute number of colonies necessary to cause clinical disease. In general, if the bacterial population in a wound exceeds 100,000 organisms per gram of tissue, an invasive infection is present.

For any inoculum, the environment determines the viability. Therefore, the presence of suitable nutrients for the organism is essential and comprises the third component of any clinical infection. Accumulation of necrotic tissue, hematoma, and foreign matter is an excellent nutrient medium for continued organism growth and spread. Of special importance to the surgeon is the concept of necrotic tissue and infection. When present at an infected site, this tissue often needs to be debrided to restore the host–bacterial balance and lead to effective wound healing. Neutrophils, macrophages, and cytokines can then accumulate in necrotic tissue, initiating a secondary inflammatory response.

Finally, for a clinical infection to arise, the body’s defenses must be overwhelmed. Even highly virulent organisms can be eradicated before clinical infection occurs if the host resistance is intact. Evolution has fortunately equipped humans with numerous mechanisms of defense, both anatomic and systemic.

Intact skin and mucous membranes provide an effective surface barrier to infection. These tissue barriers are not merely a mechanical obstacle, but also possess physiologic characteristics that provide protection. The skin inhibits bacterial cell growth by the processes of thermoregulation, turnover of keratinocytes, and acid secretion from sebaceous glands. The mucosal surfaces have also developed advanced defense mechanisms to prevent and combat microbial invasion, where specialized epithelial layers provide resistance to infection. In addition, mechanisms such as the mucociliary transport system in the respiratory tract and normal colonic flora in the gastrointestinal tract prevent invasion of organisms. Any alteration in the normal function of these anatomic barriers increases the host’s susceptibility to infection. A skin injury or a burn provides open access to the underlying soft tissues, while antibiotic use disrupts normal colonic flora. Fortunately, such breakdowns in surface barriers are dealt with by the second line of defense, the immune system.

The immune system involves complex pathways and many specialized effector responses. The initial line of defense is the more primitive and nonspecific innate system, which consists primarily of phagocytic neutrophils and the serum-based complement system. The neutrophil is able to rapidly migrate to the source of the infection and engulf and destroy the infecting organisms by phagocytosis. In the complement system, cytokines, low molecular-weight proteins including tumor necrosis factor (TNF), and many interleukins attract and activate neutrophils. In addition, the complement system, when activated, initiates a sequential cascade that also enhances phagocytosis and leads to lysis of pathogens. Neonates, particularly premature infants, have an immature immune system and are supported by the protective agents in human breast milk. ^,

In adults, comorbidities often increase the risk of surgical site infection (SSI). However, these chronic diseases are infrequently encountered in children. A prospective, multicenter study of wound infections in the pediatric population found that postoperative wound infections were more likely related to factors at the operation rather than to patient characteristics. In this study of more than 800 children, the only factors associated with an increased SSI were contamination at the time of operation and the duration of the procedure. Other investigators have similarly found that local factors at the time of operation, such as degree of contamination, tissue perfusion, and operative technique, play a more important role in initiation of an SSI than the general condition of the infant/child.

Attempting to reduce SSI with preoperative patient optimization is an ongoing quality improvement initiative across many centers and national databases that benchmark these data. Adults with positive nasal methicillin-resistant Staphylococcus aureus (MRSA) have been shown to have a higher chance of MRSA SSI; however, the rate of MRSA SSI was <2% in one study. Recent pediatric evidence suggest there is no correlation between positive nasal swabs and wound infection for elective surgeries, and Staphylococcus aureus eradication may not be needed preoperatively.

Preoperative preparation of the surgical site and the sterility of the surgical team are important in reducing the risk of postoperative infection. Hand hygiene has always been a source of attention. In the United States, the conventional method for surgical team scrubbing has been a 5-minute first scrub followed by subsequent 2- or 3-minute scrubs for subsequent cases with either 5% povidone-iodine or 4% chlorhexidine gluconate. These scrubbing protocols can achieve a 95% decrease in skin flora. ^, However, newer alcohol-based antiseptic cleaners with shorter applications, usually 30 seconds, have been shown to be as effective as, or even more effective than, hand washing in decreasing bacterial contamination.

Normothermia has also been suggested as a means to decrease the incidence of wound infections. Infants and children are at particular risk for experiencing hypothermia during surgery due to an increased area-to-body weight ratio leading to greater heat loss. Intraoperative hypothermia can potentially lead to serious complications, including coagulopathy, SSIs, and cardiac complications. A prospective, randomized trial of 200 adult patients undergoing colorectal surgery showed that intraoperative hypothermia caused delayed wound healing and a greater incidence of infections. A number of techniques are available to warm infants and children during their operation, including warming intravenous fluids or using forced-air warming systems. In addition, supplemental oxygen given during the perioperative period in adults has been shown to decrease the rate of wound infection by as much as 40%–50%. ^, Finally, adequate control of glucose levels perioperatively has also been demonstrated to decrease morbidity and mortality in both adult and pediatric surgical patients, particularly in those patients undergoing cardiac surgery.

The infection risk for operative cases can be stratified into one of four classes (Table 8.1 ), with the risk of SSI increasing with each higher classification level. Preoperative wound classification has commonly been used for SSI risk stratification, which is now used as a quality measure by hospitals and third-party payors. Classifying the operation has also been incorporated into the routine preoperative time-out sessions. Historically, the estimated SSI rate for the surgical wound classifications were: 1%–5% (Class I), 3%–11% (Class II), 10%–17% (Class III), and >27% (Class IV). However, a recent study using the American College of Surgeon National Surgical Quality Improvement Program (ACS-NSQIP) showed that superficial SSI rates were 1.76%, 3.94%, 4.75%, and 5.16%, respectively.

In the pediatric cohort, surgical wound classification discrepancies have been identified in multiple common procedures, especially in laparoscopic procedures. A multicenter study showed a total surgical wound classification concordance of 56% with variability between institutions and procedures. Also, correlation of the wound classes with risk of surgical infection remains imprecise in children. Although quality improvement (QI) initiatives have improved wound classification concordance, there is still a need for caution in using surgical wound classification as a quality benchmark. ^,

SSI is one of the most common complications in pediatric surgery and is associated with prolonged hospitalization and resource overutilization. ^, Cefazolin, a first-generation cephalosporin, is the most commonly recommended antibiotic for most surgical procedures. ^, This drug is the first-line treatment since it is the most widely studied, is effective against organisms commonly encountered in surgical site infections, is well tolerated, and is economical. One major issue surrounding its use is the 10% of patients reporting a penicillin allergy and previously reported high levels of cross-reactivity. These patients are less likely to receive cefazolin and more likely to receive an alternate antibiotic like clindamycin or vancomycin. These alternate choices may result in increased odds of developing a surgical site infection. ^, In one of the most robust systematic reviews conducted to assess the frequency of cross-reactivity between natural penicillins and cefazolin, the risk of cross-reactivity between penicillins and cefazolin was rare. Hypersensitivity reactions to cefazolin occurred in less than 1% of patients with unconfirmed penicillin allergy and in 3% of patients with allergy confirmation. Therefore, most patients with a penicillin allergy history undergoing surgical prophylaxis may safely receive cefazolin. ^,

Important points for preoperative antibiotic prophylaxis include using agents that cover the most probable intraoperative contaminants for the operation, optimal timing for the initial dose of antibiotic so that bactericidal concentrations are reached at the time of incision, and maintaining the appropriate serum levels throughout the operation. Timing of the perioperative antibiotic coverage is crucial. The first dose is generally given within 1 hour of the incision. In operations that take more than the half-life of the administered drug, a second dose of prophylactic antibiotics is needed to achieve adequate serum levels.

Prophylaxis accounts for nearly 75% of antibiotic use on pediatric surgical services. Complete compliance with antibiotic prophylaxis decreases SSI by 30%. Yet, the rate of complete compliance has been found to be as low as 6.5%. Prophylaxis is also the major cause of the inappropriate use of antimicrobials in children with prophylactic antibiotics inappropriately being administered in 40%–52% of children. A recent retrospective database review showed that there is national variation in the overall and appropriate use of antibiotic prophylaxis. Evidence suggests that a multidisciplinary approach to antibiotic prophylaxis guidelines can increase compliance within a children’s hospital.

In pediatric surgery, antibiotic coverage is typically recommended during clean-contaminated, contaminated, or dirty cases. Antibiotic prophylaxis in clean cases, such as inguinal hernias, orchiopexy, and laparoscopic pyloromyotomies, has not been shown to decrease SSI and is not warranted. ^, However, the utility of wound class in determining antibiotic prophylaxis is increasingly being challenged. As an example, there is growing evidence against the use of perioperative antibiotics in cases of elective laparoscopic cholecystectomy, even though classified as a clean-contaminated procedure. While antibiotics have improved the care we deliver by both preventing and assisting in the treatment of life-threatening infections for patients requiring operative interventions, they are not without unintended consequences. Compounded by irrational use, the development of antibiotic-resistant bacteria and adverse events including Clostridioides difficile (previously Clostridium difficile ) infections are of major concern. ^,

The current bowel prep recommendations for adults and children undergoing an elective colorectal procedure are still somewhat controversial. The 2023 clinical practice guidelines from the American Society of Colon and Rectal Surgeons and the Society of American Gastrointestinal and Endoscopic Surgeons suggest combined isosmotic mechanical bowel prep along with oral antibiotics. ^, The bowel prep includes mechanical irrigation and flushing of the colon to remove stool, oral antibiotics against colonic aerobes and anaerobes, and preoperative intravenous antibiotics that cover both common skin and colonic flora. ^, A recent large retrospective database study found that mechanical bowel preparation along with oral antibiotics reduced SSI, anastomotic leak, and ileus for adult elective colorectal cases in comparison to mechanical bowel preparation alone or no mechanical bowel prep. However, contradictory studies exist. A 2018 meta-analysis suggested that the use of a mechanical bowel prep did not affect the incidence of postoperative complications when compared to no preparation. In pediatric-specific data, the use of a mechanical bowel prep has not been consistently shown to improve outcomes.

In infants and children, protocols for bowel preparation have largely been extrapolated from the adult colorectal literature. Unfortunately, there continues to be variability in the use and type of bowel preparation used at children’s hospitals and among pediatric surgeons. Only 9%–19% of patients are receiving a mechanical bowel prep with oral antibiotics. Recent pediatric randomized trials comparing mechanical bowel preparation versus no prep found no increased risk of infectious complications and similar postoperative outcomes. However, none of the studies included an arm that used mechanical bowel prep and oral antibiotics. Future studies should focus on comparing the current recommendations versus no preparation to determine whether bowel preparation is necessary in children. If bowel preparation is used in infants and children, care must be taken to avoid dehydration.

Despite meticulous technique and perioperative antibiotics, infectious complications still occur. Postoperative wound infections can be divided into superficial surgical site infections or deep organ space infections. Early diagnosis and prompt intervention help to avoid morbidity and occasional mortality. Erythema, fever, leukocytosis, tenderness, crepitus, and suppuration are concerning diagnostic signs but are not always present. When confronted with one or more of these signs, clinical judgment is important. Treatment may include oral or intravenous antibiotics, incision and drainage (I&D), or extensive surgical debridement with supportive wound care (Figs. 8.1 and 8.2 ).

This newborn underwent open left congenital diaphragmatic hernia repair using mesh for diaphragmatic replacement along with an abdominal wall mesh bridge. An infection developed in the left upper abdominal incision (A) that required removal of the mesh. After removing the mesh, the wound was left open and a Wound V.A.C. was placed for wound healing (B). The wound healed nicely, and the Wound V.A.C. was able to be removed. The photograph in C shows almost complete healing of the wound.

This 17-year-old presented with multiple pilonidal sinuses and an abscess that required drainage in the emergency department. Due to the extensive disease, she was taken to the operating room for wide excision and primary closure. The wound broke down, and was then managed using a Wound V.A.C. These photographs show a progression in management using the Wound V.A.C. In (A), the Wound V.A.C. has been placed. In (B), during one of the early dressing changes, the Wound V.A.C. has been removed and there is visible granulation tissue. In (C), the wound has completely healed. This process took about 6 weeks and required a combination of home health and clinic visits to ensure complete healing of the wound.

An abscess is a localized collection of pus in a cavity formed by an expanding infectious process (Fig. 8.3A ). Pus is a combination of leukocytes, necrotic material, bacteria, and extracellular fluid. The usual cause is the staphylococcal species, especially methicillin-susceptible Staphylococcus aureus and MRSA. The Infectious Disease Society of America (IDSA) practice guidelines recommend I&D for purulent skin and soft tissue infections (Fig. 8.3B). Historically, I&D procedures included wound packing, which can be painful and anxiety provoking for children. Current evidence suggest that several techniques (stab incisions and placement of a drain, placement of a negative pressure device, e.g., Wound V.A.C.©, and even no packing) have been found to have similar resolution of an abscess with a low recurrence rate while avoiding cumbersome wound care when compared with packing. IDSA guidelines currently do not recommend antibiotic therapy after abscess drainage for “mild” infections. However, they do recommend antibiotics after drainage if the abscess is associated with systemic signs of infection or the patient is immunocompromised. A phlegmon is an area of diffuse inflammation with little pus and some necrotic tissue. A phlegmon can often be treated with antibiotics, although it can progress to an abscess, which may require I&D.

This young boy developed a large expanding right inguino-femoral abscess (A). (B) The abscess has been drained, and the purulent fluid is seen draining from the abscess.

The technique chosen for skin closure, as well as the suture material, can affect the rate of surgical infections. In clean and clean-contaminated cases, monofilament suture may provide the lowest risk of wound infection. Contaminated wounds have traditionally been left open to heal by secondary intention, or packed with some form of dressing, followed by delayed primary closure (DPC). Although meta-analyses have demonstrated a trend toward improved outcomes with DPC, this rarely transitioned into evidence-based recommendations due to concerns about individual study design. In 2011, there were updated recommendations for control of SSIs that advised DPC, except for cases of acute appendicitis with perforation. In the modern surgical literature, DPC has been shown to successfully decrease rates of SSI. In obese patients, the use of wicks between an interrupted closure decreased infection rates to <1%.

SSIs rarely occur during the first two postoperative days, and fever during that period usually arises from noninfectious causes. SSIs that do occur in this period are almost always due to S. pyogenes or Clostridium species. Streptococcal soft tissue infections are probably the most virulent and can arise within a few hours after a surgical procedure. High fever, delirium, leukocytosis, and severe pain are hallmarks of these infections. Clostridial gas gangrene or myonecrosis is most commonly caused by Clostridium perfringens, Clostridium novyi, Clostridium histolyticum, or Clostridium septicum . Increasingly severe pain within 24 hours at the incision site is the first reliable clinical symptom. The site may become tense and tender, with bullae filled appearing quickly. Gas in the tissue, evidenced by crepitus on examination or by imaging studies, is usually present by this late stage. Signs of systemic toxicity, including tachycardia/bradycardia, fever, and diaphoresis, develop rapidly, followed by shock and multiple organ failure. Emergent and aggressive surgical debridement and administration of systemic antimicrobials are the cornerstones of effective therapy and are crucial to ensure survival. ^,

Nosocomial infections are defined as those infections that are hospital acquired. As such, they are a potential threat to all hospitalized patients and significantly increase morbidity and mortality. Their incidence appears to be increasing as surgical care becomes more complicated and patients survive longer. The recent focus on patient safety has made prevention of nosocomial infections increasingly important. One report describing 676 operative procedures in 608 pediatric patients showed a nosocomial infection rate of 6.2%. The infectious complications included septicemia, pulmonary, urinary tract, abdominal, and diarrhea. The highest overall occurrence of infection was in infants. The most common isolates were Staphylococcus epidermidis , from septic patients, and gram-negative enteric bacteria, from organ and wound infections. Infection was associated with impaired nutrition, multiple disease processes, and multiple operations. In addition, ECMO use has been shown to correlate with an increased incidence of nosocomial infection, as do the length of the preoperative hospitalization and exposure to invasive medical devices.

Pneumonia can be a lethal nosocomial infection, with mortality ranging from 20% to 70%. It accounts for 10%–15% of all pediatric hospital-acquired infections (HAIs). The mortality rate is dependent on the causative organism. The risk factors for nosocomial pneumonia in the pediatric population include serious underlying illness, immunosuppression, and length of time on a ventilator. Measures to prevent ventilator-associated pneumonia in children include elevating the head of the bed, daily assessment of readiness for extubation, and age-appropriate mouth care.

Clostridioides difficile is a well-recognized cause of infectious diarrhea that develops after antibiotic therapy, although it accounts for only 15%–25% of antibiotic-associated diarrhea. It is a very common cause of HAI, and its incidence is increasing in frequency with associated increasing mortality. The best methods of prevention are the judicious and appropriate use of antibiotics and appropriate hand hygiene with soap and water. Our hands, transiently contaminated with C. difficile spores, and environmental contamination, are the main means by which the organism is spread within healthcare. The incidence of C. difficile infection (CDI) in children is increasing in both outpatients and inpatients. ^, An important point to note with regard to the epidemiology of C. difficile in children is the presence of asymptomatic colonization with either toxigenic or nontoxigenic strains, with rates with can exceed 40% in infants <12 months of age. ^, Colonization rates have been found to be inversely proportional to age, decreasing with increasing age. The prevalence of asymptomatic colonization with C. difficile is still elevated in the second year of life, although to a lesser degree than in infants. Therefore, testing in this population should also be avoided unless other infectious and noninfectious causes of diarrhea have been excluded. Antibiotic stewardship programs have been found to significantly decrease CDI rates, and some recommendations of these programs include minimizing the frequency and duration of high-risk antibiotic therapy and the number of antibiotic agents prescribed and targeting antibiotics based on the local epidemiology and the C. difficile strains present. Restriction of fluoroquinolones, clindamycin, and cephalosporins (except for surgical antibiotic prophylaxis) should also be considered.

The management of CDI in children is determined by the frequency and severity of episodes. Those who do not respond to treatment within 5 days should be evaluated for other causes. There is currently insufficient evidence to support probiotics as an alternative to antimicrobial therapy for CDI treatment. Initial, mild episodes of CDI may be managed with oral Metronidazole 7.5 mg/kg per dose (max 500 mg) TID or QID for 10 days or Vancomycin PO 10 mg/kg per dose (max 125 mg) QID for 10 days. Severe/fulminant disease may be treated with Vancomycin PO or PR 10 mg/kg per dose (max 500 mg) QID for 10 days, with or without Metronidazole IV 10 mg/kg per dose (max 500 mg) TID for 10 days. Initial recurrences may be managed similarly, with Rifaximin added for second or subsequent recurrences. Secondary prophylaxis with vancomycin while receiving systemic antibiotics may reduce the risk of recurrent CDI in children with the highest risk. ^, Fecal microbiota transplant (FMT), which involves transfer of stool from a healthy donor to the gastrointestinal tract of a recipient with rCDI, has gained popularity. The intent is to restore disrupted intestinal microbial composition. Despite an over 80% success rate in recent data, long-term unanticipated consequences of FMT in children remain unknown. Changes in the microbiome have been implicated to contribute to autoimmune, metabolic, and mental health disorders; hence, any treatment that involves alterations in the microbiome in children warrants further long-term investigation. Fidaxomicin has now become a first-line agent for adults but has not been recommended by major guidelines for use in children due to limited experience with use in children, its relative expense, and the adverse effects of pyrexia, abdominal pain, emesis, diarrhea, constipation, elevation in liver enzyme activity, and rash.

Central venous catheters (CVCs) are essential for managing critically ill patients. CVCs include peripherally inserted central catheters (PICCs), nontunneled/tunneled CVCs, and venous access ports. The use of CVCs in infants and children has increased as prolonged vascular access has become increasingly necessary to provide parenteral nutrition, chemotherapy, antimicrobial therapy, and hemodynamic monitoring. However, central-line–associated blood stream infections (CLABSIs) are common, despite considerable effort to reduce their occurrence, and are associated with increased hospital costs, length of stay, and morbidity/mortality. ^, CLABSIs can manifest as erythema at the site of insertion, fever, tachycardia, and/or leukocytosis. Rates of infection are influenced by patient-related factors, by type and severity of illness, and by catheter-related parameters (catheter type, purpose, and conditions under which it was placed). Coagulase-negative staphylococci , followed by Staphylococcus aureus , were the most frequently isolated causes of hospital-acquired blood stream infections in a report from the National Nosocomial Infections Surveillance System. A number of factors are associated with the development of CLABSIs, including the sterility of the insertion technique, type of solution being administered through the line, care of the catheter once inserted, proximity of the catheter to another wound, and the presence of another infection elsewhere. Updated guidelines for the prevention of intravascular catheter-related infections were published in 2014. ^, Long-term catheters should be tunneled to significantly reduce the risk of catheter-related infection. ^{, ,}

Sterile techniques should be maintained in all instances of line insertion whenever possible. Emergency situations may necessitate less-than-sterile technique. The use of maximal sterile barriers, including sterile gown, gloves, and a large sterile sheet, has been shown in adults to greatly reduce the risk of CLABSI. The single most important factor in preventing CLABSI is hand hygiene. Standardized hand hygiene programs in neonatal care units have been found to decrease CLABSI rates. ^, Studies suggest that chlorhexidine, compared with povidone-iodine, significantly reduces the incidence of CLABSI and microbial colonization, and 2% chlorhexidine preparations with alcohol are now recommended for skin antisepsis. ^{, ,} Chlorhexidine is frequently used in the neonatal intensive care unit (NICU) even though the safety and efficacy of chlorhexidine in infants under 2 months of age is not known. ^, In infants, the most common adverse effect of chlorhexidine is skin irritation. However, small studies have reported no skin irritation after chlorhexidine exposure. Even with chlorhexidine being used with increased frequency in infants, further studies are needed to strengthen the evidence for its efficacy in this patient population.

The skin and catheter hub are the most common sites/sources of colonization and infection. Thus, various methods have been used to combat these risks. Chlorhexidine bathing has been shown to decrease CLABSI rates in the NICU, but its efficacy is unknown for children in the non-ICU setting. There is also some evidence to suggest that the use of medication-impregnated dressings reduces CLABSI in comparison to other type of dressings. Silver ions have broad antimicrobial activity, and silver-impregnated cuffs have been designed as a preventive measure. ^, Such antimicrobial and antiseptic impregnated catheters and cuffs may decrease the incidence of catheter-related infections. However, in one study, chlorhexidine dressing/alcohol skin cleansing in newborn infants only reduced catheter colonization with no difference in CLABSI.

Catheters have been coated with chlorhexidine/silver sulfadiazine as well as minocycline/rifampin along with other agents. ^, The use of these antibacterial-coated catheters has been approved by the U.S. Food and Drug Administration for use in patients weighing >3 kg. It is likely that the efficacy for reducing infection decreases after being in place for longer than 3 weeks because of a decrease in the antimicrobial activity. These impregnated catheters and sponge dressings can be used if the infection rate is not decreasing with other measures.

The interval between dressing changes around CVC and its association with CLABSI has been another contentious issue. Current recommendations allow less frequent dressings changes in selected NICUs to reduce the risk of catheter dislodgement. However, a recent Cochrane review found inconclusive evidence with regard to length of interval between dressing changes and the CLABSI rate. The routine use of prophylactic antibiotics with CVC placement is also controversial. No studies in adults have demonstrated a benefit for systemic antibiotic prophylaxis after insertion of a CVC. Studies in high-risk neonates and children have demonstrated conflicting results. However, concern exists for the emergence of antibiotic resistance with the routine use of antimicrobial prophylaxis. ^,

Catheter-associated urinary tract infection (CAUTI) is the most common overall type of catheter-related infection, but there is a low incidence in children (0.2%–1.3%). The most common pathogen is Escherichia coli, followed by Candida albicans . In one report, children with CAUTI stayed 2 days longer in the hospital on average, with an average hospital cost of $7200 due to CAUTI. A recent QI project reduced CAUTI rates by implementing a prevention bundle. Similar to central lines, adding an ethanol lock to urinary catheters has been shown to be safe, and further studies are needed to evaluate if the ethanol lock reduces the rate of CAUTI.

Although the infections discussed previously are possibly preventable and occur after operations or hospitalization, some de novo infections are seen by the pediatric surgeon.

Necrotizing Soft Tissue Infection

Necrotizing soft tissue infection (NSTI) is a rapidly progressing infection of the fascial tissues and overlying skin, with a hospital mortality of 7%. Although these infections can occur as a postoperative complication or as a primary infection, necrotizing fasciitis is more likely in immunocompromised patients. However, necrotizing fasciitis often affects previously healthy children and infants. Because the diagnosis is often not obvious, the physician must look for clinical clues such as pain out of proportion to physical findings, edema beyond the area of erythema, crepitus, skin vesicles, or cellulitis refractory to intravenous antibiotics. Skin necrosis is generally a late sign and is indicative of thrombosis of vessels in the subcutaneous tissue. Necrotizing fasciitis often occurs in the truncal region in children, as opposed to adults in whom infection in the extremities is most common (Figs. 8.4 and 8.5 ). A validated NSTI scoring system called the Laboratory Risk Indicator for Necrotizing Fasciitis (LRINEC) was developed to objectively diagnose NSTI. However, this score was derived from adult data and is not widely used in children. A recent pediatric LRINEC scoring system demonstrated that a C-reactive protein >20 mg/L was the most sensitive value and a sodium level <135 mEq/L was the most specific laboratory value for improving the diagnostic accuracy of NSTI in children. Although infections with a single organism often occur in adults with necrotizing fasciitis, polymicrobial infections predominate in children. Prompt early surgical intervention, including wide excision of all necrotic and infected tissue, along with the institution of broad-spectrum antibiotics, is important to avoid progression and mortality. Necrotizing fasciitis can also occur as a complication of chickenpox. In neonates, necrotizing fasciitis is seen secondary to omphalitis, balanitis, and fetal monitoring.

This 15-year-old was ill for 2 weeks with perforated appendicitis and presented in shock. After a midline incision for exploration for a rigid abdomen, his appendix was removed. The peritoneal cavity was extensively and copiously irrigated, and the abdominal incision was left open. Two days he was found to have necrotizing fasciitis of the rectus abdominis muscles bilaterally. Eventually, despite aggressive surgical debridement, this process spread to the retroperitoneum and down the left inguinal canal through a patent processus vaginalis. One week postoperatively, he was found to have edema and erythema of the left leg that prompted exploration. The necrotizing fasciitis had progressed down all compartments of the left thigh and the lateral compartment of the left lower leg. In the upper thigh, the semimembranosus and semitendinosus muscles had to be excised due to necrotic musculature. These photographs were taken on his ninth postoperative day. (A) The abdomen is seen to be open, and the medial aspect of the left thigh is visualized. (B) The incisions in the left buttock area, the left lateral thigh, and the left lateral lower leg are seen.

This photomicrograph depicts the histologic findings of necrotizing fasciitis in the patient shown in Fig. 8.4. Note the inflammatory infiltrate on both sides of the fascia. The fascial cultures grew Escherichia coli.