Pediatric emergency medicine trisk 2293 2293
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Renal Abscesses
Renal abscesses can occur as either a complication of pyelonephritis, where they typically are caused by gramnegative rods, or from hematogenous seeding from systemic bacteremia, in which case S. aureus is the most
common etiology. Risk factors for renal abscesses due to pyelonephritis include anatomic obstruction (e.g.,
nephrolithiasis) or vesicoureteral reflux. These abscesses can occur in either the renal cortex or medulla. Risk
factors for hematogenous spread include endocarditis or intravenous drug use; in some instances, children have
had a preceding minor skin infection, with transient bacteremia seeding the kidneys. These abscesses primarily are
found in the renal cortex. Symptoms include fever, malaise, back or abdominal pain, and weight loss. The absence
of dysuria does not exclude a renal abscess. Costovertebral angle tenderness is found in a majority of adults, but is
less sensitive in children.
Laboratory findings include leukocytosis with a left shift and elevated erythrocyte sedimentation rate (ESR) and
CRP. Patients whose abscesses connect with the collecting system may have urinalyses demonstrating pyuria,
proteinuria, and bacteriuria. For patients whose abscesses are due to hematogenous spread, initial urinalyses can be
normal, but the organism will grow in culture. Renal abscesses should always be suspected in a child with a
presumed S. aureus UTI. Ultrasound often cannot distinguish a purulent collection from a hematoma, whereas a
contrasted CT can help determine the extent of disease. Medical management alone is usually sufficient for renal
abscesses less than 5 cm in diameter, whereas percutaneous drainage in addition to antibiotics is needed for larger
abscesses. Broad-spectrum antibiotics covering both gram-negative organisms (pseudomonal coverage should be
considered for immunocompromised hosts or persons who previously have had pseudomonal UTIs) and S. aureus
should be started pending culture results. Improvement is followed clinically (fever curve) and through laboratory
parameters (normalization of white count and inflammatory markers). Standard precautions are indicated.
SKIN AND SOFT TISSUE INFECTIOUS EMERGENCIES
The major infections of the skin, soft tissues, and bones include impetigo, cutaneous abscesses, cellulitis and
superficial abscesses, fasciitis, septic arthritis, and osteomyelitis. Additionally, mastitis and omphalitis occur in the
neonate. Among the disorders in this group, impetigo and cellulitis are both common complaints in the ED.
Although children with bone and joint infections are seen infrequently, the differential diagnosis of several
common complaints (e.g., fever, limp) often includes these conditions. Thus, the emergency clinician who cares
for children should be familiar with such infections, particularly because a prolonged delay in the institution of
therapy can result in appreciable morbidity.
Impetigo
Impetigo is a superficial pustular infection of the epidermis. In contrast, ecthyma involves the dermis. Bullous
impetigo is characterized by lesions greater than 1 cm in diameter. GAS is the most common cause of impetigo,
while S. aureus is the most common cause of bullous impetigo, but can also cause nonbullous impetigo. Impetigo
is predominantly a disease of the preschool-aged child, and is more common during summer months. Children
typically lack systemic signs and symptoms of infection. Skin findings include honey-crusted or bullous lesions
with minimal surrounding erythema or induration; regional adenopathy is not common. Routine laboratory
evaluation is unnecessary in the well-appearing, previously healthy child. Complications may include cellulitis and
glomerulonephritis if the child is infected with a nephritogenic strain. The risk of renal disease is not decreased by
treatment of local infection. Mupirocin can eradicate most cases of impetigo, especially if the disease is limited in
distribution, and may decrease selection for antibiotic resistance. Systemic therapy may be indicated for bullous
impetigo or if use of topical antibiotics is impractical due to extent of disease. Oral treatment options include
cephalexin, or clindamycin. TMP-SMZ offers coverage for the vast majority of staphylococcal isolates (both
MRSA and MSSA), but does not cover GAS. Knowledge of the rates of MRSA in your area can help optimize
empiric antibiotic therapy. Contact precautions should be used.
Cellulitis
Cellulitis is an infection of the skin and subcutaneous tissues. A related disease is erysipelas, which involves the
more superficial skin layers. Erysipelas lesions are beefy red, raised above the skin surface, and have very welldemarcated borders; the most common cause is GAS. The most common causes of cellulitis by location and
exposure type are listed in e-Table 94.12 . Clinical manifestations include erythema, edema, warmth, and pain;
only 10% to 20% develop fever. Regional adenopathy is common. Blood cultures rarely are positive in wellappearing immunocompetent hosts, except in children with pneumococcal, H. influenzae, or group B streptococcal
