Pediatric emergency medicine trisk 1161 1161

Inflammatory bowel disease
Systemic lupus erythematosus
Henoch–Schönlein purpura
Other
Transient synovitis of the hip
Malignancy
Leukemia
Neuroblastoma
Bone tumor
Hemophilia
A complete blood count (CBC) and differential, C-reactive protein (CRP), and
erythrocyte sedimentation rate (ESR) are indicated for the febrile child with signs
of joint inflammation, especially in the absence of trauma. Blood cultures will
have a low yield, but should be obtained in the febrile patient or when there is
concern for bone or joint infection. Additional laboratory studies, such as an
antistreptolysin-O titer or antinuclear antibody (ANA) test should be guided by
the history and physical examination. Radiographs of the affected joint are
particularly useful in the setting of trauma or acute monoarthritis without an
obvious cause to evaluate for fractures, dislocations, or occult tumors or other
bony abnormalities. The Ottawa knee rules can be used to guide the decision to
obtain radiographs of the knee following injury. In a recent validation study in
children aged 2 to 16 years of age, the rules were found to be 100% sensitive in
detecting fractures while eliminating the need for about one-third of the
radiographs, however there were a limited number of children below 5 years of
age and caution must be used when applying these rules in younger children.
Ultrasound is more sensitive than plain radiographs in detecting an effusion. In
most febrile children with monoarthritis and a joint effusion, an arthrocentesis,
usually ultrasound guided if involving the hip, is needed to assist in determining
if septic arthritis is the etiology. Magnetic resonance imaging is most useful to
detect subtle fractures not visualized on plain films and to help establish a
diagnosis of osteomyelitis.