The initial evaluation of FUO requires a thorough history and physical examination supplemented with a few screening laboratory tests (Fig. 96-2). Additional laboratory and imaging tests are guided by abnormalities on initial evaluation.
Figure 96-1 Approach to a child younger than 36 months of age with fever without localizing signs. The specific management varies, depending on the age and clinical status of the child.
Important historical elements include the impact the fever has on the child’s health and activity; weight loss; the use of drugs, medications, or immunosuppressive therapy; history of unusual, severe, or chronic infection suggesting immunodeficiency (see Chapter 72); immunizations; exposure to unprocessed or raw foods; history of pica and exposure to soil-borne or waterborne organisms; exposure to industrial or hob-by-related chemicals; blood transfusions; domestic or foreign travel; exposure to animals; exposure to ticks or mosquitoes; ethnic background; recent surgical procedures or dental work; tattooing and body piercing; and sexual activity.
The etiology of most occult infections causing FUO is an unusual presentation of a common disease. Sinusitis, endocarditis, intra-abdominal abscesses (perinephric, intrahepatic, subdiaphragmatic), and central nervous system lesions (tuberculoma, cysticercosis, abscess, toxoplasmosis) may be relatively asymptomatic. Infections are the most common cause of FUO in children, followed by inflammatory diseases, malignancy, and other etiologies (Table 96-1). Inflammatory diseases account for approximately 20% of episodes. Malignancies are a less common cause of FUO in children than in adults, accounting for about 10% of all episodes. Approximately 15% of children with FUO have no diagnosis. Fever eventually resolves in many of these cases, usually without sequelae, although some may develop definable signs of rheumatic disease over time. Common infections causing FUO in patients with known or newly diagnosed immunodeficiencyinclude viral hepatitis, Epstein-Barr virus, cytomegalovirus, Bartonella henselae, ehrlichiosis, Salmonella, and tuberculosis.
Factitious fever or fever produced or feigned intentionally by the patient (Munchausen syndrome) or the parent of a child (Munchausen syndrome by proxy) is an importantconsideration, particularly if family members are familiar with health care practices (see Chapter 22). Fever should be recorded in the hospital by a reliable individual who remains with the patient when the temperature is taken. Continuous observation over a long period and repetitive evaluation are essential.
Screening tests for FUO include complete blood count with WBC and differential count, platelet count, erythrocyte
Admit, obtain appropriate tests Begin appropriate therapy
Additional tests (special cultures, PCR, serology, biopsy) and imaging studies (CT, MRI, radionuclide scans)
Figure 96-2 Approach to the evaluation of fever of unknown origin (FUO) in children. Screening laboratory tests include a complete blood count and differential white blood cell count, platelet count, erythrocyte sedimentation rate, hepatic transaminase levels, urinalysis, bacterial cultures of urine and blood, chest radio-graph, and evaluation for rheumatic disease with antinuclear antibody, rheumatoid factor, and serum complement (C3, C4, CH50). PCR, polymerase chain reaction.
Abscesses: abdominal, brain, dental, hepatic, pelvic, perinephric, rectal, subphrenic, splenic, periappendiceal, psoas Cholangitis Infective endocarditis Mastoiditis Osteomyelitis Pneumonia Pyelonephritis Sinusitis