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Definition of the Complaint


The complaint of fever accounts for a large portion of ambulatory pediatric visits. While classically defined as a temperature greater than 38.0°C for neonates and greater than 38.5°C for older children, the term ”fever” is subject to significant interpretation. An isolated temperature measurement of 38.0°C in a toddler may not be meaningful; however recurrent daily temperatures of 38.0°C during a period of several weeks may indicate an underlying pathology.


Practitioners must also remember that body temperature normally fluctuates throughout the day. Body temperature tends to be lower in the early morning and peaks in the evening. Certain conditions or activities, such as exercise, warm baths, or hot drinks, also affect the measured temperature. Additionally, temperature values of axillary measurements may be 0.5°C-1.0°C lower than oral, rectal, or tympanic measurements. To compensate for such discrepancies, parents are sometimes instructed to add 0.5°C or 1.0°C to axillary measurements to approximate the ”real” temperature. Such ”corrections” may further cloud evaluation of the febrile child.


Complaint by Cause and Frequency


Fever may develop in response to injury, infection, autoimmune disease, or malignancy. The release of endogenous pyrogens triggers a cascade of reactions that ultimately raise the hypothalamic set-point. Fever may also be caused when the body’s heat production or environmental heat overwhelms heat loss mechanisms or when heat loss mechanisms are deficient. Viruses are the most common cause of fever in children. Specific common causes of fever are too numerous to list here but less common causes of fever are listed in Table 11-1.

Table Graphic Jump Location
Table 11-1. Less Common Causes of Fever.

Clarifying Questions


The clarifying questions listed below may help provide clues to the diagnosis.


  • What temperature value is the parent using to define a fever?
    • While 98.6°F is commonly considered the normal body temperature, normal body temperature exhibits significant daily variation with a nadir in the early morning and a peak in the early evening.
  • Are there symptoms of specific illness?
    • The presence of certain complaints such as bloody diarrhea, cough, and stiff neck suggests specific diagnostic categories.
  • Is there exposure to animals?
    • Animal exposure refers ...

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