Pediatric Fever of Unknown Origin.

Fever is a common complaint in children. In most cases, fevers are due to selflimited viral infections and require no more than symptomatic treatment. Sometimes fever is due to common bacterial infections that are diagnosed by history and physical examination and require antibiotic treatment without laboratory evaluation. In a few clinical situations, the cause of fever is not easily identified. Fever without a source (FWS)mayneed further evaluation that includes laboratory tests or imaging. Rarely, the fever is more prolonged, requires more intensive evaluation, and falls in the category of fever of unknown origin (FUO). There is often confusion about the terms FUO and FWS. Distinguishing between FUO and FWS is important and is based on duration of fever. FWS can progress to FUO if no cause is elicited after 1 week of fever. The current incidence and prevalence of pediatric FUO remain unclear. Several factors contribute to the difficulty in determining the epidemiology, including the lack of a standardized definition, clinical criteria, and coding using the International Classification of Diseases-9 code for the condition. Furthermore, the causes of FUO often have an overlapping collection of symptoms and insidious disease courses. The general direction of the evaluation varies based on patient presentation, geographic location, associated symptoms, environmental exposures, physician experience, and available testing techniques.