[Fever of unknown origin--pyelonephritis? Pneumonia? Mastoiditis? Ethmoiditis?].

Fever of unknown origin is alarming phenomenon in childhood. Diagnostic procedures should be focused on severe bacterial infection: pyelonephritis, pneumonia and other respiratory tract infections such as mastoiditis and sinusitis in particular ethmoiditis. The principles of treatment and diagnostics were discussed depending on age and general status of the child.