Clinical pyelonephritis is a common disorder of infancy and early childhood. The diagnosis seems to be frequently overlooked. It is recommended that all infants and children with febrile infection and all with a “failure to thrive” picture should have a urine examination (sediment, dipslide culture) if the cause of the disease is not obvious. Clinical pyelonephritis if untreated, may run with a high immediate mortality rate or often develop into a chronic disease (failure to thrive picture), as suggested by studies in the pre-antibiotic era. Renal calculi, hypertension and chronic renal failure are long-term consequences, the appearance of which may be delayed for one or more decades after an early infantile infection. With adequate care, the immediate and longterm prognosis is excellent, i.e. kidney damage due to infection is preventable.

Urinary tract infection is one of the most common bacterial infections in industrialized countries. There are very few reports of this disease from developing countries and its existence is sometimes questioned. Properly designed epidemiologic studies are urgently needed to see whether this disease is or is not a threat to child health in developing countries.