Focal Acute Nephritis. A Case ReportFocal acute nephritis (FAN) or acute lobar nephronia is a rare clinical picture characterized by an infection localized in the kidney, with an infl ammatory mass without liquefaction.Of variable clinical manifestations, diagnosis is achieved through CT scanning.Histologically, unlike acute pyelonephritis, it does not present a diffuse infi ltrate.Objective: Case report of FAN in a pediatric patient.Case Report: Ten year old male complaining of abdominal pain, presents painful percussion in the right lumbar fossa.Urinary analysis and culture were negative, renal sonogram was negative.Abdominal CT scan showed multiple hypodense renal foci.He responded well to cephotaxim, being discharged in the third day of hospitalization with completion of treatment as outpatient.Differential diagnosis with Acute Pyelonephritis is very important, as it requires controlled and opportune treatment to prevent renal absceses.Diagnosis of this pathology must be pursued despite a normal UA.