Pathophysiology
Renal cortical abscess results from hematogenous spread of bacteria from a primary extrarenal focus of infection. The source is not apparent in up to one third of cases at the time of diagnosis. Staphylococcus aureus is the etiologic agent in 90% of cortical abscess cases. In contrast, renal corticomedullary abscess develops as an ascending infection by organisms already isolated from the urine. Severe renal parenchymal involvement in combination with corticomedullary abscess is more likely to extend to the renal capsule and perforate, thus forming a perinephric abscess. Renal corticomedullary infections include the below acute and chronic infectious processes of the kidney.
Acute focal bacterial nephritis