A febrile patient with a renal space-occupying lesion evolving into renal abscess: Acute focal bacterial nephritis

Acute focal bacterial nephritis or focal non-liquefied pyelonephritis was first described in 1979 by Rosenfield et al. [1] In 12 patients he described a characteristic combination of three uroradiological findings, by ultra- sonography a relatively sonolucent mass disrupting corticomedullary definition, a solid appearance of the mass on other radiological investigations, and a posit- ive radionuclide image. Triangular or round hypodense areas seen in these investigations were compared to chest X-rays in acute lobar pneumonia and the term acute lobar nephronia used to describe such lesions. Numerous cases have since been reported in both adult and paediatric literature. As the lesion may mimic tumour and intrarenal abscess both clinically and radiologically, it is an important differential diagnosis of a renal space-occupying lesion.