Acute focal bacterial nephritis with incipient abscess formation

This 42-years old man had pain and tenderness in the left lumbar region with pus cells in the urine. Ultrasound showed a focal hypodense lesion in the left kidney. The CT showed a lesion with a wedge-shaped appearance (Figs. 1, 2), showing significant hypodensity and an almost well-defined well (Fig. 3), suggesting the development of an abscess.

Acute focal bacterial nephritis can progress to abscess formation in severe or untreated cases.