Lobar nephronia in a transplanted kidney.

We report a patient who presented with a solid mass in her graft 15 years after renal transplantation. The appearances by ultrasound were consistent with either malignancy or lobar nephronia (focal acute bacterial nephritis). Biopsy confirmed the diagnosis of a lobar nephronia with marked inflammatory infiltrate and frank pus formation. Treatment with antibiotics was associated with resolution of the mass. Lobar nephronia is a diagnosis based upon renal ultrasonography and must be considered in a patient with a solid mass in the kidney.