Inflammatory pseudotumor of the kidney with renal artery penetration.

Inflammatory pseudotumor (IPT) is a quasineoplastic lesion that most commonly involves the lung and the orbit; kidney involvement is rare. We report a case of inflammatory pseudotumor of the kidney. The patient was a 61-year-old man who presented with no symptoms. Nonenhanced computed tomography (CT) demonstrated an ill-defined, isodensity mass measuring 3.5 cm in the lower portion of the left kidney. Contrast-enhanced CT showed that branches of the renal artery without encasement penetrated the tumor; there was a little enhancement in the mass on the arterial phase and homogeneous enhancement on the venous phase. On magnetic resonance imaging the mass showed intermediate signal intensity on T1-weighted images (T1WIs) and low signal intensity on T2WIs. Most IPTs of the kidney appear as an ill-defined, hypovascular, homogeneous tumor on CT images, with variable signal intensity on MRI T1WIs and low signal intensity on T2WIs. Our case had the same imaging findings, with branches of the renal artery penetrating the tumor. If the renal tumor has these radiological findings, the tumor may be IPT.