Perinephric stranding and bulky psoas mimicking pyelonephritis in a case of non-Hodgkin lymphoma of kidney.

A 68-year-old male patient presented with fever and right groin pain. He had leukocytosis with azotemia. Computed tomography revealed enlarged right kidney with thickening and enhancement of walls of pelvicalyceal system and perinephric fat stranding, suggestive of pyelonephritis. Multiple enlarged lymph nodes encased right renal vessels and were present in the retrocaval region. The right psoas muscle was bulky. Fine-needle aspiration cytology and biopsy from the lesions showed features of non-Hodgkin lymphoma. Immunohistochemistry confirmed the diagnosis of diffuse, large, B-cell lymphoma. We emphasize lymphoma in differential diagnosis of atypical renal imaging suggestive of pyelonephritis and perinephritis.