Submitted by Laura Sheiman, MD, Department of Radiology, Weill Cornell Medical Center, New York-Presbyterian Hospital, New York, NY.
A 53-year-old woman presents for surveillance imaging. Numerous hypodense renal masses were detected.
The differential diagnosis for multiple bilateral renal masses includes:
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Bilateral renal lymphoma
A computed tomography (CT) exams showed the kidneys were enlarged. Numerous hypodense renal masses are seen bilaterally, measuring up to 3 cm in the upper pole of the right kidney. Retroperitoneal lymphadenopathy is partially visualized.
Clinical history is imperative in the differential diagnosis of multiple bilateral renal masses. This patient had a known history of nonHodgkin lymphoma (follicular lymphoma) with extensive lymphadenopathy within the chest, abdomen, and pelvis. Follow-up imaging after chemotherapy demonstrated resolution of bilateral solid renal masses.
Renal lymphoma is usually a secondary manifestation of systemic disease. Primary renal lymphoma is thought to be rare.4 Renal lymphoma may present as a variety of imaging findings. These findings include solitary renal mass, multiple renal masses, perinephric soft-tissue mass, diffuse renal infiltration, direct extension from retroperitoneal lymphadenopathy, and/or enlargement of the kidneys.4 The most common presentation is multiple renal masses, seen in 50% to 60% of cases, which may be unilateral or bilateral.4 Involvement of the kidneys by nonHodgkin lymphoma is seen in about 3-8% of patients by imaging; however, on autopsy, the frequency of involvement increases to around 38%.3 Patients with renal lymphoma are generally asymptomatic with normal renal function maintained.3
Renal cell carcinoma tends to have a more heterogeneous appearance than renal lymphoma. 2 Although bilateral renal cell carcinoma is uncommon, this may be seen in patients with syndromes such as von Hippel Lindau. 2 Associated tumor invasion of the renal vein with possible extension into the inferior vena cava (IVC) would suggest renal cell carcinoma over other diagnoses. 1 In patients with a known primary malignancy, metastatic disease should be considered in the differential diagnosis. Breast cancer, lung cancer, gastric cancer, melanoma and other malignancies may metastasize to the kidneys and present as renal masses.3
Lastly, pyelonephritis may have a variety of imaging appearances. Diagnosis can be confirmed by clinical history and urinalysis. In patients with a complicated history, follow-up imaging to document resolution may be helpful.1