Perinephric fluid collections due to renal lymphangiectasia.

Fluid collections around the kidneys on cross-sectional imaging may be caused by urine, blood, pus, lymph, or plasma. Ultrasonography (US), computed tomography (CT), and magnetic resonance imaging (MRI) can not only show and characterize the fluid, but also may help determine the underlying cause of the perinephric fluid collection, such as ureteric obstruction, kidney injury, infection, or renal lymphangiectasia. Renal lymphangiectasia is characterized by abnormal and ectatic lymphatic vessels within and around the kidneys. Dilated lymphatics may result in peripelvic cysts (intrarenal lymphangiectasia) and perinephric fluid collections (extrarenal lymphangiectasia), which can be visualized using US, CT, and MRI. Proper diagnosis on imaging helps in planning a conservative management approach to this benign condition, which requires intervention for only significant symptoms or complications. We describe a 60-year-old man with normal kidney function and bilateral perinephric fluid collections in whom renal lymphangiectasia was diagnosed noninvasively on the basis of characteristic findings on US, CT, and MRI.