Radiology of perinephric fluid collections.

The perinephric spaces consist of the subcapsular, perirenal, anterior and posterior pararenal spaces. Fluid may collect in one or more of these compartments; this can be readily demonstrated by cross-sectional imaging, particularly computed tomography (CT). This pictorial review illustrates the radiological manifestations of perinephric fluid collections with their differential diagnosis including perinephric abscess, perirenal urine collection, subcapsular and perirenal hematoma, renal lymphangiomatosis, pancreatic pararenal fluid collections and transudate fluid associated with nephropathies.