The role of imaging in the active surveillance of small renal masses.

Up to 66 % of renal cell carcinomas are detected as small renal masses before the presence of clinical symptoms. Small renal mass treatment has evolved from the exclusive use of radical nephrectomy to the use of nephron sparing procedures where possible. An increase in elderly and comorbid patients, together with the notion that just 20 % of small renal masses show high malignant potential, has prompted interest in active surveillance as a treatment option. Modern imaging techniques provide objective follow-up parameters, namely size, invasion of collecting system or perirenal fat and enhancement patterns, with minimal complication risks or patient discomfort. This review evaluates recent developments in the field of active surveillance for small renal masses. Special focus is placed on the role of imaging in the primary decision making and subsequent follow-up during active surveillance.