Retrospective studies indicate that active surveillance for clinically localized, small renal masses (cT1a, <=4cm) is safe. It is our hypothesis that active surveillance is safe and efficacious when compared prospectively to patients undergoing immediate intervention for their small renal mass.

All patients are offered active surveillance or immediate intervention, as applicable, prior to being offered consent for the DISSRM Registry. All patients are enrolled and followed prospectively. Surveillance patients are followed per protocol with serial imaging, blood work and quality of life questionnaires. Intervention patients are followed at the discretion of the attending surgeon with serial QOL appointments/questionnaires.

Inclusion Criteria:

• Must have a solid, enhancing renal mass ≤4cm at its greatest dimension found on incidental scanning in the last 6 months.
• Age ≥ 18 and able to read, understand and sign informed consent.
• Must be willing to adhere to the treatment algorithm and time constraints therein.

Exclusion Criteria:

• Cannot have suspicion of metastases to the kidney if any other malignancy diagnosed within two years of study entry.

All adult patients (18-100) presenting with a clinically localized, solid renal mass (cT1a, <=4cm).