The purpose of this research study is to create a prospectively maintained, multicenter database of patients undergoing renal biopsy for renal masses performed percutaneously (through skin), via an 18 gauge biopsy needle (.048 inches). In this database, the investigators will collect and maintain the data from the biopsy procedure. This will allow us to evaluate our experience with this procedure as well as to participate in multi-institutional collaborative studies in the future. At University of California Irvine, the investigators routinely biopsy patients with renal masses under real-time ultrasound control. Percutaneous renal biopsy under ultrasound guidance is a routine procedure performed to diagnose renal mass histopathology. The safety and efficacy of this procedure has been well documented in the literature. The indications for percutaneous renal biopsy have expanded as there has been a substantial increase in the number of renal masses that are being diagnosed, and the acceptance of percutaneous biopsy continues to expand in parallel. The biopsy procedure is part of your normal standard of care and if not being done for this research project.

Inclusion Criteria:

• Must be undergoing standard percutaneous renal biopsy
• Patients must be ≥18 years of age
• Must be able to understand and render voluntary, written informed consent

Exclusion Criteria:

• Patients <18 years of age
• Pregnant women
• Coagulopathy
• Active urinary tract infection

We do not intend to release individual data to other researchers.