Renal biopsy is defined as:

• A. Removal of a piece of kidney tissue for microscopic evaluation, usually ultrasound-guided
• B. Visualization of the bladder with a scope
• C. Injecting contrast into the renal artery
• D. Using CT to measure renal function

Answer: (A)

Renal biopsy involves removing a small piece of kidney tissue for microscopic examination, usually obtained under ultrasound guidance to target specific areas and reduce risk. This procedure helps diagnose and characterize kidney diseases by letting the pathologist study the tissue's structure and any abnormalities.

The other options describe different procedures: visualizing the bladder with a scope is cystoscopy, which examines the bladder lining rather than taking a tissue sample from the kidney; injecting contrast into the renal artery is renal arteriography, an imaging study of blood vessels rather than tissue sampling; and using CT to measure renal function refers to imaging or functional assessment, not biopsy.