Which prefix refers to the kidney?

The prefix that refers to the kidney is "Ren/o." This term is derived from the Latin word "renes," which means kidneys. It is commonly used in medical terminology to form words related to the kidneys, such as "renal," which pertains to anything associated with the kidneys, including conditions, functions, and anatomy. Understanding this prefix is essential for recognizing various medical terms related to renal health and diseases.

The other prefixes refer to different organs or systems: "Gastro/o" pertains to the stomach, "Hepato/o" relates to the liver, and "Cardi/o" refers to the heart. Thus, they are not associated with the kidneys, making "Ren/o" the correct choice when discussing terms related to renal anatomy and functions.