What is the relationship between kidneys and high blood pressure?

Close relationship: The kidneys are one of the primary filters of toxins from blood. They also serve to maintain salt and water balance in the body. The kidneys release chemicals that increase blood pressure to maintain a consistant flow of blood through them. The process is very efficient until outside forces come into play such as obesity, diabetes, high cholesterol, excessive salt intake.

Organ system: Kidney is one of the organ system that regulate the blood pressure -- so if you have high blood pressure, your kidney is evaluated as well because it can effect and be effected by high blood pressure.