High Blood Pressure (Hypertension)
Blood travels away from the heart through special blood vessels, called arteries, to all parts of the body. The pressure of the blood against the walls of the arteries as the heart pumps is what is measured. The blood pressure measurement has two number: a top one, and a bottom one. The top number (systolic) is the pressure when the heart pumps blood out. The bottom number (diastolic) is the pressure when the heart relaxes before the next beat.
When blood pressure is high and left untreated, it can damage the blood vessels that carry blood throughout the body. The smaller blood vessels are the ones usually affected first. Kidneys have small blood vessels that can become damaged by high blood pressure. This can lead to chronic kidney disease (CKD). Because one of the jobs of the kidneys is to control blood pressure this can cause more problems. Renin is a hormone produced by the kidneys. When the kidneys are not working properly, they may release renin, causing blood pressure to go up even higher.
National Kidney Foundation
How is High Blood Pressure Treated?