The connection between hypertension, or high blood pressure, and renal failure, also called kidney failure, lies in the fact that the kidneys help to control blood pressure. If the kidneys organs fail, that necessary control is lost, and blood pressure can become too high. Renal failure has occurred when the kidneys can no longer adequately filter metabolic waste products from the bloodstream. This filtration, however, is not the only problem that results from failure.
There are three major factors that affect blood pressure: the amount of blood pumped by the heart, the diameter of the blood vessels and the volume of fluids in the bloodstream. High volumes of blood pumped by the heart, constricted blood vessels and a high volume of fluids in the bloodstream all increase pressure. Low volumes of blood pumped by the heart, dilated blood vessels and a low volume of fluids in the blood stream decrease pressure.
Changes in the amount of blood pumped by the heart, in the diameter of the blood vessels and in the volume of blood in the bloodstream can be controlled by properly functioning kidneys in conjunction with the sympathetic nervous system. If blood pressure is too high, the kidneys can increase excretion of salt and water in order to reduce the blood volume and lower the pressure. Likewise, they can decrease excretions of salt and water to increase blood volume and raise pressure if it falls too low. This is only one aspect of the connection between hypertension and renal failure in which excretion of salt and water would not be carried out by these organs.
Another very important connection between hypertension and renal failure has to do with the ability of the kidneys to secrete renin, an enzyme that stimulates the production of angiotensin II, a hormone that causes constriction of the arterioles, the smallest of all arteries. The secretion of renin also causes yet another hormone, aldosterone, to be produced, and it triggers an increase in the retention of water and salt by the kidneys.
Blood vessels can be thought of as being similar to plumbing pipes. If the pipes are narrowed or constricted, water will flow more forcefully or with more pressure. If they are widened or dilated, the same amount of water would flow through them with considerably less pressure. The same principles apply to blood vessels and the pressure with which blood flows through them.
After renal failure occurs, the extremely important role that the kidneys should play in the regulation of blood volume, the diameter of blood vessels and the amount of blood pumped by the heart cannot take place as it should. It might be said that the body's dependence upon such regulations is why there is the close connection between hypertension and renal failure. It should also be remembered that hypertension, over the course of years, can damage vital organs, particularly the kidneys. Hypertension and renal failure cannot be separated because of the role the kidneys play in maintaining normal blood pressure.
