End Organ Damage

End organ damage or target organ damage refers to damage happening in major organs that are circulated by the circulatory system due to hypertension, hypotension or hypovolemia.

The organs normally affected are:

The eyes- Acute BP elevation typically causes reversible vasoconstriction in retinal blood vessels, and hypertensive crisis may cause papilledema. More prolonged or severe hypertension leads to exudative vascular changes, a consequence of endothelial damage and necrosis. Other changes (eg, arteriole wall thickening) typically require years of elevated BP to develop. Smoking compounds the adverse effects of hypertension on the retina.

Hypertension is a major risk factor for other retinal disorders (eg, retinal artery or vein occlusion, diabetic retinopathy). Also, hypertension combined with diabetes greatly increases risk of vision loss. Patients with hypertensive retinopathy are at high risk of hypertensive damage to other end organs.

Kidney- High blood pressure makes the heart work harder and, over time, can damage blood vessels throughout the body. If the blood vessels in the kidneys are damaged, they may stop removing wastes and extra fluid from the body. The extra fluid in the blood vessels may then raise blood pressure even more. It’s a dangerous cycle.

High blood pressure is one of the leading causes of kidney failure, also called end-stage renal disease (ESRD). People with kidney failure must either receive a kidney transplant or have regular blood-cleansing treatments called dialysis. Every year, high blood pressure causes more than 25,000 new cases of kidney failure in the United States.

Heart- As vessel diameters grow smaller and smaller, the result is not unlike what occurs to water flow out of a hose when a small kink is placed in it. In order for it to bypass this increased resistance to flow, it must be pushed with a greater pressure or force. In much the same way, an increase in the body's blood vessel resistance to flow places a new burden upon the heart to push blood through the smaller opening. It is largely unknown why the body chooses to raise resistance to flow even after it becomes a chronic burden on the heart.

Reference:

http://kidney.niddk.nih.gov/kudiseases/pubs/highblood/
http://www.merck.com/mmpe/sec09/ch106/ch106f.html
http://www.heartfailure.org/eng_site/hf_causes_hypertension.asp#