Hypertension

Definition:

A disorder characterized by high blood pressure; generally this includes systolic blood pressure (the "top" number, which represents the pressure generated when the heart beats) consistently higher than 140, or diastolic blood pressure (the "bottom" number, which represents the pressure in the vessels when the heart is at rest) consistently over 90.

Causes, incidence, and risk factors:

Blood pressure is determined by the amount of blood pumped by the heart, and the size and condition of the arteries. Many other factors can affect blood pressure, including volume of water in the body; salt content of the body; condition of the kidneys, nervous system, or blood vessels; and levels of various hormones in the body. Caucasian men and African-Americans of both sexes have a higher incidence of significant hypertension.

"Essential" hypertension has no identifiable cause. It may have genetic factors and environmental factors, such as salt intake or others. Essential hypertension comprises over 95% of all hypertension.

"Secondary" hypertension is hypertension caused by another disorder. This may include:

• adrenal gland tumors
• Cushing's syndrome
• kidney disorders
  • glomerulonephritis
  • renal vein thrombosis
  • renal artery occlusion (renal artery stenosis)
  • renal artery embolism
  • renal failure

• use of medications, drugs, or other chemicals
• pregnancy or use of oral contraceptives
• hemolytic-uremic syndrome
• Henoch-Schonlein purpura
• periarteritis nodosa
• radiation enteritis
• retroperitoneal fibrosis
• Wilms' tumor
• other disorders