Approximately 5 percent of people with hypertension or high blood pressure suffer from renal or renovascular hypertension, caused by narrowing or blockage in the arteries to the kidneys. With this blockage, the kidneys see a reduction of blood pressure and compensate for it by causing a rise in overall blood pressure, thus resulting in systemic hypertension. Early in its course, this hypertension can be treated with medication. However, as the blockage worsens, the hypertension may become severe and difficult to control, even with multiple medications. Furthermore, it may result in sudden severe spikes in blood pressure, which can be extremely dangerous. In these cases, treatment of the underlying blockage may help to eliminate or significantly reduce the hypertension to allow better control on fewer medications.
Hypertension itself can have a devastating effect on the kidneys (as well as many other organs in the body). Exposure to abnormally high blood pressure over time will lead to damage of the kidney and a reduction in its ability to function normally. With an estimated reserve of approximately 75 percent, damage to the kidneys may not show up on routine blood tests until the damage is fairly severe and possibly irreversible. Early diagnosis and treatment is critical to protect renal function.
In addition to intrinsic kidney damage from exposure to high blood pressure, the kidneys may also lose function from decreased blood flow. Over time the kidney may atrophy or whither, losing its ability to function. If the blockage becomes severe, blood to the kidney may stop flowing altogether resulting kidney failure. Should that occur, preservation of the other kidney is crucial to maintaining overall kidney function and avoiding dialysis and/or the need for transplant.
The majority of renovascular hypertension is caused by plaque buildup in the arteries, also known as atherosclerosis. The incidence increases with age. Other risk factors for the development of atherosclerosis include tobacco use, poor diet, diabetes and genetics. The buildup of plaque is a slow, progressive disease, frequently beginning in young and middle-aged adults. However, as the buildup is generally slow, a severe blockage does not often become apparent until a person reaches their 60s or 70s.. Early recognition and modification of risk factors is crucial in slowing and possibly reversing the process at a young age.
Another less common cause of renovascular hypertension, which is often present in younger patients, particularly young women, is called fibromuscular dysplasia or FMD. In FMD, there is an abnormal buildup of tissue in the arterial wall, resulting in a narrowing of the arterial wall. The cause of FMD is not known, although there is likely a genetic predisposition. It should be suspected when hypertension is diagnosed at a young age, particularly in women.