High blood pressure (hypertension) is a leading cause of kidney disease and kidney failure (end-stage renal disease). Kidney disease can also cause a type of high blood pressure called renal hypertension.
Hypertension can cause damage to the blood vessels and filters in the kidney, making removal of waste from the body difficult. Once a person is diagnosed with end-stage renal disease, dialysis—a blood-cleansing process—or kidney transplantation is necessary.
What Are the Symptoms of Kidney Disease?
The symptoms of kidney disease include:
- High/worsening blood pressure
- Decrease in amount of urine or difficulty urinating
- Edema (fluid retention), especially in the lower legs
- A need to urinate more often, especially at night
How Is Kidney Disease Diagnosed?
As with high blood pressure, you may not realize that you have kidney disease. Certain laboratory tests can indicate whether your kidneys are eliminating waste products properly. These tests include serum creatinine and blood urea nitrogen; elevated levels of either can indicate kidney damage. Proteinuria, an excess of protein in the urine, is also a sign of kidney disease.
Who Is At Risk for Kidney Disease Owing to High Blood Pressure?
Kidney disease caused by high blood pressure affects every group and race. However, certain groups are at higher risk, including:
- Native Americans
- Natives of Alaska
- People who have diabetes
- People with a family history of high blood pressure and kidney disease
How Can I Prevent Kidney Disease?
To prevent kidney damage from high blood pressure:
- Try to keep your blood pressure controlled.
- Make sure you get your blood pressure checked on a regular basis.
- Eat a proper diet.
- Get moderate exercise, such as walking, 30 minutes daily.
- Take the medication your doctor prescribes.
How Is Kidney Disease Treated?
For patients who have high blood pressure and kidney disease, the most important treatment is to control their blood pressure through lifestyle changes. Drugs can lower blood pressure and protect the kidneys from further damage, especially in people with diabetes. However, treatments need to be individualized.
The most important blood pressure medications to treat renal hypertension include:
- Angiotensin-converting enzyme inhibitors. These include ramipril, benazepril, captopril, lisinopril, and others.
- Angiotensin II receptor blockers. Examples include candesartan, losartan, olmesartan, and valsartan.
What Is Renal Hypertension?
Although hypertension is a leading cause of kidney disease, there is a type of hypertension that is actually caused by kidney disease. Renal hypertension, also called renovascular hypertension, is elevated blood pressure caused by kidney disease. It can usually be controlled by the same blood pressure drugs. Some people with renal hypertension can be helped by angioplasty, stenting, or surgery on the blood vessels of the kidney.
What Causes Renal Hypertension?
Renal hypertension is caused by a narrowing in the arteries that deliver blood to the kidney. One or both kidneys' arteries may be narrowed. This condition is called renal artery stenosis.
When the kidneys receive low blood flow, they act as if the low flow is owing to dehydration, so they respond by releasing hormones that stimulate the body to retain sodium and water. Blood vessels fill with additional fluid, and blood pressure goes up.
The narrowing in one or both renal arteries is most often caused by atherosclerosis (hardening of the arteries). This is the same process that leads to many heart attacks and strokes. A less common cause of the narrowing is fibromuscular dysplasia. This is a condition in which the structure of the renal arteries develops abnormally for unclear reasons.
What Are the Symptoms of Renal Hypertension?
Renal hypertension usually causes no symptoms. The narrowing in the arteries can't be felt. Unless it's dangerously high, high blood pressure causes no symptoms either. Symptoms of severely elevated blood pressure include:
- Blurry or double vision
- Bloody (pink-colored) urine
- Chest pain
The vast majority of people with renal hypertension never experience these (or any) symptoms. High blood pressure is dangerous, partly because there are no symptoms, so organ damage can occur slowly without being recognized.
What Are the Treatments for Renal Hypertension?
For most people with renal hypertension due to renal artery narrowing, medications can effectively control blood pressure. However, more than one blood pressure drug is often needed.
In some people with renal hypertension due to narrowing of the renal artery, even taking three or more medications every day may not adequately control blood pressure. In these situations, a procedure to improve blood flow to the kidneys may help.
Possible procedures include:
Angioplasty. A doctor threads a catheter through a large artery in the groin and advances it into the renal artery. A balloon is then inflated for a few moments. This widens the artery and improves blood flow.
Stenting. During angioplasty, a wire-mesh stent can be expanded inside the renal artery. The stent stays in place. This keeps the artery open after the balloon is removed. Research, however, has not shown that stenting is more effective than medication for most people with renal hypertension.
Surgery. A surgeon can bypass the narrowed renal artery by sewing a healthy blood vessel next to it. Surgery is generally considered only when angioplasty and stenting are not possible and is only rarely performed.
These procedures are similar to those used to improve blood flow in the heart in people with coronary artery disease.