Renal hypertension, also called renovascular hypertension, is elevated blood pressure caused by kidney disease. It can usually be controlled by blood pressure drugs. Some people with renal hypertension can be helped by angioplasty, stenting, or surgery on the blood vessels of the kidney.
Causes of 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 is a condition called renal artery stenosis.
When the kidneys receive low blood flow, they act as if the low flow is due 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, or 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.
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
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.
Renal hypertension can cause chronic kidney disease. This is a slow decline in kidney function. Until the condition is well advanced, chronic kidney disease also causes no symptoms.
Because there are usually no symptoms, a doctor may suspect renal hypertension when someone has uncontrolled high blood pressure despite multiple medications or has unexplained chronic kidney disease.
Renal Artery Stenosis
Renal artery stenosis is a narrowing of arteries that carry blood to one or both of the kidneys. Most often seen in older people with atherosclerosis (hardening of the arteries), renal artery stenosis can worsen over time and often leads to hypertension (high blood pressure) and kidney damage. The body senses less blood reaching the kidneys and misinterprets that as the body having a low blood pressure. This signals the release of hormones from the kidney that lead to an increase in blood pressure. Over time, renal artery stenosis can lead to kidney failure.
Causes of Renal Artery Stenosis
About 90% of the time, renal artery stenosis is caused by atherosclerosis, a process in which plaque made up of fats, cholesterol, and other materials builds up on the walls of the blood vessels, including those leading to the kidneys.
More rarely, renal artery stenosis can be caused by a condition called fibromuscular dysplasia, in which the cells in the walls of the arteries undergo abnormal growth. More commonly seen in women and younger people, fibromuscular dysplasia is potentially curable.
Risk Factors for Renal Artery Stenosis
Renal artery stenosis is often found by accident in patients who are undergoing tests for another reason, such as:
- Older age
- Female sex
- Other vascular disease (such as coronary artery disease and peripheral artery disease)
- Chronic kidney disease
- Tobacco use
- Abnormal cholesterol level
Symptoms of Renal Artery Stenosis
Renal artery stenosis usually does not cause any specific symptoms. Sometimes, the first signs of renal artery stenosis are high blood pressure that is extremely hard to control, worsening of previously well-controlled high blood pressure, or elevated blood pressure that affects other organs in the body.
Diagnosis of Renal Artery Stenosis
If your doctor suspects that you have renal artery stenosis, he or she may order tests to either confirm suspicions or rule it out. These include:
- Blood tests and urine tests to evaluate kidney function
- Kidney ultrasound, which uses sound waves to show the size and structure of the kidney
- Doppler ultrasound, which measures blood-flow speed in arteries to the kidney
- Magnetic resonance arteriogram and computed tomographic angiography, imaging studies that use a special dye (contrast medium) to produce a 3-D image of the kidney and its blood vessels
Treatments for Renal Artery Stenosis
Initial treatment for renal artery stenosis is often medication. The condition may require three or more different drugs to control high blood pressure. Patients may also be asked to take other medications, such as cholesterol-lowering drugs and aspirin.
In some cases, an intervention such as angioplasty, often with stenting or surgery, may be recommended. With angioplasty, a catheter is inserted into the body through a blood vessel and guided to the narrowed or blocked renal artery. A balloon on the catheter is then inflated to open up the inside of the artery. A stent can then be placed to keep the area open.
Surgery to bypass the narrowed or blocked portion of the artery and/or remove a non-functioning kidney may be done for some patients.
If you're diagnosed with renal artery stenosis, it's important to discuss the risks of the different treatments with your doctor. The side effects of blood pressure medications include dizziness, sexual problems, headache, and cough. Complications of angioplasty include bruising, bleeding, additional kidney damage, and the possibility that the arteries can close again.