Renal artery stenosis (RAS) is a condition in which the arteries that supply blood to the kidneys narrow. The renal arteries are responsible for carrying oxygen-rich blood to your kidneys, which in turn helps the kidneys rid your body of waste and excess fluid. Over time, RAS can lead to high blood pressure, edema, and kidney damage.
Symptoms of renal artery stenosis
Unfortunately, there aren’t any detectable symptoms specific to RAS. However, you might start having symptoms as the condition progresses. Signs and conditions related to RAS include:
- continued high blood pressure (hypertension) despite taking medications to help lower it
- decreased kidney function
- fluid retention
- edema (swelling), especially in your ankles and feet
- decreased or abnormal kidney function
- an increase of proteins in your urine
You should see your doctor if you experience any unusual symptoms related to blood pressure or fluid retention. Only then will they be able to determine your overall kidney function and whether you need testing for RAS.
Progressing kidney disease may cause the following symptoms:
- changes in urine output
- darkened skin
- edema that spreads to the face and other areas of the body
- muscle cramps
- nausea or vomiting
- sudden, unintentional weight loss
Causes and risk factors
RAS is primarily caused by a buildup of fatty substances and cholesterol (atherosclerosis) in the renal arteries. These substances harden as they accumulate in the arterial walls. This not only narrows the arteries, but it also decreases overall blood flow. According to the Cleveland Clinic, this makes up about 80 percent of all RAS cases.
A less common cause is a condition called fibromuscular dysplasia. This occurs when muscles outside of the arteries grow abnormally and push back on the arteries, causing them to narrow. Fibromuscular dysplasia occurs more often in women. Some babies are also born with the condition.
Other less common causes include:
- abdominal growths that place pressure on the kidneys (extrinsic compression)
- vasculitis, or swelling of the blood vessels
- neurofibromatosis, or the growth of tumors on nerve tissue
RAS can develop in both men and women. It’s more common in older adults. According to the Mayo Clinic, you may also be at risk if you develop hypertension before the age of 30.
Other risk factors for renal artery stenosis are similar to those of other forms of atherosclerosis. These include:
- a diet high in fat, sodium, and sugar
- family history of heart disease
- high cholesterol
- sedentary lifestyle, or a lack of exercise
Complications of renal artery stenosis
Decreased blood flow through your renal arteries can increase your overall blood pressure, leading to hypertension. RAS can also produce edema. The swelling can worsen over time as the condition progresses. Sometimes fluids can build up in your lungs, a condition called flash pulmonary edema.
Over time, renal artery stenosis can also damage kidney tissues. This can lead to kidney failure in severe cases and may require a kidney transplant.
Testing and diagnosis
Often, RAS is detected during an examination for another condition, such as hypertension. After your doctor performs a physical exam and looks at your medical records for any risk factors, they’ll likely order a urine test to measure proteins and overall kidney function. A blood test can also measure both kidney function and blood pressure-regulating hormones.
Your doctor may also order one or more of the following imaging tests to get a better look at your renal arteries:
- CT scan
- magnetic resonance angiography (MRA), a test that provides 3-D images of the area being investigated
- renal arteriography, which involves injecting a contrast material into your blood vessels so they show up on X-rays
How is renal artery stenosis treated?
Treatment for RAS depends on a combination of medications and lifestyle changes. Certain medical procedures may also be necessary.
One of the first ways to treat this condition is with medications. Your doctor may prescribe medications to help relax blood vessels so they don’t narrow. Options include:
- angiotensin II receptor blockers (ARBs)
- calcium channel blockers
- angiotensin converting enzyme (ACE) inhibitors
Alpha-beta-blockers and beta-blockers can also help by decreasing blood vessel dilation.
Your doctor may also recommend diuretics to reduce swelling and fluid retention. These are available in both prescription and over-the-counter forms.
Even if you take medications for RAS and other underlying conditions, certain lifestyle changes can help. These include:
- getting regular exercise
- losing or maintaining weight, if necessary
- quitting smoking
- cutting back on alcohol or caffeine
- consuming less sodium
- managing stress
- getting adequate sleep
If medication and lifestyle changes aren’t enough to limit the effects of RAS, the condition may progress. Eventually, your kidneys could become damaged. In such cases, your doctor may recommend certain procedures that improve arterial function. These include renal artery bypass surgery and renal stenting.
How to prevent renal artery stenosis
Since RAS often occurs in conjunction with other conditions, the best way to prevent it is to adopt a healthy lifestyle. You’ll also want to stay on top of any medications you take for underlying conditions you may already have.
RAS is a potentially serious condition. Left untreated, it can lead to permanent kidney damage. It’s important to see your doctor if you have any unusual symptoms or if you think an underlying condition like hypertension is getting worse.