What causes a narrowed kidney artery?

Most often atherosclerosis (plaque build-up), which accounts for about 90% of cases and affects mainly older adults with heart-disease risk factors. A smaller share (about 10%) is due to fibromuscular dysplasia, which tends to affect younger adults, more often women.

Does renal artery stenosis cause symptoms?

Often not directly. It is usually suspected because of hard-to-control or early/late-onset high blood pressure, or worsening kidney function — rather than symptoms you would notice yourself.

Why can it raise blood pressure?

The narrowed artery reduces blood flow, so the kidney releases hormones that signal the body to raise blood pressure. This "renovascular hypertension" can be resistant to usual treatment.

With kidney function tests plus imaging of the renal arteries — Doppler ultrasound, CT angiography or MR angiography, and sometimes catheter angiography in selected cases.

Not usually. For most people, medicines and lifestyle to control blood pressure and cardiovascular risk are the mainstay. Angioplasty/stenting is reserved for selected situations such as fibromuscular dysplasia or hard-to-control blood pressure. Your doctor will advise what is right for you.

Renal Artery Stenosis: Causes, Blood Pressure & Treatment (Singapore)

Written & reviewed by the BestDoctors.sg editorial team · Last updated 1 Sep 2026 · General information, not medical advice

Quick answer. Renal artery stenosis (RAS) is a narrowing of one or both arteries that supply the kidneys, reducing blood flow. The two main causes are atherosclerosis (furring-up of the arteries – by far the most common, in older adults with heart-disease risk factors) and fibromuscular dysplasia (a non-inflammatory artery-wall problem, more often in younger women). It matters because reduced blood flow can trigger high blood pressure that is hard to control, and can impair kidney function. It often causes no symptoms, so it is usually suspected from clues such as severe or drug-resistant high blood pressure or worsening kidney function.

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In a medical emergency, or for severe or sudden symptoms such as breathing difficulty, chest pain, fainting or stroke signs, call 995 immediately.

Renal artery stenosis is one of the reasons blood pressure can stay stubbornly high despite several medicines – the kidney, sensing reduced flow, keeps signalling the body to raise it.

What it is

Each kidney is fed by a renal artery that branches off the body’s main artery, the aorta. These vessels carry a large share of the blood the heart pumps, because the kidneys constantly filter blood to remove waste and balance fluid, salts and blood pressure. In renal artery stenosis, one or both of these arteries becomes narrowed, so less blood reaches the kidney behind the narrowing.

The kidney is very sensitive to how much blood is flowing through it. When flow falls, it wrongly interprets this as low pressure in the whole body and releases hormones (part of the renin–angiotensin system) that raise blood pressure and make the body hold on to salt and water. The result can be blood pressure that climbs and stays high – a form of secondary hypertension, meaning high blood pressure with an identifiable underlying cause. Over months and years, poor blood supply can also shrink the affected kidney and gradually reduce its filtering ability. Because the change is slow and often silent, RAS may go unnoticed until blood pressure becomes hard to control or routine blood tests show the kidneys are struggling.

Symptoms

Renal artery stenosis usually causes no direct symptoms of its own. You cannot feel an artery narrowing, and many people have it for years without knowing. Instead, it tends to reveal itself through its effects on blood pressure and kidney function. Clues that may prompt a doctor to consider it include:

High blood pressure that is severe, or resistant despite taking several blood-pressure-lowering medicines together;
Blood pressure that appears suddenly at an unusually young age, or that starts or worsens sharply later in life;
Worsening kidney function on blood tests, particularly a step-down soon after starting certain blood-pressure medicines that act on kidney blood flow;
Episodes of fluid retention – swelling of the legs, or sudden breathlessness from fluid building up on the lungs.

Some people also have signs of narrowed arteries elsewhere, such as reduced blood flow to the legs or a history of heart or stroke problems, because the same disease process affects arteries throughout the body.

What causes it

There are two main causes, and they tend to affect different groups of people.

Atherosclerosis is by far the most common cause. This is the gradual build-up of fatty, calcified plaque inside the artery wall – the same process that narrows the arteries of the heart and legs. It usually affects older adults who have cardiovascular risk factors, and often the narrowing sits where the renal artery joins the aorta.

Fibromuscular dysplasia (FMD) is a much less common cause. It is not caused by plaque or inflammation; instead, the artery wall itself develops abnormal areas of thickening and narrowing, sometimes giving the vessel a “string of beads” appearance on imaging. FMD more often affects younger adults, and women in particular. It is important to distinguish because it often responds well to a procedure to widen the artery. Rarer causes include a blood clot, a tear in the artery wall, or pressure on the artery from outside.

Who is at risk

Because most renal artery stenosis is caused by atherosclerosis, the risk factors are the familiar ones for artery disease in general:

Older age;
Smoking;
Diabetes;
High cholesterol;
Existing high blood pressure;
Known artery disease elsewhere – coronary heart disease, narrowed leg arteries, or a previous stroke.

For fibromuscular dysplasia the picture is different: it is less clearly tied to lifestyle, tends to appear in younger women, and its exact cause is not fully understood. If you have several atherosclerosis risk factors alongside blood pressure that is difficult to manage, a doctor may be more inclined to look for RAS.

How it is diagnosed

Because RAS is usually silent, diagnosis starts with the clues above and a few basic checks, then moves to imaging of the kidney arteries. A doctor or specialist can assess which tests are appropriate. Typical steps include:

Blood pressure measurement, including how well it responds to treatment;
Blood and urine tests of kidney function, such as creatinine and estimated filtration rate (eGFR) – see kidney function tests & eGFR;
Doppler ultrasound of the renal arteries, which uses sound waves to look at blood flow and is often the first imaging test as it involves no radiation or contrast dye;
CT angiography or MR (magnetic resonance) angiography, which give detailed pictures of the arteries;
Catheter angiography in selected cases, where dye is injected directly into the arteries – this is the most precise test and can be combined with treatment during the same procedure.

Complications

Left untreated, or when the narrowing is severe, renal artery stenosis can lead to:

Resistant high blood pressure that stays high despite several medicines, which itself raises the long-term risk of heart attack, stroke and heart failure;
Chronic kidney disease – a gradual, lasting decline in kidney function from long-term poor blood supply (see chronic kidney disease);
Flash pulmonary oedema – sudden flooding of the lungs with fluid, causing acute breathlessness, which can happen when both kidneys are affected.

Sudden, severe breathlessness is a medical emergency: call 995 or go to the nearest A&E straight away.

Treatment

Treatment aims to control blood pressure, protect the kidneys and reduce the wider risk of heart and blood-vessel disease. For most people, particularly those whose RAS is due to atherosclerosis, the foundation is medical management and lifestyle change:

Blood-pressure-lowering medicines to bring blood pressure into a safe range. Some classes are especially useful in this setting but can affect blood flow within the kidney, so kidney function is monitored carefully after starting or adjusting them – the right choice is decided by a doctor;
Cholesterol-lowering treatment and, where appropriate, medicines to reduce clotting risk, to slow artery disease;
Lifestyle measures – stopping smoking, reducing salt, staying active, eating well and keeping to a healthy weight.

A procedure to widen the artery – angioplasty, in which a balloon is inflated inside the narrowed segment, sometimes with a small metal stent left in place to hold it open – is considered only in selected cases. These may include blood pressure that stays dangerously high despite good medical treatment, kidney function that is worsening, or repeated episodes of fluid on the lungs. For most people with atherosclerotic RAS, routine stenting has not been shown to work better than good medical therapy, so it is not done automatically. Fibromuscular dysplasia is different – it often responds well to angioplasty, and a procedure may be offered earlier in younger patients. In a small number of cases, surgery to bypass or repair the artery is considered.

Living with it and monitoring

Renal artery stenosis is usually a long-term condition managed alongside your other cardiovascular risks. Day to day, the most useful things you can do are within your control:

Keep blood pressure controlled – take medicines as prescribed and, if advised, monitor your readings at home;
Attend kidney monitoring – regular blood tests track kidney function and pick up any decline early;
Do not smoke – this is one of the single most important steps to slow artery disease;
Stick with your medicines – do not stop or change blood-pressure or cholesterol treatment on your own, as some need careful monitoring in this condition;
Manage the wider picture – cholesterol, diabetes, diet, activity and weight all matter for the arteries throughout your body.

In Singapore, a GP or polyclinic doctor can start the assessment, check your blood pressure and kidney tests, and refer you to a cardiologist, nephrologist or vascular specialist where needed. Reliable general health information is also available through HealthHub.

When to see a doctor

See a doctor if your blood pressure is hard to control despite treatment, if it appears suddenly or very high, or if routine kidney tests are worsening. It is also worth seeking advice if you develop new leg swelling or unexplained breathlessness on exertion. Seek urgent care – call 995 or go to A&E – for sudden severe breathlessness, chest pain, or symptoms of a stroke, which can be signs of a serious problem needing immediate attention.

Related kidney & urinary conditions

Sources

Cleveland Clinic — renal artery disease: definition, ~a proportion atherosclerosis vs ~a proportion FMD, warning signs, diagnosis, treatment.
Cleveland Clinic — renovascular hypertension: how a narrowed renal artery drives resistant high blood pressure.
StatPearls (NIH) — renal artery stenosis: atherosclerosis vs FMD, ACE/ARB clue, RAS as a cause of resistant hypertension.
Medscape — treatment and management: stenting not routine for all atherosclerotic RAS; ACE/ARB monitoring.

General information only. This guide is general information about a kidney or urinary condition and is not a diagnosis or personalised medical advice. See a doctor — a GP, urologist or nephrologist — for assessment, tests and treatment. Go to A&E if you suddenly cannot pass urine and have a painful, full bladder, or if you have severe flank pain with fever.

Renal Artery Stenosis (Narrowed Kidney Artery) in Singapore