What is Renal Artery Stenosis?

Before getting to know what renal artery stenosis is, we first need to understand the anatomical position of the renal arteries. They are paired arteries that supply blood to the adrenal glands, which are attached to both the kidneys. 

In scientific terms, stenosis means narrowing of the arteries, which limits the blood supply to the kidneys. This article will discuss the causes of renal artery stenosis (RAS) and how it can possibly be fatal.

Causes of renal artery stenosis

Renal artery stenosis (RAS) may be related to several factors, like the patient’s age and gender.¹

Hypertension (high blood pressure) may be another cause of RAS. Frequent changes in blood pressure may lead to abnormal blood flow/circulation to the renal artery.²

High cholesterol leads to the formation of plaques in the renal arteries, which could cause them to narrow. Plaques consist of fats (including cholesterol), calcium, and immune cells. This could lead to atherosclerosis, or narrowed arteries due to plaque build-ups.

Renal fibromuscular dysplasia is another cause, which occurs due to abnormalities in the muscle tissue of the arteries located in the kidney, causing them to look like loose string. It is most common among young people assigned female at birth (AFAB).

Atherosclerosis and renal fibromuscular dysplasia may also result in high blood pressure.

Signs and symptoms of renal artery stenosis

Impaired renal function generally means the kidney is not functioning properly. This may be termed as kidney failure, also known as acute kidney injury. This results in low blood flow, which causes atrophy meaning that cells start dying. A slight abdominal pain can be seen in patients suffering from RAS.

Headaches are another sign of the disorder. They occur because of stress and anxiety, which is a psychological consequence for patients with RAS.

RAS may also cause an increase in blood pressure. High blood pressure can, in turn, raise the risk of atherosclerosis, which affects the renal artery.²

Heart disease can be a major sign of RAS. Due to hypertension, RAS patients may suffer heart attacks or strokes.

Management and treatment

• Bypass surgery seeks to open a bypass around the restricted or blocked portion of the renal artery to restore normal blood flow to the damaged kidney
• Angioplasty surgery is generally done to open up the blocked arteries by inserting stents. A stent stretches the artery walls, creating enough space for blood to flow
• Percutaneous transluminal renal angioplasty (PTRA) is a procedure where a catheter (a thin tube) with a small balloon at the end is fed through an artery until it reaches the blocked artery. The balloon is then inflated to flatten any plaques. In patients with fibromuscular dysplasia, PTRA is the preferred treatment
• Blood pressure medications, such as ACE inhibitors, can be used to control the stenosis in many cases

Diagnosis

• Arteriography or angiography: Contrast arteriography is a direct method to visualise the renal artery using. A contrast dye is injected so that arteries can be seen on an X-ray. It is less invasive compared to other diagnostic methods²
• Magnetic resonance angiogram (MRA): This method helps to identify the location of the plaque formed in the walls of the artery³
• Doppler ultrasound: To evaluate blood flow speed in the arteries, Doppler sonography combines classic ultrasound imaging with a Doppler machine, which converts ultrasound waves reflecting off flowing blood into audible signals. Doppler ultrasounds are generally done before surgery
• Computerised tomography (CT) scan: a CT scan is similar to an MRA in that it helps detect the formation of plaques and calcified elements³
• Several lab tests can help diagnose RAS, including biopsies, urine tests, and blood tests

Risk factors

• High cholesterol is a major risk factor for developing RAS because cholesterol build-up in the arteries can reduce the blood supply
• Being overweight or obese is associated with an increased risk of developing RAS. Obesity can contribute to the development of high blood pressure and atherosclerosis
• Diabetes may also contribute to the development of atherosclerosis and can damage blood vessels
• Smoking damages blood vessels and accelerates the progression of atherosclerosis

Complications

PTRA-specific complications include renal artery dissection (a tear in the renal artery wall) and lipid embolism (a piece of fat gets stuck in the artery, blocking blood flow). 

Haemostasis in the groin, further bleeding, and kidney toxicity due to contrast dyes are all minor side effects. Up to 9.4% of patients experience major problems, which include cholesterol embolism, renal artery dissection, a blood clot in the renal artery, and acute kidney damage requiring dialysis (where a machine is used to filter the blood instead).⁴

Other complications include fluid retention (oedema), kidney damage, and ischaemic nephropathy (kidney disease due to a blockage of blood flow).

FAQs

Who is at risk of renal artery stenosis?

RAS is generally seen in elderly people. Smoking and obesity can also trigger RAS. You should immediately seek advice from healthcare professionals if you experience any of the symptoms. However, being aware of the risk factors may encourage people to take preventive steps and seek care if they notice any symptoms or have any concerns about RAS. RAS can be avoided by having routine check-ups, and leading a healthy lifestyle.

Summary

Renal artery stenosis, or RAS, is the narrowing of your renal artery due to the build-up of fats and other biological elements on the walls of the artery. This makes it difficult for blood to flow into your kidney, where blood filtration takes place. 

There are several causes of stenosis including high blood pressure, eating habits (e.g. foods high in cholesterol), and lifestyle. Some signs of RAS may be severe headaches, impaired kidney function, and differences in blood pressure. Despite this, RAS can be managed by taking precautions like regular check-ups, avoiding high-cholesterol foods, and generally leading a good lifestyle. 

While there are treatments available, there are also complications surrounding the condition including further bleeding, high blood pressure, and kidney damage. You should immediately seek help from a doctor if any signs are visible.