Renal Impairment

Renal impairment is a condition where the kidneys lose their ability to filter blood properly, affecting millions of people worldwide and potentially leading to serious health complications if left untreated.

Table of contents

• What is renal impairment?
• How your kidneys normally work
• Types of kidney impairment
• Stages of chronic kidney disease
• Warning signs and symptoms
• Common causes and risk factors
• How renal impairment is diagnosed
• Treatment options
• Living with renal impairment
• Preventing kidney damage

What is renal impairment?

Renal impairment, also called kidney impairment or renal insufficiency (poor kidney function), occurs when your kidneys cannot work as well as they should^[1]. This condition means your kidneys have difficulty filtering waste products and excess water from your blood^[9].

Renal impairment can be temporary or long-lasting. When the condition persists for three months or longer, it is called chronic kidney disease (CKD)^[2][10]. In some cases, renal impairment may be due to reduced blood flow to the kidneys caused by narrowed arteries, a condition called renal artery stenosis^[9].

More than 1 in 7 American adults has chronic kidney disease, and as many as 9 in 10 don’t know they have it^[8]. Kidney failure affects over 750,000 people in the United States each year and around 2 million people worldwide^[1].

How your kidneys normally work

Your kidneys are bean-shaped organs about the size of your fist. They sit under your ribcage, toward your back. Most people have two working kidneys, though you can live well with only one kidney as long as it functions properly^[1].

Your kidneys perform several important jobs to keep you healthy. One of the most important functions is helping your body eliminate toxins. Your kidneys filter your blood and send waste products out of your body in urine^[1]. In fact, they filter all the blood in your body every 30 minutes^[3].

Beyond filtering blood, your kidneys also help control blood pressure, signal the body to make red blood cells, help keep your bones healthy, and regulate blood chemicals that are essential to life^[3][8]. When the kidneys don’t work properly, waste and fluid build up in your body, which can lead to other health problems^[8].

Types of kidney impairment

There are two main types of kidney impairment based on how quickly the condition develops^[3][18].

Acute kidney injury (also called acute kidney failure) is loss of kidney function that develops quickly—over a few hours or days. It can be mild, or severe enough to cause kidney failure. Many people with acute kidney injury will recover over time. This could take days, weeks, or months. However, for some people, acute kidney injury can cause death or permanent damage that leads to chronic kidney disease^[3][18].

Chronic kidney disease (CKD) is when your kidneys have been damaged in a way that can’t be reversed. Chronic kidney disease takes months or years to develop^[3][18]. It is a long-term condition where the kidneys do not work as well as they should and slowly gets worse over time^[7].

Stages of chronic kidney disease

There are five stages of chronic kidney disease based on how well your kidneys filter substances. Healthcare providers measure this using the estimated glomerular filtration rate (eGFR), which is calculated through a blood test^[1][10].

A normal eGFR is above 90. The lowest eGFR is 0, which means there’s no remaining kidney function^[1].

Stage I: Your eGFR is higher than 90. At this stage, your kidneys have mild damage but still function normally^[1].

Stage II: Your eGFR is between 60 and 89. You have more damage to your kidneys than in stage I, but they still function well^[1].

Stage III: Your eGFR is between 30 and 59. You may have mild or severe loss of kidney function. This is the most common stage, and you may start to notice symptoms at this stage^[1][5].

Stage IV: Your eGFR is between 15 and 29. You have severe loss of kidney function. With the right treatment, many people can stay in this stage and never advance to stage 5^[1][5].

Stage V: Your eGFR is below 15. Your kidneys are nearing or at complete failure. Generally, this is when you would start to have symptoms and may need dialysis or a kidney transplant^[1][5].

Warning signs and symptoms

Many people experience few or no symptoms in the early stages of kidney disease. In fact, there are usually no symptoms of kidney disease in the early stages, and it may only be diagnosed if you have a blood or urine test for another reason^[1][7].

If your kidneys aren’t working properly, you may notice one or more of the following signs^[1][3][7]:

• Extreme tiredness (fatigue)
• Nausea and vomiting
• Confusion or trouble concentrating
• Swelling (edema), particularly around your hands, ankles, or face
• Changes in how often you urinate
• Blood in your urine
• Cramps (muscle spasms)
• Dry or itchy skin
• Poor appetite, or food may taste metallic
• Shortness of breath

The first symptom of acute kidney failure is usually a decreased amount of urine^[3][18]. You should see your doctor urgently or go to your local hospital emergency department if you notice you are suddenly making less urine than usual, together with other symptoms of acute kidney failure^[3].

Common causes and risk factors

Diabetes and high blood pressure are the most common causes of chronic kidney disease and kidney failure. Unmanaged diabetes can lead to high blood sugar levels that damage the kidneys over time^[1][7].

Other causes of chronic kidney disease include^[7]:

• High blood pressure—over time, this can strain the small blood vessels in the kidneys and stop them from working properly
• High cholesterol—this can cause a build-up of fatty deposits in the blood vessels supplying your kidneys
• Kidney infections
• Glomerulonephritis—kidney inflammation
• Autosomal dominant polycystic kidney disease—an inherited condition where growths called cysts develop in the kidneys
• Blockages in the flow of urine—for example, from kidney stones that keep coming back or an enlarged prostate
• Long-term, regular use of certain medicines—such as lithium and non-steroidal anti-inflammatory drugs (NSAIDs)

Renal insufficiency may also be caused by reduced blood flow to the kidneys due to renal artery disease. The risk factors for this type of renal impairment are those associated with atherosclerosis (hardening of the arteries): older age, gender, family history, race or ethnicity, genetic factors, high fats in the blood, high blood pressure, smoking, diabetes, and obesity^[9].

You are at greater risk for kidney disease if you have^[25]:

• Diabetes
• High blood pressure
• Heart disease
• A family history of kidney failure

How renal impairment is diagnosed

Chronic kidney disease can be diagnosed using blood and urine tests. These tests look for high levels of certain substances in your blood and urine that are signs your kidneys are not working properly^[7].

The main tests include^[7]:

• Blood tests to measure your eGFR (estimated glomerular filtration rate)
• Urine tests to check for blood or protein in your urine

The results of your blood and urine tests can be used to determine the stage of your kidney disease. This is a number that reflects how severe the damage to your kidneys is, with a higher number indicating more serious chronic kidney disease^[7].

If you’re at high risk of developing kidney disease (for example, you have a known risk factor such as high blood pressure or diabetes), you may be advised to have regular tests to check for chronic kidney disease so it’s found at an early stage^[7].

Renal artery disease can usually be diagnosed through duplex ultrasound scanning and other non-invasive tests, including CT angiography and MR angiography. However, the definitive test is contrast angiography, which involves the injection of dye^[9].

Treatment options

There’s no cure for chronic kidney disease, but treatment can help relieve the symptoms and stop it from getting worse^[7][13]. Your treatment will depend on the stage of your chronic kidney disease.

The main treatments include^[7][13]:

• Lifestyle changes to help you stay as healthy as possible
• Medicine to control associated problems such as high blood pressure and high cholesterol
• Dialysis—treatment to replicate some of the kidney’s functions, which may be necessary in advanced (stage 5) chronic kidney disease
• Kidney transplant—this may also be necessary in advanced (stage 5) chronic kidney disease

Patients with renal insufficiency who have mild or moderate symptoms can be treated with medication and monitored regularly through blood pressure measurements and blood tests to monitor kidney function^[9].

Medications

There’s no medicine specifically for chronic kidney disease, but medicine can help control many of the problems that cause the condition and complications that can happen as a result^[13].

For high blood pressure, people with kidney disease should usually aim to get their blood pressure below 140/90 mmHg. Medicines called angiotensin-converting enzyme (ACE) inhibitors or angiotensin-receptor blockers (ARBs) are often used^[13].

If you also have type 2 diabetes or a high albumin to creatinine ratio, you may be offered a type of medicine called an SGLT2 inhibitor, such as dapagliflozin, which helps lower blood sugar and can reduce damage to your kidneys^[13].

You may be prescribed medicines called statins to reduce your risk of developing cardiovascular disease, including heart attack and stroke^[13].

Dialysis

Dialysis is a treatment that replicates some of the kidney’s functions when they can no longer work adequately. There are two main types of dialysis^[11]:

Hemodialysis is done through cleaning the blood through a machine. You attend a dialysis center three times a week for about four hours each time, although it can be done at home in certain circumstances^[11].

Peritoneal dialysis involves putting fluid into your abdomen, which takes out the toxins and is then drained. This can be done either during the day or overnight on a machine^[11].

Kidney transplant

A kidney transplant involves surgically placing a healthy kidney from a donor into your body. The donor kidney can come from a deceased donor or a living donor. A transplant offers the potential for a more active and longer life compared to dialysis^[14][17].

Living with renal impairment

Taking an active role in managing chronic kidney disease will help you feel better and improve your overall well-being^[24].

Take your medicine

It’s very important that you take any prescribed medicine, even if you feel well. Some medicines are designed to prevent serious problems in the future. Check with your care team if you plan to take any painkillers or nutritional supplements, as these can sometimes affect your kidneys or interfere with your medicine^[23][24].

Eat a healthy diet

A healthy, balanced diet can help improve your general health and reduce your risk of developing further problems^[23]. A kidney-friendly diet should include plenty of fruit and vegetables, meals with starchy foods, some dairy or dairy alternatives, some beans or pulses, fish, eggs or meat as a source of protein, and low levels of saturated fat, salt, and sugar^[23].

While you should limit salt, your food doesn’t have to be bland. Get creative with herbs, spices, mustard, and flavored vinegars in your favorite recipes^[24].

Be physically active

Regular physical activity can help improve your general health. Exercise is good for anyone with kidney disease, whether you have mild, moderate, or severe chronic kidney disease. It can boost your energy, help you sleep, strengthen your bones, help prevent depression, and may reduce your risk of problems such as heart disease^[23][24].

If you have mild to moderate chronic kidney disease, you should be able to be active as often as someone with healthy kidneys. If you have later-stage chronic kidney disease, you may become tired more quickly. Speak with your doctor about which physical activity is right for you^[24].

Other lifestyle measures

Additional lifestyle measures include^[23][24]:

• Stop smoking if you smoke
• Limit how much alcohol you drink
• Keep your blood pressure below 140/90 mmHg (or the target set by your doctor)
• If you have diabetes, stay in your target blood sugar range as much as possible
• Get your annual flu shot

Preventing kidney damage

You can protect your kidneys by preventing or managing health conditions that cause kidney damage, such as diabetes and high blood pressure^[25].

Steps you can take to prevent chronic kidney disease include^[25]:

• Make healthy food choices—choose fresh fruits, fresh or frozen vegetables, whole grains, and low-fat or fat-free dairy products
• Cut back on salt and added sugars—aim for less than 2,300 milligrams of sodium each day
• Choose foods that are healthy for your heart and entire body
• Be physically active
• Maintain a healthy weight
• Get enough sleep
• Manage stress
• Control blood pressure and blood sugar if you have diabetes

Early recognition of chronic kidney disease is important. If you have risk factors such as diabetes, high blood pressure, heart disease, or a family history of kidney failure, you should have regular tests to check for chronic kidney disease so it can be found at an early stage^[7][8].