kidney on one side

Overview

Having one kidney means you have only one working kidney instead of two. This can happen if you were born with one kidney (called renal agenesis), had one removed during surgery (nephrectomy), or if one kidney does not work properly. A single kidney can do the job of two, but it needs extra care to stay healthy.

Having one kidney is not very common, but it is not extremely rare. About 1 in 1,000 people are born with one kidney, and many others have a kidney removed due to donation, injury, or disease.

Anyone can have one kidney – from birth, after surgery, or because one kidney stops working. It affects children, adults, and older people equally.

Symptoms

Common symptoms

• Most people with one kidney have no symptoms and feel perfectly well.
• Some may have slightly higher blood pressure over time.
• If the single kidney becomes overworked or damaged, you might notice swelling in the legs or face, fatigue, or changes in urination.

Symptoms in children

• Children with one kidney often have no symptoms. They grow and develop normally.
• Rarely, a child may have other urinary tract issues like reflux (urine backing up to the kidney).

Symptoms in older adults

• Older adults with one kidney may be more likely to develop high blood pressure or a small decline in kidney function over many years.
• They should monitor for signs like swelling in the ankles or shortness of breath.

Causes

Main causes

• Born with only one kidney (renal agenesis) – the other never formed.
• One kidney removed because of cancer, infection, a blockage, or injury.
• One kidney stops working or is very small (dysplasia) and the other takes over.
• Donating a kidney for transplant.

Risk factors

• Family history of kidney problems or being born with one kidney.
• Certain conditions that may lead to kidney removal, such as kidney cancer, severe kidney stones, or recurrent infections.
• High blood pressure or diabetes – these can damage a single kidney faster.

When to see a doctor

See a doctor urgently if:

• If you have sudden flank pain, blood in urine, or cannot urinate – see a doctor right away or call emergency services.
• If you have signs of a urinary tract infection (burning with urination, fever, chills) – seek same-day care.

Book a routine appointment if:

• If you know you have one kidney, see your doctor at least once a year for blood pressure check and a blood test (creatinine) to monitor kidney function.
• If you notice any new swelling, fatigue, or changes in urine, schedule an appointment.

Diagnosis

Having one kidney is often found by accident during an ultrasound or scan for another reason. Or it may be discovered when a child is born with other health issues.

Tests that may be done

• Ultrasound – sound waves create a picture of your kidneys to see size and structure.
• Blood test (creatinine) – checks how well your kidneys are filtering waste.
• Urine test – looks for protein or blood that could mean kidney damage.
• Blood pressure measurement – high blood pressure can be a sign the kidney is working too hard.

What to expect at your appointment

If you are diagnosed with one kidney, your doctor will likely schedule regular check-ups (once a year or so) to monitor your kidney function and blood pressure. You may also be advised to avoid certain medications, like ibuprofen, without talking to your doctor first. No special preparation is needed for most tests.

Treatment

There is no cure or treatment needed for having one kidney because it can often do the work of two. But you need to take care of it to keep it healthy. Treatment focuses on protecting your kidney from injury and monitoring for any decline in function.

Self-care at home

• Drink plenty of water (6-8 cups a day) unless your doctor tells you otherwise.
• Avoid high-impact or contact sports (like football, boxing, or martial arts) – if you do play, wear protective gear.
• Do not take non-steroidal anti-inflammatory drugs (NSAIDs) like ibuprofen, naproxen, or high-dose aspirin without talking to your doctor – these can harm the kidney.
• Control your blood pressure and blood sugar if you have diabetes.
• Eat a balanced diet with moderate protein and salt.

Medical treatments

If your single kidney starts to show signs of stress – like rising creatinine or high blood pressure – your doctor may prescribe medications to lower blood pressure or protect kidney function. These are usually ACE inhibitors or ARBs, but your doctor will choose the right one for you. Regular monitoring is the main medical treatment.

When is surgery considered?

Surgery is not needed just because you have one kidney. You may only need surgery if there is a problem with that kidney, such as a tumor, blockage, or severe stone that cannot be treated otherwise.

Living with this condition

Having one kidney rarely affects daily life. You can work, exercise (with caution), travel, and enjoy most activities. Just keep up with your check-ups and listen to your body.

Lifestyle tips

• Stay active with low-impact exercise like walking, swimming, or cycling.
• Avoid smoking and limit alcohol – these can stress your kidneys.
• Maintain a healthy weight to reduce the risk of high blood pressure and diabetes.
• Wear a seatbelt in the car – this helps protect your kidney in an accident.

Diet and exercise

A heart-healthy diet is good for your kidney: lots of fruits, vegetables, whole grains, and lean protein. Do not eat too much salt (try for less than 2,300 mg a day). Drink enough fluids to keep your urine light yellow. Most people do not need a special kidney diet unless your kidney function drops. Exercise regularly but avoid heavy lifting or sports that could cause a direct hit to your back.

Mental health and emotional wellbeing

Some people feel anxious about having only one kidney – worried about injury or future health. This is normal. Talking to your doctor or a counselor can help. Remember that most people with one kidney live long, normal lives without complications.

Prevention

If you are born with one kidney, it cannot be prevented. But you can prevent problems by taking good care of the kidney you have. Avoid injury, manage health conditions well, and follow your doctor's advice.

Vaccines

Stay up to date on routine vaccines, especially the flu vaccine and pneumonia vaccine, because kidney infections can be more serious in a single kidney.

Screening programmes

If you have high blood pressure, diabetes, or a family history of kidney disease, your doctor may recommend yearly urine and blood tests to catch any decline early.

Complications

If left untreated

• High blood pressure – the single kidney works harder, which can raise blood pressure over time.
• Chronic kidney disease – if the single kidney becomes damaged, it may slowly lose function, leading to kidney failure (though this is uncommon with good care).
• Injury to the kidney – a direct blow or accident can harm the only working kidney.
• Urinary tract infections – if the kidney is abnormal or there is reflux, infections may occur.

Long-term outlook

The outlook for most people with one kidney is excellent. With regular check-ups and healthy habits, a single kidney can function well for a full lifetime. Even if problems arise, early treatment can keep your kidney working well for many years. It is possible to live a long, active, and healthy life with one kidney.

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