The heart–kidney connection

Understanding the heart–kidney connection

The heart and kidneys work as partners. The heart pumps blood to the kidneys at a steady pressure; the kidneys, in turn, filter that blood, remove waste, balance salt and water, and help control blood pressure through hormones. When one organ struggles, it changes the workload and signals reaching the other — which is why heart disease and kidney disease so often travel together, a relationship clinicians sometimes call the cardiorenal connection.

Each kidney contains around a million tiny filtering units. They rely on a steady, well-pressured blood supply to work properly. If the heart's pumping ability falls, less blood reaches the kidneys and they filter less efficiently. If the kidneys are damaged instead, they struggle to remove excess salt and water, fluid builds up in the circulation, and the heart has to work harder against that extra volume. Either direction can set up a cycle where each organ makes the other's job harder.

What you may notice

Symptoms can come from the heart, the kidneys, or both together. These are common descriptions patients use, offered to help you describe your own experience to a clinician — not a checklist for diagnosing yourself.

• ●Swelling in the legs, ankles or around the eyes
• ●Breathlessness, especially lying flat or on exertion
• ●Reduced, dark or frothy urine, or the opposite — passing unusually large amounts
• ●Blood pressure that is difficult to control despite treatment
• ●Fatigue, poor appetite, nausea or itching in more advanced kidney disease
• ●Confusion or drowsiness, usually a sign of advanced illness needing prompt attention

How heart and kidney problems affect each other

The relationship runs in both directions, and several shared conditions can strain both organs from the start.

When heart problems strain the kidneys

If the heart's pumping is weakened by heart failure, or blood pressure inside the circulation rises or falls abnormally, the kidneys receive less effective blood flow and begin to filter less well. Some heart medicines that protect the heart, such as certain diuretics, also need careful kidney monitoring because of how they work.

When kidney problems strain the heart

Kidneys that cannot remove enough salt and water allow fluid to build up in the circulation, raising blood pressure and forcing the heart to pump against a larger volume over time. Kidney disease also commonly causes anaemia, a low blood count that forces the heart to work harder to deliver oxygen, and can disturb blood potassium levels enough to affect the heart's rhythm.

Shared underlying causes

High blood pressure and diabetes are the two most common conditions that damage the heart and kidneys together, often over many years and without early symptoms. This is why control of both is protective for two organs at once, not just one.

Medicines and contrast dye

Certain painkillers, some herbal preparations, and the contrast dye used in some heart imaging tests can each place extra strain on the kidneys, particularly if kidney function is already reduced — one reason your clinician checks kidney function before some procedures.

Who is more likely to be affected

These factors make a combined heart and kidney problem more likely, and are worth mentioning at your appointment:

• ●High blood pressure — very common in Nigeria and often undiagnosed, it is the leading shared driver of heart and kidney damage
• ●Diabetes
• ●Anaemia
• ●A family history of heart disease, kidney disease or diabetes
• ●Existing heart failure or a previous heart attack
• ●Existing kidney disease of any cause
• ●Obesity and a sedentary lifestyle
• ●Regular use of anti-inflammatory painkillers or unregulated herbal remedies

What happens if this goes untreated

Left unaddressed, the cycle between the two organs tends to worsen gradually rather than suddenly — which is also why early, consistent treatment makes a real difference.

Progressive fluid overload. Kidneys that cannot clear enough fluid allow it to build up in the lungs and legs, worsening breathlessness and swelling and straining the heart further.

Worsening kidney function. A heart that pumps less effectively delivers less blood to the kidneys over time, gradually reducing their filtering capacity.

Rhythm disturbance. Kidney disease can disturb blood potassium and other electrolytes enough to trigger dangerous heart rhythms.

Dialysis dependence. In advanced kidney failure, the kidneys can no longer filter the blood adequately on their own and dialysis becomes necessary to do this mechanically.

How Cardiocare investigates it

The right pathway depends on your symptoms, examination and overall health, drawing on cardiology and nephrology working together. It typically includes some or all of the following:

• 01
  History and examination. Your symptoms, medicines, and an examination of your heart, blood pressure and any swelling.
• 02
  Kidney and electrolyte blood tests. Measuring how well the kidneys are filtering and whether salts such as potassium are in balance.
• 03
  Urine testing. Checking for protein, blood or other markers of kidney strain.
• 04
  Blood pressure and fluid assessment. Including ambulatory blood pressure monitoring where a fuller pattern is needed.
• 05
  ECG and echocardiogram. A painless recording of the heart's electrical activity and a painless ultrasound of its structure and pumping, when heart disease is suspected.
• 06
  Full blood count. To check for anaemia, common in kidney disease and a strain on the heart.
• 07
  Joint cardiology and nephrology review. For combined heart and kidney disease, treatment is planned across both specialties together.

How the heart–kidney connection is treated

Treatment aims to protect both organs at once, since improving one usually helps the other.

Lifestyle and fluid control

Reducing salt intake, following personalised fluid guidance, and tracking weight or swelling if instructed can reduce the strain on both the heart and kidneys.

Medicines, by class

Several medicine groups protect both organs together, and your clinician will discuss which combination and dose suit your situation:

• ●ACE inhibitors or ARBs — lower blood pressure and specifically protect kidney filtering units over time
• ●Diuretics — help the kidneys remove excess salt and fluid, easing the heart's workload
• ●SGLT2-inhibitor medicines — originally developed for diabetes, now used for their combined heart and kidney protective effect
• ●Medicines to correct anaemia or electrolyte imbalance — where blood counts or potassium levels need adjustment

Dialysis

When kidney function falls low enough that it can no longer safely filter the blood, dialysis takes over that filtering role mechanically. Cardiocare's dialysis centre is integrated with cardiology and critical care, so heart and kidney treatment can be coordinated within one hospital system.

Living with a heart–kidney condition: everyday self-care

• ✓Follow your personalised salt and fluid advice rather than a generic diet
• ✓Avoid unprescribed painkillers and unregulated herbal remedies
• ✓Monitor your weight or swelling if your clinician has asked you to
• ✓Take blood pressure, heart and kidney medicines exactly as prescribed, even when you feel well
• ✓Keep both cardiology and nephrology appointments — each visit informs the other
• ✓Stay well hydrated within your personal fluid limits, especially in Abuja's heat

Preparing for your appointment

What to bring

• ✓A list of all medicines you take, including herbal and over-the-counter products
• ✓Any previous blood or urine test results, scans or hospital letters
• ✓Your HMO card or payment details
• ✓A valid means of identification

What we will ask

How your swelling, breathlessness or urine habits have changed, your blood pressure history, and your full list of medicines, including herbal products.

Questions worth asking us

• ●Is my heart affecting my kidneys, my kidneys affecting my heart, or both?
• ●What tests do I need, and what will each involve?
• ●How much salt and fluid should I have each day?
• ●Which of my medicines protect my kidneys, and which need kidney monitoring?