Cardiorenal syndrome is a spectrum of disorders affecting the heart and kidneys. Dysfunction in either organ can trigger negative changes in the other.

Properly functioning heart and kidneys are critical to health. If either organ fails, it causes a strain on the other, resulting in a cycle of decline. Cardiorenal syndrome can cause a range of severe symptoms and lead to long-term organ damage. The condition can affect a person’s lifespan.

While full recovery is unlikely, treatment can reduce symptoms and support the functioning of the heart and kidneys.

This article looks at cardiorenal syndrome, including its causes, symptoms, and treatment options.

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Heart and kidney dysfunction often occur together, and an issue in one organ may lead to a problem in the other. Experts refer to this association as cardiorenal syndrome. The problem may either be chronic or acute.

Cardiorenal syndrome is an umbrella term for multiple subtypes, which doctors classify depending on the underlying disease and duration of symptoms.

Certain people have an increased risk of developing cardiorenal syndrome, including those with the following conditions:

The syndrome is also more common in older adults.

The five subtypes of cardiorenal syndrome include:

  • Type 1: A rapid decline in heart function leads to an acute decrease in kidney function. This is the most common type.
  • Type 2: Chronic heart problems result in a continued reduction in kidney function.
  • Type 3: A rapid decline in kidney function causes an acute reduction in heart function.
  • Type 4: Chronic decline in kidney function results in long-term heart problems.
  • Type 5: Systemic diseases, such as diabetes or sepsis, cause heart and kidney failure.

Each type disrupts multiple bodily processes uniquely and may require different management strategies. People with different subtypes may also have different outlooks.

Signs and symptoms of cardiorenal syndrome vary by type but may include the following:

The heart and kidneys have a dependent and bidirectional relationship, whereby the dysfunction of one can lead to the dysfunction of the other.


For example, a condition affecting the heart can result in the organ being unable to pump properly, which reduces cardiac output. This results in less blood flowing to the kidneys, which doctors call renal hypoperfusion. The body then reserves sodium to preserve plasma volume and compensate for the reduced blood supply.

However, sodium also causes vasoconstriction in the kidneys, narrowing their tiny arterioles. These arterioles, the smallest branches of an artery, further branch into clusters of blood vessels called glomeruli. The glomeruli act as the kidneys’ filters.

Vasoconstriction reduces the glomerular filtration rate and increases glomerular filtration pressure, both of which impact the functioning of the kidneys. The narrowing of blood vessels also causes a further decrease in blood supply to the kidneys. When prolonged, this causes renal injury due to low oxygen levels.

Other causes

Other mechanisms for inducing cardiorenal syndrome exist.

Causes vary and can include:

Doctors use a medical history and physical examination to tailor their diagnostic approach.

Initial tests typically include the following:

  • Complete blood count: This test looks at the different components in the blood.
  • Complete metabolic panel: This panel looks at kidney and liver function.
  • Urine studies: These may involve tests such as microscopy, protein-to-creatinine ratio, and sodium level checks.
  • Brain natriuretic peptide (BNP) test: BNP molecules elevate when the heart cannot pump properly.
  • Troponin tests: The presence of this protein in the blood is usually a marker of heart damage.

An electrocardiogram and cardiac monitoring help doctors evaluate any underlying irregular heartbeats contributing to or resulting from the cardiorenal syndrome.

A renal ultrasound can help evaluate kidney size and function. A doctor may suspect chronic kidney disease if a person has smaller kidneys and increased renal echogenicity, which is the ability of the kidneys to reflect ultrasound waves. Increased echogenicity can be a sign of kidney injury.

Unfortunately, no existing therapies can help reduce the impact of cardiorenal syndrome. However, treatments that help reduce symptoms and prevent further damage to the heart or kidneys are available.

Most people with cardiorenal syndrome have volume overload, meaning there is too much fluid in the body and the kidneys cannot remove enough of it. Therefore, doctors may prescribe medications, such as diuretics, to reduce fluid volume. These might include:

  • furosemide (Lasix)
  • torsemide (Demadex)
  • bumetanide (Burinex or Bumex)

While diuretics are the cornerstone of heart failure management, other treatments and medications may help with cardiorenal syndrome, including:

  • Ultrafiltration: A mechanical process that removes fluid from the blood.
  • Vasodilators: Drugs that relax the muscles around blood vessels, allowing them to dilate and improve circulation.
  • Inotropes: Drugs that help improve the heart’s pumping ability.
  • Neprilysin inhibitors: A newer class of medications that help reduce pressure on the kidneys.

Cardiorenal syndrome is a serious condition, and people with the syndrome typically have a poor outlook. However, a person’s outlook can depend on the underlying cause and how well their condition responds to treatment.

Combined heart failure and chronic kidney disease lower life expectancy significantly.

Below are answers to some common questions about cardiorenal syndrome.

Is it reversible?

Although doctors may initially reverse some of the consequences of cardiorenal syndrome, the damage is ultimately irreversible.

However, doctors can prescribe medications that help ease symptoms.

Is cardiorenal syndrome heart failure?

Cardiorenal syndrome encompasses both heart and kidney failure, but it is not itself a type of heart failure.

Heart failure occurs when the organ cannot pump enough blood and oxygen around the body.

What complications can occur due to cardiorenal syndrome?

Complications that can occur due to cardiorenal syndrome include liver failure and respiratory failure requiring ventilation.

A person may also have worsening renal failure that requires temporary or long-term dialysis.

Heart and kidney dysfunction can co-occur, and issues within one organ can result in problems in the other. This association is known as cardiorenal syndrome.

At least five types of cardiorenal syndrome exist. Each type has unique causes and affects the body differently. Although symptoms may vary by type, cardiorenal syndrome typically causes nonspecific symptoms, for example, low blood pressure.

Treatment can help ease symptoms and usually involves diuretics. In cases where diuretics are not useful, other measures are available to treat heart failure, such as ultrafiltration.

Generally, the outlook for someone with cardiorenal syndrome is poor. However, a person’s outlook can depend on various factors, such as the condition type and response to treatment.