How does COVID-19 affect the kidneys?

The coronavirus COVID-19 is a disease that mainly affects the lungs, but we know that it also affects the kidneys. Some early studies in China revealed it and now the same possibility is still being studied in the world.

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Knowing how COVID-19 affects the kidneys has been added to the list of questions about the development of this disease that the scientific community has. New symptoms are added every day and also new complications derived from the disease.

The doubt appeared with patients who presented a condition called acute kidney injury at their hospitalization . At that point, doctors in China already wondered how COVID-19 affects the kidneys. Thus, working hypotheses emerged that were corroborated or discarded according to the research.

The mechanism is still unclear at present, but nephrologists agree that there is some kidney damage from SARS-CoV-2 , which varies in frequency. While some geographic areas have registered less than 1% of patients with acute kidney injury, in other countries there is talk of up to 30% incidence.

Patients in whom COVID-19 affects their kidneys have a worse prognosis. Acute kidney injury is difficult to treat in intensive care units.

Scientific studies on how COVID-19 affects the kidneys

At the start of the coronavirus outbreak in China, there were a number of scientific publications that already alerted to kidney damage from SARS-CoV-2. Some studies were based on few patients, but others could include up to almost 1,000 individuals.

One of the initial publications  looked for the incidence of acute renal failure in patients with coronavirus. Kidney failure is the inability of the kidney to perform its filtering tasks .

In this study, up to 9% of the patients had insufficiency . This results in the presence of proteinuria , that is, the loss of protein through the urine. There is also elevation of a substance called creatinine in the blood, which becomes toxic when it exceeds a certain amount.

The patients with this whole picture underwent a renal tomography and the images revealed that 100% of them had alterations in the kidneys . Mainly, there was inflammation and fluid accumulation.

Another pioneering scientific study on how COVID-19 affects the kidneys also comes from China. In it, the researchers found kidney failure in 3% of those hospitalized, but 40% hematuria, which is the presence of blood in the urine.

Chinese scientific studies warned about kidney damage associated with coronavirus infections

Keep reading: Hematuria: what are its symptoms and causes?

The Three Factors of Coronavirus Kidney Damage

We could say that there are three aspects to consider in kidney involvement by COVID-19. These factors can act alone or combine, varying their presence in each patient. Sometimes, the damage is direct by the SARS-CoV-2 and, other times, we arrive at an indirect damage derived from the established treatment .

The three factors are:

  • The virus itself:Nephrologists agree that the kidneys are organs directly attacked by the disease, such as the lungs . The respiratory and renal systems have substances in common such as renin and angiotensin, which are linked by a receptor that could be the entry protein of SARS-CoV-2 to cells.
  • Systemic symptoms:When a severe form of COVID-19 occurs, many organs are affected by the same body failure. It is somewhat similar to what happens in pneumonia from other causes, which can lead to kidney failure due to a cascade of effects.
  • Treatment:Although there is no fully effective coronavirus treatment protocol, alternatives with various drugs are being investigated. Among them, there are some who have kidney side effects that can lead to failure on their own.

The coronavirus enters the renal cells and can damage them, but there is also damage from the medications and the treatment used.

Find out more: How the coronavirus infects cells

How does COVID-19 affect the kidneys?

The theory of SARS-CoV-2 entering renal cells lies in our knowledge of how the coronavirus infects lung cells. And we already know that the key to entry is the ACE2 protein .

The virus can enter lung cells because the spicules on its surface coincide in part with a receptor that humans already have: ACE2 . This receptor, which is also a protein, is in the lungs to intervene in the regulation of blood pressure.

The regulatory system to which we refer is the renin-angiotensin. It is one of the strengths of drug treatment of high blood pressure. For this reason, hypertensive patients are also suspected to have higher mortality in this pandemic .

It turns out that the kidneys also express similar proteins, due to their participation in the same renin-angiotensin system. It is hypothesized that COVID-19 can follow a similar path in kidney cells as it does in lung cells .

Kidney patients are a risk group for COVID-19

It should be clear that patients with kidney disease are among the risk groups during the pandemic. Therefore, they must take extreme care and social isolation.

It is essential that they continue with their medication . In case of having to consult for symptoms, the doctor who receives them must have all the patient’s history to implement the therapy that best suits that case.

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