In 2020, COVID-19, a novel coronavirus, began impacting the globe. Caused by the SARS-CoV-2 virus, COVID-19 has resulted in 172 million diagnoses and 3.7 million deaths worldwide. While acute kidney failure is not common in all patients with COVID-19, a retrospective study highlighted how acute kidney injury (AKI) is more common in hospitalized patients. According to a story in the Nephrology Times, researchers sought to understand how and why proteinuria (excess protein in the urine) played a role in COVID-19 severity and patient outcomes.

In particular, researchers wanted to see whether proteinuria could be used as a prognostic tool or marker. A prognostic marker means that it can predict the likely outcome of a condition. Ultimately, researchers determined that early proteinuria in patients with COVID-19 signified worse renal outcomes and higher mortality rates. Check out the study design and findings published in the Clinical Journal of the American Society of Nephrology (CJASN). 

The Research

At first, there was little understanding of the intersection of COVID-19 and renal involvement. However, researchers now know that those with more severe COVID-19 cases are more likely to experience renal impacts. For example, less than 5% of patients with COVID-19 experienced kidney failure. But when looking at hospitalized patients, particularly those who died or entered the intensive care unit (ICU), the number significantly raises to an estimated 65%. Other studies performed from New York to China found that hospitalized patients with COVID-19 were much more likely to present with proteinuria or hematuria (blood in the urine), or that nearly half developed AKI.

Thus, researchers wanted to understand whether proteinuria was an adequate prognostic marker. Within this retrospective study, researchers evaluated data from 200 patients. These patients were treated at the Hôpital Européen George Pompidou in Paris on or before April 15, 2020. Of the patients, 28.5% were female and 71.5% were male. The median patient age was 63. More than half of the patients were overweight. Additionally, 51% reported a history of hypertension, with 25% reporting a history of diabetes. Although a small amount, some patients had previously had chronic kidney disease (CKD) or received kidney transplants.

Study Findings

Upon hospitalization, doctors evaluated the patients’ health via urine collection and analysis. Proteinuria was analyzed using urine protein-creatinine ratio (UPCR). Ultimately, researchers determined:

• The median UPCR when patients were admitted was 0.86 g/g.
• Ultimately, 84 patients (42%) had UPCR ≥1 g/g at admission. After evaluation, doctors determined that this UPCR was associated with more need for dialysis, increased ICU admission, and higher mortality rates.
• According to doctors, those with UPCR ≥1 g/g were more likely to have hypertension (high blood pressure) and be older in age.
• BMI, diabetes, CKD, and biological sex did not seem to influence proteinuria.
• 58 patients died prior to the follow-up period. Altogether, the data shows that those who died typically passed within 10 days of hospitalization.
• 88 patients were diagnosed with AKI during their stay in the hospital. Of these, 27 ultimately needed renal replacement therapy.

In the end, the research shows that proteinuria (measured by UPCR) can be an effective prognostic measure to determine which patients with COVID-19 may develop AKI. This finding could help inform treatment moving forward.

Proteinuria

When your kidneys are healthy, they help filter waste and extra fluid from the body. They also allow necessary elements, like protein, to pass through the kidneys and enter the bloodstream. However, proteinuria occurs when excess protein is expelled from the body via urine. This means that the kidneys are not functioning as well as they could.

In some cases, healthy individuals also pass protein in the urine. Proteinuria can also occur due to a temporary condition such as stress, kidney stones, low blood pressure, or dehydration. Between high levels of protein are being expelled, proteinuria can point to a much more serious issue. As listed above, COVID-19 can cause proteinuria. Other conditions include chronic kidney disease (CKD), multiple myeloma (MM), kidney cancer, congestive heart failure, or preeclampsia (among others).

At first, many people do not notice proteinuria-related symptoms. However, if proteinuria progresses or kidney function lessens, symptoms include:

• Foamy and/or bubbly urine
• Appetite loss
• Fatigue
• Nausea and vomiting
• Swelling in the face, abdomen, feet, and ankles
• Shortness of breath
• Frequent urination
• Muscle cramps which worsen at night
• Puffiness around the eyes that worsens in the morning

Learn more about proteinuria.