Nearly One-Third of Individuals Exposed to COVID-19 Experience Kidney Complications

Medical News: Kidney problems have become an unexpected but significant concern for patients hospitalized with COVID-19. Nearly one-third of these patients experience some form of kidney complication, primarily acute kidney injury (AKI), leading to worsened health outcomes and greater risks of long-term kidney disease. This Medical News report highlights recent research findings on the types of kidney damage seen in COVID-19 patients and the potential factors involved. The research, conducted by Dr. Ankita Muthya, Dr. Elif Ekinci, and Dr. Ashani Lecamwasam from the University of Melbourne’s Department of Medicine and Austin Health, examined reports and studies on kidney biopsies performed on COVID-19 patients from August 2020 to November 2021.


Nearly One-Third of Individuals Exposed to COVID-19 Experience Kidney Complications

A Range of Kidney Pathologies Observed
The study looked at 14 separate studies involving 159 COVID-19 patients with kidney complications, analyzing case reports, cohort studies, and autopsy data. Acute tubular necrosis (ATN) was identified as the most common kidney condition among these patients, followed by a unique condition called collapsing glomerulopathy (CG), which mainly affected individuals of African descent with specific genetic markers. This study sheds light on the diverse range of kidney pathologies linked to COVID-19, offering a better understanding of how the virus affects the kidneys.
 
Acute Tubular Necrosis and Kidney Complications
Acute tubular necrosis (ATN), present in 40.1% of cases, is a type of kidney injury where the cells lining the kidney’s tiny tubules are damaged due to poor blood flow, inflammation, or toxins. Among COVID-19 patients, ATN often results from issues such as low blood pressure, low oxygen levels, or blood clots triggered by the virus. In some cases, muscle breakdown associated with COVID-19 can also release toxins into the bloodstream, further damaging the kidneys.
 
In addition, the researchers found that about 29% of the cases featured collapsing glomerulopathy (CG), a type of kidney disorder characterized by scarring of the tiny filtering units (glomeruli). Interestingly, CG was most common among patients of African descent who carried specific APOL1 gene variants, previously linked to a higher risk of kidney disease in people with African ancestry. While more studies are needed to fully confirm this connection, it appears that a combination of genetic factors and COVID-19 infection increases the risk of CG among certain populations.
 
Glomerular Diseases and Immune Responses
The study also uncovered other glomerular diseases in COVID-19 patients, including focal segmental glomerulosclerosis (FSGS), membranous nephropathy (MN), and minimal change disease (MCD). These conditions involve various forms of damage to the glomeruli, the kidneys’ filtration units. In the case of membranous nephropathy, the immune system mistakenly attacks the kidneys, leading to scarring and protein leakage. Some patients with FSGS or MCD were found to have APOL1 gene variants, suggesting a genetic vulnerability to kidney issues triggered by the immune response to COVID-19.
 
Interestingly, MN and some other forms of glomerular diseases have been linked to the presence of anti-PLA2R antibodies, indicating that the immune system’s reaction to COVID-19 may play a role in certain kidney disorders. For those with membranous nephropathy, high levels of these antibodies often predict a more severe disease course, which may require additional monitoring and treatment.
 
Direct Infection of Kidney Cells: A Possible Link
In certain cases, SARS-CoV-2, the virus responsible for COVID-19, has been found directly in kidney tissues. While this is not observed in all cases, studies have identified viral particles in the cells of kidney tubules, indicating that direct infection might play a role in some types of COVID-19-related kidney damage. However, the research team noted that direct viral infection of kidney cells is uncommon and likely not the primary cause of kidney complications in most cases. Instead, the virus’s effect on blood vessels, immune response, and inflammation likely drives the majority of kidney issues.
 
Other Less Common Kidney Issues
While ATN and CG were the most frequently seen conditions, the researchers identified several other kidney pathologies in COVID-19 patients, though these were less common. These include forms of immune complex glomerulonephritis (GN), in which the body’s immune system attacks kidney tissues, causing inflammation and damage. Other immune-related conditions included anti-glomerular basement membrane (anti-GBM) disease and lupus nephritis, which were seen in a small percentage of patients.
 
Anti-GBM disease, for example, is a rare autoimmune disorder that targets the kidney’s filtering system, and the study found that it might be triggered by COVID-19 infection. Meanwhile, lupus nephritis is a type of kidney inflammation associated with lupus, an autoimmune condition, that may worsen with COVID-19.
 
Contributing Factors to Kidney Damage in COVID-19
Understanding the causes behind these kidney pathologies reveals that multiple factors may contribute to kidney damage in COVID-19 patients. COVID-19 often leads to low blood pressure, which reduces blood flow to the kidneys, while inflammation and blood clotting, common in COVID-19, can further harm kidney tissues. The cytokine storm, an overactive immune response to COVID-19, is another suspected factor, with certain cytokines linked to increased blood vessel permeability and inflammation in the kidneys.
 
Additionally, COVID-19 patients who require intensive care or mechanical ventilation are at higher risk of kidney issues, likely due to increased oxygen demands, fluid imbalances, and other factors. In patients with pre-existing conditions like diabetes or chronic kidney disease, the virus may also interact with existing kidney health issues, worsening kidney damage.
 
Conclusion: Implications for COVID-19 Treatment and Future Research
Kidney damage remains a significant concern for hospitalized COVID-19 patients. This review shows that while some kidney injuries are directly related to the virus’s impact on the kidneys, others stem from complex interactions between COVID-19, immune responses, and underlying genetic factors. For those at higher risk, particularly individuals of African descent with certain genetic variants, early monitoring of kidney function may help reduce the severity of COVID-related kidney complications.
 
Furthermore, understanding the variety of kidney issues caused by COVID-19 can inform targeted treatments. For example, patients with CG may benefit from early intervention with corticosteroids, while those with high levels of anti-PLA2R antibodies may require immunosuppressive treatments. Continued research is needed to clarify the long-term impact of COVID-19 on kidney health, including how different virus variants and vaccination status may influence kidney outcomes.
 
The study findings were published in the peer-reviewed journal: Internal Medicine Journal. (Wiley)
https://onlinelibrary.wiley.com/doi/10.1111/imj.16540
 
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