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Covid-19: It's not only about the lungs, but also the kidneys

COVID-19,caused by the novel coronavirus–SARS-CoV-2,commands attention because of the severe acute respiratory illness that accompanies it. However, it is now known that this 'great invader' causes disorders of various organ systems, including the kidney, which is a cause for concern.

Early reports from China suggested a lower incidence (3%-9%) of Acute Kidney Injury (AKI) in those with COVID-19. Later reports however, indicated an incidence of AKI that varied from 0.5% to 39%. Recent data from New York hospitals (Northwell, Mount Sinai) revealed an AKI incidence of 36.6%-46%. The Northwell study also identified factors in those at risk for AKI as older age, black race, hypertension, diabetes mellitus, cardiovascular disease, vasopressor use and need for ventilation. All COVID-19 patients do not develop AKI (elevated blood urea or creatinine levels), but could possibly have substantial sub-clinical kidney injury. AKI develops within a week after hospitalisation, with a characteristic spike around the time for incubation need. Increased urinary excretion of protein (69-85%) and blood (64-75%) is observed. The more sinister elevations in blood urea and creatinine occurs in patients with more critical illness.

Damage to the kidney with resultant AKI could be caused by sepsis with release of overwhelming amounts of cytokines (cytokine storm), inadequate oxygen delivery, lowered blood pressure or direct cellular injury. Increased clotting with small vessel thrombosis could occur and result in blocking of the kidney filters. ACE2 receptors, the docking sites for the virus, abound not only in the lungs but also in the kidneys.

In the initial part of the illness, close attention is devoted to fluid adequacy. Overzealous fluid administration, however, may push the patient to early renal replacement therapy (RRT). Therefore, efforts should be directed to optimize fluid balance. When renal replacement therapy is essential, it may be initiated depending on the patient's condition. CRRT or haemodialysis may be supported by extracorporeal organ support systems. Innovative modifications of techniques to provide safe and efficient dialysis may be required. Increased clotting of dialysis blood circuits may, however, make dialysis challenging.

Prognosis in AKI varies. Some patients may have complete recovery, others recover incompletely and are predisposed to future chronic kidney disease. For some, the outcome is fatal, the mortality beingmuch higher in patients with AKI than those without.

The joint statement of three important nephrology societies-ERA, ASN and ISN, underlines the need to be prepared for the onslaught of COVID-19 associated AKI. The need for RRT in AKI patients could be in the ballpark range of about 25%. Rather than being 'blind-sided, it is imperative that hospitals should prepare themselves for a surge by anticipating numbers and needs for RRT without having to scramble for dialysis machines and dialysate/dialysis supplies.

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