Long COVID and the kidney.

Long coronavirus disease (COVID) - commonly defined as symptoms and/or long-term effects that persist for at least 3 months after acute infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and cannot be explained by an alternative diagnosis - is a complex, multifaceted and heterogeneous disease that affects many organ systems, including the kidney. COVID-19 can cause acute kidney injury, and several studies have reported an increased risk of chronic kidney disease (CKD) following COVID-19, suggesting that CKD can be a manifestation of long COVID. Furthermore, patients with CKD are at an increased risk of severe COVID-19 and of long COVID. COVID-19 has also been associated with the development of COVID-19-associated nephropathy, which is a collapsing form of focal segmental glomerulosclerosis, and an increased incidence of new-onset vasculitis. Some early reports described associations of COVID-19 and/or SARS-CoV-2 vaccines with relapse or new-onset of other glomerular diseases, but this link was not confirmed in large population-based studies. SARS-CoV-2 vaccination reduces the risk of COVID-19 and long COVID and is particularly important for protecting vulnerable populations such as patients with CKD. Structured long-term follow-up of patients with COVID-19 and post-infectious sequelae is needed to provide further insight into the trajectory of long COVID and enable identification of those at risk of CKD.