The pathophysiological mechanisms of AKI in COVID-19 patients
As many as 40% of patients with a severe form of COVID-19 may develop AKI, while around 20% may require RRT (7). Determining the risk of developing AKI in SARS-CoV-2 infected patients is an important step for the patient’s prognosis and early implementation of preventive and protective measures (7). Since the classical AKI indicators, serum creatinine and urine output, represent only established kidney damage, much attention has focused on novel biomarkers, particularly on markers of acute tubular stress and/or damage (7).
The origin of AKI in COVID-19 is complex and multifactorial and may occur as a result of intrarenal inflammation, increased vascular permeability, volume depletion and cardiomyopathy (8). Autopsy reports indicate that the virus can directly infect the renal endothelial cells, tubular epithelium and podocytes through an angiotensin-converting enzyme 2-dependent pathway, thus causing renal endothelial damage, collapsing glomerulopathy and acute tubular necrosis (8). Volume depletion at admission may be a common trigger for AKI since patients typically present with fever and pre-admission fluid replenishment is rarely performed (8). Cardio-renal syndrome, and particularly right ventricular failure secondary to pneumonia, might lead to kidney congestion and subsequent AKI. Left ventricular dysfunction, on the other hand, may cause arterial underfilling and kidney hypoperfusion (9). Other potential mechanisms of AKI include SARS-CoV-2-related immune response dysregulation, rhabdomyolysis, macrophage activation syndrome, and development of microemboli and microthrombi in the context of hypercoagulability (8).
Treatment options for AKI in COVID-19 patients
Conservative management of AKI in COVID-19 patients requires careful correction and constant monitoring of volume status to regulate commonly present volume depletion, but avoid volume overload and reduce the risk of pulmonary edema, right ventricular overload, congestion and subsequent AKI (9). Continuous RRT is the preferred modality of hemodialysis in hemodynamically unstable patients with COVID-19 who failed to respond to conservative measures (9). Detailed guidance on how to manage AKI with continuous RRT is presented in Figure 2 of reference 9 (https://www.thelancet.com/journals/lanres/article/PIIS2213-2600(20)30229-0/fulltext#figures)