Discussion:
In this study, 46 patients who developed kidney injury after COVID-19 infection or had an aggravation of the original kidney injury were included.The patients with new-onset renal damage mainly present with AKI and NS, while the patients withaggravated renal damage mainly presents with CKD and NS. 20% of the patients presented with impaired renal function.A previous international meta-analysis involving 49,048 patients found that the incidence of AKI among hospitalized patients with COVID-19 in the United States and Europe was as high as 28.6%, while the incidence in Asia was 5.5%[3]. In our study, 19.6% of patients developed AKI, with a significantly lower incidence and milder clinical symptoms. The reason might be that compared with the Delta variant in the pandemic waves before 2022, the Omicron variantis more transmissible but lessintrinsic virulent[4].
Among 38 patients with renal biopsy in this study, IgAN was the most common pathological type, other pathological diagnoses included MN, FSGS, acute interstitial nephritis(AIN), mesangial proliferative glomerulonephritis(MsGPN), EPGN, henoch-schonlein purpura nephritis(HSPN), TMA, and LN.Currently, GC has been reported as the most common pathological manifestation of COVID-19 associated nephropathy, which is mostly seen in patients with African ancestry and is associated with a high-risk APOL1 genotype[5]. The differences of pathological type of COVID-19 associated kidney injury may be related to race, region and strain variation. Compared with European and American populations, the frequency and percentage of population attributable risk (PAR%)of the risk alleles of IgAN-susceptible genes were significantly higher in the Chinese population[6]. Compared with the database of kidney biopsies over a 10-year period prior to the pandemic in our center, IgAN accounted for a higher proportion of COVAN patients. Ma Y et al. speculated that SARS-CoV-2 invaded respiratory tract and intestinal mucosa through the encoded S protein, activated antigen presenting cells, stimulated B cells to transform into Gd-IgA1λB cells and secreted Gd-IGa1through T-cell dependent and independent pathways, and then formed immune complexes deposited in the mesangium of the glomeruli, ultimately leading to the occurrence of IgAN[7]. Among other pathological types, a patient diagnosed with TMAhada more severe renal pathological lesion and poorer prognosis.
80% of patients with COVID-19 associated kidney injury had normal serum C3 complement level, a few patients had increased or decreased C3 level. In renal tissues, C3 deposits were observed in 68.4% of patients. Some scholars believe that low serum C3 level indicates overactivation and depletion of the complement system, which is related to the severity of the disease and poor prognosis[8-10]. It is currently believed that complement is involved in the indirect mechanism of COVID-19 kidney injury: SARS-CoV-2 binds to endothelial angiotensin converting enzyme 2 (ACE2), activates the lectin pathway and classical pathway of complement, recruits neutrophils and monocytes/macrophages, releases proteases,cytokinesand reactive oxygen species, leads to inflammation, subcutaneous matrix destructionand vasculitis-like lesions[11].
Among the 17 patients of follow-up, 29% of them experienced deterioration of renal function after treatment, but no patients developed to ESRD. However, in a cohort study of AKI in hospitalized patients with COVID-19 in 2020, 46% of hospitalized patients experienced AKI, 19% of the AKI patients entered dialysis and 50% died[12]. At present, there are few international reports on the prognosis of patients with Omicron infection. The possible reasons for the favorable prognosis of patients in this study are as follows: Firstly, international guidelines for treatment of SARS-CoV-2 infection have been developed. Antiviral drugs such as Nematovir, Azfudine and Monoravir as well as neutralizing antibody drugs such as ambavir/Romisivirwere available for targeted antiviral therapy. Early detection and treatment can be achieved in most patients. Secondly, the involved patients were mainly infected with Omicron variant. Compared to the initial strain reported internationally, Omicron variant was less virulent and less likely to cause severe cases.