Background
At the winter of 2019, Coronavirus Disease 2019 (COVID-19), an emerging infectious disease with unclear etiology broke out in Wuhan City, Hubei Province, China [
1]. Later, this unknown virus was clarified and named as severe acute respiratory syndrome coronaviruse-2 (SARS-CoV-2) [
2,
3]. Now, it has been pandemic across the world. Up to January 1st, 2021, there were approximate 90 million accumulated confirmed patients of SARS-CoV-2 infections in 220 countries, of them about one million cases have died [
4]. All humanity is sustained huge disaster from SARS-CoV-2 [
5,
6]. Therefore, all medical staff, scientific research personnel and all sectors of the entire society must cooperate to decrease COVID-19 spread and seek for effective cures drugs and method.
Previous studies have demonstrated that COVID-19 patients mainly accompanied with fever, diarrhea, dry cough, lymphocyte reduction and radiographic evidence of pneumonia [
7]. Now, more and more studies have confirmed that SARS-CoV-2 not only evoked severe acute respiratory syndrome, but also induced multiple organ injuries, such as myocardial injury, lymphocyte reduction and even liver dysfunction [
8‐
11]. Nevertheless, the clinical characteristics of renal dysfunction caused by SARS-CoV-2 are rarely described. Moreover, the clinical significance of SARS-CoV-2-induced renal dysfunction and its recovery situation are still ambiguous.
This research primarily explored whether SARS-CoV-2-evoked renal dysfunction, its risk factors and prognosis after discharge among COVID-19 patients. Our data reveal that male, higher age and hypertension are three independently risk factors of renal dysfunction. Our research firstly demonstrates that SARS-CoV-2-evoked renal dysfunction are not fully recovered in 2 weeks after discharge.
Discussion
This research primarily analyzed SARS-CoV-2-evoked renal dysfunction, its risk factors and prognosis in 2 weeks after discharge in a hospital-based retrospective cohort study. Our results indicate that male gender, older age and hypertension are three independently risk factors of renal dysfunction among COVID-19 patients. In addition, SARS-CoV-2-evoked renal dysfunction was not fully recovered in 2 weeks after discharge.
Mounting evidences have confirmed that SARS-CoV-2 injection evoked multiple organ injuries, primarily containing liver dysfunction, myocardial injury, lymphocyte reduction and even respiratory failure [
8‐
11]. In this research, the levels of serum uric acid, urea nitrogen, creatinine, cystatin C and eGFR were detected and renal dysfunction was evaluated among COVID-19 patients between on admission and discharge. Our results indicated that creatinine and cystatin C were increased, eGFR was decreased in severe COVID-19 patients. No difference of uric acid, urea nitrogen and cystatin C were observed between mild and severe COVID-19 patients. Furthermore, the number of COVID-19 patients with renal dysfunction was more in severe patients than those in mild patients. Renal dysfunction was more pervasive in severe patients with COVID-19. Our data indicate that renal dysfunction is positively correlated with the severity of COVID-19 patients on admission.
Earlier studies have confirmed that older age elevated the risk of death in COVID-19 patients [
12,
13]. Several comorbidities aggravated the severity of COVID-19 patients [
14,
15]. In this research, the influences of demographic characteristics on renal dysfunction were evaluated. No difference of urea nitrogen was observed in different gender patients. Uric acid and cystatin C were decreased, eGFR was increased in females. Additionally, we found that the levels of uric acid, urea nitrogen, creatinine and cystatin C were higher and the level of eGFR was lower in the older patients. Furthermore, the influences of basic complications on renal dysfunction were analyzed. Our results indicated that the levels of urea nitrogen and cystatin C were increased in COVID-19 patients with hypertension. Further analysis found that uric acid, urea nitrogen, creatinine and cystatin C were increased and eGFR was decreased in COVID-19 patients with diabetes. Furthermore, we also found that eGFR was decreased in COVID-19 patients with other chronic diseases. These evidences suggest that male gender, older age, diabetes and hypertension may aggravate the risk of renal dysfunction in COVID-19 patients. For the sake of analyzing the risk factors of renal dysfunction among COVID-19 patients, multivariate logistic regression analysis was carried out. These data demonstrate that male gender, older age and hypertension are three independent risk factors of renal dysfunction among COVID-19 patients. In brief, male elderly subjects with hypertension elevates the risk of renal dysfunction in COVID-19 patients.
The prognosis of renal dysfunction remained obscure among COVID-19 patients. This is an important doubt which is worthy of exploring whether renal dysfunction of COVID-19 patients is reversed in 2 weeks after discharge. In the present project, 150 cases with COVID-19 were followed up and renal dysfunction were accessed. Every index of renal function and the rate of renal dysfunction were compared between on admission and in 2 weeks after discharge among COVID-19 patients. No difference of urea nitrogen, creatinine, cystatin C and eGFR were confirmed between on admission and after discharge. However, the level of uric acid was slightly increased in 2 weeks after discharge compared with on admission among COVID-19 patients. Moreover, the abnormal number of patients with creatinine, cystatin C and eGFR were similar between on admission and in 2 weeks after discharge. Interestingly, a few patients with serum creatinine, cystatin C and eGFR were still out of the normal range in 2 weeks after discharge. These data suggest that renal function indexes of 3.33% cases with COVID-19 were not fully recovered in 2 weeks after discharge. Hence, whether SARS-CoV-2-caused a long-time renal dysfunction is required to explore in the next therapeutic methods.
The mechanism of SARS-CoV-2-caused renal dysfunction is still unknown. More and more reports have revealed that SARS-CoV-2 plays a pathogenetic role in COVID-19 patients through binding to receptor of angiotension converting enzyme (ACE)2 [
16,
17]. At present, several researches demonstrated that ACE2 can express in renal tubular epithelium [
18]. Therefore, we speculate that SARS-CoV-2 may directly damage kidney tissue through binding to the ACE2 receptor. Besides, earlier studies found that inflammatory cytokines were dramatically elevated in patients with COVID-19 [
19‐
21]. It is generally known that cytokine storm was associated with the process and the levels of IL-6 and CRP can predict the severity and prognosis of COVID-19 patients [
22,
23]. IL-6 is a multifunctional cytokine that transmits cell signaling and regulates immune cells [
24]. CRP is an acute-phase proinflammatory cytokine and a sensitive biomarker of infection and tissue damage [
25]. The secreting of CRP or IL-6 always induces cytokine storm and damages multiple organs function. In this study, the correlations between inflammatory cytokines and renal dysfunction were evaluated among COVID-19 patients. The results indicated that there were positive correlations between renal dysfunction with IL-6 and CRP in COVID-19 patients. Consequently, these results reveal that cytokine storm may involve in the process of SARS-CoV-2-induced renal dysfunction.
There are several weaknesses in this study. Firstly, this was only a single center research, all patients were from Fuyang City in Anhui Province. Source of patients may cause selection bias. All patients with COVID-19 were timely found and treated in the Fuyang City, so COVID-19 patients only were mild and severe cases in Fuyang City. The prevalence was very low and severity of renal dysfunction was modest. Secondly, renal dysfunction was evaluated only through the linear determination of biomarkers and not in an accepted and comparable way (AKIN, KADIG, etc), more assessment methods are needed to evaluate the renal dysfunction in the next project. Thirdly, because of minor specimen, a larger sample size is needed to perform. Fourthly, this current study was only a hospital-based retrospective cohort study, the mechanism by which SARS-CoV-2-induced renal dysfunction in COVID-19 patients was unclear. We can’t exclude the effect of drug use patterns and doses on renal dysfunction in COVID-19 patients. More animal studies and in vivo experiment are needed to conduct in the future research.
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