# Evaluation of Chronic Kidney Disease Risk Factors after Radical Nephrectomy
## 4 Discussion  
In our study we determined that CKD is a frequent complication following RN. A longer IOH time, higher perioperative blood loss and postoperative AKI with CKD upstage were factors of increased risk for postoperative eGFR decline and a higher chance of CKD 12 months after RN. Other findings suggest that patients with higher preoperative eGFR and contralateral kidney CT volume are associated with a decreased probability of postoperative RF reduction. Risk factors found in the study, due to their potentially avoidable nature, are important for the prevention of postoperative adverse effects. Preoperative RF depends on preexisting risk factors, such as age, hypertension and DM [4; 5]. Previous authors' analysis found that 20-25% of patients with kidney lesions have already developed CKD before surgical treatment [22; 23]. The association between RCC and CKD is bidirectional and includes multiple factors. An increase in tumor mass, intratumoral neovascularization and blood flow can further worsen RF, as it decreases nephron mass and the blood flow of healthy kidney parenchyma [24]. The likelihood of further decline in RF is a major problem to consider when deciding on the surgical approach and the follow-up plan for oncological patients. In [PERSON] et al. 's study, it was found that the mean decrease in eGFR after RN was 24.2 \(\pm\) 12.40 mL/min/1.73 m\({}^{2}\)[22]. RF is generally better preserved using nephron-sparing techniques such as PN [25]. However, these techniques are not always feasible when dealing with larger tumors. The preservation of RF after RN depends on both patient and tumor characteristics. Previous studies have shown that RF deteriorates significantly 3 years following RN with 37% developing postoperative CKD [26]. Figure 8: ROC analysis of predicting clinically significant AKI after radical nephrectomy. Abbreviations: AUC—area under the curve. Older age was found to be a major risk factor for new-onset CKD and CKD upstage after RN. During the natural aging process, eGFR decreases by approximately 1% with each additional year of age [27]. Age as an independent predictor of postoperative CKD is consistent with previous studies. There is an association between older age and lower eGFR 3 years after RN (OR = 1.041, 95% CI 1.007-1.078, \(p\) = 0.017) [26; 28]. As shown in [PERSON] et al. 's study, the mean ages of participants who developed postoperative CKD and those who did not were 63.7 \(\pm\) 3.5 and 52.7 \(\pm\) 13.3 years, respectively (\(p\) < 0.001). In a veteran study by [PERSON] et al., the association between age and increased rate of CKD after RN was particularly pronounced as 15% of patients over 70 years developed stage 4 CKD with decreased sCr clearance up to 15-29 mL/min compared with 1.4% in patients <50 years. The risk of developing stage 4 or higher CKD increased by 18% with every 10 year increase in age in patients with normal or near-normal RF (HR = 1.64, 95% CI 1.43-1.89) [17]. Data from the RESURGE project suggests that PN is the recommended surgical treatment for patients of advanced age, whenever possible [29]. Preoperative eGFR is described as a significant factor of RF change after surgery [30; 31]. Finding an abnormal eGFR preoperatively is related with an increased risk of mortality in RN patients with every 10 mL/min decrease in eGFR; however, in patients with normal preoperative sCr clearance, this risk is uncommon (HR = 1.11, CI 1.07-1.14) [32]. Further data showed that even slightly decreased eGFR (60-89 mL/min) before RN suggested the presence of CKD of stage 3a or lower 1 year after RN (OR = 4.4, CI 2.1-9.5, \(p\) < 0.001) [31]. The reason behind this association may be that preoperative eGFR reflects not only the function of the affected kidney but also the function of the remaining kidney, which becomes the main contributor to RF after RN. Lower preoperative eGFR may indicate the existence of other comorbidities that affect the remaining kidney.