RN is the classical treatment for localized renal cell carcinoma. Ideally, it should not cause CKD if the contralateral kidney is well preserved since the good renal function can be maintained by the remaining kidney in renal transplant patients. However, opponents proposed that kidney transplant patients were well selected and that their clinical outcomes could not be used to predict the outcome of RN patients, who are usually elderly and have decreased renal function preservation. Some of them have an underlying chronic disease, which will cause worsening kidney function over time [5]. In addition, pathology examination of radical nephrectomy always shows some kidney disease in the “no-tumor part” [6], which may be associated with CKD after RN [7]. Therefore, the probability of CKD after radical nephrectomy is often higher than expected.
Previously, Minato [8] found that the incidence of CKD 3-year after radical nephrectomy was 37%. Jeon [9] found that 41.7% T1a patients will suffer from CKD after nephrectomy. In our study, 43.4% of patients had CKD postoperatively after a relatively long follow-up. We also found that only 26 patients (13.7%) with normal immediate postoperative (within one week) eGFR develop CKD within 5 years. Xu [10] also showed that CKD incidence was much higher in patients who developed postoperative acute kidney injury than in patients who did not (18.64% vs. 5.94%), which means that acute kidney injury after nephrectomy may be a new nomogram to predict postoperative renal function.
Spontaneous recovery of kidney function was observed in 40 (21.2%) patients who had CKD after RN in our study. We consider that their kidney functions maybe haven’t been damaged seriously by functional compensation. Their postoperative eGFR values were usually more than 50 ml/min/1.73m2. In our study, we found that renal function worsened immediately after RN but improved thereafter, this finding is similar with Yokoyama’s study [8]. 155 patients were followed up for more than 6 years, among whom 78 patients did not develop CKD all the time. Thus, we found that if CKD did not occur within 5 years after surgery, it would not happen in following time. We considered that the kidney function would undergo compensatory recovery within 5 years after nephrectomy. Therefore, a routine examination for kidney function would not be necessary since the 5th year, possibly avoiding the unnecessary cost of the related items.
Previous studies showed that, age, race, sex, diabetes, hypertension, smoking, obesity, proteinuria and some clinical factors were risk factors for chronic kidney disease [11,12,13,14]. In our study, there were significant differences between the CKD group and the no-CKD group in age, sex, preoperative GFR value, preoperative contralateral GFR value, β2-microglobulin, tumor size and Immediate postoperative eGFR value. Multiple regression analysis showed that age, preoperative contralateral GFR value and Immediate postoperative eGFR value were independent risk factors of CKD postoperatively.
The preoperative evaluation of kidney function was very important for renal cancer patients. We consider preoperative dynamic renal scintigraphy was useful for evaluation of the contralateral kidney function and prediction the risk of acute renal failure after surgery. In our study, approximately 50% of patients developed postoperative CKD if their contralateral GFR value was less than 40 ml/min/1.73m2. If the contralateral GFR value was less than 30 ml/min/1.73m2, the incidence increased to nearly 70%.
According to the data from the United States Renal Data System [15], approximately 60% of patients with end stage renal disease (ESRD) were older than 75 years. In our study, both the univariate analysis and the multiple regression analysis showed that age was one of the risk factors of postoperative CKD (P < 0.001). Our stratified analysis showed that the risk of CKD increased with age. Moreover, there was a high incidence of CKD among patients older than 75 years old. So, the selection of proper surgery plan and preoperative suggestions seemed to be very important in older patients. Thus, we conclude that careful patient selection in elderly patient group was very important.
Our univariate analysis showed that “tumor size” was significantly different between CKD group and no-CKD group, however, multiple regression analysis not confirming that “tumor size” was an independent risk factor. In our study, 345 patients with T1 stage underwent radical nephrectomy, and 137 of them were T1a stage. Although studies have shown that the oncological outcome in terms of overall survival following partial nephrectomy equals that of radical nephrectomy in patients with T1 stage, clinically it is sometimes difficult to choose a surgical plan for renal tumors with relatively small volumes. It depends on the location of tumors (especially endophytic or parapelvic tumors), surgeon’s technique, and the patient’s requirement for surgical effect and safety. In our study, we analyzed the patients of T1-2N0M0 stage, with the 5-years incidence of CKD for the T1a, T1b, and T2 stages of 45.7, 41.5 and 27.2%, respectively, and the P value was 0.025. That is, the incidence of CKD in patients with localized renal cell carcinoma decreases with increased tumor size. In other words, the incidence of CKD was higher at the T1a stage than at the T1b stage. Several studies [16, 17] also reported a higher risk of postoperative CKD in patients with small tumors than those with larger tumors. As most renal cell carcinoma was slow-growing, we hypothesized that the compensation of the contralateral kidney was more developed before RN in larger ipsilateral tumor sizes, and patients were better able to tolerate the loss of nephrons during RN. Recently, Robert [18] found a significant interaction between age and tumor size, that is, tumor size may not have a protective effect on postoperative renal function, but this needs to be confirmed by further studies. Given that tumor size and age play important roles, partial nephrectomy may be a better choice for T1a stage or elder patients in order to decrease the incidence of postoperative CKD. However, it must be weighed against the increase in the perioperative risk especially for older individuals.