Comparison of renal function after donor and radical nephrectomy

Abstract

Glomerular filtration rate (GFR) is directly proportionate to nephron reserves. In this respect, it is known that the patients who underwent radical nephrectomy due to renal tumor are under high risk of chronic kidney disease (CKD) in the long term. In this study, it was aimed to compare post-operative renal functions of patients who underwent radical nephrectomy due to renal malignancy and who underwent donor nephrectomy as renal donors, to observe whether renal failure process develops or not, and to determine the factors that affect post-operative renal functions. 70 patients who underwent donor nephrectomy as renal donors and 130 patients who underwent radical nephrectomy due to renal tumor were studied. When we divided the groups as those with a GFR of below 60 mL/min/1.73 m² and those with a GFR of above 60 mL/min/1.73 m², we observed that GFR values of patients who underwent radical nephrectomy had a significantly stronger tendency to stay below 60 mL/min/1.73 m² compared to patients who underwent donor nephrectomy (p < 0.001). When we divided the groups as those with a GFR of below 30 mL/min/1.73 m² and those with a GFR of above 30 mL/min/1.73 m², we observed that there were no patients in donor nephrectomy group whose GFR values dropped below 30 mL/min/1.73 m² and there was not a statistically significant difference between the groups (p = 0.099). If possible, nephron sparing methods should be preferred for patients to undergo nephrectomy because of the tumor without ignoring oncologic results and it should be remembered that patient’s age and pre-operative renal functions may affect post-operative results in donor selection.

• Chronic
• donor
• GFR
• kidney
• nephrectomy

Introduction

Chronic kidney disease (CKD) is a clinical process consisting of several phases and it requires dialysis in final phases.1 The morbidities that it causes on patients result in increased mortality rates.2

The parameter that indicates renal functions in a healthy individual is glomerular filtration rate (GFR). Studies have shown that a GFR level less than 60 mL/dk/1.73 m² was associated with cardiovascular pathologies and increased mortality.3

GFR can be measured with various methods and formulas. Endogenous creatinine clearance test on 24-h urine gives the most accurate results. However, there is not a statistically significant difference between modification of diet in renal disease (MDRD) formula and endogenous creatinine clearance test.4^,5

GFR is directly proportionate to nephron reserves. In this respect, it is known that patients who underwent radical nephrectomy due to renal tumor are under high risk of CKD in long term.6 On the other hand, living donors consist of an important part of organ pool necessary for renal transplant which is the standard treatment of end-stage CKD.7 An increase in blood pressure and proteinuria have been seen in patients after donor nephrectomy, and some studies have reported that there was not significant deterioration of kidney function compared to radical nephrectomy.8

In this study, it was aimed to compare post-operative renal functions of patients who underwent radical nephrectomy due to renal malignancy and who underwent donor nephrectomy as renal donors, to observe whether renal failure process develops or not, and to determine the factors that affect post-operative renal functions.

Materials and methods

The data patients between 2007 and 2012 were examined retrospectively. Seventy of whom underwent donor nephrectomy (Group A) as renal donors and 130 of whom underwent radical nephrectomy (Group B) due to renal tumor and also did not have any contraindications to be a donor. Patients with properties that could affect renal functions negatively, such as diabetes, hypertension, body mass index (BMI) above 30 and smoking were not included in the study.

Renal functions of the patients were evaluated using the data obtained from laboratory parameters of their last pre-operative and post-operative polyclinic checks. In calculation of e-GFR, MDRD formula [GFR = 186 × Serum creatine −1.154 × age −0.203 × 1.212 (if the patient is black) × 0.742 (if the patient is female)] was used. Genders, ages and follow-up time of the patients were recorded. The patient groups were classified among themselves as those with a post-operative e-GFR of above and below 60 mL/min/1.73 m² and those with a post-operative e-GFR of above or below 30 mL/min/1.73 m².

In order to compare the decrease in pre-operative and post-operative GFR levels between two groups, first the percentage changes were calculated, and after the parametric test assumptions of new percentage changes were tested, t test was used on independent groups in order to make a comparison between groups. In order to find whether other variables obtained in the study were different between groups; Student’s t test or Mann–Whitney U test were used for continuous variables and chi-square test and/or Fisher’s exact chi-square test were used in order to test the homogeneity of the categorical variables’ distribution according to the groups. In order to summarize the findings of the study average ± standard deviation and/or median (minimum-maximum), and also frequency density and percentages were used. SPSS 15.0 (for Windows) was used for statistical analysis and the limit of significance was p < 0.05.

Results

There were 28 male (40%) and 42 female (60%) in Group A (n = 70), and there were 77 male (59.3%) and 53 female (40.7%) in Group B (n = 130) (Table 1).

Table 1. Age, gender and follow-up time of the groups.

	Group A	Group B	p Value
Number of patients	70	130
Gender (male/female)	28/42	77/53	p = 0.009
Age	51 (22–75)	62 (25–76)	p < 0.001
Follow-up time (months)	20.29	19.08	p = 0.089

The median of patients age was 51 (min: 22–max: 75) for Group A and the median of patients age was 62 (min: 25–max: 76) for Group B. There was a statistically significant difference between the patient ages of two groups (p < 0.001) (Table 1).

There was not a statically significant difference between groups in terms of follow-up time. Average follow-up time of Group A and Group B were 20.2 and 19 months respectively (p = 0.089) (Table 1).

The average pre-operative GFR of Group A was 108.6 mL/min/1.73 m² and the average pre-operative GFR of Group B was 93.4 mL/min/1.73 m² and in this respect there was a statistically significant difference between the groups (p < 0.010) (Table 2).

Table 2. Preoperative and postoperative GRF data of the groups.

	Group A	Group B	p Value
Preop GFR (avg.)	108.674 (SD 22.59)	93,488 (SD 26.14)	p < 0.001
Postop GFR (avg.)	70,958 (SD 16.30)	61,276 (SD 20.34)	p = 0.001
Postop GFR ≤60	18 (%25.7)	66 (%50.8)	p < 0.001
Postop GFR >60	52 (%74.3)	64 (49.2)
Postop GFR ≤30	0 (%0)	7 (%5.4)	p = 0.099
Postop GFR >30	70 (%100)	123 (%94.6)

In terms of the difference between pre-operative GFR values and post-operative GFR values of Group A and Group B, i.e., the reduction rates of post-operative GFR values, there was not a statistically significance difference between the groups (p = 0.783).

When we divided the groups as those with a GFR of below 60 mL/min/1.73 m² and those with a GFR of above 60 mL/min/1.73 m², we observed that GFR values of patients who underwent radical nephrectomy had a significantly stronger tendency to stay below 60 mL/min/1.73 m² compared to patients who underwent donor nephrectomy (p < 0.001) (Table 2).

When we divided the groups as those with a GFR of below 30 mL/min/1.73 m² and those with a GFR of above 30 mL/min/1.73 m², we observed that there was no patients in donor nephrectomy group whose GFR values dropped below 30 mL/min/1.73 m² and there was not a statistically significant difference between the groups (p = 0.099) (Table 2).

Discussion

The most predictable result of nephron loss that occurs after nephrectomy will be a deterioration of renal functions in long-term follow-ups. This decrease in GFR may change depending on additional morbidities such as patient’s age, pre-operative GFR, hypertension, hyperlipidemia and diabetes.9 Certain adaptive mechanisms which depending on factors related to patient act a part after post-operative GFR reduction. In a study on renal functions after traumatic renal loss, it has been reported that the remaining kidney contributed to adaptive mechanism with a 70% functional increase.10

Regardless of the reason, each nephron loss incurs a risk in terms of renal failure. For this reason, patients who underwent radical nephrectomy due to renal tumor, who underwent donor nephrectomy as a living renal donor and who underwent nephrectomy due to other reasons such as trauma are under risk of renal failure.

It is known that operative treatment of renal tumor increases the rate of CKD and chosen operative method has a direct effect on post-operative renal functions.6^,11 Nephron sparing methods have satisfying results in terms of conservation post-operative renal functions, especially for patients with high risk of CKD. Some studies have reported that CKD was 11 times more common in patients who underwent radical nephrectomy compared patients who underwent partial nephrectomy.12 In a different study, it has been reported that the rate of having a post-operative GFR below 60 mL/min/1.73 m² after radical nephrectomy was 26%.12 In our study, the rate of having a GFR below 60 mL/min/1.73 m² after radical nephrectomy was 50.8% and the rate of having a GFR below 30 mL/min/1.73 m² after radical nephrectomy was 5.4%. In another study, it has been reported that the reduction in GFR after radical nephrectomy was 30%.9 In our study, the reduction in GFR after radical nephrectomy was 33.7% (SD 16.1).

There have been studies in which the parameters that predict CKD after radical nephrectomy were analyzed. Advanced age, smoking, low pre-operative GFR and diabetes have been found to be potential risk factors for renal failure.12 It has been observed that especially age and pre-operative GFR were closely related to post-operative CKD.3

On the other hand, the treatment of end-stage CKD is renal transplantation. Living donors consist of an important part of organ pool. The process of removing the kidney of these individuals is referred to as donor nephrectomy. Various studies have been conducted on follow-ups of donors since this surgical procedure was defined. In the first 15–20 years, researchers could not find any difference of post-operative renal functions and survival between patients with congenital solitary kidney and patients who underwent nephrectomy due to other reasons and donors.13 It has been reported in some of the following studies that donors had proteinuria and increase arterial blood pressure.14^,15

Fehrman-Ekholm et al. published the most comprehensive study on donor nephrectomy follow-ups in 2001.16 In this study, it has been reported that three donors developed CKD and one received dialysis treatment out of 403 donors. The average GFR was 72 mL/min/1.73 m² in their 12-year-follow-up. It has been found that hypertension prevalence was not different form general population. In other study, Ellison et al. has reported that incidence of necessity for dialysis after donor nephrectomy was 0.04%.17 Although follow-up time of our study were shorter, there was no patients with GFR values below 30 mL/min/1.73 m², there were 18 patients with GFR values under 60 mL/min/1.73 m² (25.7%) after donor nephrectomy. Average GFR of our patients was 70.9 mL/min/1.73 m² through follow-up. In some study, GFR reduction after donor nephrectomy was 20–25%.8^,16 In our study, this reduction was 34.29% (SD 10.5).

In the only study in the literature on comparison of donor nephrectomy (Group 1)—radical nephrectomy (Group 2),9 the average patient age of Group 2 was significantly higher than the other group. At the end of one year after the operation, GFR reduction was 30.4% for Group 2 and 34% for Group 1 (p = 0.30). In our study, the average age of the group with patients who underwent radical nephrectomy was significantly higher than donor nephrectomy group. Also, at the end of approximately 20 months of follow-up, GFR reduction was 33.70% for radical nephrectomy group and 34.29% for donor nephrectomy group, and this difference was statistically insignificant (p = 0.783). In this study, pre-operative GFR values for Group 1 and Group 2 were 89.7 and 78.8 mL/min/1.73 m², respectively. This difference is statistically significant (p = 0.001). In this study, which regards GFR 45 mL/min/1.73 m² as limit for chronic renal failure, CKD rate of Group 2, which was the radical nephrectomy group, was significantly higher compared to Group 1, which was the donor nephrectomy group. These rates were 16.2% for Group 2 and 5.3% for Group 1 (p < 0.005). It has been mentioned in the study that this difference between the groups might have been related to age and pre-operative GFR differences. In our study, pre-operative GFR of donor nephrectomy group (Group A) was 108.6 mL/min/1.73 m² and pre-operative GFR of radical nephrectomy group (Group B) 93.4 mL/min/1.73 m² (p < 0.001). According to the findings of our study, we also think that the fact that CKD rate was higher in radical nephrectomy group compared to donor nephrectomy group may be related to age and pre-operative GFR differences, which is compatible with the literature.

Patients who underwent nephrectomy, regardless of the reason, are under increased risk of CKD. If possible, nephron sparing methods should be preferred for patients to undergo nephrectomy because of tumor without ignoring oncologic results and it should be remembered that patient’s age and pre-operative renal functions may affect post-operative results in donor selection.

Declaration of interest

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.