The behavior of renal function after nephrectomy in the donor is well described, according to Prieto-Matienzo et al. [12] at one month after nephrectomy 48.7% of their population presented a GFR of < 60 ml/min/1.73m2, classifying them as patients with CKD, of these same patients at one year after nephrectomy, only 34.4% of the cases had CKD, also demonstrating a recovery of renal function. While in the population studied by Rivas-Nieto et al. [13] the same significant decrease in GFR was demonstrated up to the sixth month of follow-up with recovery at one year, but as in our study this increase continues to be significantly lower than the preoperative value. However, the Rivas-Nieto study adds an important factor, the postoperative measurement evaluates the function of a single kidney, so it is considered that there is a significant increase taking as a starting point the GFR of a single kidney [13].
In our study we evaluated the presence of albuminuria levels in 24-hour urine samples at five year follow-up, which serves as a parameter on renal function but also as a determinant that allows estimating the risk of developing CKD in the long term, finding the presence of albuminuria in 73% of our population; according to the analysis proposed by Gaillard and Courbebaisse [14] albuminuria levels below 30 mg/day are recommended, while values between 30 and 100 mg/day are recommended to estimate the risk of renal failure.
The meta-analysis of Li et al. [15] shows that at 6 months at least 5.3% of the population studied had microalbuminuria, and from the evaluation carried out at 6 months to 5 years post nephrectomy the affected population had increased to 8.7%, in comparison with our population where at the same time 57.6% of the total population had microalbuminuria. This figure is much higher in comparison, possibly signifying a variation both in the total population studied and in the number of studies analyzed by Li et al., as well as this one with prolonged follow-up, showing at 10 years post nephrectomy 25.6% with microalbuminuria [15]. It is concluded that the rate of microalbuminuria, macroalbuminuria and proteinuria increases with time after donation.
Another factor considered was BMI, which is a conditioning factor for the recovery of renal function, the importance of which lies in the risk of obesity to develop proteinuria and CKD [16, 17]. It has been generally agreed on using BMI to evaluate obesity and in any case exclude from donation candidates with a BMI > 35 kg/m2, although due to the shortage of donors, some places have agreed to broaden the selection criteria for living donor candidates, without accepting any definitive limit [16, 18].
In addition, according to the study by Reza-Escalera et al. [19] found that a reduction in glomerular filtration rate below 60 mL/min/1.732 in kidney donor patients was significantly related to overweight and obesity.
According to the data collected in our study, we found that despite the patient's BMI there will always be a decrease in post-donation GFR; a higher GFR was observed at the beginning of the study in patients with a normal BMI compared to the group of overweight and obese patients, and this predominant value was maintained throughout the time intervals. According to the research by Matas and Rule [20] for each unit increase in BMI above 27 there is an associated significant increase of 7% in the risk of end-stage CKD.
Another variant to study has been the difference in renal evolution between male and female sex, in our population 57% of the total were female donors; in the review by Asgari and Hilton [21], more than half of the living kidney donors are women and are of childbearing age, which may assume greater risks throughout their lives. The reason for this is explained by Ross and Thistlethwaite [22] where they state that although men and women in a family are wage earners, men tend to earn more than women, which may lead families to support women as donors. Despite this, comparing renal function between the two sexes, there was no significant difference.
Our study has some limitations, among which the most relevant is perhaps the time frame analyzed, since having a larger database the follow-up of these patients could have been for a longer observation period, due to the lack of follow up of the patients most of them were not considered for the study, as well as the possibility of analyzing more relevant variables within the donor complications such as the risk of developing systemic arterial hypertension or secondary bone diseases. In spite of this, the Mexican donor population has not been studied in depth; the studies carried out in Mexico have concentrated mainly on the evolution of the kidney recipient and not on the possible complications the donor may develop, reasons for which living donor kidney donation may be favored.
This study demonstrated the presence of a decline in GFR in the renal donor; this decline was shown drastically in the first three months of follow-up after nephrectomy. Subsequent evaluations showed a gradual recovery of renal function towards higher values, although without reaching baseline levels.