Nephrology Service Central Hospital of Maracay Maracay, Aragua State Venezuela
Sir,
Life expectancy and quality of life are greater with kidney transplantation than with maintenance dialysis. However, living unrelated donors remain an underutilized source of donation despite the evidence of excellent outcomes [1]. In a recent issue of Nephrology Dialysis Transplantation, Gohh et al. communicated their experience with the case of a 50-year-old woman who was a volunteer and an altruistic kidney donor for an unrelated and unknown recipient [2]. For many years, both the medical profession and society at large have agreed that the use of organs from living donors is justified by the psychological benefit to the donor, who experiences the altruistic satisfaction of having assumed a risk in order to help another person. In fact, several scientific papers supporting the above-mentioned benefits with kidney transplantation from living unrelated donors have been published in recent years [1,3,4]. At the time of writing, due to these benefits, the use of organs from a non-related donor volunteer seems to be a useful alternative [14].
Transplantation of organs from living donors has always involved a balance of the physical risk and the psychological benefits to the donor vs the benefits to the recipient [3]. In the case reported by Gohh et al., a 50-year-old donor is described who has a creatinine clearance of 88 ml/min. They wrote ... On 1-year follow-up she continues to feel quite well, without any residual discomfort from the surgical procedure ... [2]; but there is no comment at all about her current renal function. Weas nephrologists and regular journal readersthink that knowing her renal function status 1 year after the nephrectomy is indeed important in this case. The donor described is a female patient starting has 6th decade of life, and it has been reported that after age 35 years the glomerular filtration rate (GFR) declines between 0.8 and 1 ml/min/year [5]. She had a creatinine clearance of 88 ml/min when nephrectomy was performed and theoretically she lost at that time about 50% of her total renal function. Thus, two relevant questions must be asked: was the remaining kidney capable of successfully assuming the functional overload and of maintaining a normal, or near normal, renal function? Furthermore, what will be her likely future renal function? We would also like to obtain information on her blood pressure, proteinuria, serum creatinine and creatinine clearance, or better still, a more precise estimation of GFR during follow-up to give us an idea of the potential risk with respect to renal function deterioration and possible future renal outcome.
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Division of Transplant Services Rhode Island Hospital/ Brown University Providence RI USA
Sir,
Santa Cruz and colleagues raise concerns of the safety of using kidneys from living donors in kidney transplantation and, in so doing, appropriately emphasize the importance of the meticulous evaluation of potential donors. In the early 1980s, Brenner et al. demonstrated in animal remnant models that as renal mass progressively decreases, glomerular hydrostatic pressure, perfusion rate, and hypertrophy of the remaining glomeruli increase [1]. These compensatory haemodynamic changes in the glomeruli were postulated to be maladaptive, and studies with rats have shown that progressive glomerulosclerosis develops after severe reduction in renal mass (five/sixth nephrectomy model). These observations may be relevant to the kidney donor because of the invariable increase in renal blood flow and glomerular filtration rate (GFR) per nephron in the remaining kidney following unilateral nephrectomy, leading to the assumption that the haemodynamic and metabolic changes to which the solitary kidney is exposed may be sufficient to cause progressive glomerulosclerosis. However, somewhere along the extrapolation of animal data to humans, the term remnant kidney became confused with remaining kidney.
There are now a number of studies that have documented the long-term safety of unilateral nephrectomy in otherwise healthy individuals. A meta-analysis of 48 different studies by Kasiske et al. on the long-term effects of unilateral nephrectomy in man demonstrated that although GFR was reduced by an average of 17.1% following these procedures, proteinuria was negligible and there was no increased prevalence of hypertension [2]. Furthermore, a recent study, which followed living donors for 20 years or more, demonstrated that neither age at nephrectomy, length of time with a single kidney, nor donor gender had any bearing on donor remnant renal functions [3].
These excellent results demonstrate that the hyperperfusion hypothesis is not applicable to the live donor who is otherwise healthy, and thus highlights the importance of a stringent screening process. The evaluating physician must ensure the absence of any kidney or systemic disorders that could pose a future risk to either donor or recipient. An assessment of the GFR is a critical and standard component of the evaluation of living kidney transplant donors, both for donor safety and optimal recipient results [4]. In their letter, Santa Cruz et al. allude to the fact that the donor's glomerular filtration rate was only 88 ml/min prior to nephrectomy. Although we agree that the measurement of creatinine clearance may not be the most reliable indicator of GFR because of errors in collection, we do estimate the GFR by averaging a minimum of two collections to improve accuracy. What is considered to be an adequate donor GFR is controversial. In their examination of practice patterns of UNOS-approved transplant centres, Bia et al. found that over half of centres would exclude an otherwise healthy donor if the creatinine clearance was under 80 ml/min/1.73 m2 [5].
Our donor also exhibited a number of characteristics that generally portend a good prognosis post-nephrectomy. Her weight was ideal with a body-mass index of 23. Furthermore, she was on a self-imposed vegetarian low-protein diet. It has now been 27 months since her living donor nephrectomy. She continues to do remarkably well with no limitations in her activity. She is normotensive (average BP 120/76 mmHg) and is monitored at least on a quarterly basis. Her serum creatinine was 1.1 mg/dl earlier this year and her urinalysis demonstrated no evidence of proteinuria. Incidentally, she continues to give altruistically, donating blood on a regular basis. Although her follow-up is admittedly limited, we believe that our donor and all living donors who have been adequately evaluated are at an acceptably minimal risk of progressive harm to the other normal kidney.
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