What Are the Risks for the Donor?
The risks for the living donor have to be categorized into survival, surrogate parameters for survival and financial issues.
The most important question is whether a donor is risking his life or whether a living donation may shorten their life expectancy. Currently, in all publications, living donors have been found to have a longer or equal lifespan when compared with matched healthy controls; thus, there is not yet any evidence that live donation reduces the life expectancy of the donor. However, there is an important bias because only well-screened donors are allowed to donate their kidneys and the so-called healthy controls include ill persons, too. There should be no doubt that a living donation is a surgical procedure and carries some small but inherent risks. Thus, a living donor is certainly better off if he does not donate a kidney. So the question should be rephrased. How many, if any, life years are lost due to donation?
There are some circumstances associated with living donation which give rise to the thought that there might be a shortening of lifetime due to donation. We now know that an increase in creatinine and the development of hypertension ranks among the most important risk factors for cardiovascular events and, thus, cardiovascular death.
After donation, a number of donors develop an elevated creatinine, which could be associated with an increased cardiovascular mortality. At present, we cannot define a creatinine threshold above which a donation is associated with an increased cardiovascular mortality. There are a number of problems with the definition of a creatinine threshold. While in former times mostly people below the age of 50 years were considered potential donors, the age of donation is now rapidly increasing. It is well known that the glomerular filtration rate (GFR) decreases with age. Thus, although the creatinine may be in the normal range, the calculated or measured GFR may be markedly reduced. Thus, as the GFR will decrease after donation, the donor may have a GFR <40 afterwards. Does this render him unsuitable for donation? There are no data on this issue, but one might speculate that an elderly donor will die from causes unrelated to donation, such as infections or accidents, before he suffers from relevant problems due to donation.
If we define a GFR below which a donation is unsuitable, where could be the limit? To answer this question, it might be helpful to look at it from the other direction. A donation is thought to help the recipient in such a way that he is off dialysis, has a better quality of life and generally longer survival. An elderly donor may view the donation as a direct gift to his or her partner in life or family member, although only in rare cases does a grandmother donate a kidney to her granddaughter, for example. Of course, in a perfect world, the recipient and the donor should be off dialysis for the rest of their lives.
It may be argued that for the elderly in particular, kidney function is of utmost importance as renal function is known to decline with age. On the other hand, most of these donors would gladly accept a modest shortening of their lifespan if they could live this period with their partners or family member. Let us not forget that in the vast majority of cases, the motivation for donation is determined by emotions. In these cases, it is sometimes hard to prevent a donation even in situations of enormous risk to the donor.
Both the recipient and the donor should be without the risk of starting dialysis during their respective lifespans. Based on the available data, a minimum GFR of 30 mL/min 1 year after transplantation should be the goal. This implies a GFR of >70 mL/min in the donor as ~10–20 mL/min are lost due to the operation.
Unfortunately, this suggestion cannot be based on real-life data as the number of these donors has increased only recently and thus the follow-up is not yet long enough for a large enough population. Even for younger donors, the follow-up is limited to 5- or 15-year data, which is not particularly benficial as life expectancy in modern societies ranges between 75 and 85, implying a minimum follow-up of 20–30 years is necessary in order to offer meaningful data. Even for people who have lost one of their kidneys due to an accident or a tumour, such long-term data does not exist in large enough numbers. Furthermore, in these patients, the underlying disease or accident necessitating the nephrectomy may have an additional impact on survival. Probably, the most important factor which has an additional impact on survival is hypertension. There is no question that an increasing number of donors suffer from hypertension. This is likely attributable to donation although the rate of hypertension does not seem to be higher than in the general population. Furthermore, nowadays, imperfect donors are accepted and some of them have hypertension even before donation. These are elderly people who would like to donate their kidney to their partner in life or their children.
Thus, the question arises, what level of hypertension can be accepted before donation? Again there are two questions to be answered. From the perspective of the donor, the question is whether a certain level of hypertension can be defined either by duration or severity which renders the donation too risky with regards to overall survival. From the perspective of the recipient, a certain level of hypertension defined by duration, type and number of antihypertensive drugs, secondary complications or height may define an additional risk for a short graft survival which may even shorten overall patient survival given the additional ordeal of transplantation. Based on the available data, such a threshold cannot be clearly defined.
However, there are ways to narrow down these questions. First of all, it is safe to say that kidneys with damage due to hypertension are most often combined with other problems in the donor, such as hypertensive eye disease or arteriosclerosis. Furthermore, such a kidney is likely to leak protein or there may be elevated creatinine, which makes donation a problem for recipient and donor. Under these conditions, a donation does not make a lot of sense from the donor perspective.
The major question remains what to do in the case of more than one anti-hypertensive drug in a potential donor with well-controlled hypertension and no apparent side effects. As hypertension will certainly worsen after donation, this may be decided on a case to case basis in consideration of additional risk factors or diseases in the donor as well as the age of the donor. The older the donor, the more likely there will be no reduction in overall survival due to donation, so that an otherwise healthy donor of 70 years of age may have no real risk for donation, while a 30-year-old may. However, this is more speculation as existing data are based on an ultimate selection in the potential donors of every age.
The consensus on proteinuria is much more advanced. Here, most guidelines suggest to restrict donation to people with a proteinuria of <300 mg/day. Although this threshold is somewhat arbitrary, a higher level of proteinuria clearly is associated with an increase risk of developing a kidney disease. However, we cannot rule out that such a threshold is too lax for younger donors and too strict for older ones as it will take some time to progress from low proteinuria to advanced kidney disease with all of its implications.
Obesity and an impaired glucose tolerance are factors which only come into the equation as an add on. Both entities alone are not absolute contraindications to donation. However, in the context of additional risk factors, they may be taken as a reason to favour the rejection of the donor.
Haematuria and overt diabetes mellitus on the other side are considered absolute contraindications to donation. In conclusion, a donation may cause some damage to the donor which would not occur without donation.
Nephrol Dial Transplant. 2012;27(6):2166-2170. © 2012 Oxford University Press