Kidney

Data from the USA for 2015 showed that around 30% of all kidney transplants (n=18,597) were from living donors (n=5,626), with 12,971 recipients receiving kidneys from deceased donors (Hart et al., 2017).

In Europe in 2012, over 80% of kidney transplant donors (n=18,244) were deceased, although the relative number of living and deceased donors varies markedly across the continent. For example, the proportion of living kidney transplant donors was 55% in the Netherlands, 23% in Germany, and 37% in the UK (Heemann and Renders, 2012). In Japan around 80% of kidney transplants are from living donors, while in countries such as Egypt and Pakistan, kidney transplantation is totally reliant on living kidney donors (Delanaye et al., 2012).

Overall recipient survival rates are higher in patients who received a graft from live donors. One-year graft survival in 2012 was 97% in living donor kidney transplant recipients whereas it was only 92% in recipients of a deceased donor (United States Renal Data System (USRDS), 2015). Longer term graft survival is also higher in recipients of live donors compared to transplants from deceased donors. In 2010, five-year survival rates among recipients of a living donor kidney were 93.5% whereas they were only 86.8% in recipients of a deceased donor kidney. Ten-year graft failure rates for deceased donor transplants were 52.8% whereas they were only 37.3% in recipients of a live kidney donor (Hart et al., 2017). Furthermore, rates of acute rejection during the first-year post-transplantation are higher for kidney grafts from deceased donors than they are for those from living donors (Hart et al., 2017).

UK guidelines for living donor kidney transplantation are available (Andrews et al., 2012; British Transplantation Society and Renal Association, 2011).

Timing of renal transplantation

The timing of renal replacement therapy in patients with acute kidney injury is the subject of debate with two studies (ELAIN and AKIKI) providing conflicting results.

The ELAIN study compared early initiation of kidney transplantation (n=112) – within 8 hours of diagnosis of stage 2 AKI (using the KDIGO classification), with delayed transplantation (n=119) – within 12 hours of diagnosis of stage 3 AKI. Early initiation of kidney transplantation significantly reduced 90-day mortality compared with delayed initiation; 90-day mortality rates were 39.3% (44 of 112 patients) versus 54.7% (65 of 119 patients) respectively (Hazard Ratio (HR)=0.66; 95% confidence interval (CI), 0.45–0.97; p=0.03) (Zarbock et al., 2016).

The AKIKI study compared timing of kidney transplantation in patients with stage 3 AKI, with transplantation in the early group (n=311) being initiated shortly after randomisation (median 2 hours), and in the delayed group (n=308) with the development of ≥1 severe biochemical or clinical abnormalities developed (severe hyperkalaemia, metabolic acidosis, pulmonary oedema, blood urea nitrogen level >112 mg/dL, or oliguria for >72 hours after randomisation). There was no significant difference in 60-day mortality rates with rates in the early and delayed transplantation groups being 48.5% (95% CI, 42.6–53.8) and 49.7% (95% CI, 43.8–55.0) respectively (Gaudry et al., 2016).

The AKIKI and ELAIN trials fundamentally differed in trial design and sample size, with additional large multicentre randomised trials needed to resolve the issue of timing of kidney transplantation (Bagshaw et al., 2016).

ABO incompatible renal transplantation

Progress in desensitisation methods has resulted in the growing use of ABO incompatible kidney transplantation (ABO-iKT) in both the USA and UK in recent years. Current protocols involve pre-transplantation removal of ABO antibodies using plasmapheresis or immunoadsorption; coupled with induction and maintenance of immunosuppression e.g. with tacrolimus and mycophenolate mofetil to prevent ABO antibodies reappearing (Muramatsu et al., 2014; Koo and Yang, 2015).

Risk to living kidney donors

Although data for the post-operative mortality risk for living kidney donation is limited, the mortality risk for donors at 90 days was estimated from US registry data, as 0.03% (3.1 per 10,000 donors; 95% confidence interval (CI), 2.0–4.6) (Segev et al., 2010). Ninety-day mortality was higher in men than women (0.051% vs. 0.017%), in Afro-Americans than Caucasians (0.076% vs. 0.026%) and in patients with pre-existing hypertension than in normotensive patients (0.37% vs. 0.013%) (Segev et al., 2010; Delanaye et al., 2012).

A review of the available evidence concluded that living kidney donation was a relatively safe procedure, although selection of obese or proteinuric subjects increases the risk to donor safety (Delanaye et al., 2012). Comparison of the 15-year observed risks of end stage renal disease (ESRD) in living kidney donors in the US, with projected long-term risk among living kidney donor candidates, showed that observed risks were 3.5 to 5.3 times higher than the projected risks (in the absence of donation) for groups stratified by race and gender. Respective projected 15-year risks (in the absence of donation) and observed risks (after donation) were 0.21% and 0.96% for black males; 0.12% and 0.59% for black women; 0.07% and 0.34% for white men; and 0.04% and 0.15% for white women (Grams et al., 2016).

The RELIVE study of long term living kidney donors reported that the majority of live donors (84%) were satisfied with their lives, although lower satisfaction scores were associated with financial difficulties associated with donation and prolonged recovery time (Messersmith et al., 2014). The majority (95%) of kidney donors viewed their experience of donation positively, with negative experience associated with donor complications, recipient graft failure and psychological difficulties (Jacobs et al., 2015).