By Joshua Augustine, MD
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Progress in kidney transplantation has improved survival, and created challenges. The pool of eligible patients is increasing, but organ supply remains inadequate. In this article, I address issues surrounding the waiting list and source of donated organs.
As early as the 1990s, it was recognized that kidney transplant offers a survival advantage for patients with end-stage renal disease over maintenance on dialysis. Although the risk of death is higher immediately after transplant, within a few months it becomes much lower than for patients on dialysis. Survival varies according to the health of the patient and the quality of the transplanted organ.
In general, patients who obtain the greatest benefit from transplants in terms of years of life gained are those with diabetes, especially those who are younger. Those ages 20 to 39 live about eight years on dialysis versus 25 years after transplant.
Contraindications to Transplant
There are multiple contraindications to a solitary kidney transplant (Table 1), including smoking. Most transplant centers require that smokers quit before transplant. Long-standing smokers almost double their risk of a cardiac event after transplant and double their rate of malignancy. Active smoking at the time of transplant is associated with twice the risk of death by 10 years after transplant compared with that of nonsmokers. Cotinine testing can detect whether a patient is an active smoker.
Organs are scarce
The number of patients on the kidney waiting list has increased rapidly in the last few decades, while the number of transplants performed each year has remained about the same. In 2016, about 100,000 patients were on the list, but only about 19,000 transplants were performed. Wait times, especially for deceased donor organs, have increased to about six years, varying by blood type and geographic region.
However, deceased donor rates have gone up with the opioid crisis, and there is a higher percentage of deceased donor kidneys coming from people who have died from overdose.
Placement on the waiting list for a deceased donor kidney transplant occurs when a patient has an estimated glomerular filtration rate (GFR) of 20 mL/min/1.73 m2 or less, although referral to the list can be made earlier. Early listing remains advantageous, as total time on the list will be counted before starting dialysis. “Preemptive transplant” means the patient had no dialysis before transplant; this applies to about 10 percent of transplant recipients. These patients tend to fare the best and are usually recipients of a living-donor organ.
Most patients do not receive a transplant until the GFR is less than 15 mL/min/1.73 m2.
Since 2014, wait time has been measured from the beginning of dialysis rather than the date of waiting-list placement in patients who are listed after starting dialysis therapy. This approach is fairer, but sometimes introduces problems. A patient who did not previously know about the list may suddenly jump to the head of the line after 10 years of dialysis, by which time comorbidities associated with long-term dialysis make the patient less likely to gain as much benefit from a transplant as people lower on the list. Time on dialysis, or “dialysis vintage,” predicts patient and kidney survival after transplant, with reduced survival associated with increasing time on dialysis.
Shorter wait for a suboptimal kidney
The aging population has increased the number of older patients being listed for transplant, presenting multiple challenges. Patients age 65 or older have a 50 percent chance of dying before they receive a transplant during a five-year wait. A patient may shorten the wait by joining the list for a suboptimal organ. All deceased-donor organs are given a Kidney Donor Profile Index score, which predicts the longevity of an organ after transplant. The score is determined by donor age, kidney function based on the serum creatinine at the time of death and other donor factors.
A kidney with a score higher than 85 percent is likely to function longer than only 15 percent of available kidneys. Patients who receive a kidney with that score have a longer period of risk of death soon after transplant and a slightly higher risk of death in the long term than patients who receive a healthier kidney, although on average they still do better than patients on dialysis.
Older patients should be encouraged to sign up for both the regular waiting list and the suboptimal kidney waiting list to reduce the risk of dying before they get a kidney.
Living-Donor Organ Transplant
Living-donor organ transplant is associated with a better survival rate than deceased donor organ transplant, and the advantage becomes greater over time. At one year, patient survival is more than 90 percent in both groups, but by five years about 80 percent of patients with a living donor organ are still alive versus only about 65 percent of patients with a deceased-donor organ.
The waiting time for a living-donor transplant may be only weeks to months, rather than years. Because increasing time on dialysis predicts worse patient and graft survival after transplant, the shorter wait time is a big advantage.
In addition, because the donor and recipient are typically in adjacent operating rooms, the organ sustains less ischemic damage. In general, the kidney quality is better from healthy donors, resulting in superior function early on and longer graft survival by an average of four years. If the living donor is related to the recipient, human leukocyte antigen matching also tends to be better and predicts better outcomes.
Opting for a living-donor organ also entails special challenges. In addition to the ethical issues surrounding living-donor organ donation, an appropriate donor must be found. Donors must be highly motivated and pass physical, laboratory and psychological evaluations.
For older patients, if the donor is a spouse or close friend, he or she is also likely to be older, making the organ less viable than one from a younger person. Even an adult child may not be an ideal donor if there is a family propensity to kidney disease, such as diabetic nephropathy. No test is available to determine the risk for future diabetes, but it is known to run in families.
Kidney transplant improves survival and long-term outcomes in patients with renal failure. Before transplant, patients should be carefully evaluated for cardiovascular and infectious disease risk.
Dr. Augustine is staff in the Department of Nephrology and Hypertension, Glickman Urological & Kidney Institute.
This post is excerpted and adapted from an article that originally appeared in Cleveland Clinic Journal of Medicine. Visit the journal website to read the full article, Kidney Transplant: New Opportunities and Challenges.