"This shows that a small kidney stone should not preclude people from being donors," says George Chow, M.D., Mayo Clinic urologist and senior investigator of the study. "It's not likely for the stones to grow if transplanted."
His colleague investigator, Khai-Linh Van Ho, M.D, Mayo Clinic urology fellow, agrees. "This is good news. We found the stones did not affect the function of the kidney. As far as we know with 26 months of follow-up, we've had no loss of kidneys from obstruction. The grafted kidney survival rate was 97 percent -- the same as the national survival rate for living kidney donation. That's relatively safe."
In the Mayo study, a retrospective chart and radiograph review of 710 donor kidneys, 44 had stones. Of these, 86 percent had 1- to 2-millimeter stones and 14 percent had 3- to 6-millimeter stones. CT scans performed an average of 10.5 months after transplant surgery in 14 patients showed no stones in six patients, stable stone size in four patients and increase in stone size averaging 2.9 millimeters in four patients. No loss of the transplanted kidneys occurred due to stone obstruction in the patients studied.
The question of how patients fare when transplanted with a kidney containing stones has arisen due to shortage of available kidneys, indicate Drs. Chow and Ho. Due to the scarcity, study of transplantation of more "marginal" kidneys has become relevant, they say.
"It's a matter of supply," says Dr. Ho. "Demand has so far outpaced supply of kidneys that we're now considering use of all kinds of kidneys. We're expanding the criteria with transplant. Thus, donors with, say, a very small stones or hypertension are now considered."
Helping patients is the reason for investigating transplant of kidneys that previously would have been considered questionable, explain Dr. Ho and Dr. Chow. "Our motivation is to save lives and improve quality of life," Dr. Ho says. "The idea is that patients would do better off dialysis and mortality rates would decrease. There would also be fewer burdens on the economy if more patients were transplanted and off dialysis."
Mortality rates are high for patients on kidney dialysis, according to the Mayo researchers. They cite a 50 percent mortality rate within five years of starting dialysis.
Transplantation of a kidney which has stones occurs with full consent of the donor, recipient and transplant surgeon, and only after all parties undergo in-depth discussion about the kidney and any potential risks, says Dr. Ho.
Although risks of transplanting a kidney with stones would potentially include obstruction from the stone, the Mayo researchers did not see this issue in the patients they studied. A stone in one patient grew and he developed urinary tract infections, which were remedied surgically.
The investigators recommend that any patients transplanted with a kidney which has stones should have close follow up with tests dedicated to kidney stone detection. They also advise that the patient should be vigilant in looking out for stone obstruction symptoms like nausea and vomiting; bloody, cloudy or foul-smelling urine; or a persistent urge to urinate.
The Mayo study was undertaken due to lack of published literature regarding long-term outcomes with transplanting kidneys which have stones.
One out of 10 Americans develops kidney stones. Ten percent of those with kidney stones do not have symptoms.
The abstract of the study, No. 1622, entitled "Prevalence and Early Outcome of Donor Graft Lithiasis in Living Renal Transplants at the Mayo Clinic," will be presented in a poster session at the American Urological Association meeting in San Antonio. See www.aua2005.org for details.
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