Incidental renal stones in potential live kidney donors: prevalence, assessment and donation, including role of ex vivo ureteroscopy

WHAT'S KNOWN ON THE SUBJECT? AND WHAT DOES THE STUDY ADD?: Previously, donors with asymptomatic stones found incidentally on CT were not considered ideal donor candidates because of the presumed risk of morbidity to both the donor and recipient. Increasingly, studies show that these risks are low. This study aims to evaluate the long-term safety of using ex vivo ureteroscopy to remove the stones from the donor kidney on the bench before donation. Outcomes so far suggest that this technique can safely render a kidney stone-free before transplantation. This has led to 20 more transplants in our institution than would otherwise be possible.

Objectives: To evaluate the prevalence of asymptomatic renal stones in our potential donor population. To assess the safety and success of ex vivo ureteroscopy (ExURS) to remove stones from explanted donor kidneys before transplantation.

Patients and methods: We conducted a retrospective analysis of 377 computed tomography (CT) angiograms of potential kidney donors between October 2004 and May 2007 to assess the prevalence of asymptomatic renal stones in our donor population. Between October 2005 and October 2011, kidneys from suitable donors underwent ExURS. Stones were removed using basket extraction or were fragmented with holmium laser on bench before transplantation. Immediate and long-term complications of the transplanted recipients were recorded. Donors were followed with yearly ultrasonography of the remaining kidney in addition to standard follow-up protocol.

Results: Review of 377 CT angiograms between October 2004 to May 2007 showed a 5% prevalence of asymptomatic renal stones. Out of 55 potential donors (19 identified between October 2004 to May 2007 and a further 36 identified since May 2007), 20 donors with stones proceeded to donation, with stone size ranging from 2 to 12 mm. Of the patients, 17 proceeded to ExURS. Stones were removed in 10 patients; five with basket retrieval, four with laser fragmentation and one with both laser fragmentation and basket retrieval. There were no early or late allograft stone-related complications and no evidence of stones on follow-up imaging at a mean (range) of 10 (1-24) months. There has been no reported stone recurrence in any of the donors to date and no stone on ultrasonography of eight donors with >1-year follow-up (mean 26 months, range 12-49 months).

Conclusions: Asymptomatic renal stones are present in 5% of our donors. ExURS can be safely used to remove stones in these kidneys before transplantation, without the risk of subjecting the donor to an additional stone-removing procedure. Continued long-term follow-up of donors and recipients is still required to ensure the safety of this approach.