Preimplant biopsy of donor kidneys doesn’t accurately predict the organs’ viability and leads to many acceptable kidneys being discarded, according to two separate reports published online in the Clinical Journal of the American Society of Nephrology.
Biopsies are obtained routinely from donor kidneys in the United States, and unfavorable biopsy findings are the most frequently cited reason for discarding donor kidneys as unacceptable. Ideally, such samples would be obtained by core needle biopsy, would not be frozen, would be thoroughly examined by a pathologist with special training in reading kidney biopsies, and would be assessed meticulously for chronic tubular atrophy, arteriolar hyalinosis, interstitial inflammation, interstitial fibrosis, and the presence and severity of acute tubular necrosis.
In actual practice, however, these samples are almost always obtained by wedge biopsy, are frozen, and are rushed through a perfunctory examination by whatever pathologist is available so that the organ can be transplanted as quickly as possible if it is found to be acceptable. So many clinicians have questioned whether the results of such biopsies actually assess the organs’ viability and predict graft failure, both groups of researchers noted.
In what they described as the largest cohort study to date on this issue, one team analyzed data regarding 651 consecutive kidney transplants performed during a 2-year period, for which four organ procurement organizations obtained the kidneys from 369 deceased donors. The four organizations performed wedge biopsies immediately after procurement, and different pathology services evaluated frozen sections from these organs and reported their findings to potential transplant centers.
Patient outcomes were tracked using information in the United Network for Organ Sharing (UNOS) database, said Dr. Isaac E. Hall of the section of nephrology and the program of applied translational research, Yale University, New Haven, Conn., and his associates.
They assessed whether a biopsy finding of acute tubular necrosis correlated with the graft’s performance after transplantation. Acute tubular necrosis was reported in 110 biopsies (17%) overall. The four procurement organizations varied widely in their reported rates of the abnormality, from a low of zero cases to a high of 25% of cases. This variation suggests that the process of obtaining and interpreting these biopsies is, at best, not uniform among procurement groups, according to the investigators.
During a median follow-up of 1 year, the primary outcome of interest – delayed graft function – occurred in 45% of kidneys that were reported to have tubular necrosis and in 39% of those reportedly free of such necrosis. This is a nonsignificant difference. There also was no significant difference in the secondary outcome of graft failure between recipients of organs with acute tubular necrosis, compared with recipients of organs without it.
In summary, there was no significant association between biopsy reports of acute tubular necrosis and graft viability. "It is reasonable to question whether acute tubular necrosis, or acute kidney injury in general for that matter, truly causes important allograft outcomes," Dr. Hall and his colleagues wrote (Clin. J. Am. Soc. Nephrol. 2014 [doi:10.2215/CJN.08270813]).
In the second study, Dr. Bertram L. Kasiske of the Scientific Registry of Transplant Recipients, Minneapolis Medical Research Foundation, and his associates assessed the records for 83 kidneys that were discarded because of unfavorable biopsy findings (cases) and 83 contralateral kidneys from the same donors that were transplanted (contralateral controls). They compared these findings with those for 151 transplanted kidneys from 83 deceased donors who were matched for the index cases’ donor profiles.
"Ours is the first controlled study to compare biopsy findings between discarded kidneys and matched transplanted kidneys," Dr. Kasiske and his colleagues noted.
They found that most of the biopsy reports were of low quality, and very few indicated the amounts of tubular atrophy, interstitial inflammation, arteriolar hyalinosis, or acute tubular necrosis. The percentage of glomerulosclerosis was often the only finding upon which to base the decision of whether to use or discard the allograft.
But the percentage of glomerulosclerosis overlapped substantially between cases (discarded kidneys) and controls (transplanted kidneys). This suggests that "information obtained from procurement biopsies is of low quality and may lead to unnecessary discard of transplantable kidneys," Dr. Kasiske and his associates wrote (Clin. J. Am. Soc. Nephrol. 2014 [doi:10.2215/CJN.07610713]).
"A reasonable conclusion from this and other studies is that the widespread practice of routinely obtaining procurement biopsies should be abandoned, as has been successfully done in Europe," they noted.
Dr. Hall’s study was supported by the American Heart Association, the Roche Organ Transplantation Research Foundation, the National Institute of Diabetes and Digestive and Kidney Diseases, and the U.S. Health Resources and Services Administration. Dr. Kasiske’s study was supported by the Minneapolis Medical Research Foundation, the Organ Procurement and Transplantation Network, the Scientific Registry of Transplant Recipients, and the United Network for Organ Sharing. Both research groups reported no potential financial conflicts of interest.