Biopsy results poorly predict long-term function of donor kidneys: A discussion with Dr. Sumit Mohan

Background
Despite an increasing shortage of donor organs, about one in five deceased donor kidneys is currently discarded in the United States—a record high. The most commonly cited reason for discarding these organs: biopsy findings. However, few studies have looked deeply into the association between histological findings and long-term organ function and survival.

To that end, a new study evaluated 975 kidney transplant patients to determine whether expertly-performed needle core biopsies could predict post-transplant renal function in both living and deceased donor kidneys. The study, published in the Journal of the American Society of Nephrology, also investigated whether such biopsies can foretell the early and long-term outcomes of kidney transplants.

In this interview, nephrologist and lead investigator Sumit Mohan, MD, MPH, discusses the findings of this investigation. He also talks about the high rate of discarded kidneys and the advantages of living vs deceased donor kidneys, as well as his preferred biopsy method.

MDLinx: Why did you decide to undertake this particular study?

Dr. Mohan: Biopsy findings are the single-most cited reason for declining the use of a kidney, despite the fact that biopsies that are rushed while trying to place an organ are less than ideal and are often wrong. It was also unclear how much of an impact histology findings have in regard to long-term outcomes. Although we were not able to look at kidneys that were discarded, our findings suggest that we need to reduce the number of biopsies and use the results of biopsies in context without overweighing them. 

MDLinx: Why are so many donor kidneys currently discarded?

Dr. Mohan: There isn't a simple answer for this and it's been the focus of considerable analysis by my group for the past several years. For example, we showed in a 2016 study that donor kidneys are less likely to be procured and more likely to be discarded due to the "weekend effect" at hospitals. Part of the reason, however, is risk aversion in the current regulatory environment and potentially the interaction between the allocation system and available resources.

MDLinx: What were the main differences you found between living donor kidneys and deceased donor kidneys?

Dr. Mohan: Living donor kidneys are not subjected to cold storage and it appears that the absence of hypothermic storage and transport appears to have a positive impact on outcomes. 

MDLinx: You wrote that most (73%) deceased donor kidneys with suboptimal biopsy results were still functioning at five years. What are the implications of this? 

Dr. Mohan: This is in comparison to the average survival on dialysis after five years currently of approximately 36%. In short, transplantation with a suboptimal kidney will still result in a doubling of the probability of being alive in five years. 

MDLinx: What is your preferred method of biopsy, and why? 

Dr. Mohan: Core biopsies are the way to go. They provide more representative samples and do less damage to the organ. Unfortunately, not all organizations involved in procurements make the biopsy gun needed for this readily available. 

MDLinx: Is there a better way to select donor kidneys other than by histology? 

Dr. Mohan: There are clinical characteristics as well as the KDRI (Kidney Donor Risk Index) and the recent KDPI (Kidney Donor Profile Index), which are scores used by UNOS (United Network for Organ Sharing) for organ allocation. The histology is useful only in occasional cases when the KDPI is not as helpful as one might imagine. 

MDLinx: What's your next step in this line of investigation? 

Dr. Mohan: We are now comparing these reperfusion biopsies that happen after implantation of a kidney with the biopsies that are performed prior to the kidney being accepted to see what the agreement is and what sources of error exist.

About Dr. Mohan: Sumit Mohan, MD, MPH, is an Associate Professor of Medicine and Epidemiology at Columbia University Medical Center, in New York, NY, and the Deputy Editor of Kidney International Reports.