Long-term Kidney Transplant Survival Across the Globe.

BACKGROUND: The outcomes after kidney transplantation (KT), including access, wait time, and other issues around the globe, have been studied. However, issues do vary from one country to another. METHODS: We obtained data from several countries from North America, South America, Europe, Asia, and Australia, including the number of patients awaiting KT from 2015, transplant rate per million population (pmp), proportion of living donor and deceased donor (LD/DD) KT, and posttransplant survival. We also sought opinions on key difficulties faced by each of these countries with respect to KT and long-term survival. RESULTS: Variation in access to KT across the globe was noted. Countries with the highest rates of KT pmp included the United States (79%) and Spain (71%). A higher proportion of LD transplants was noted in Japan (93%), India (85%), Singapore (63%), and South Korea (63%). A higher proportion of DD KTs was noted in Spain (90%), Brazil (90%), France (85%), Italy (85%), Finland (85%), Australia-New Zealand (80%), and the United States (77%). The 5-y graft survival for LD was highest in South Korea (95%), Singapore (94%), Italy (93%), Finland (93%), and Japan (93%), whereas for DD, it was South Korea (93%), Italy (88%), Japan (86%), and Singapore (86%). The common issues surrounding KTs are access and a limited number of LDs and DDs. Key issues identified for long-term survival were increasing age of donors and recipients, higher recipient comorbidity, and posttransplant events, such as alloimmune injury to the kidney, infection, cancer, and suboptimal adherence to therapy. CONCLUSIONS: A unified approach is necessary to improve issues surrounding KT as the demand continues to increase.

OPTN/SRTR 2022 Annual Data Report: Introduction.

The OPTN/SRTR 2022 Annual Data Report presents the status of the solid organ transplant system in the United States from 2011 through 2022. Organ-specific chapters are presented for kidney, pancreas, liver, intestine, heart, and lung transplant. Each organ-specific chapter is organized to present waitlist information, donor information (both deceased and living, as appropriate), transplant information, and patient outcomes. Data pertaining to pediatric patients are generally presented separately from the adult data. In addition to the organ-specific chapters, the reader will find chapters dedicated to deceased organ donation, vascularized composite allografts, and the COVID-19 pandemic. The data presented in the Annual Data Report are descriptive in nature. In other words, most tables and figures present raw data without statistical adjustment for possible confounding or changes over time. Therefore, the reader should keep in mind the observational nature of the data when attempting to draw inferences before trying to ascribe a cause to any observed patterns or trends. This introduction provides a brief overview of trends in waitlist and transplant activity from 2012 through 2022. More detailed descriptions can be found in the respective organ-specific chapters.

OPTN/SRTR 2022 Annual Data Report: Pancreas.

The postpandemic recovery did not occur in pancreas transplantation as in other organs. The number of pancreas transplants in the United States decreased to 918 in 2022 from 963 in 2021. The number of simultaneous pancreas-kidney transplants decreased to 810 in 2022 from 820 in 2021, but the largest decrease was in pancreas transplant alone: 62 in 2022 compared with 92 in 2021. Pancreas-after-kidney transplants decreased to 46 in 2022 from 51 in 2021. The trend of increasing proportions of pancreas transplants in patients with type 2 diabetes seen over the past few years ended in 2022; there were 22.4% of such transplants in 2022 compared with 25.8% in 2021. The proportion of recipients older than 45 years decreased in 2022 as well. However, the proportions of candidates with type 2 diabetes and older candidates on the waiting list did not decrease. The number of pancreas donors decreased and the pancreas nonuse rate increased in 2022. Outcomes after pancreas transplant continued to improve, with an impressive 8.1% pancreas and 4.3% kidney graft failure rate for simultaneous pancreas-kidney transplant at 1 year in 2022. The proportion of pancreas transplants performed by medium-volume centers (11-24 transplants/year) returned to 37.2% in 2022 from a high of 48.3% in 2021, whereas the proportion of those done by large-volume centers (25 or more transplants/year) returned to 25.3% in 2022 from a low of 15.9% in 2021.

OPTN/SRTR 2022 Annual Data Report: Kidney.

The year 2022 had continued successes and challenges for the field of kidney transplantation, as the community adapted to ongoing surges of the COVID-19 pandemic and broader geographic organ distribution. The total number of kidney transplants in the United States reached a record count of 26,309, driven by continued growth in deceased donor kidney transplants (DDKTs). The total number of candidates listed for DDKT rose slightly in 2022 but remained below 2019 listing levels, with 12.4% of candidates having been waiting 5 years or longer. Following the height of the COVID-19 pandemic, pretransplant mortality in 2022 declined across age, race and ethnicity, sex, and blood type groups. Pretransplant mortality continued to vary substantially by donation service area. The proportion of deceased donor kidneys recovered but not used for transplant (nonuse rate) rose to a high of 26.7% overall, with greater nonuse of biopsied kidneys (39.8%), kidneys from donors aged 55 years or older (54.7%), and kidneys with a kidney donor profile index (KDPI) of 85% or greater (71.3%). Nonuse of kidneys from donors who are hepatitis C virus (HCV) antibody positive rose to 30.2% but only slightly exceeded that of HCV antibody-negative donors. Disparities in access to living donor kidney transplant (LDKT) persist, especially for non-White and publicly insured patients. Delayed graft function continues an upward trend and occurred in 26.3% of adult kidney transplants in 2022. Five-year graft survival after LDKT compared with DDKT was 90.0% versus 81.4% for recipients aged 18-34 years and 80.8% versus 67.8% for recipients aged 65 years or older, respectively. The total number of pediatric kidney transplants performed in 2022 decreased to 705, its lowest point in the past decade; 502 (71.2%) were DDKTs and 203 (28.8%) were LDKTs. Among pediatric recipients, LDKT remains low, with continued racial disparities. The rate of DDKT among pediatric candidates has decreased by almost 25% since 2011. Congenital anomalies of the kidney and urinary tract remain the leading primary kidney disease diagnosis among pediatric candidates with a reported diagnosis. Most pediatric deceased donor recipients received a kidney from a donor with a KDPI of less than 35%. The rate of delayed graft function was 5.8% in 2022 and has been stable over the past decade. Long-term graft survival continues to improve, with superior outcomes for living donor transplant recipients.

OPTN/SRTR 2022 Annual Data Report: Heart.

The number of heart transplants in the United States has continued to increase. Since 2011, pediatric heart transplants have increased 31.7% to 494 and adult heart transplants have increased 85.8% to 3,668 in 2022. The numbers of new candidates for pediatric and adult heart transplants have also increased, with 703 new pediatric candidates and 4,446 new adult candidates in 2022. Adult heart transplant rates continue to rise, peaking at 122.5 transplants per 100 patient-years in 2022; however, the pediatric heart transplant rate decreased to its lowest rate in the past decade, 104.2 transplants per 100 patient-years, a decrease of 13.9% from 121 transplants per 100 patient-years in 2011. Despite this, pretransplant mortality among pediatric candidates has decreased by 52.2%, from 20.8 deaths per 100 patient-years in 2011 to 10.0 deaths per 100 patient-years in 2022, but remains excessive for candidates younger than 1 year at 25.7 deaths per 100 patient-years. Among adult candidates, pretransplant mortality declined from 15 deaths per 100 patient-years in 2011 to 8.7 deaths per 100 patient-years in 2022. Since 2011, posttransplant mortality has been stable to slightly better; among recipients who underwent transplant in 2015-2017, the 1-, 3-, and 5-year pediatric survival rates were 93.7%, 89.2%, and 85.0%, respectively, and the adult survival rates were 91.3%, 85.7%, and 80.4%. Donor trends have been favorable, with an increase in the numbers of hearts recovered and growing numbers of hearts procured after circulatory death.

OPTN/SRTR 2022 Annual Data Report: Liver.

In 2022, liver transplant activity continued to increase in the United States, with an all-time high of 9,527 transplants performed, representing a 52% increase over the past decade (2012-2022). Of these transplants, 8,924 (93.7%) were from deceased donors and 603 (6.3%) were from living donors. Liver transplant recipients were 94.5% adult and 5.5% pediatric. The overall size of the liver transplant waiting list contracted, with more patients being removed than added, although 10,548 adult patients still remained on the waiting list at the end of 2022. Alcohol-associated liver disease continued to be the leading diagnosis among both candidates and recipients, followed by metabolic dysfunction-associated steatohepatitis. Simultaneous liver-kidney transplant was the most common multiorgan combination, with 800 liver-kidney transplants performed in 2022; in addition, there were 303 new listings for kidney transplant via the safety net mechanism. Among adults added to the liver waiting list in 2021, 39.9% received a deceased donor liver transplant within 3 months; 45.7%, within 6 months; and 54.5%, within 1 year. Pretransplant mortality decreased to 12.3 deaths per 100 patient-years in 2022, although still 15.6% of removals from the waiting list were for death or being too sick for transplant. Graft and patient survival outcomes after deceased donor liver transplant improved, approximating pre-COVID-19 pandemic levels, with 5.1% mortality observed at 6 months; 6.8%, at 1 year; 12.7%, at 3 years; 19.8%, at 5 years; and 35.7%, at 10 years. Five-year graft and patient survival rates after living donor liver transplant exceeded those of deceased donor liver transplant. Candidates receiving model for end-stage liver disease exception points for hepatocellular carcinoma constituted 15.5% of transplants performed in 2022, with similar transplant rates and posttransplant outcomes compared to cases without hepatocellular carcinoma exception. In 2022, more pediatric liver transplant candidates were added to the waiting list and underwent transplant compared with either of the preceding 2 years, with an uptick in living donor liver transplant volume. Although pretransplant mortality has improved after the recent policy change prioritizing pediatric donors for pediatric recipients, still, in 2022, 50 children died or were removed from the waiting list for being too sick to undergo transplant. Posttransplant mortality among pediatric liver transplant recipients remained notable, with death occurring in 4.0% at 6 months, 6.0% at 1 year, 8.2% at 3 years, 9.8% at 5 years, and 13.9% at 10 years. Similar to adult living donor recipients, pediatric living donor recipients had better 5-year patient survival compared with deceased donor recipients.

OPTN/SRTR 2022 Annual Data Report: Deceased Organ Donation.

The Scientific Registry of Transplant Recipients uses data collected by the Organ Procurement and Transplantation Network to calculate metrics such as organs recovered per donor, organs transplanted per donor, and organs recovered for transplant but not transplanted (ie, nonuse). In 2022, there were 14,905 deceased donors, a 7.5% increase from 13,863 in 2021, and this number has been increasing since 2010. The number of deceased donor organs used for transplant increased to 37,334 in 2022, a 4.6% increase from 35,687 in 2021; this number has been increasing since 2012. The increase may be due in part to the rising number of deaths of young people amid the ongoing opioid epidemic. The number of organs transplanted included 10,130 left kidneys, 10,039 right kidneys, 298 en bloc kidneys, 922 pancreata, 8,847 livers, 83 intestines, 4,169 hearts, and 2,633 lungs. Compared with 2021, transplants of all organs except pancreata and intestines increased in 2022. In 2022, 3,563 left kidneys, 3,673 right kidneys, 156 en bloc kidneys, 366 pancreata, 965 livers, 4 intestines, 54 hearts, and 219 lungs were not used. These data suggest an opportunity to increase the number of transplants by reducing the number of unused organs. Despite the COVID-19 pandemic, there was no dramatic increase in the number of unused organs and there was an increase in the total numbers of donors and transplants.

OPTN/SRTR 2022 Annual Data Report: COVID-19.

This chapter updates the COVID-19 chapter from the 2021 Annual Data Report with trends through November 12, 2022, and introduces trends in recovery and use of organs from donors with a positive COVID-19 test. Posttransplant mortality and graft failure, which remained a concern in all organs at the last report due to the Omicron variant wave, have returned to lower levels in the most recent available data through November 2022. Use of organs from donors with a positive COVID-19 test has grown, particularly after the first year of the pandemic. Mortality due to COVID-19 should continue to be monitored, but most other measures have sustained their recovery and may now be responding more to changes in policy than to ongoing concerns with COVID-19.

OPTN/SRTR 2022 Annual Data Report: Vascularized Composite Allograft.

This year's chapter on vascularized composite allograft (VCA) encompasses reviews of data collected from 2014 (when VCA was included in the Final Rule) through 2022. The present Annual Data Report shows that the number of VCA recipients in the United States continues to be small and has remained consistent from the prior report. The data continue to be limited by sample size, with trends persistently demonstrating a predominance of White males in the young/middle-aged population as both donors and recipients for nonuterus VCA transplants, and White women younger than 35 years as the predominant recipients of uterus transplant. Similar to the 2021 report, there were only eight failed uterus grafts and one failed nonuterus VCA graft reported from 2014 through 2022. Standardization of definitions of success and failure as well as outcome measures for the different VCA types remain unmet needs in VCA transplantation.

Pharmacomicrobiomics: Immunosuppressive Drugs and Microbiome Interactions in Transplantation.

The human microbiome is associated with human health and disease. Exogenous compounds, including pharmaceutical products, are also known to be affected by the microbiome, and this discovery has led to the field of pharmacomicobiomics. The microbiome can also alter drug pharmacokinetics and pharmacodynamics, possibly resulting in side effects, toxicities, and unanticipated disease response. Microbiome-mediated effects are referred to as drug-microbiome interactions (DMI). Rapid advances in the field of pharmacomicrobiomics have been driven by the availability of efficient bacterial genome sequencing methods and new computational and bioinformatics tools. The success of fecal microbiota transplantation for recurrent Clostridioides difficile has fueled enthusiasm and research in the field. This review focuses on the pharmacomicrobiome in transplantation. Alterations in the microbiome in transplant recipients are well documented, largely because of prophylactic antibiotic use, and the potential for DMI is high. There is evidence that the gut microbiome may alter the pharmacokinetic disposition of tacrolimus and result in microbiome-specific tacrolimus metabolites. The gut microbiome also impacts the enterohepatic recirculation of mycophenolate, resulting in substantial changes in pharmacokinetic disposition and systemic exposure. The mechanisms of these DMI and the specific bacteria or communities of bacteria are under investigation. There are little or no human DMI data for cyclosporine A, corticosteroids, and sirolimus. The available evidence in transplantation is limited and driven by small studies of heterogeneous designs. Larger clinical studies are needed, but the potential for future clinical application of the pharmacomicrobiome in avoiding poor outcomes is high.

A randomized controlled trial of preemptive rituximab to prevent recurrent focal segmental glomerulosclerosis post-kidney transplant (PRI-VENT FSGS): protocol and study design.

Background: Focal segmental glomerulosclerosis (FSGS) is a common cause of end-stage kidney disease requiring kidney transplantation and can recur in the allograft in 30-80% of recipients resulting in reduced graft survival. Plasmapheresis has shown efficacy in treating some cases of recurrent FSGS but isolated plasmapheresis has not demonstrated efficacy in preventing recurrent FSGS. Rituximab has had anecdotal success in preventing recurrence in a single center study but has not been studied in combination with plasmapheresis for preventing FSGS recurrence. Methods: We are conducting a randomized, controlled, multicenter clinical trial of adult and pediatric kidney transplant recipients with primary FSGS to assess whether plasmapheresis in combination with rituximab prevents recurrent disease post-transplantation. Discussion: Rituximab combined with plasmapheresis is a promising, novel therapy to prevent recurrent FSGS, a disease with limited therapeutic options and no consensus guidelines for prevention or treatment. Clinical trial registration: https://clinicaltrials.gov/ct2/show/NCT03763643, identifier NCT03763643.

Cancer Mortality Among Solid Organ Transplant Recipients in the United States During 1987-2018.

BACKGROUND: Solid organ transplant recipients (ie, "recipients") have elevated cancer risk and reduced survival after a cancer diagnosis. Evaluation of cancer mortality among recipients can facilitate improved outcomes from cancers arising before and after transplantation. METHODS: We linked the US transplant registry to the National Death Index to ascertain the causes of 126 474 deaths among 671 127 recipients (1987-2018). We used Poisson regression to identify risk factors for cancer mortality and calculated standardized mortality ratios to compare cancer mortality in recipients with that in the general population. Cancer deaths verified with a corresponding cancer diagnosis from a cancer registry were classified as death from pretransplant or posttransplant cancers. RESULTS: Thirteen percent of deaths were caused by cancer. Deaths from lung cancer, liver cancer, and non-Hodgkin lymphoma (NHL) were the most common. Heart and lung recipients had the highest mortality for lung cancer and NHL, whereas liver cancer mortality was highest among liver recipients. Compared with the general population, cancer mortality was elevated overall (standardized mortality ratio 2.33; 95% confidence interval, 2.29-2.37) and for most cancer sites, with large increases from nonmelanoma skin cancer (23.4, 21.5-25.5), NHL (5.17, 4.87-5.50), kidney cancer (3.40, 3.10-3.72), melanoma (3.27, 2.91-3.68), and, among liver recipients, liver cancer (26.0, 25.0-27.1). Most cancer deaths (93.3%) were associated with posttransplant cancer diagnoses, excluding liver cancer deaths in liver recipients (of which all deaths were from pretransplant diagnoses). CONCLUSIONS: Improved posttransplant prevention or screening for lung cancer, NHL, and skin cancers and management of liver recipients with prior liver cancer may reduce cancer mortality among recipients.

OPTN/SRTR 2021 Annual Data Report: COVID-19.

This chapter updates the COVID-19 chapter from the 2020 Annual Data Report with trends through February 12, 2022, and introduces trends in COVID-19-specific cause of death on the waiting list and posttransplant. Transplant rates remain at or above prepandemic levels for all organs, indicating a sustained transplantation system recovery following the initial 3-month disruption due to the onset of the pandemic. Posttransplant mortality and graft failure remain a concern in all organs, with rates surging corresponding to waves of the pandemic. Waitlist mortality due to COVID-19 is also a concern, particularly among kidney candidates. While the recovery of the transplantation system has been sustained in the second year of the pandemic, ongoing efforts should focus on reducing posttransplant and waitlist mortality due to COVID-19, and graft failure.

OPTN/SRTR 2021 Annual Data Report: Vascularized Composite Allograft.

Year 2020 marked the first OPTN/SRTR Annual Data Report that included a chapter on vascularized composite allograft (VCA), which encompassed reviews of data collected between 2014 (when VCA was included in the Final Rule) and 2020. The present Annual Data Report shows that the number of VCA recipients in the United States continues to be small and trended downward in 2021. While data continue to be limited by sample size, trends continue to show a predominance in White, young/middle-aged, male recipients. Similar to the 2020 report, eight uterus and one non-uterus VCA graft failures were reported from 2014 through 2021. Critical to advancement of VCA transplantation will be the standardization of definitions, protocols, and outcome measures for the different VCA types. Like intestinal transplants, it is likely that VCA transplants will be concentrated and performed at referral transplant centers.

OPTN/SRTR 2021 Annual Data Report: Deceased Organ Donation.

The Scientific Registry of Transplant Recipients uses data collected by the Organ Procurement and Transplantation Network to calculate metrics such as donation rate, organ yield, and rate of organs recovered for transplant but not transplanted (ie, nonuse). In 2021, there were 13,862 deceased donors, a 10.1% increase from 12,588 in 2020, and an increase from 11,870 in 2019; this number has been increasing since 2010. The number of deceased donor transplants increased to 41,346 transplants in 2021, a 5.9% increase from 39,028 in 2020; this number has been increasing since 2012. The increase may be due in part to the rising number of deaths of young people amid the ongoing opioid epidemic. The number of organs transplanted included 9,702 left kidneys, 9,509 right kidneys, 551 en bloc kidneys, 964 pancreata, 8,595 livers, 96 intestines, 3,861 hearts, and 2,443 lungs. Compared with 2019, transplants of all organs except lungs increased in 2021, which is remarkable as this occurred despite the COVID-19 pandemic. In 2021, 2,951 left kidneys, 3,149 right kidneys, 184 en bloc kidneys, 343 pancreata, 945 liver, 1 intestine, 39 hearts, and 188 lungs were not used. These numbers suggest an opportunity to increase numbers of transplants by reducing nonused organs. Despite the pandemic, there was no dramatic increase in number of nonused organs and there was an increase in total numbers of donors and transplants. The new Centers for Medicare & Medicaid Services metrics for donation rate and transplant rate have also been described and vary across organ procurement organizations; the donation rate metric varied from 5.82 to 19.14 and the transplant rate metric varied from 18.7 to 60.0.

OPTN/SRTR 2021 Annual Data Report: Heart.

The past 5 years have posed challenges to the field of heart transplantation. The 2018 heart allocation policy revision was accompanied by anticipated practice adjustments and increased use of short-term circulatory support, changes that may ultimately serve to advance the field. The COVID-19 pandemic also had an impact on heart transplantation. While the number of heart transplants in the United States continued to increase, the number of new candidates decreased slightly during the pandemic. There were slightly more deaths following removal from the waiting list for reasons other than transplant during 2020, and a decline in transplants among candidates listed as status 1, 2, or 3 compared with the other statuses. Heart transplant rates decreased among pediatric candidates, most notably among those younger than 1 year. Despite this, pretransplant mortality has declined for both pediatric and adult candidates, particularly candidates younger than 1 year. Transplant rates have increased in adults. The prevalence of ventricular assist device use has increased among pediatric heart transplant recipients, while the prevalence of short-term mechanical circulatory support, particularly intra-aortic balloon pump and extracorporeal membrane oxygenation, has increased among adult recipients.

OPTN/SRTR 2021 Annual Data Report: Liver.

In 2021, liver transplant volume continued to grow, with a record 9,234 transplants performed in the United States, 8,665 (93.8%) from deceased donors and 569 (6.2%) from living donors. There were 8,733 (94.6%) adult and 501 (5.4%) pediatric liver transplant recipients. An increase in the number of deceased donor livers corresponded to an increase in the overall transplant rate and shorter waiting times, although still 10.0% of livers that were recovered were not transplanted. Alcohol-associated liver disease was the leading indication for both waitlist registration and liver transplant in adults, outpacing nonalcoholic steatohepatitis, while biliary atresia remained the leading indication for children. Related to allocation policy changes implemented in 2019, the proportion of liver transplants performed for hepatocellular carcinoma has decreased. Among adult candidates listed for liver transplant in 2020, 37.7% received a deceased donor liver transplant within 3 months, 43.8% within 6 months, and 53.3% within 1 year. Pretransplant mortality improved for children following implementation of acuity circle-based distribution. Short-term graft and patient survival outcomes up to 1 year worsened for adult deceased and living donor liver transplant recipients, which is a reversal of previous trends and coincided with the onset of the COVID-19 pandemic in early 2020. Longer-term outcomes among adult deceased donor liver transplant recipients were unaffected, with overall posttransplant mortality rates of 13.3% at 3 years, 18.6% at 5 years, and 35.9% at 10 years. Pretransplant mortality improved for children following implementation of acuity circle-based distribution and prioritization of pediatric donors to pediatric recipients in 2020. Pediatric living donor recipients had superior graft and patient survival outcomes compared with deceased donor recipients at all time points.

OPTN/SRTR 2021 Annual Data Report: Pancreas.

The number of pancreas transplants in the United States was largely unchanged in 2021 at 963 transplants compared with 962 in 2020, showing that recovery from the COVID-19 pandemic was not as pronounced in pancreas transplantation as in other organs. The number of simultaneous pancreas-kidney transplants (SPKs) decreased from 827 to 820, whereas the number of pancreas-after-kidney transplants and pancreas transplants alone increased marginally to compensate. The proportion of patients with type 2 diabetes on the waiting list increased to 22.9% in 2021, compared with 20.1% in 2020. Consequently, the proportion of transplants in patients with type 2 diabetes increased from 21.3% in 2020 to 25.9% in 2021. The proportion of transplants in older recipients (aged 55 years or older) also increased to 13.5% in 2021 from 11.7% in 2020. Outcomes after SPK continue to be the best of the three categories of pancreas transplants: 1-year graft failure for kidney at 5.7% and pancreas at 10.5% for transplants performed in 2020. The proportion of pancreas transplants performed by medium-volume centers (11-24 transplants per year) increased sharply to 48.3% in 2021 from 35.1% in 2020, with a corresponding decrease in transplants in large-volume centers (25 or more transplants per year) to 15.9% in 2021 from 25.7% in 2020.

OPTN/SRTR 2021 Annual Data Report: Kidney.

The year 2021 marked both successes and challenges for the field of kidney transplantation, in the context of the ongoing COVID-19 pandemic and broader geographic organ distribution. The total number of kidney transplants in the United States reached a record count of 25,487, driven by growth in deceased donor kidney transplants. The total number of candidates listed for deceased donor kidney transplant rose slightly in 2021 but remained below 2019 listing levels, with nearly 10% of candidates having been waiting 5 years or longer. Pretransplant mortality declined slightly among candidates of Black, Hispanic, and other races, in parallel with increasing numbers of Black and Hispanic transplant recipients. In the context of broader organ sharing, there is growing disparity in pretransplant mortality among non-metropolitan compared with metropolitan residents. The proportion of deceased donor kidneys recovered but not used for transplant (nonuse rate) rose to a high of 24.6% overall, with greater nonuse among biopsied kidneys (35.9%), kidneys from donors aged 55 years or older (51.1%), and kidneys with kidney donor profile index (KDPI) of 85% or greater (66.6%). Nonuse of kidneys from donors who are hepatitis C virus (HCV) antibody positive only slightly exceeded that of HCV antibody-negative donors. Disparities in access to living donor kidney transplant persists, especially for non-White and publicly insured patients. Delayed graft function continues an upward trend and occurred in 24% of adult kidney transplants in 2021. Five-year graft survival after living compared with deceased donor transplant was 88.6% versus 80.7% for recipients aged 18-34 years, and 82.1% versus 68.0% for recipients aged 65 years or older. The total number of pediatric kidney transplants performed increased to 820 in 2021, the highest number since 2010. Despite numerous efforts, living donor kidney transplant remains low among pediatric recipients, with continued racial disparities. The rate of deceased donor transplants among pediatric candidates recovered in 2021 from a low in 2020. Congenital anomalies of the kidney and urinary tract remain the leading primary kidney disease diagnosis among pediatric candidates. Most pediatric deceased donor recipients receive a kidney from a donor with KDPI less than 35%. Graft survival continues to improve, with superior outcomes for living donor transplant recipients.

OPTN/SRTR 2021 Annual Data Report: Introduction.

The OPTN/SRTR 2021 Annual Data Report presents the status of the solid organ transplantation system in the United States from 2010 through 2021. Organ-specific chapters are presented for kidney, pancreas, liver, intestine, heart, and lung transplant. Each organ-specific chapter is organized to present waitlist information, donor information (both deceased and living, as appropriate), transplant information, and patient outcomes. Data pertaining to pediatric patients are generally presented separately from the adult data. In addition to the organ-specific chapters, you will find chapters dedicated to deceased organ donation, vascularized composite allograft, and the COVID-19 pandemic. The data presented in the Annual Data Report are descriptive in nature. In other words, most tables and figures present raw data without statistical adjustment for possible confounding or changes over time. Therefore, the reader should keep in mind the observational nature of the data when attempting to draw inferences before trying to ascribe a cause to any observed patterns or trends. This introduction provides a brief overview of trends in waitlist and transplant activity. More detailed descriptions can be found in the respective organ-specific chapters.