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.