What Is Organ Donation? Consent, Death and a Permanent Shortage

Countries take fundamentally different approaches, and the differences produce measurable variation in donation rates:

• •Opt-in systems, where a person must positively register or carry a card, which was the traditional model in most countries
• •Opt-out or deemed consent systems, where adults are presumed willing unless they have registered an objection, adopted in Spain, Austria, Belgium, Wales, England, Scotland and elsewhere
• •Soft versions of both, where families are consulted regardless of the register and can effectively veto, which describes almost every real system including those described as presumed consent
• •Mandated choice, where people must record a decision either way when obtaining a licence or similar document
• •Priority systems, notably in Israel, where registered donors receive preference if they later need an organ themselves
• •Living donation, governed separately and much more strictly, requiring independent assessment that consent is free and unpaid

Spain has the highest deceased donation rate in the world and is frequently cited as proof that presumed consent works, which is misleading in an instructive way. Spain introduced its opt-out law in 1979 and its donation rate barely moved for a decade. The rise began after 1989 with organisational changes: a national coordinating body, transplant coordinators based in every hospital and usually intensive care doctors rather than administrators, systematic identification of potential donors, professional training in how to approach families, and audit of every death in intensive care to find missed opportunities. Family refusal rates fell because of how conversations were conducted, not because the law removed the need for them, since Spanish practice always consults the family. The general finding across countries is that legislation alone produces modest effects while investment in coordination, staffing and family support produces large ones, and the Welsh and English experience after moving to deemed consent showed smaller changes than campaigners had predicted, with consent rates rising gradually alongside the accompanying publicity and infrastructure.

Most deceased donation depends on a definition of death that many people are unaware of. Death determined by neurological criteria, meaning the irreversible loss of all brain function including the brainstem, allows a patient's circulation to be maintained artificially while organs remain viable, and it is the basis for most organ retrieval. That definition was formalised in the late 1960s, was developed partly in response to intensive care creating a state that previous definitions could not describe, and remains philosophically contested by a minority of clinicians and ethicists and religiously contested in some traditions, with several countries and jurisdictions providing accommodations. The alternative pathway is donation after circulatory death, where a patient not meeting neurological criteria has treatment withdrawn and organs are retrieved after circulation stops and a mandatory observation period has passed, which yields fewer usable organs and has expanded substantially in several countries. The dead donor rule, that retrieval must not cause death, underpins both pathways and is the ethical foundation that public confidence depends on.

Once an organ becomes available, allocation is governed by published algorithms balancing medical urgency, expected benefit, tissue matching, waiting time and geography, and the weightings embody genuine ethical disagreements about whether to prioritise the sickest patient or the one who will gain the most years. Almost every country prohibits payment for organs, on grounds of exploitation and coercion, and the prohibition drives a documented international trade in which poor donors receive small sums and poor outcomes, which international declarations have sought to suppress. Iran operates a regulated compensated kidney donation system and is the standing exception cited in a long-running debate about whether regulated payment would reduce suffering or create it. Living donation now supplies a large share of kidney transplants, and paired exchange schemes match incompatible donor-recipient pairs with other pairs, sometimes producing long chains initiated by a single altruistic donor. Xenotransplantation from genetically modified pigs has moved from theory to a small number of human cases and may eventually change the supply question entirely.

Transplant numbers are limited by supply, so law and hospital organisation decide them more than surgery does. Spain's world-leading rate followed a decade after its opt-out law and came from coordinators in every hospital and trained family conversations, not from the legislation. Most donation depends on death defined by irreversible loss of brain function. Payment is prohibited nearly everywhere, which drives an exploitative international trade.