An unpaired organ is an organ present in the human body only once, whose complete removal kills the donating person. Examples: heart, complete liver, pancreas.
From this it follows: complete removal requires postmortem donation. A living donation of the whole organ is structurally excluded.
Magisterial formulation
John Paul II, in his address to the 18th International Congress of the Transplantation Society (Rome, 29 August 2000), made the paired/unpaired distinction explicit in magisterial terms:
“Vital organs which occur singly in the body can be removed only after death, that is from the body of someone who is certainly dead. This requirement is self-evident, since to act otherwise would mean intentionally to cause the death of the donor in disposing of his organs.”
Thus the Principle of Totality (Pius XII, 1956), which permits the living donation of paired organs, does not apply to unpaired organs: here the condition “no serious functional impairment” would be violated — the removal means the donor’s death.
Concrete unpaired organs
Heart — strictly unpaired. The only source is postmortem donation (donation after circulatory death or donation after brain death). Living donation is not possible.
Liver (complete) — complete liver transplantation only post mortem. However, the liver is at the same time divisible: a partial-liver living donation (usually the left lobe) is possible because the liver regenerates. Donor mortality risk is about 0.28 percent.
Pancreas — complete donation only post mortem; partial living donation possible.
Structural asymmetry to donation after circulatory death
From the unpaired nature there follows a structural intensification of the problem of donation after circulatory death:
| Aspect | Paired organ (kidney) | Unpaired organ (heart) |
|---|---|---|
| Living donation possible? | yes, low risk | no |
| Donation after circulatory death avoidable? | yes, through living donation | no |
| Permanence tension | mitigable (an alternative exists) | unavoidable |
| Assessment of donation after circulatory death | one source among several | the only new source |
Heart donation after circulatory death (Switzerland 2023, worldwide 9 countries, 24 percent of US heart donations in 2025) is therefore the paradigmatically problematic case of the donation-after-circulatory-death debate: where no living-donation alternative exists, the entire ethical burden falls on the determination of permanence — and precisely here the position held here sees the sharpest tension with the Dead Donor Rule.
Substance-ontological position
For unpaired organs, the violation of the Dead Donor Rule through the permanence determination of donation after circulatory death is structurally reinforced, because the living-donation alternative does not exist. The position of the ontology held here: donation after circulatory death for unpaired organs potentially violates the Dead Donor Rule and the Personalist Norm — and thus more sharply than for paired organs. The precautionary principle of Benedict XVI demands, in this situation, the especially strict adoption of the sharper condition — not permanence, but irreversibility.
Ontological classification
Superordinate concept: Donor Organ
Ontological relations:
- permits no living donation of the complete form
- disjoint with: Paired Organ
- requires: Postmortem Donation for complete donation
- concrete examples: heart, complete liver, pancreas
- grounds the intensification of the: Dead Donor Rule tension in unpaired donation after circulatory death
Chapter assignment: Chapter 4: What Is Human Personhood? (German)
Sources: Generated by querying the Personhood ontology.
Further sources:
- John Paul II (2000): Address to the 18th International Congress of the Transplantation Society, Rome, 29 August 2000.
- Pius XII (1956): Anesthesia: Three Moral Questions. Georgetown University Library Repository.
- Joshi, Yashutosh; Wang, Katherine; MacLean, Campbell et al. (2024): The Rapidly Evolving Landscape of DCD Heart Transplantation. Current Cardiology Reports 26: 1499—1507.
- Changes in Organ Donation after Circulatory Death in the United States (2025), PMC.