The organ that cannot be transplanted is the brain.
The brain is the organ that cannot be transplanted because the brain is a complex organ and delicate organ that is responsible for controlling of all the bodily functions.
The brain is also very and extremely difficult to reconnect and to disconnect to another body without causing severe damage.
The lungs are often the most difficult organ to transplant as a result of several factors which include a higher risk of chronic rejection as well as infection and difficulty in preserving the donor lungs for transplant.
Some factors that make lung transplants pretty challenging to transplant include.
High Risk of Chronic Rejection.
A significant percentage of lung transplant recipients develop chronic lung allograft dysfunction also known as CLAD within 5 years, which is a form of chronic rejection.
Infection Vulnerability.
The lungs are susceptible to infections, especially in the late stages of a lung donor's life, which can also complicate the transplant process.
Preserving donor lungs for transplant can also be difficult as they are fragile and also susceptible to damage.
Lung transplant recipients also have a lower long term survival rate when compared to other organ transplants, partly due to CLAD.