In today's Halakha we will focus exclusively on living donors. The cases under this category are, for example, kidney donation; bone marrow and blood donation.
It is a consensus among modern orthodox rabbis that one should be willing to undergo a minor risk in order to save someone else's life.
In the past, many rabbis, among them Rabbi Yitzchak Weiss and Rabbi Eliezer Yehuda Waldenberg z'"l, had certain reservations about the permission to donate a kidney, because they thought that although a person can have a normal life with one kidney, the risks involved for the living donor, during and after surgery, were too high and would endanger his life.
In our days, however, donors are carefully screened physically and psychologically, and the surgical and post-surgical risks of complications for the donor have diminished dramatically, thanks to the advances of modern medicine. Today it is consented by most (if not all!) Modern Orthodox rabbis thatdonating a kidney is at least permitted, if not mandatory. Nevertheless, one may never obligate or coerce someone else to donate an organ, even to save the life of another person.
In his rabbinical response Rabbi Obadia Yosef evaluates the objections of Rabbi Weiss and Rabbi Waldenberg, and asserts that since today the risks involved in kidney donation are so low, it is considered a great Mitzvah to donate a kidney, fulfilling the commandment of saving a life, (piquach nefesh). Donating a kidney to save a life, he suggests, might be also required by the Tora's commandment "lo ta'amod al dam re'ekha", "You shall not stand still while your fellowman bleeds to death (i.e. is dying)" .
To understand the impact of this great Mitzva, let us keep in mind that a typical patient who receives a kidney, will live 10 to 15 years longer with a kidney transplant than if kept on dialysis.
(to be continued...)
For a comprehensive and reliable source of information about Jewish Law and organ transplant see Halachic Organ Donors Society