I had a kidney transplant and paid all the donors expenses, what expenses can I deduct?

Yes, to properly answer this question, I researched this document from the IRS.  Although this document references compensation for egg donors, I will advise, without reservation, that this applies to Kidney donors also in accordance with § 213(a) of the Internal Revenue Code.

Given the facts, "a taxpayer may deduct expenses paid during the taxable year, not compensated for by insurance or otherwise, for medical care of the taxpayer, spouse, or dependent, to the extent the expenses exceed 7.5 percent of adjusted gross income, under § 213(a). Section 213(d)(1)(A) provides that medical care includes amounts paid for the diagnosis, cure, mitigation, treatment, or prevention of disease, or for the purpose of affecting any structure or function of the body. It also mentions that You have represented that you will pay the fee to the donor, the fee to the agency that procured the donor, the donor’s medical and psychological testing expenses, the insurance for post-procedure medical or psychological assistance to the donor, and the cost of the legal contract between you and the donor, in order to enable you to obtain a donated egg for implantation into your body. Because these costs are preparatory to the performance of your own medical procedure, the expenses are medical care for purposes of § 213."

In view of this ruling, all expenses may be deductible except for lost wages because that is not mentioned in this ruling.