Learn English – Best word for Spanish “integral”

I'm not sure it fits exactly, but there is a phrase with similar intent in the medical profession: "life over limb". It directly mirrors your gangrene example because you might have to sacrifice part of a healthy limb to save the patient's life.

It is sometimes used beyond the literal meaning as well. For instance, moving a patient with a suspected neck injury might risk paralysis, but might be done anyway when the alternative is certain death. Someone might justify that decision by saying "life over limb."

Consultatory exists, but I'd probably go for consultative. From the Oxford English Dictionary:

Consultatory: pertaining to or serving for consultation (e.g. of an oracle, etc.); having the character of consultation or deliberation, consultative.

1600 Abp. Abbot Exp. Jonah 80 Here the lot is consultatorie+because they could not tell who it was that had done the deede, they will put it to their Gods. 1664 Evelyn Sylva (1776) 168 Formerly they made consultatory staves of this tree. 1876 Bancroft Hist. U.S. III. viii. 395 Their decision would be only consultatory, and have no more weight than royal instructions.

Consultative: of or pertaining to consultation; having the right or power to advise or join in consultation; deliberative, advisory: said chiefly of a body whose function is to take part in a consultation, but not to vote upon the decision.

1583 Stubbes Anat. Abus. ii. 107 To have a consultatiue, exhortatiue, or consentatiue voice onely. 1846 Grote Greece i. xx. II. 91 The Council is a purely consultative body assembled+solely for his information and guidance. 1878 Gladstone Prim. Homer 117 In this consultative and executive body, discussion is quite free.