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I am very sorry to hear about the loss of your pet.
First of all, understand that medical malpractice is subjective (veterinary malpractice is medical malpractice). There is no specific "chart" or anything of this nature that determines what is medical malpractice and what is not. Every case is a case by case basis.
So is this medical malpractice? Likely, yes.
The elements of a cause of action in tort for professional negligence are: (1) the duty of the professional to use such skill, prudence, and diligence as other members of his profession commonly possess and exercise; (2) a breach of that duty; (3) a proximate causal connection between the negligent conduct and the resulting injury; and (4) actual loss or damage resulting from the professional's negligence." (See generally, 4 Witkin, Summary of Cal. Law (8th ed. 1974) Torts, § 488 et seq., p. 2749.) Budd v. Nixen, 491 P. 2d 433 - Cal: Supreme Court 1971.
So let us put this all together: Medical malpractice is a CLEAR departure from standard practice. The Plaintiff (client) must prove that this departure CLEARLY AND DIRECTLY caused the condition, and that another vet in a similar condition and place would not have caused the pet to perish.
I would talk to an attorney face to face. This may be something worth pursuing.
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