In my opinion, this will be a tough case. The normal statute of limitations on a medical malpractice claim in California is one year from the date the malpractice occurred or from the "discovery" of the malpractice. First hurdle will be trying to argue that you didn't discover that they had removed your full stomach until 10 years later. The second hurdle will be whether or not you "consented" to a full stomach removal vs. partial gastric bypass.
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As I am not a California attorney, I can't speak to specific laws that might affect your case. However, I can address the medicine involved and what likely happened.
First, the statute of limitations likely bars any legal action as your surgery occurred so long ago.
Second, my guess is that when you had the surgery you signed a lot of paperwork beforehand. If you look closely at the fine print, you probably consented to the procedure and all it was intended to do. You may not have been given an opportunity to verbally hear all of the details, but it was probably in the consent papers that you signed.