The spotting after a hysterectomy is generally from the vaginal wall. The blood is not hormonal blood from the uterus (dam niddah) but the result of trauma (dam makkah) and, as such, does not render a woman niddah. As long as a woman is not in niddah going into the procedure, the procedure should not render her niddah.

Since a total hysterectomy presents the last time a woman will have uterine bleeding, we generally recommend immersing a week following the procedure, without bedikot or a bracha. But in your case, where you have had no bleeding for years, no immersion is needed.

Refuah sheleimah!