We follow the halachic ruling that a woman typically observes a modified process of becoming tehorah following a total hysterectomy, out of stringency: waiting seven days from the procedure, disregarding bleeding, then immersing without a blessing. She then does not become niddah again.
In the case of a hysterectomy with the cervix remaining, there is concern that some uterine lining might be retained. In that case, one can still become niddah. This cannot be known until after the procedure. If some residual uterine tissue that could theoretically still bleed is retained, please get back to us with more information.
Please write back with any further questions.