What Causes Bleeding After Uterus Removal?

Hi... My mom is 52 years old. 6 months before she got bleeding Suddenly. Then she undergone an uterus removal operation and stone which was found near uterus was also removed. That stone is normal fluid stone known after biopsy. Now again she s gettin bleeding. Ultrasound scan says no adnexal masses or fluid. Actually what is the problem.? Really scared. Pls clear us.