My cat is 13 years old. She is having a hard with getting rid of her bowel movement so she drags her behind. What can I do to help her?

,Constipation and Your Cat (http://www.petshealth.com/dr_library/felconstip.html) you may find this helpful. I will say that one of my cats is over 11 years old and he has never had this problem, he eats 1/2 can of wet food with his dry food every day. I also keep an eye out to make sure I see him drinking water.