Constipation in cats can be minor or major: poor or abolished peristalsis can be severe in certain individuals and are difficult to treat.
Surgery/peristaltic agonist medications/dietary Rx are all used to establish normal or semi-normal outflow. Minor cases can be treated with stool softners and laxatives while under medical supervision. I have even used cow's milk to cause a low grade loose stool in some minor cases (some animals become lactose intolerant and this can cause bloating/cramping so be careful).
The pumpkin is a vey good stool softner, also. Have your veterinarian obtain some lactulose for you, it is a sweet, thick and sticky liquid and should help. Also discuss dietary changes that may help. My recommendations are too generic to help the individual case.
Dr. Van Lienden
Dr. Raymond Van Lienden DVM
The Animal Clinic of Clifton
12702 Chapel Road, Clifton
Virginia, U.S.A. 20124