I have some experience with this and check out this website:
http://www.thensome.com/megacolon.htm
and if in doubt take your feline to another vet for a second opinion. Good Luck.
My 14 year old cat that I just had to put to sleep did the same thing. In the last 2-3 years of her life she started to pee outside the box when she got constipated. Evantually in the end she was unable to go by herself despite subQ fluids, lactulose several times a day, and cisperaide. Everyone told me thrroughout this time give her wet food but she just refused to eat any. I tried everything. I know this won't help much but it just seems liekt here were cycles of good and bad. Many people suggest getting more boxes, spyaring a non enzyme spray where they go, putting more water dishes out. The poop outside the box wasnt that bad it was the pee that was unbearable.
They also sell Pet-enema's online at amazon they are much better than the mineral oil ones. My cat surprising let me give them to her when she was really constipated and unbearable. Her issue was she would become Obstinated where only manually extraction would help.
hi, I 'm sorry I don't quite understand you're post, why do you think you're kitty is constipated because you find poop on the floor?
He maybe having a litter box issue but not necessarily constipated?
Are the stools hard and small or what?