Yup, Manx kitties sometimes have problems with incontinence or constipation because of their tails; the danger with the constipation is that it could lead to Megacolon. Lactulose is a softener frequently used with spinal cord injured critters; it's Rx, but cheap, and it's a sweet, yummy liquid you can put on food or whatever. The best thing is that it's consistent and easily measured for consistent (can't think of a synonym) results.