I found reference to one study from 1985 on how long it takes to know if cats are likely to recover urinary continence (Smeak DD, Olmstead ML. Fracture/luxations of the sacrococcygeal area in the cat: a retrospective study of 51cases. Vet Surg 1985; 14:319–24.).
"The prognosis based on a case series of 51 cats with sacrococcygeal injuries was good for return of normal urinary function in cats that had intact anal reflex and perineal sensation at the time of initial presentation. If normal urination returned, it did so between 2–30 days (mean 13 days). Every cat that could not urinate normally within 1 month remained incontinent during the 2–36 month follow-up period. Tail function may take several months or longer to improve. In the same study, tail function returned to its fullest extent between 7–150 days (mean 31 days). For this reason the authors do not recommend early tail amputation."
I found that summary in this article (which is about lots of issues around pelvic trauma, not just incontinence):
http://www-staro.vef.unizg.hr/org/kirur ... trauma.pdf
I do not know of any studies (though there may be some), but I do know of a cat whose case did not agree with the above statement from the study quoted. Raz (Erasmus) began urinating on his own at 14 weeks post injury.Philacatshia wrote:Every cat that could not urinate normally within 1 month remained incontinent during the 2–36 month follow-up period.
Here is a detailed thread about what all his family went through with him.
and here is an excellent website about his recovery timeline.