This could be due to a disc problem in the spine which is a likely cause for the lack of anal sphincter control. Disc issues in this breed are a known problem.
You can read about disc disease here
http://uwveterinarycare.wisc.edu/sa_services/surg/neurology/ivdd.htm
http://www.veterinarypartner.com/Content.plx?P=A&A=2373
This might also be due to a tail pull or break injury. Pulling on the tail can stretch and damage nerves, muscles and ligaments.
This could be due to a prostate problem or possibly a perianal tumor. Those can both block stool passage and might make raising the tail uncomfortable.
Netuered dogs can have prostate gland infections and tumors but its more common in intact males.
You can read about the prostate here
http://www.peteducation.com/article.cfm?c=2+2109&aid=914
and painful defecation is one symptom listed.
Hope this helps you!
Dog Expert:Rescue, Train,Breed,Care
30+ yrs dog home vet care & nursing, rescue, behavior&training, responsible show breeding, genetics