I am sorry to hear about Nismo's problems. How old is Nismo? Is the rectal prolapse improving? What is being done to treat the rectal prolapse and the infection?
There are nerves that control the anal and bladder sphincters that come off of the spine. If there is neurologic damage or malformation then these can lead to problems. Since the nerves come off the spine, are there any problems walking?
Does the pet have sphincter tone? During a neurologic examination, one of the tests done is to lightly pinch (I use light pressure with forceps) the sides of the anus and see if it 'winks' back. If it winks back, that is evidence that the nerves are working.
Can radiographs (X-Rays) be taken? Sometimes puppies can have congenital issues like spina bifida, etc...
I have also worked with some very young boston terrier puppies that will poop while they walk and it be a difficult behavioral issue.
I hope this helps
Christopher A. Lee, D.V.M., C.V.L.S.
Promoting surgical options and pet comfort through the use of lasers.