From the book the Joy of Chinchillas
If your animal is straining to pass feces, this can be sery serious. The worst case scenario is that the intestines get pushed out. This can also happen in severe diarrhea. If you get to a veterinarian quickly (and before tissue death), the intestines can be pushed back in and the rectum loosely sutured shut. The animal is put on a low dose of an atropine derivative to slow down the movement of the smooth muscles of the intestines. It also sedates the animal for the next ten days. For the next ten days, keep the animal quiet, and on a bland soft diet of baby food and cereals (not rice cereal because it causes constipation). When the stitches are removed, gradually return to a normal diet. CAUTION: the atropine is to slow down the motility of the bowel, to stop the chinchilla from further straining. If the problem is an obstruction )and your veterinarian should have ruled that out) the further slowing of the bowel could lead to gangrene of the bowel, and death of the chinchilla. Your care and attentive observation of your animal will be the key to it's recovery.