This excerpt taken from

Descenting
Judith A. Bell, DVM, PhD

Occasionally young kits have a prolapsed rectum, indicated by protrusion of bright pink tissue from the anal opening. This has been attributed to the descenting surgery, but rectal prolapses also occur in kits that have not had the surgery. It may be due to the weaning process, when kits suddenly eat only dry food without the laxative effect of milk. Firmer, drier stool causes mild straining that may induce a temporary rectal prolapse, which usually disappears without treatment. Proliferative colitis can also cause rectal prolapse.

Read More on Prolapsed Rectum

Severe diarrhea may cause prolapsed rectum. This is an emergency, and the ferret should be seen by a veterinarian as soon as possible.