Cloacal prolapse or vent prolapse is a condition where the inner tissues of the cloaca protrude (hang out) from the vent, exposing the intestines, cloaca or uterus. The cloaca is the part of the bird’s body which stores urates, feces, urine and egg. The cloacal lips (or vent) are used to control the passage and frequency of droppings and other eliminations.
Mature Umbrella and Moluccan cockatoos suffer more often from cloacal prolapse, as do hand-fed birds. However, cockatoos not bred by humans are not affected by cloacal prolapse.
Cloacal prolapse occurs when long-term strain is put onto the vent. Usually the reasons are both physical and behavioral.
Hand raised and hand fed birds with delayed weaning show a greater tendency towards cloacal prolapse. Birds who are extremely attached to one person and recognizing the person as either a mate or a parent also have a higher chances of having cloacal prolapse. Such birds will hold feces for long time, and also cry out for food thus repeatedly strain their cloaca and vent in the process. The misplaced sexual attraction towards the person also causes stretching and opening of the vent.
It also occurs in birds that have a habit of holding in the stool for long periods of time, like overnight, instead of dropping it as it is comes to cloaca.
Any combination of the above reasons can lead to straining, dilating and stretching of the vent, making the bird an ideal candidate for cloacal prolapse.