This is a common occurrence in captive hens, most notably in cockatiels, budgerigars, and lovebirds. Usually these birds are chronic egg layers, and calcium deficiency, general depletion of nutritional stores, and potential oviductal inertia may be causes. Supportive care (ie, rehydration, injectable calcium, increased humidity, warmth) before attempting extraction of the egg is critical.
Oxytocin and the avian equivalent, arginine vasotocin, both cause uterine contractions and may induce oviposition, as can the prostaglandins F2α and E2. If the egg is adherent to the uterine wall or unable to descend (often due to soft tissue swelling or collection of urates and stool), the administration of these drugs could theoretically lead to uterine rupture, but this has rarely been reported.
If the egg does not pass with medical management, inhalant anesthesia and manual extraction may be used. The decreased stress (due to decreased pain) and increased muscle relaxation warrant the slight anesthetic risk. The head and thorax should be held elevated to aid respiration. Barring adherence of the egg to the uterus, steady digital pressure applied between the end of the sternum and the egg will cause the slow descent of the egg. At this point, the uterus will often evert and reveal the white pinhole where the uterine opening is located. This opening will gradually dilate. Very seldom will any additional pressure or manipulation be required. After the egg is delivered, the uterus will normally involute. If any hemorrhage has occurred, antibiotics are indicated to prevent cloacal or uterine infection. Postoperatively, the hen will continue to be depressed, with labored breathing, and often will not appear clinically normal for 24 hr. A second egg may be produced by the following day, so repeated palpation is indicated.
Egg binding may also be seen in larger psittacines, although excessive previous laying is not as commonly associated with the condition in these birds. Obesity, general nutritional inadequacy, behavioral, and husbandry conditions may be involved.
Cystic Ovarian Disease
Birds with cystic ovarian disease often present with a history of previous egg production. Egg laying may not have occurred for several years. Owners may have noticed reproductive behavior until the recent onset of illness. Generally, these birds are depressed, inactive, and often dyspneic. Abdominal palpation often reveals distention with ascitic fluid.
The fluid from cystic ovarian disease is usually a transudate, although it should be examined for evidence of secondary infection or egg-yolk peritonitis. Careful aspiration of fluid from the ventral midline may relieve respiratory distress.
Radiographs, when the bird is stable, will often demonstrate hyperostosis of the femurs and other long bones. On the lateral view, the ventriculus will be displaced cranially, and a space-occupying mass will be noted in the renal and gonadal area. Ultrasonography can often detect cystic follicles, in additional to normal follicular development.
Treatment with leuprolide acetate (100–800 μg/kg, IM, every 30–45 days) will cause follicular atresia and a decrease in cystic ovarian size and activity. Surgery may not be needed if there is no concurrent infection or neoplasia.
This syndrome is extremely common in adult Umbrella and Moluccan cockatoos. The exact cause has not been proven, but the following characteristics have been associated with most cases: 1) hand-raised birds, 2) delayed weaning and/or continued begging for food, 3) close attachment to at least one person, 4) signs of either a child/parent or a mate/mate relationship with the owner, who may not be aware of these signs, and 5) a tendency to hold the stool in the vent for prolonged periods (eg, overnight), rather than defecating in the cage. Cockatoos that are independent of humans do not have this medical problem. Although the etiology is unknown, proposed causes include prolonged begging for food, causing straining and dilation of the vent; misplaced sexual attraction to a person, causing vent straining and movement; and retention of stool in the vent for prolonged periods, stretching and dilating the vent. The cause may be a combination of these factors.
If detected and treated early, surgery combined with behavioral modification can correct the problem and prevent secondary infections and other complications. Owners may be unwilling to alter their behavior, because often their attraction to the bird is due to its willingness to allow stroking and cuddling. If the bird still perceives its owner as either a parent or mate, it will continue to strain and the problem will likely recur. Behaviors that should be avoided include stroking the bird, especially on the back (ie, petting); feeding the bird warm foods, or food by hand or mouth; and cuddling the bird close to the body. If an owner is serious about trying to change their bird's behavioral patterns, consultation with a board-certified veterinary behaviorist who is experienced with psittacines is advisable.
Last full review/revision July 2011 by Teresa L. Lightfoot, DVM, DABVP (Avian)