Egg binding is defined as failure of an egg to pass through the oviduct at a normal rate. Most companion birds lay eggs at intervals of greater than 24 hours. Individual birds can vary further, making it hard to determine if there is a problem in the early stages of disease. Dystocia implies mechanical obstruction or cloacal dysfunction, and is more advanced than egg binding alone. The most common areas for this to occur are the distal uterus, vagina, and vagina-cloacal junction. The prevention of chronic laying is important to the prevention of egg-binding and cloacal prolapses.

Etiology

Egg binding is multi-factorial in origin; its causes vary by species. Chronic egg laying can physically exhaust the reproductive tract and cause a serious metabolic drain, particularly on calcium stores. Calcium, vitamin E, and selenium deficiencies and other forms of malnutrition can play a role. Obesity and inadequate exercise can contribute to poor muscle strength. Oviductal disease such as trauma or infection can lead to smooth muscle dysfunction in the uterus.

Affected hens may have a genetic predisposition to egg binding or dystocia. Concurrent illness and stress may predispose an individual to problems. Birds that are bred out of their natural season and virginal hens are both predisposed to egg binding and dystocia.

Clinical signs

Clinical signs associated with egg binding and dystocia vary according to severity, size of the bird, and the degree of secondary complications. Small birds (finches, canaries, budgies, lovebirds, cockatiels) are frequently the most severely affected, possibly due to their small size. Common signs include acute depression and anorexia. Affected hens are frequently fluffed and are less vocal. Abdominal straining, distention, and cloacal prolapse may be present. Hens may exhibit a wide stance and persistent tail wagging. Respiratory difficulty may be manifested as open-mouth breathing or tail-bobbing. Failure to perch, lameness, weakness, or paralysis may occur. Sudden death is possible.

Pathologic processes

An egg that becomes lodged in the pelvic canal puts pressure on pelvic blood vessels, kidneys, and ischiatic nerves. Circulatory disorders, nerve damage, lameness, and paralysis may result. Pressure necrosis of oviductal wall can occur. Dystocia can interfere with normal defecation and micturation, resulting in ileus and renal dysfunction. Metabolic disturbances and pain may lead to anorexia, dehydration, and further deterioration. Compression of caudal thoracic and abdominal air sacs may lead to increased respiratory rate, dyspnea, and cyanosis.

Diagnosis/testing

The diagnosis of egg binding and dystocia can be made on history and physical examination alone. Frequently the patient is not stable enough to tolerate other diagnostic procedures. A rapid diagnosis and treatment are important for a successful outcome, and the patient may not be stable enough to survive other diagnostics. Physical examination may reveal depression, lethargy, poor body condition, or dehydration. Compression of the caudal thoracic and abdominal air sacs may result in dyspnea, increased respiratory rate, or cyanosis. Affected hens may not be able to stand or perch due to hind limb paresis or paralysis.

An egg is typically palpated in the caudal abdomen however cranially-located eggs, soft-shelled eggs, and non-shelled eggs may not be palpable. Eggs may be located within the oviduct or ectopically within the coelom. To locate the egg, careful abdominal palpation, cloacal examination, and radiographs are usually employed however ultrasound, laparoscopy, and/or laparotomy are sometimes required. Radiography and ultrasound aid in the evaluation of the number, size and shape of eggs. Soft-shelled or non-shelled eggs may not be visible on radiographs. If obstruction or motility disorders are present, multiple eggs may be identified.

Fecal examination, CBC, chemistries, and bacterial cultures are performed as indicated to identify any predisposing illness. Hypercholesterolemia, hyperglobulinemia, and hypercalcemia are normal in an ovulating hen. Hypocalcemia (low total and/or ionized calcium levels) may be observed if a hen has been on a calcium-poor diet or has been laying excessively, resulting in depletion of calcium stores. Care must be taken that stress due to diagnostic testing is minimized for unstable patients. Perform tests incrementally as supportive care continues.