Egg binding is defined as failure of an egg to pass through the oviduct at a normal rate.
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.
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.
Dystocia results when a developing egg in the distal oviduct obstructs the cloaca or causes oviductal tissue to prolapse. Affected eggs may be malformed or normal in size. Oviductal torsion and oviductal or abdominal masses compressing the oviduct can also obstruct passage of an egg and result in dystocia. Occasionally, a persistent right oviduct is the cause.
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 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.
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.
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.
Treatment for egg binding and dystocia varies depending on the severity of signs and the patient's overall condition. The primary goal is to stabilize patient in order that further treatment is possible. Supportive care includes increasing environmental temperature, fluids, and nutritional support. Parenteral calcium injections and injectable vitamin D and vitamin A may help to correct underlying problems due to nutrition. Broad-spectrum antibiotics may be indicated if the integrity of the oviduct or cloaca has been compromised by prolapse, surgery, or injury. Analgesics are indicated if the patient is likely to be in pain. In many cases, supportive care alone is enough to allow the egg to pass.
In cases of cloacal/oviductal prolapse, rapid management is necessary to prevent tissue necrosis. The prolapsed tissues need to be moistened, cleaned, and lubricated with sterile lubricant jelly. Handle prolapsed tissue with utmost care. Reduction of the prolapse may not be possible until the retained egg is removed. If an egg is located within the prolapsed tissue, the egg should be removed, and any lacerations or incisions repaired. After removal of the egg and flushing of the oviduct, any prolapsed tissue should be lubricated and replaced, and stay sutures should be placed if indicated.
Medical therapy may be used to induce oviductal contractions. These treatments may result in expulsion of the egg if there is sufficient oviductal contractility, the uterus is intact, the egg is in the oviduct, and there is no oviductal obstruction. Medicines useful for induction include oxytocin, prostaglandin F2alpha (Lutalyse), prostaglandin E2 (Prepidil Gel), and arginine vasotocin. PGF2a, oxytocin, and arginine vasotocin act specifically on the uterus, causing powerful uterine contractions. These three drugs do not, however, cause relaxation of the uterovaginal sphincter while inducing uterine contraction. Therefore, if the uterovaginal sphincter is not dilated, severe pain and /or rupture of the uterus is possible. PGE2 gel is more expensive but has several advantages over PGF2 a in that PGE2 is applied topically to the uterovaginal sphincter, so its effects are local, not systemic. PGE2 also causes relaxation of the uterovaginal sphincter while causing oviductal contractions. Contact with these drugs should be avoided by women.
In the author's practice, hens presenting for egg binding are generally administered warm LRS at approximately 3% BWt SQ, tube fed if necessary, and placed in an incubator. The patient is generally given an injectable vitamin ADEC combination (ADEC injectable, Vetafarm, www.vetafarm.com.au/) 0.10cc/150g BWt IM, and calcium gluconate 100mg/kg IM. After 8-12 hrs, the fluids and calcium injection are repeated, and one hour later PGF2a is administered. The author places a small cotton swab (the cotton bud from a Q-tip) saturated with PGF2a directly into the cloaca, where PGF2a is systemically absorbed. If there are no results the process is repeated in 8-12 hrs. The retained egg is generally produced after 1-2 doses of PGF2a. Side effects of PGF2a include hypertension, bronchoconstriction, and general smooth muscle stimulation. Wear gloves and avoid contact with the droppings of affected birds.
If supportive care and medical therapy fail to induce oviposition, manual delivery of the egg may be possible. With the patient under general anesthesia, sterile lubricant jelly is placed in the cloaca. Using a cloacal speculum (e.g. bivalve nasal speculum or curved Carmalt forceps) the vaginal opening of the oviduct can be dilated by inserting a lubricated cotton-tipped applicator that is gently advanced in a twirling motion. Careful digital pressure is applied to the egg, and it is gently massaged in a caudal direction.
Ovocentesis and implosion of an egg may be performed to facilitate its passage. If the egg is distally positioned, aspiration of the egg contents may be performed cloacally. The egg is manipulated so that it is visible through the cloaca, and a needle is inserted through the visible shell surface. The contents of the egg are aspirated into the syringe, while the shell is manually collapsed, and the pieces expelled through the cloaca. The author has found that removal or the shell fragments is easier if the empty egg shell is flushed with warm sterile saline and then filled with sterile lubricant jelly. The interior of the egg shell is then scored using a blunt probe (18ga curved feeding needle), and the shell is folded in on itself. As the shell collapses, sterile lubricant jelly surrounds the shell fragments, lubricates them, and dilates the oviduct. Using alligator forceps, removal of the shell fragments is easier than when using only saline, and the viscous nature of sterile jelly allows it to carry shell fragments with it. Following removal of shell fragments, the oviduct and cloaca are flushed with sterile saline, and radiographs are taken to ensure that all fragments have been removed.
If the egg cannot be visualized through the cloaca due to a more cranial location, transabdominal ovocentesis may be performed. The abdomen is aseptically prepared, and the egg is manipulated directly against the abdominal wall, displacing other abdominal organs so they are not damaged during aspiration. A needle is inserted through the skin and abdominal wall into the egg. The contents of the egg are aspirated into the syringe while the egg is manually collapsed. The patient should demonstrate immediate improvement of clinical signs relating to the pressure and volume of the retained egg. Eggshell remnants may be expelled through the cloaca naturally or with clinical assistance. If shell fragments are not expelled within 24-48 hours, it may be necessary to remove them either by a cloacal or laparotomy approach. Use radiographs to confirm that eggshell pieces have been completely expelled or removed.
Surgical removal of a retained egg or eggshell can be accomplished via a laparotomy. The left lateral approach to the abdomen generally provides the greatest exposure to the reproductive tract. The anesthetized hen is placed in right lateral recumbency with the left leg pulled caudally. Clear surgical drapes provide for greater patient monitoring. Radiosurgical instruments and hemostatic clips are essential to provide complete intraoperative hemostasis. Salpingohysterectomy should be considered in hens with a history of chronic egg-laying and/or egg binding, however, oviductal size and vascularity are increased during reproduction and increase surgical risk. Therefore, it may be prudent to perform a hysterotomy, remove the problem egg/shell fragments, and delay removal of the oviduct until the patient is more stable and the reproductive tract can be brought out of activity.
The oviduct is incised directly over the egg/shell fragments, avoiding obvious blood vessels, and the egg/shell fragments are removed. Gentle handling is essential, as the oviduct is fragile and easily tears. Examine the oviduct for gross abnormalities and collect samples for culture, cytology, and histopathology as indicated. The oviduct cannot be flushed with copious fluids, as flushing may introduce fluid into the respiratory tract (abdominal air sacs). Rather, sterile, saline-soaked cotton tipped applicators can be used to clean tissues prior to closing. The oviduct is closed with absorbable monofilament suture (e.g. 5-0 or 6-0 polydioxanone) in a simple continuous pattern. An inverting pattern is not recommended as this may reduce diameter of the oviduct.
After treatment it is recommended that affected hens be rested from reproductive stimuli for a minimum of 2-4 weeks, and for the remainder of the reproductive season if possible. Identify and correct the etiology that initiated dystocia prior to resuming breeding.
Potential complications of treatment for egg binding and dystocia include oviductal trauma, rupture of the egg, and displacement of the egg or fragments into an ectopic position. Coelomitis may result from the presence of yolk, eggshell fragments, or bacteria in the coelomic cavity. Retained shell fragments in the oviduct can lead to adhesions, stricture, granuloma, and blockage of the oviduct. Uterine infection, scarring, and stricture may result, even if egg/shell fragments are successfully removed.
Correct the likely causes of egg binding by proving birds with the proper diet and preventing obesity. Provide a staple diet of approximately 80% formulated pellets (e.g. Harrison's Bird Diet, Zupreem, Lafeber's, Roudybush, Kaytee Exact) and 20% fresh foods (vegetables, fruits, pasta, rice, beans, etc) is generally recommended. Seed mixes contain an overabundance of fat and inadequate protein and vitamins, and seeds allow for selective feeding. Anecdotal evidence suggests that a reduction in caloric intake will reduce or stop egg-production. Additionally, oatmeal, mashed potatoes, cooked rice and other warm, moist "mashes" need to be reduced or eliminated, as these may mimic the nuptial feeding behavior of nesting birds as they regurgitate to feed each other.
Environmental changes that need to made include a reduction of the photoperiod to 8-10 hours of daylight per day. Remove nest boxes, dark cavities, and all potential nesting materials (e.g. shredded paper). Allow any eggs that are laid to accumulate; do not remove them from the designated site so as to discourage the hen from laying further eggs to replace those which are removed. Cage furnishings (toys, perches, food dishes) should be rearranged, and the location of the cage should be changed so as to discourage territorial behavior and "broodiness". Toys, mirrors, and other items toward which the bird has a sexual affinity should be removed from the enclosure. Any perceived or actual mate should be removed from the cage or room. In some instances, visual and auditory separation from an actual or perceived mate may be necessary (as is often the case with cockatiels). Birds that have bonded with one person and may perceive that person as a mate should be cared for by another person. Stimulatory petting (rubbing the pelvis, dorsum, and cloacal region) and beak kissing should be avoided.
Leuprolide acetate (Lupron) is a long-acting GNRH analog that suppresses LH and FSH levels. Repeated injections down-regulate the ovary and prevent ovulation. Leuprolide 700-800µg/kg IM q14days for 3 injections usually stops reproductive activity. Maintenance of inactivity is possible with less frequent dosing. For best results, the environmental changes outlined above should be used in conjunction with this drug. Leuprolide is stable in a standard freezer for at least 9 months.
Salpingohysterectomy (removal of the oviduct) is indicated for the prevention of egg production and to resolve disease conditions associated with egg production. During reproduction the oviduct is hypertrophied and blood supply to the ovary and oviduct is significant. Therefore, it is recommended to delay surgery if possible until the reproductive tract is in an inactive state, thereby reducing the risk of hemorrhage to the patient. The oviduct is generally removed without the ovary, as removal of the ovary is technically challenging because of its proximity to major blood vessels. Through a feedback mechanism, removal of the uterus causes the ovary to remain inactive in most, but not all, pet bird species. Ducks, geese, and swans may still ovulate into the coelom, so removal of the ovary should be considered.
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