Dr. Barbara Oglesbee
Updated: September 23, 2014 Obstruction – ingested foreign objects or neoplasia (tumors)
The crop is a pouch-like enlargement of a bird's esophagus. It is located at the base of the neck, between the jaw and the breast muscle. The crop functions to store and moisten food, and can hold a large volume. Food from the crop is gradually passed into the stomach throughout the day. The crop also stores food to be regurgitated to feed baby birds or the bird's mate, during nesting. Crop stasis is a condition in which the crop fails to empty at a normal rate.
Normally, ingested food moves from the crop through the thoracic esophagus, to the first stomach, called the proventriculus. From there, it moves to the second stomach, the ventriculus, then through the intestines. Movement of food through the entire gastrointestinal tract is controlled by highly coordinated waves of contractions, called peristalsis. Disruption of peristalsis prevents food from moving through the intestinal tract, causing food to back up into the crop. Crop stasis is similar to a clogged drain, where the sink fills up with water. Just as the problem is not the sink, but the drain, most cases of crop stasis is caused by disease in the lower intestinal tract, not the crop itself.
Obstruction of the intestinal tract at any point can also prevent food from moving. If the bird continues to eat (or is force fed) in the face of gastrointestinal tract obstruction or disruption of peristalsis, food will eventually back up into the crop.
There are many causes of crop stasis. A few of the most common include:
Viral diseases –especially Avian Bornavirus (Proventricular Dilatation Disease) and, in young birds, Polyomavirus
Bacterial infection - occurring anywhere in the intestinal tract
Fungal infection - in the crop or proventriculus
Metabolic diseases – liver disease, pancreatitis
Toxins – especially heavy metals such as lead or zinc
Improper feeding formula – in young, unweaned birds
Baby birds that are being hand-fed a feeding formula may develop crop stasis due to improper temperature of the formula (too hot or too cold), improper consistency of the formula (too thick or thin), or environmental problems, such as a cold temperature or low humidity.
What to Watch For
Vomiting, regurgitation or diarrhea
Overdistension of the crop
Undigested food in the droppings, or a foul odor to the droppings
Listlessness or lethargy - excessive sleepiness, ruffled feathers, tucking the head under the wing. These symptoms warrant an immediate visit to the veterinarian. Birds that are too weak to stay on a perch are in critical condition.
Decreased appetite in adult birds
Lack of a feeding response (bobbing or begging) in baby birds
The veterinarian will recommend specific diagnostic tests depending on several factors, like the duration of crop stasis, whether the crop is emptying slowly or not emptying at all, the age of the bird and other symptoms that are present. To find the cause of crop stasis in adult birds extensive diagnostic testing is usually required.
A complete history is extremely helpful in reaching a diagnosis. Be prepared to tell your veterinarian when you first noticed a slow-down in crop emptying, the type and consistency of feeding formula, and if other symptoms are present. Additionally describe your bird's chewing habits and note any potential exposure to other birds.
Diagnostic testing your veterinarian may perform include:
A thorough physical examination
Sampling the crop and/or feces for bacterial culture and cytology (looking at cell types for evidence of infection or inflammation)
A complete blood count (CBC) and serum biochemistry panel
Radiography (X-Rays) to look evidence of intestinal disease, size and density of the liver, kidneys or other organs. Often a Barium contrast study is needed to detect slowing of intestinal motility or the presence of foreign material and tumors.
Infectious disease testing – especially for Avian Bornaviruses, Polyomavirus and Chlamydia
A surgical biopsy of the crop may be needed to diagnose Bornavirus
Endoscopy – viewing the intestinal tract an endoscope to collect samples for biopsy or culture
Treatment for crop stasis may include any combination of:
Hospitalization for intravenous or subcutaneous (under the skin) fluids and injectable medications for critically ill or dehydrated birds
Antibiotics or antifungal medications
Anti-inflammatory medications, such as celecoxib or other non-steriodal anti-inflammatory drugs, if bornavirus is confirmed or suspected.
Medications to protect the intestinal tract , such as antacids, or medications alter the motility of the intestinal tract such as metoclopramide.
Surgery or endoscopy to relieve intestinal obstructions
If the gastrointestinal tract is functioning properly, the crop of a normal adult bird should empty at a regular rate. Generally, the crop remains relatively small and not noticeable by most bird owners. If you notice a swelling on the neck just before the entrance to the thorax, and the swelling does not decrease in size or disappear after a few hours, consult your veterinarian.
The crop in neonatal or baby birds is much more noticeable, since it is larger than an adult's crop and it does not have the same covering of feathers. The crop should empty at a steady pace following feeding. If the crop is not emptying at a normal rate, make sure the temperature and consistency of the food is correct, and that the bird is housed at the proper environmental temperature and humidity. If the crop is not emptying properly following theses measures, seek veterinary attention.
After seeing your veterinarian, be sure to:
Give all medication as directed, for as long as directed, even after the symptoms appear to be gone.
Watch for a change in the droppings, or the development of vomiting, regurgitation and report any changes to your veterinarian.
If improvement is not seen, report this to your veterinarian.