Updated: September 23, 2014
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:
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
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:
Treatment for crop stasis may include any combination of:
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:
Crop stasis refers to a condition where the crop, which is a diverticulum of the esophagus, stops emptying and becomes distended with fermenting food and fluids. This is a serious, life-threatening condition and needs to be treated by a veterinarian immediately.
Normal Digestive Process
The upper gastrointestinal of pet birds has several unique features and when food is ingested, it goes through the following process:
Movement of food from the crop to the proventriculus to the ventriculus is dependent on highly coordinated contractions (peristalsis). If the proventriculus is empty, food will move immediately into the proventriculus without being retained in the crop. If food is present in the proventriculus, it will be stored in the crop.
In birds with normal gastrointestinal tract motility, peristaltic waves can be observed moving across the surface of the crop. These waves are easy to see in baby birds, since the crop lacks a covering of feathers. When the crop is filled with food, 1-3 peristaltic waves should move across the crop per minute. In normal birds, peristaltic waves are coordinated throughout the entire gastrointestinal tract, and the waves observable in the crop reflect movement of the gastrointestinal tract as a whole. Any disease process that inhibits peristalsis or disrupts its coordination will cause crop stasis.
Many diseases, both within the intestinal tract and in other organ systems, disrupt or inhibit peristalsis. Additionally, any physical obstruction occurring along any point within the gastrointestinal tract will cause food to back up into the crop. There is a tendency to think of crop stasis as a problem with the crop itself. Although disease within or surrounding the crop can cause crop stasis, the disorder more often lies in the lower intestinal tract or disease in other systems. It may help to think of the crop as a kitchen sink. When the kitchen sick backs up, the problem is in the plumbing, not in the sink itself.
There are many causes of crop stasis in birds. Crop stasis can be caused by diseases of the digestive tract or can occur as the result of toxicities, disease of the nervous system or metabolic diseases. Many contagious diseases cause crop stasis, so it is important to inform your veterinarian of any potential contact - direct or indirect - with other birds. Possible causes of crop stasis in birds include:
A thorough history is extremely important in the diagnosis of crop stasis. Be prepared to tell your veterinarian:
Your veterinarian will recommend specific diagnostic tests depending on the duration of crop stasis, whether the crop is emptying slowly or not emptying at all, the age of the bird and if other symptoms are present. To find the cause of crop stasis in adult birds extensive diagnostic testing is usually required. Any combination of the following may be recommended:
Your veterinarian may recommend one or more of the diagnostic tests described above. In the meantime, treatment of the symptoms might be needed, especially if the problem is severe. The following treatments may be applicable to some, but not all birds with crop stasis. Therapy is not a substitute for definite treatment of the underlying disease responsible for your bird's condition.