Regurgitation occurs when there is either an anatomic obstruction or a physiologic weakness in the esophagus. In either case, food is retained in the esophagus and, if it passively migrates back into the oropharynx, can be regurgitated. The problem should be diagnosed quickly in an attempt to solve it before the esophagus becomes irreversibly-dilated or the patient experiences an aspiration pneumonia.
First, be sure to try to distinguish vomiting from regurgitation. We usually start doing this by considering the history and physical examination. This can be hard to do, and the following are guidelines only — some animals that clearly appear to be vomiting are in fact regurgitating and vice-verse. In particular, it is very easy for a vomiting dog to appear to be regurgitating. However, these guidelines are still useful and usually point us in the correct direction.
If you are still confused as to whether the patient if vomiting or regurgitating, the most definite method of distinguishing vomiting from regurgitation usually consists of performing plain thoracic radiographs, possibly followed by a barium contrast esophagram. There are some causes of regurgitation that will be missed by such studies, but they are far and few between.
- Prodromal nausea is commonly found with vomiting. Since vomiting is a centrally-mediated response, other signs such as salivating, discomfort and "gurgling" stomach are often seen beforehand. Many animals that are about to vomit will pace, whine or show some sort of anxiety or discomfort. With regurgitation the animal may be sitting and suddenly "gag" up some material. In general, animals know that they are going to vomit, but they are often unaware that they are going to regurgitate until they actually start doing it. Sometimes the regurgitation is as much a surprise to them as it is to the client. These are not absolutes - animals don't always read the book.
- Retching typically follows prodromal nausea and is characterized by forceful, abdominal contractions in animals that are vomiting. (You will see some abdominal contractions with regurgitation but they are not severe or forceful and they do not tend to be repetitive.) If you're not sure what retching is like, just think back to the last time you had to vomit. Don't just ask owners "Did the animal retch?" because they may consider any contractions of the abdomen to be retching. Clearly describe precisely what you mean so that they can give you an accurate answer.
- The material the animal expels sometimes help us distinguish what is going on. If possible, let the client describe the material first so they're not just agreeing with you to make you happy. So-called "undigested" material can be either vomited or regurgitated. If it is digested, then this would indicate that the material came from either the stomach or intestines; however, it can be very difficult or impossible to visibly differentiate undigested material that was chewed up, mixed with mucus and saliva and has been sitting in the esophagus for a long time from digested material.
Mucus can come from either the salivary glands (i.e., the regurgitating animal) or the stomach (i.e., the vomiting animal).
- Red blood can be seen with either vomiting or regurgitation, but semi-digested blood that looks like coffee grounds is only seen with vomiting. However, finding digested blood does not ensure that the bleeding originated in the stomach.
Bile indicates that the material is from the stomach or intestines. Bile is a green, yellow or dark brown color. Don't just ask if the animal is vomiting bile; many clients assume that vomitus contains bile (i.e., my animal "vomited", therefore it must have vomited bile). Clearly describe what you mean by "bile".
- The amount of material ejected from the mouth varies from large to small with both vomiting and regurgitation. Likewise, the timing of the episode relative to eating can vary from immediately after eating to 1 ½ days after the last meal, regardless of whether the animal is vomiting or regurgitating. Don't forget that you can regurgitate mucus even though you have not eaten for days.
Physical examination may also help distinguish vomiting from regurgitation. Occasionally the esophagus is so dilated and flaccid that it can be seen expanding and collapsing near the thoracic inlet as the animal breathes (much like a bellows). A particularly nice trick is to test the expelled material with a urine dipstick. If the pH of the material that the animal spit out is < 5 or if bile is present, then the material has been vomited. Otherwise, it has probably been regurgitated. Do not trust the reaction for blood. It is invariable positive and does not help distinguish vomiting from regurgitation.