Swallowing and regurgitation

1 Swallowing and regurgitation

The oesophagus and swallowing

The oesophagus is divided into the cervical, thoracic and abdominal parts.

The cervical oesophagus runs ventral and to the left of the trachea, and thoracic oesophagus runs to the left of the trachea until the tracheal bifurcation, where it is dorsal to it, and then moves to the right of the aortic arch. There is a short abdominal oesophageal segment between the diaphragm and the stomach. The oesophageal muscularis in the dog is striated throughout the oesophagus; whereas in the cat the caudal oesophagus (thoracic and abdominal sections) contains an increasing amount of smooth muscle until the final 2 to 3 cm which is entirely smooth muscle.

The gastro-oesophageal sphincter (GES) is important in maintaining a high pressure zone between the oesophagus and the stomach so that gastric contents are less likely to be refluxed into the oesophagus. The type of food eaten affects the GES pressure. Protein meals increase the pressure, likely due to an increase in gastrin. Fat decreases GES pressure due to cholecystokinin stimulation and also inhibition of gastrin mediated pressure increases.

The GES relaxes transiently to allow for eructation of gas; during this relaxation fluid may also be refluxed into the oesophagus. This is a normal event, but in some dogs it may occur excessively or the rate of clearance of the acid from the oesophagus may be delayed, resulting in oesophagitis.

Swallowing involves three coordinated phases: oropharyngeal, oesophageal and gastro-oesophageal. Pharyngeal contact with food stimulates pharyngeal peristaltic contractions that push the food from the base of the tongue to the laryngopharynx and into the oesophagus. In the oesophagus, the bolus is initially carried by the primary peristaltic wave generated by the pharynx. If the primary peristaltic wave does not result in the bolus reaching the stomach, a secondary peristaltic wave is initiated by local oesophageal distension. The swallowing reflex in the dog requires sensation of the bolus within the oesophagus. Oesophageal peristaltic speed is faster in the dog than in the cat; in dogs, water moves at 80 to 100 cm/second compared to 1 to 2 cm/second in the cat.


Regurgitation is expulsion of food or saliva from the pharynx or oesophagus and most often is caused by oesophageal disease.

Regurgitation must be differentiated from vomiting, although there are animals that present with both problems. Regurgitation is generally a passive action with no evidence of nausea. Some animals will retch due to the presence of food in the pharynx, which may be confused with an active action.

Regurgitated food is undigested and may be cylindrical in shape from having been formed in the oesophagus. The pH should not be acidic, although as gastric contents are not always acidic this may not be a useful way to distinguish between regurgitation and vomiting. Regurgitated material rarely contains bile, unless there has been gastro-oesophageal reflux prior to regurgitation. Regurgitation may occur immediately after eating or may occur several hours later, especially if the disorder is in the lower cervical or thoracic part of the oesophagus.

Dysphagia may occur in some animals with regurgitation and repeated swallowing attempts may be seen. Aspiration pneumonia is a serious risk in animals that are regurgitating and if present they may present with concurrent cough, respiratory distress or fever. Some animals with oesophageal disorders may also show nasal discharge due to ingesta entering through the nasopharyngeal opening.

In addition to aspiration pneumonia, common sequelae to chronic regurgitation are weight loss or poor growth as the animal is unable to assimilate sufficient nutrients.

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Sep 22, 2016 | Posted by in SMALL ANIMAL | Comments Off on Swallowing and regurgitation

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