History: There is increased respiratory effort on presentation with an out-pocketing of air in the neck visible at the thoracic inlet with each expiration. Herniation of lung through the thoracic inlet is suspected. The abdomen is distended. Lateral and ventrodorsal radiographs were acquired (Figure 1).
Images: Lateral and ventrodorsal views of the body.
- The cardiac silhouette is at the upper limit of normal for size, likely normal variation for the age.
- The pulmonary vessels are normal.
- In the ventrodorsal view there is focal alveolar opacity in the lateral margin of the right caudal lung lobe.
- The visible portion of the esophagus is markedly gas distended and causes ventral displacement of the trachea and compresses the heart base.
- The stomach is moderately distended with gas along with a lesser amount of fluid and multiple foci of mineral debris.
- Several small intestinal segments are at the upper limit of normal for size and contain gas.
- The serosal contrast is poor, consistent with the age of the patient.
- A primary consideration for the gaseous distention of the thoracic esophagus and stomach, and the gas within the small intestine, is pronounced aerophagia secondary to an upper airway abnormality such as a nasopharyngeal polyp. A generalized neuromuscular dysfunction affecting the esophagus and stomach cannot be ruled out however this is less likely.
- Most likely the reported outpouching of the neck during respiration is due to gas within the esophagus and not herniation of the cranial lung lobes through the thoracic inlet.
- The alveolar opacity in the right lung is most likely due to atelectasis secondary to the adjacent esophageal enlargement however a focal area of pneumonia, possibly due to aspiration, cannot be ruled out.
Megaesophagus in cats can occur secondary to various causes, including vascular ring anomaly, dysautonomia and congenital neuromuscular dysfunction. Myasthenia gravis is also a potential cause but the presence of smooth muscle in the feline esophagus reduces the incidence of this association.
The purpose of this patient description is to emphasize the extent to which, in cats, the esophagus and gastrointestinal tract can distend secondary to severe aerophagia. (Byron, Shadwick, & Bennett, 2010) Although aerophagia in dogs can also result in the presence of air in the esophagus and gastrointestinal tract, the degree of dilation seen here, especially in the esophagus, would be unusual for aerophagia in dogs.
This report also emphasizes the importance of evaluating for causes of upper airway obstruction in cats suspected of having severe aerophagia, and in young cats a common cause of such an obstruction is a nasopharyngeal polyp (Figure 2). Importantly, the gaseous distention of the esophagus and gastrointestinal tract due to aerophagia resulting from upper airway obstruction is often reversible. (Byron, Shadwick, & Bennett, 2010)
Byron, J., Shadwick, S., & Bennett, A. (2010). Megaesophagus in a 6-month-old cat secondary to a nasopharyngeal polyp. Journal of Feline Medicine and Surgery, 12, 322-324. doi:10.1016/j.jfms.2009.09.002