Diagnosing and treating esophageal diseases in dogs and cats (Proceedings)
Basic anatomy and Physiology
The basic anatomical structures of the esophagus are the upper esophageal sphincter (UES), the body of the esophagus and the lower esophageal sphincter (LES). The entire canine esophagus is composed of two layers of striated muscle, while the distal third of the feline esophagus is composed of striated muscle1, 2. The esophagus is innervated by the vagus nerve and its branches (glossopharyngeal, pharyngeal, recurrent laryngeal nerves) 1. The UES, composed of the cricopharyngeus and thyropharyngeus muscles and the cricoid cartilage, remains closed at all times, relaxing momentarily to allow passage of a bolus 2. The LES is a physiologic rather than a true anatomic sphincter2. It is composed of an outer longitudinal muscle layer and an inner smooth muscle layer 2. In health, the LES remains closed except to allow passage of a bolus and prevents reflux of stomach contents into the esophagus 2. Esophageal peristalsis is stimulated by the oropharyngeal stage of swallowing and the movement of a bolus across the UES (primary peristalsis) as well as by distension of the body of the esophagus by the bolus (secondary peristalsis) 2.
Clinical signs of Esophageal DiseaseRegurgitation is the hallmark clinical sign of esophageal disease. Differentiation of regurgitation from vomiting is essential. Regurgitation is the passive, retrograde movement of ingested material, usually before it reaches the stomach. Food and fluid move in an orad direction by force of gravity. Regurgitated material is expelled with minimal or no premonitory signs of nausea, distress or retching / abdominal effort. The regurgitant material originates from the oral cavity, pharynx or esophagus and as such is usually undigested. Regurgitation may occur immediately after intake of food but is often delayed for several hours or more. Additional clinical signs can include repeated attempts to swallow a single bolus, painful swallowing and failure to thrive or loss of body condition. Aspiration pneumonia, (dyspnea, cough, nasal discharge, fever, moist crackles on thoracic auscultation) is a common complication1.
Persistent right aortic arch (PRAA)
Vascular ring anomalies are congenital malformations of the major vessels of the heart that entrap the esophagus and cause esophageal obstruction1. The most common vascular ring anomaly in dogs and cats is persistence of the right aortic arch. The esophagus and trachea are entrapped by the pulmonary artery / heart base on the left and ventrally, the aorta on the right, and the ligamentum arteriosum dorsolaterally on the left1. Clinical signs of regurgitation and failure to thrive (stunted growth, thin body condition) most commonly develop at the time of weaning, when the animal first attempts to ingest solid food. Respiratory signs such as cough, dyspnea, nasal discharge and fever signal secondary aspiration pneumonia. Plain thoracic radiographs are potentially diagnostic and may reveal: (1) Lateral: esophageal body dilation cranial to the base of the heart and possibly ventral curvature of the trachea cranial to the heart; (2) VD or DV: Leftward deviation of the trachea cranial to the cranial border of the cardiac silhouette is a reliable sign of PRAA in dogs.1,3 Abrupt attenuation of the barium column at the base of the heart and cranial esophageal dilatation is expected on barium contrast esophagram. Thoracic radiographs must be carefully evaluated for other intrathoracic pathology or anomalies and evidence of secondary aspiration pneumonia. In some cases, fluoroscopic or computed tomography evaluation may be necessary. Definitive treatment is surgical ligation and transection of the ligamentum arteriosum1. Supportive care may need to include treatment of aspiration pneumonia (broad spectrum antibiotics, supplemental oxygen, nebulization, etc) and gastrotomy tube feeding. 90% of animals display significant clinical improvement post-operatively1. Some degree of esophageal hypomotility and regurgitation may persist post-operatively, especially if clinical signs were severe and / or longstanding. Early diagnosis and prompt treated is recommended1.