Imaging Evaluation of Dogs and Cats with Dysphagia

The current literature is reviewed in this paper regarding the application of diagnostic imaging in the evaluation of swallowing disorders of the dog. The applications of radiography, contrast radiography, and contrast videofluoroscopy are discussed with pertinent case examples provided for emphasis. The indications for image-guided interventions are also described. 1. Introduction Dysphagia, or difficulty with swallowing, is a clinical symptom that may arise from a variety of diseases. Traditionally, dysphagias are classified based on the location of the abnormality (Table 1) [1, 2]. Oropharyngeal dysphagias involving the oral phase of swallowing typically result in abnormal prehension and can be diagnosed by watching the patient eat. However, oropharyngeal dysphagias affecting the pharyngeal and cricopharyngeal phases of swallowing often present with clinically similar signs such as gagging, retching, and the necessity to attempt swallowing multiple times prior to success. Myotomy or myectomy may result in clinical improvement in patients with delayed or absence of opening of the upper esophageal sphincter but animals with disorders of pharyngeal contraction will become clinically worse with surgery [3]. Moreover, animals with combined disease affecting both the pharyngeal and cricopharyngeal phases of swallowing may be poor surgical candidates. Table 1: The origin and types of dysphagia are described. Standard veterinary diagnostic imaging techniques can provide information regarding pharyngeal, cricopharyngeal, and esophageal anatomy [4]. However, many disease processes more specifically affect function with little or no anatomic alteration. In addition, certain anatomical alterations such as hiatal hernias are transient such that the point-in-time imaging capabilities provided by plain radiography may not capture the abnormality. Functional and transient abnormalities are particularly common in dysphagic animals. Although radiographs with or without oral barium administration may help define certain causes for dysphagia, real-time imaging techniques such as contrast fluoroscopy provide a means for visualizing esophageal function allowing for detection of subtle and transient abnormalities [4]. 2. Normal Swallowing Anatomy and Physiology Swallowing is a complex physiologic process that propels a bolus of liquid of food from the oral cavity to the stomach. The actions involving the lapping of liquid and prehension and chewing of food are voluntary and require coordinated movements of the tongue and jaws. Once a bolus is propelled into the pharyngeal