Topography of the gastro-oesophageal junction in the dog revisited: possible clinical implications

A Comparative Assessment of the Diagnosis of Swallowing Impairment and Gastroesophageal Reflux in Canines and Humans

Swallowing impairment is a highly prevalent and clinically significant problem affecting people and dogs. There are myriad causes of swallowing impairment of which gastroesophageal reflux is the most common in both species. Similarities in anatomy and physiology between humans and canines results in analogous swallowing disorders including cricopharyngeus muscle achalasia, esophageal achalasia, hiatal herniation, and gastroesophageal reflux with secondary esophagitis and esophageal dysmotility. Accordingly, the diagnostic approach to human and canine patients with swallowing impairment is similar. Diagnostic procedures such as swallowing fluoroscopy, high-resolution manometry, pH/impedance monitoring, and endolumenal functional luminal imaging probe can be performed in both species; however, nasofacial conformation, increased esophageal length, and the difficulty of completing several of these procedures in awake dogs are inherent challenges that need to be considered. Human patients can convey their symptoms and respond to verbal cues, whereas veterinarians must rely on clinical histories narrated by pet owners followed by comprehensive physical examination and observation of the animal eating different food consistencies and drinking water. Dogs may also be unwilling to drink or eat in the hospital setting and may be resistant to physical restraint during diagnostic procedures. Despite the species differences and diagnostic challenges, dogs are a natural animal model for many oropharyngeal and esophageal disorders affecting people, which presents a tremendous opportunity for shared learnings. This manuscript reviews the comparative aspects of esophageal anatomy and physiology between humans and canines, summarizes the diagnostic assessment of swallowing impairment in both species, and discusses future considerations for collaborative medicine and translational research.

Computed tomographic comparison of esophageal hiatal size in brachycephalic and non-brachycephalic breed dogs

OBJECTIVE

To determine whether an anatomical difference in esophageal hiatus (EH) size exists between brachycephalic and nonbrachycephalic dogs.

STUDY DESIGN

Retrospective clinical study.

ANIMALS

Client-owned dogs (n = 87).

METHODS

Clinical records and images of dogs that underwent computed tomography between June 2015 and September 2018 were reviewed. For the first part of the study, EH and aortic (Ao) cross-sectional surface areas were measured in brachycephalic (group 1) and nonbrachycephalic dogs of similar body size (<15 kg) without respiratory or gastroesophageal (GE) signs (group 2) by using multiplanar reconstruction. Esophageal hiatus:aortic ratio was calculated. In the second part of the study, absolute EH measurements were also compared in weight-matched (WM) dogs (8-10 kg) from groups 1 and 2.

RESULTS

Mean (±SD) of EH:Ao values for group 1 (8.1 ± 2.8) were higher (P < .0001) than those for group 2 (3.7 ± 1.1). In addition, EH measurements of 20 WM dogs in group 1 were higher than those of 20 dogs in group 2 (P < .05).

CONCLUSION

Esophageal hiatus cross-sectional surface area (directly and indirectly measured) in brachycephalic dogs was considerably larger than that in nonbrachycephalic dogs of generally similar body size.

CLINICAL SIGNIFICANCE

Results of this study provide evidence to support the existence of a specific anatomical factor that could likely correlate to functional GE alterations (eg, regurgitation, gastroesophageal reflux, and sliding hiatal hernia) commonly seen in brachycephalic dogs.

Clinical findings, diagnostic test results, and treatment outcome in cats with hiatal hernia: 31 cases (1995-2018)

Background

Information regarding clinical signs, assessment, treatment, and outcome in cats with hiatal hernia (HH) is limited.

Objectives

To characterize the clinical presentation of HH and medical and surgical outcomes in a cohort of affected cats.

Animals

Thirty‐one client‐owned cats with HH.

Methods

Medical records of cats with HH were retrospectively reviewed for signalment, history, results of diagnostic tests, details of surgical and medical treatments, complications, and outcome. Long‐term follow‐up data were obtained by telephone communication. Relationships between clinical variables and outcome were evaluated by regression analysis.

Results

Type I HH was present in 85.7% (24/28) of cats, and 64.5% (20/31) were >3 years of age at diagnosis. Twenty‐one of 31 (67.7%) cats underwent surgical repair including phrenoplasty, esophagopexy, and left‐sided gastropexy, and 10 of 31 cats were treated medically without surgery. Concurrent illness was common, and 77.4% cats had comorbidities. All cats survived to discharge, and median time to death or follow‐up was 959 days (range, 3‐4015 days). Cats treated medically survived longer than cats treated surgically, with median time to death or follow‐up of 2559 and 771 days, respectively.

Conclusions and Clinical Importance

Type I HH is the most common type of HH in cats. A congenital etiology is possible, but many cats with HH were >3 years of age at diagnosis and suffered from comorbidities, including upper airway obstruction. Case selection and the presence of comorbidities likely influenced the outcome. Cats with HH may not be diagnosed until disease is advanced or concurrent illness draws attention to clinical signs.

Clinical topographical anatomy of the gastro-oesophageal junction in the cat

Objectives The purpose of the present study was to describe histologically the gastro-oesophageal junction in the cat and interrelationships of this region. Our hypothesis was that cats are devoid of abdominal oesophagus. Methods Three centimetres of the terminal oesophagus, the phreno-oesophageal membrane with 1-2 cm margins of the diaphragmatic crural muscle and the proximal 3 cm of the gastric cardia were obtained from nine domestic shorthair cats and one domestic longhair cat that were euthanased for reasons other than digestive tract pathology. Longitudinal samples were examined histologically. Evaluated parameters included the location of the phreno-oesophageal membrane with reference to the transition between the oesophageal and gastric mucosa, the thickness of the circumferential smooth muscle of the muscular layer of the distal oesophagus at points 3 mm and 6 mm cranial to the mucosa transition, and the thickness of the circumferential smooth muscle layer at the mucosa transition level. Median differences in the thickness of the smooth muscle layer were compared by performing non-parametric statistical analysis using the Mann-Whitney U-test. Results The transition of the oesophageal to gastric mucosa was abrupt and corresponded to the point of insertion of the phreno-oesophageal membrane at the diaphragm level in all cats. The mean thickness of the circumferential smooth muscle layer at the point of oesophageal to gastric mucosa transition was significantly greater than the mean thickness of the oesophageal circumferential smooth muscle layer at 3 mm and 6 mm cranial to the mucosa transition ( P ⩽0.05). The increased muscle thickness at the gastro-oesophageal junction correlates with the accepted location of the high-pressure zone, reflecting the caudal oesophageal sphincter. It seems that the whole oesophagus was situated within the thoracic rather than the abdominal cavity. Conclusions and relevance No distinct abdominal oesophagus was observed in nine domestic shorthair cats and one domestic longhair cat. These findings might have implications for the pathophysiology of hiatal hernia in cats.

Histomorphology and immunohistochemistry of the lower esophageal sphincter of the least shrew (Cryptotis parva)

The biochemical and histopathological changes in the lower esophageal sphincter (LES) in the pathogenesis of gastroesophageal reflux disease have gained interest. The least shrew is able to vomit in response to emetogens and provides a good model to study the histology of this phenomenon relative to the published reports in the commonly used but vomit-incompetent laboratory species. The LES is located at the junction of the esophagus and stomach. It typically closes at rest and opens in response to swallowing. Our findings demonstrate that the least shrew does not have a well-defined LES, lacks esophageal glands and has a mucosal valve-like projection from the terminal end of the esophagus before joining the gastric epithelium at the lesser curvature. In addition, the least shrew has thoracic and abdominal components prior to joining the gastric epithelium. The mucosal lining of the esophagus is folded, becoming clearly convoluted and forming a bucket-like structure at the level of the esophageocardiac junction (ECJ). No significant differences are to be found between the structure and thickness of the wall before and after the ECJ. Thus, the ECJ forming the LES is relatively less complex than those of other mammals including man. The distribution of enterochromaffin (EC) cells is confined to the lamina propria of the junction and is not associated with the cardiac glands, suggesting its functional involvement with the smooth muscle in and around the ECJ. In conclusion, the least shrew's anatomical sphincter appears ill-defined and is replaced by a less sturdy valve-like mucosal flap.

Hiatal Hernia in the Dog: A Clinical Report of Four Chinese Shar Peis

Four Chinese shar pei littermate puppies were presented for vomiting, regurgitation, hypersalivation, and poor growth. Diagnosis of hiatal hernia was made for each of the four dogs based on survey radiographs and barium esophagram studies. All dogs initially underwent medical therapy, to which only one dog responded. All dogs underwent surgical treatment, which included manual hernia reduction followed by phrenoplasty, esophagopexy, and left incisional gastropexy, 5 to 40 days following initiation of medical therapy. The three surgical techniques described eliminated the need to enter the pleural cavity and offered excellent long-term results with no recurrence of clinical signs following surgery.