Regurgitation in dogs: diagnostic approach
Regurgitation in dogs is generally indicative of a condition affecting the oesophagus.1
Introduction
Regurgitation is defined as the retrograde expulsion of food and/or fluids from the oesophagus due to functional impairment or mechanical obstruction.2
However, owners cannot always tell the difference between regurgitation and vomiting or even expectoration.3 It is therefore important to determine whether the patient genuinely regurgitates or not during their first visit, since this will have a direct bearing on possible differential diagnoses and the tests required. Regurgitation is characterised by passive evacuation of fluids or food, usually with an undigested appearance, from the oesophagus.1,3 On the other hand, vomiting is an active process that evacuates the remains of wholly or partially digested food from the gastrointestinal tract in a coordinated action that also involves the nervous and musculoskeletal systems.1
Pathophysiology
The oesophagus carries solids and fluids from the oral cavity to the stomach. From an anatomical perspective, the canine oesophagus is formed from striated muscle and innervated by somatic branches of the vagus nerve. On swallowing, the cranial oesophageal sphincter relaxes to allow solids and fluids to enter the proximal oesophagus. This simultaneously triggers a series of primary and secondary peristaltic contractions that push the contents to the distal stomach. Here, the stomach sphincter temporarily relaxes to allow the food bolus into the stomach.1,3
Regurgitation in dogs: differential diagnosis
The presence of regurgitation is established based on a thorough anamnesis of the case and physical examination, plus other signs of oesophageal disease, such as owners reporting that their dog makes several attempts to swallow food, changes in the dog’s appetite or signs of odynophagia, dysphagia, excessive salivation, etc.1 If the owners cannot provide much information, it may prove useful if they could record a video of the animal when it is eating or showing any of the reported signs.3
Once the presence of regurgitation has been established, the next step is to assess the potential differential diagnoses.1
Oesophageal lesions may be due to:
- Inflammation: oesophagitis, gastro-oesophageal reflux, oesophageal fistula.
- Obstruction: oesophageal stenosis, hiatal hernia, neoplasms, gastro-oesophageal intussusception, foreign bodies, vascular ring anomalies.
- Changes in motility: idiopathic megaoesophagus, dysautonomia or oesophageal diverticula.1,2
Some of these are outlined below.
Oesophagitis is usually due to the ingestion of foreign bodies or irritating substances or to gastro-oesophageal reflux. The term ‘oesophageal fistula’ refers to an abnormal communication between the oesophagus and adjacent anatomical structures, usually the lungs or airways, although sometimes the fistula can extend into the pleural space or cervical tissue.1
Idiopathic megaoesophagus is the most common cause of regurgitation in dogs. It is characterised by the presence of hypomotility and progressive oesophageal dilation with regurgitation and a decline in body condition score.1
Dysautonomia is a neuropathy of the autonomic nervous system whose precise aetiology is yet to be determined. Initially discovered in cats, it has since been reported in dogs as well. It courses with oesophageal hypomotility and regurgitation.1,2
Oesophageal diverticula are circumscribed pouches in the wall of the oesophagus that interfere with normal motility patterns. They can be congenital or acquired.1,2
Oesophageal stenosis is a narrowing of the oesophagus caused by the ingestion of foreign bodies or irritating substances that damage the mucosa or by oesophageal surgery. It may also be the result of intraluminal or extraluminal masses (neoplasms and abscesses).1
Hiatal hernia is due to the cranial displacement of part of the stomach and the abdominal oesophagus through the oesophageal hiatus (sliding hernia). This is the most common form in dogs. It can also be caused by stomach herniation in the mediastinum adjacent to the oesophagus (paraoesophageal hiatal hernia).1
Oesophageal neoplasms can affect the normal passage of food through the oesophagus, leading to regurgitation. These are estimated to account for < 0.5% of tumours in dogs. They may be primary (mainly osteosarcomas and fibrosarcomas), metastatic or spread from tissues next to the oesophagus.1
Foreign bodies (typically bones and coins) are a common cause of oesophageal disease with regurgitation in dogs.1,2
Vascular rings are congenital malformations of various arteries which, due to their anatomical location, press on the oesophagus, preventing the normal passage of food. Although a persistent right aortic arch is the most common form of vascular abnormality, others include an aberrant left or right subclavian artery, right dorsal aorta, double aortic arch, left aortic arch or right arterial ligament.1,2
Gastro-oesophageal intussusception is a rare disease that generally affects puppies. It is an invagination of the stomach into the oesophagus. Most dogs with intussusception already have an underlying oesophageal disease (usually megaoesophagus). Gastro-oesophageal intussusception is a serious and potentially fatal condition.1
Lastly, regurgitation is considered a common postoperative complication in dogs that have had surgery for brachycephalic syndrome, especially young dogs.4
Regurgitation in dogs: diagnostic approach
The diagnostic approach to regurgitation in dogs should include a blood count, full blood biochemistry, urinalysis and stool analysis. This initial information can be used to rule out systemic or metabolic diseases that may cause oesophageal clinical signs.1,2
- As for diagnostic imaging tests, these should initially include plain X-rays of the neck and chest.If these do not lead to a diagnosis, contrast-enhanced X-rays and videofluoroscopy are then indicated.
- Endoscopy can be very useful in the assessment and treatment of these patients, particularly in cases of stenosis, oesophagitis or the presence of intraluminal masses or foreign bodies.
- Lastly, oesophageal manometry and gammagraphy may facilitate the diagnosis of certain motility disorders, although these techniques are only available in a few referral centres, so their use is limited to cases in which the above methods fail to reach a conclusive diagnosis.1,3
Conclusions
Although it may sometimes seem unnecessary, the first step when assessing regurgitation in dogs is to determine whether the patient has been regurgitating, vomiting or expectorating, as this is not always clear from the initial information provided by the owner. The most appropriate diagnostic tests should then be selected, starting with the simplest before using more complex tests, depending on each case. For instance, for regurgitation in a German Shepherd puppy, the primary clinical suspicion should be a persistent right aortic arch, so X-rays should be taken to confirm this diagnosis (left deviation of the trachea and oesophageal dilation of the portion cranial to the heart).
