Oropharyngeal and Esophageal Diseases

2. Oropharyngeal and Esophageal Diseases

Swallowing Disorders and Diseases of the Esophagus

Clinical Signs Associated with Swallowing Disorders

Dysphagia is defined as difficult or painful swallowing (odynophagia) and can result from conditions of the oral cavity, pharynx and esophagus. The complete swallowing sequence involves oropharyngeal, esophageal and gastro-esophageal phases. The oropharyngeal phase can be further subdivided into oral, pharyngeal and cricopharyngeal stages. Abnormalities of any of these stages can result in dysphagia. Disorders are usually functional or morphological; most functional disorders are the result of failure, spasm or incoordination of the normal neuromuscular activity. Regurgitation is almost effortless expulsion of food from either the oropharynx or esophagus. This should be differentiated from vomiting (Table 1).

The main clinical signs associated with swallowing disorders are listed in Table 2.

Diagnosis of Esophageal Disease

For animals presenting with esophageal disease, a staged approach to diagnosis is usually required.

Signalment and History

Breed, gender and age can all provide clues as to the likely diagnosis. In this regard, young dogs are more likely to suffer from congenital diseases. A thorough history is essential, in order to establish the pattern of clinical signs, in terms of duration, progression, frequency and severity. Further clues as to the underlying etiology may be evident e.g., ingestion of a foreign body.

Physical Examination

Physical examination is often normal although, if regurgitation is severe, body condition may be poor. Diseases of the oral cavity can often be directly visualized, but the pharynx and cricopharynx cannot be examined without sedation or general anesthesia. If the cervical esophagus is dilated, this can often be palpated or visualized.

Further Diagnostic Investigations

History and physical examination confirms signs consistent with a swallowing disorder, and may give a clue as to the exact region involved (Table 3). However, a definitive diagnosis can rarely be established at this stage and additional procedures are required.

Radiography (Direct or Indirect Signs)

Survey radiographs. Many swallowing disorders can be detected with plain radiography. A gas-filled esophagus can be seen with megaesophagus, sometimes evident as a tracheal stripe sign. Most foreign bodies (especially bone material) are also evident with plain radiography.

Barium Esophagram ± Fluoroscopy

In some cases contrast radiography is required, although this is unnecessary (and can even be dangerous e.g., inhalation of barium) if a diagnosis is evident on the plain radiograph. Barium mixed with food is preferable for esophageal studies; iodine-based contrast agents should be used if perforation is suspected. If available, fluoroscopic analysis is preferable because it provides dynamic information on oral cavity, pharyngeal and esophageal function. All swallowing phases can be examined and characterized.

Endoscopy

This is not essential for many esophageal diseases e.g., megaesophagus, but is the method of choice for most other conditions. This procedure is also essential for diagnosis of all organic causes (e.g., esophagitis - Figure 6 -, gastro-esophagal reflux, stenosis, esophagal neoplasia). Flexible endoscopy is preferable to rigid endoscopy for viewing the esophagus. Endoscopy can also be therapeutic e.g., foreign body removal, esophageal stricture dilation, and placement of percutaneous esophagostomy tubes.

Figure 6. Esophagial mucosa: secondary inflammatory aspect lesions in the presence of gastroesophageal reflux. Cardial incontinence is present. (© V. Freiche).

Specific Swallowing Disorders

The major swallowing disorders are listed in Table 4.

Oropharyngeal Neuromuscular Dysfunction

These can result in disruption of any of the oropharyngeal stages of swallowing (oral, pharyngeal or cricopharyngeal). Cricopharyngeal dysmotility can result either from failure of the cricopharynx to contract (chalasia) or relax (achalasia). The etiology of these disorders is poorly understood, but some cases are associated with neurological (brain stem disease, peripheral neuropathies), neuromuscular (myasthenia gravis, polymyositis) or metabolic (hypothyroidism) derangements. Cricopharyngeal achalasia is described in young dogs as a congenital failure.

Most of these disorders are treated medically. If a specific cause can be documented this should be treated. Otherwise treatment is usually supportive e.g., nutritional support (via gastrostomy tube) or postural feeding. If cricopharyngeal achalasia is present, this can be managed surgically e.g., by cricopharyngeal myotomy. Given that in many cases, an underlying disorder is not found, the prognosis is usually guarded.

Megaesophagus and Esophageal Dysmotility

Megaesophagus refers to esophageal global dilatation and dysfunction/paralysis, and has numerous possible causes (Table 5). Pathogenesis is characterized by failure of progressive peristaltic waves. Esophageal dysmotility is the term used to describe defective esophageal motility without overt dilation of the esophagus (e.g., visible on radiography). The same diseases that cause megaesophagus are also responsible for esophageal dysmotility. Megaesophagus can be primary or secondary. The most important cause of acquired megaoeosphagus is myasthenia gravis (MG). In focal MG, megaosophagus may be the only clinical sign. The main clinical sign of megaesophagus is regurgitation (without pain), and a dilated cervical esophagus may be seen. Secondary signs (pyrexia, coughing, dyspnea, weight loss) may also be present and are usually due to nasal reflux, inhalation pneumonia, and malnutrition.

There is no effective medical or surgical therapy for idiopathic megaesophagus and all methods are supportive (see below). For secondary megaesophagus, treatment involves treating the underlying cause. Examples include using steroid replacement for hypoadrenocorticism, and using a combination of anticholinesterases (e.g., pyridostigmine) and immunosuppressive medication (glucocorticoids, azathioprine, mycophenolate or cyclosporin) to treat MG.

There is always a danger of aspiration and subsequent pneumonia and, therefore, prognosis is guarded. However, some idiopathic cases in young dogs recover spontaneously, whilst recovery of function occasionally occurs in secondary megaesophagus if the underlying cause is treated.

Esophagitis and Esophageal Ulceration

Esophagitis is defined as inflammation of the esophagus, and has a number of potential causes (Table 6). Ulceration (and subsequent stricture formation) can develop if esophagitis is severe.

Clinical signs of esophagitis include chronic vomiting/regurgitation, hypersalivation and anorexia due to the pain associated with swallowing. Endoscopy is advisable and the stomach and the duodenum should be examined if chronic vomiting is present.

Treatment is symptomatic. In addition to nutritional support (see below), attention must be given to providing adequate fluid therapy. Recommended drug therapy includes the use of broad-spectrum antibacterials, analgesics, mucosal protectants (sucralfate), gastric acid blockers (e.g., H2antagonists such as ranitidine, famotidine, or proton pump inhibitors such as omeprazole), and motility modifiers e.g., metoclopramide.

Esophageal Obstruction

Esophageal obstruction can be intraluminal, intramural or extramural, and can be partial or complete (Table 7). If the obstruction is long-standing, the esophagus cranial to the obstruction can become dilated and hypomotile. Other complications of esophageal obstruction include esophagitis and esophageal rupture leading to mediastinitis (not often described in dogs).

Esophageal strictures are the result of luminal narrowing caused by fibrosis. The fibrosis develops in the healing phase after esophageal ulceration, which is in turn caused by foreign bodies, ingestion of caustic material, esophageal burns (from ingestion of hot foodstuffs), diseases that cause esophagitis, gastric reflux (most common after general anaesthesia), and drug therapy (e.g.,  doxycycline). The diagnostic approach described above is applicable to esophageal strictures, with esophageal contrast studies and endoscopy most applicable.

Treatment involves widening dilation of the stricture, either by balloon dilation or bougienage. Nutritional support is often required during the period of therapeutic dilations (see below).

Esophageal foreign bodies are relatively common in dogs and types include bones, needles, wood and fish-hooks. Foreign bodies occur most commonly in young animals, and Terrier breeds (e.g., West Highland White Terrier) are predisposed. Clinical signs are usually acute in onset and include dysphagia, regurgitation, ptyalism and anorexia (if the presence of the foreign body causes pain).

If obstruction is incomplete, ingestion of liquids but not solids is tolerated and there may be a delay before the animal is presented to the veterinarian. If perforation is present, mediastinitis can develop leading to signs of depression and pyrexia. A combination of plain radiography and esophagoscopy are suitable to make the diagnosis. Contrast studies are rarely required; barium may mask the foreign body and it should be avoided if perforation is suspected.

The majority of esophageal foreign bodies can be removed, perorally, under endoscopic guidance. On rare occasions, surgical esophagostomy is required to remove the foreign body, but this should be a last resort. Again nutritional support may be required during the convalescent phase (see below). If lesions are severe, a percutaneous gastrostomy tube (PEG) must be placed.

Vascular ring anomalies (VRA) are congenital malformations of the aortic arches, and constrict the esophagus at the level of the heart base. The esophagus cranial to the obstruction can then become dilated and aperistaltic. VRA are most common in Irish Setters and German Shepherds (e.g., same as for idiopathic megaesophagus).

Clinical signs include acute onset of regurgitation and poor weight gain, and are usually first noted at the timing of weaning (e.g., when solids are administered for the first time). Contrast radiographic studies are the best methods of diagnosis.

Surgical management is the treatment of choice, but success depends upon how longstanding the problem is. The more delayed the presentation, the greater the size of the associated esophageal dilatation and the less likely the signs are to resolve. Given that these animals are often poorly grown, nutritional support is required to improve condition prior to surgery (see below). The prognosis is guarded; these patients are at poor surgical risk due to malnutrition and the potential for aspiration pneumonia. Further, the esophageal cranial dilatation may persist despite correction of the VRA.

Hiatal Hernia

A hiatal hernia is a herniation of part or all of the gastresophageal junction and stomach through the esophageal hiatus of the diaphragm into the thorax. The condition can sometimes be exacerbated by increased inspiratory effort due to upper airway obstruction (e.g., laryngeal paralysis). The most severe, but thankfully rare, form is the gastro-esophageal intussusception, which occurs in young dogs with a breed predisposition for Shar-pei dogs. Clinical signs include acute onset of vomiting, regurgitation and dyspnea, leading to shock and death. Paraesophageal hernia involves herniation of the stomach parallel to the esophagus. Sliding hiatal hernia often presents in an intermittent fashion.

Shar-pei puppies present a breed predisposition for gastro-esophageal intussusception. (© Badeau). To view click on figure

Fluoroscopy or endoscopy may be required to demonstrate the problem but, unless the hernia develops during visualization, it is often missed. Repeated evaluation may be required. This type of hernia may cause reflux esophagitis intermittent regurgitation and vomiting.

Many hernias can be successfully managed medically with modification of feeding behavior (small frequent meals, upright feeding) and drugs to treat associated reflux esophagitis. Surgical management is required for intussusception or persistent herniation.

Esophageal Neoplasia

Esophageal neoplasia is a rare cause of progressive regurgitation, often with blood. It has been reported to be associated with hypertrophic osteopathy (Marie's disease). The most common types of neoplasia in dogs include smooth muscle tumors, carcinoma, fibrosarcoma, and osteosarcoma (which is associated with Spirocerca lupi infection especially in South America, Africa or La Reunion Island). Esophageal neoplasia is invariably malignant, treatment options are limited and prognosis is grave (because the diagnosis is usually made too late).

Feeding from a height helps swallowing in esophageal disease. (© Royal Canin).

Esophageal Diverticula

Esophageal diverticula are focal dilatations of the esophageal wall, and can either be congenital or can arise secondary to other esophageal diseases. Two types are described:

• Pulsion Diverticula - These occur cranial to an esophageal lesion e.g., vascular ring anomalies.
• Traction Diverticula - These develop as a result of inflammation and fibrosis within the esophagus, which distracts the esophagus causing a diverticulum.

Diverticula must be differentiated from esophageal redundancy e.g., kinking of the esophagus seen in young brachycephalic breeds and Shar-pei dogs. Diagnosis is made with radiography (+/- barium studies). Small diverticula rarely cause a problem, and conservative treatment is appropriate (e.g., soft diet fed from an upright position). Larger (multilobulated) diverticula are more problematic and may require surgery, although prognosis is poor.

Swallowing disorders and esophageal diseases are a significant problem for the affected individual, however, they occur less frequently in practice compared to the disorders of the gastrointestinal tract. Acute and chronic diseases of the stomach, the small and large intestine are of major practical significance and require thorough clinical workup of the patient to avoid misleading diagnosis and treatment.

Nutritional Management of Swallowing Disorders

Feeding from a Height - Food and water bowls can be placed in a high place. Small dogs can be fed "over-the shoulder". These patients can also be held vertical for a short while after feeding to encourage passage of food to stomach ([Guilford & Matz 2003]). In patients that tolerate liquids poorly, fluid requirements can be fulfilled with ice cubes.

Alter Food Consistency - The optimum type of food varies between cases. For some, liquidized high quality diets are best, for others, wet food or moisturized dry food is suitable. Diet viscosity should also be considered.
Diets may be applied either by syringe or as small solid boluses depending on the underlying disease or the preference of the patient or of the owner.

Ensure Adequate Nutrient Intake - Patients with swallowing disorders need to be fed for shorter or longer times and depending on the duration of the disease the intake of fluid, energy and nutrients has to be balanced.
Ideally, the diet should deliver all required nutrients in a reasonable volume. To maintain the energy balance of the patient, high fat diets are preferred because these diets provide high energy density so that the patients' energy requirements can be met in a smaller volume of food.

Assisted Feeding e.g., Gastrostomy Tube - see Chapter 14 - For many diseases (e.g., esophageal stricture and esophageal ulceration), a period of assisted feeding is required whilst the primary disease is treated. Short to medium term assisted feeding can sometimes be of benefit in patients with megaesophagus, since it enables improvements in body condition and gives the patient time to adjust to alterations in oral feeding (Marks et al. 2000; Devitt et al. 2000; Sanderson et al. 2000).
Many owners readily accept to feed their dogs with feeding tubes.