Lesson 67: Disorders of the pharynx and esophagus, and dyshagia

How are tonsils described in dogs and cats?

Compact tonsils lying within crypts.

How is tonsillar tissue described in other domestic species?

Diffuse tonsillar tissue scattered in the pharyngeal mucosa.

What is the function of tonsils?

Some protection against entry of infection into the alimentary and respiratory tracts.

What is a clinical expression of tonsillar disease?

Painful swallowing.

Name one type of response to injury seen in the tonsils.

Disturbances of growth.

Name a second type of response to injury seen in the tonsils.

Lymphoid necrosis.

Name a third response to injury seen in the tonsils.

Tonsillitis.

Name a fourth type of response to injury seen in the tonsils.

Neoplastic diseases.

What is hyperplasia of the tonsils considered?

A disturbance of growth.

What is a common presentation of diffuse "tonsillar" hyperplasia?

Common in foals.

What leads to chronic irritation and tonsillar hyperplasia?

Exposure to the environment, bacteria, and viruses.

Name a viral cause of lymphoid necrosis in cats.

Feline panleukopenia.

Name a viral cause of lymphoid necrosis in dogs.

Canine parvoviral infection.

Besides parvovirus, what other canine virus causes lymphoid necrosis?

Canine distemper.

Which viral disease listed causes lymphoid necrosis?

Bovine Viral Diarrhea (BVD).

What is a potential cause of tonsillitis related to systemic disease?

Systemic disease (e.g., ICH/Infectious Canine Hepatitis).

What is a neoplastic disease affecting the tonsils (L)?

Lymphosarcoma.

What is a neoplastic disease affecting the tonsils (R)?

Squamous cell carcinoma.

What commonly affects the pharynx?

Infectious diseases of the URT and upper digestive tract.

Name a sign of respiratory distress associated with pharyngeal disorders.

Stridor.

Name another sign of respiratory distress associated with pharyngeal disorders.

Coughing.

What sign related to breathing may occur due to pharyngeal disorders?

Dyspnea.

Clinical signs of pharyngeal disorders are exacerbated by what factors?

Excitement, heat, stress, or exercise.

What are the two categories of lesions listed for the pharynx?

Inflammation (Pharyngitis) and Pharyngeal obstruction.

What is a common etiology of pharyngitis?

Trauma.

What is a second common etiology of pharyngitis?

Bacterial and viral agents (as for the nasal cavity).

What type of pharyngitis lesion involves blood?

Hemorrhagic inflammation.

What is a serious sequela of pharyngitis?

Aspiration pneumonia.

Name two examples of intraluminal foreign bodies that may obstruct the pharynx.

Medicament boluses, apples, or potatoes.

Where can masses in the surrounding tissue cause pharyngeal obstruction?

Thyroid gland, thymus, or parathyroid glands.

In which animals is improper use of drenching or balling guns a source of trauma?

Sheep, cattle, and pigs.

What type of trauma can cause perforation of the caudodorsal wall of the pharynx?

Improper use of drenching or balling guns.

What is a minimal sequela of trauma to the pharynx?

Local edema and inflammation.

What is a serious sequela of trauma to the pharynx?

Complete luminal obstruction by exudate.

What is a pharyngeal diverticulum?

A pouch in the pharyngeal wall rostral and dorsal to the esophageal entrance.

In which species is a pharyngeal diverticulum noted?

Pigs.

What foreign material may lodge in the pharyngeal diverticulum of a pig?

Barley awns.

What is a risk if a diverticular wall is perforated by awns or syringes?

Exudate can extend into the mediastinum.

How is esophageal healing described?

Relatively rapid.

What is the normal epithelial turnover rate for the esophagus?

5 to 8 days.

What can result from a breach of the epithelial barrier (ulceration) due to acid reflux or mechanical damage?

Circumferential scarring.

What results from circumferential scarring of the esophageal lumen?

Permanent narrowing (strictures) and predisposition to future obstruction.

What animal is unable to vomit, losing an important mechanism for toxin elimination?

Horses.

What portal of entry allows caustic chemicals to enter the esophagus?

From the oral cavity passing to the stomach or rumen.

What is a common portal of entry into the mediastinum from the thoracic cavity?

Penetration or obstruction by foreign objects.

What iatrogenic event is a portal of entry into the esophagus?

Puncture not uncommon following passage of stomach tubes.

How does the stratified squamous epithelium of the esophagus differ between pigs/horses/ruminants and dogs/cats?

It is keratinized in pigs, horses, and ruminants, but nonkeratinized in dogs and cats.

Which domestic animals have striated muscle throughout the esophagus?

Ruminants and dogs.

Which part of the horse's esophagus is composed of smooth muscle?

The distal third.

What is another term for esophageal obstruction?

Choke.

What is Megaesophagus also known as?

Esophageal ectasia.

What is the physiological mechanism leading to Megaesophagus?

Insufficient, absent, or uncoordinated peristalsis in the mid- and cervical esophagus.

What is a secondary cause of megaesophagus related to vascular rings?

Persistence of the right aortic arch (PRAA).

What structures form the vascular ring in PRAA?

Aorta, pulmonary artery, and ductus arteriosus.

Where does the esophageal obstruction occur due to PRAA?

Cranial to the heart.

What is acquired megaesophagus also known as in relation to function?

Esophageal achalasia.

What is the key mechanism in acquired megaesophagus (achalasia)?

Failure of relaxation of the distal esophageal (cardiac) sphincter.

Name an autoimmune disease secondary to which acquired megaesophagus may occur.

Myasthenia gravis (disorder of acetylcholine receptors).

What is the key clinical sign of megaesophagus?

Regurgitation after ingestion of solid food.

What serious secondary condition is often associated with megaesophagus?

Aspiration pneumonia.

What finding may be present radiographically in megaesophagus?

Esophagus is dilated anterior to the lesion and retains radiopaque dyes.

What is a common cause of squamous cell carcinomas in cattle esophagus?

Bracken fern (Pteridium aquilinum) consumption (± papilloma virus infection).

What are fibrosarcomas of the esophagus in dogs often associated with?

Spirocerca lupi infestation.

Name one anatomic location where choke frequently occurs.

Cranial to the first rib at the thoracic inlet.

Name a second anatomic location where choke frequently occurs.

Base of the heart.

What key indicator sign may be seen in choke?

Nasal discharge of feed material and saliva.

What complication can occur if foreign bodies are lodged against the epithelium for longer than 2 days?

Circumferential pressure necrosis of the esophageal mucosa.

What complication results from acid reflux of stomach contents into the esophagus?

Chemical burning of the distal or aboral esophagus (acid reflux esophagitis).

What is the most pathogenic esophageal parasite of dogs?

Spirocerca lupi.

What are two severe clinical sequelae of Spirocerca lupi infestation?

Aortic aneurysms and esophageal fibrosarcomas or osteosarcomas.

In what climates do S. lupi infestations typically occur?

Warmer climates.

What is dysphagia?

Difficulty in swallowing.

What cranial nerves are involved in neuromuscular causes of dysphagia?

Cranial nerve dysfunction (V, VII, IX, X, XII).

What condition involves antibodies blocking acetylcholine receptors, causing dysphagia?

Acquired Myasthenia gravis.

Name a structural cause of dysphagia.

Congenital defects (e.g., cleft palate, cricopharyngeal achalasia).

What is regurgitation?

The passive expulsion of undigested food or liquid from the esophagus without retching, nausea, or abdominal effort.

What is the most common cause of regurgitation?

Megaesophagus.

How does regurgitated food often appear?

Undigested food, often tube-shaped (retains esophageal shape).

How is regurgitation distinguished from vomiting clinically?

Regurgitation involves passive expulsion with no nausea, retching, or abdominal contractions.