Conformational Disorders

14 Conformational Disorders



Dawn D. Kingsbury



1. Name some conformational disorders of the upper respiratory tract.
• Nasal: Cleft palate, stenotic nares, nasal dermoid sinus, primary ciliary dyskinesia, nasopharyngeal polyps

• Palate, pharynx, and larynx: Elongated soft palate, choanal atresia, nasopharyngeal polyps, cricopharyngeal achalasia, laryngeal hypoplasia, laryngeal collapse, laryngeal paralysis, everted laryngeal sacculi, laryngeal edema, subglottic stenosis

2. Name some conformational disorders of the lower respiratory tract.
• Trachea and bronchi: Tracheal or bronchial compression due to lymphadenomegaly, thymic mass or branchial cyst, tracheal hypoplasia, primary ciliary dyskinesia, osteochondral dysplasia

• Lung: Pulmonary emphysema

• Diaphragm: Hernia (peritoneopericardial, pleuroperitoneal, hiatal)

• Thoracic wall and sternum: Rib abnormalities or fractures, which in the worst-case scenario result in a flail chest, pectus excavatum

3. Into what general categories can conformational disorders be classified?

Disorders can be classified by the presenting signs. The breathing pattern can help localize the disorder. An obstructed breathing pattern is found in cases of upper and lower airway disease, while a restricted pattern indicates disease in the thoracic wall, sternum, or diaphragm. Abnormal breath sounds are common in upper airway disease. Stertor (snore) is found in nasal or pharyngeal disease and stridor (wheeze) in laryngeal or lower airway disease. A voice change and inspiratory dyspnea are often noted in the history of dogs with laryngeal disease. Patients with disease in the lower airways may present with a cough, tachypnea, or varying degrees of respiratory distress.


Conformational changes may be congenital or acquired. Acquired disease may be secondary to physical characteristics such as negative intra-airway pressure generated during inspiration in brachiocephalic airway syndrome, inflammation or infection, nasopharyngeal polyps, or diaphragmatic hernia due to trauma. Changes may be structural or functional, static or dynamic. Having this knowledge helps determine what diagnostic tests are appropriate. For example, a direct examination of the larynx is needed to make a diagnosis of laryngeal paralysis; fluoroscopy or bronchoscopy may be needed to document tracheal or bronchial compression or obstruction due to lymphadenomegaly, which cannot be entirely ruled out by examination of static thoracic radiographs.


4. Name some breeds of dogs known to have predispositions for certain conformational disorders.

Brachycephalic breeds have their own syndrome—brachycephalic airway syndrome—and may be predisposed to pectus excavatum.


As a subset of the brachycephalics, English Bulldogs, Boston Terriers, and Boxers have a predisposition for tracheal hypoplasia.


The Chinese Shar-Pei has a risk similar to that of brachycephalic breeds of airway disease, specifically brachycephalic airway syndrome, and hiatal hernia.


Brachycephalic breeds, including Shih Tzus, Bulldogs, Pointers, and Swiss Sheepdogs, may inherit cleft palates.


Congenital laryngeal paralysis has been reported in Bouvier des Flanders, Bull Terriers, Dalmatians, Rottweilers, Siberian Huskies, and German Shepherds.


Many of these dogs will have other concurrent neurological abnormalities. Heritability has been proposed as the cause of these abnormalities in most cases.


A recent prospective study concluded that Labrador Retrievers and Rottweilers have a significantly higher risk for acquired laryngeal paralysis. Other large breeds including Irish Setters, Golden Retrievers, and Afghans, are also considered to be predisposed.


Bichon Frise, Border Collie, Bullmastiff, Chihuahua, Chinese Shar-Pei, Chow Chow, Dachshund, Dalmatian, Doberman Pinscher, English Springer Spaniel, English Pointer, English Setter, Golden Retriever, Gordon Setter, Miniature Poodle, Newfoundland, Old English Sheepdog, Rottweiler, and Staffordshire Bull Terrier are all breeds with reported cases of primary ciliary dyskinesia (PCD) or Kartagener’s syndrome. With the exception of Newfoundlands, in which PCD shows an autosomal recessive pattern of heritability, sporadically reported cases do not represent specific breed predisposition for PCD. There is a rhinitis/bronchopneumonia syndrome in Irish Wolfhounds that is not PCD and is likely heritable.


5. Briefly describe a typical history for a dog with the following respiratory tract conformational disorders.
• Cleft palate: Pups may have drainage of milk from nares during or after nursing (nasal regurgitation) and rhinitis. Respiratory distress may be seen secondary to aspiration pneumonia.

• Stenotic nares: Brachycephalic breeds with stenotic nares will have intolerance to heat, exercise, and stress with inspiratory stertor and asphyxia. Early in the disease course, signs may be relieved by open-mouth breathing, but it is often part of brachycephalic airway syndrome, which incorporates other defects such as elongated soft palate, and leads to progressive, persistent signs.

• Congenital laryngeal paralysis: A young dog will present with inspiratory stridor and dyspnea that may be episodic but worsens with exercise.

• Hypoplastic trachea: At least half of the affected dogs have some degree of dyspnea; a quarter have stridor and/or coughing; an eighth have gagging and/or exercise intolerance, and a minority (∼10%) have either more severe signs like syncope or may have no signs at all.

• Primary ciliary dyskinesia: Early in life, affected dogs will have a chronic recurring nasal discharge, coughing, sneezing, and abnormal respiratory sounds. Respiratory distress may accompany bouts of bronchopneumonia.

• Pulmonary emphysema: Respiratory distress can result if rupture of a bulla causes a pneumothorax, but often it is an incidental finding.

6. What is a “swimmer” puppy?

A swimmer puppy has an abnormal thoracic conformation (pectus excavatum) resulting from abnormal locomotion. Typically a puppy presents by 12 weeks of age for an inability to walk and moves around on its sternum by flailing its abducted limbs. Dorsal to ventral narrowing of the thorax develops and results in a flattened appearance. Often environmental factors such as hard slippery flooring contribute to an inability of the puppy to adduct its limbs and stand. Orthopedic abnormalities such as dislocation or subluxation of the shoulder, elbow, hip, or stifle should be ruled out. Correcting limb position and realigning joints (using hobbles to prevent abduction) typically eliminate the need for any thoracic splinting.

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Jul 31, 2016 | Posted by in INTERNAL MEDICINE | Comments Off on Conformational Disorders

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