Study Notes on Oral Cavity and Oropharynx Surgery in Small Animals

Surgery of the Oral Cavity and Oropharynx in Small Animals

Overview

  • Course: Small Animal Surgery

  • Course Code: VMS 5649

Key Anatomical Structures

  • Hard Palate

  • Soft Palate

  • Oral Cavity

  • Oropharynx

  • Lips

  • Tongue

  • Salivary Glands

Learning Objectives

  • Understand the causes of congenital oronasal fistula.

  • Differentiate between primary and secondary palate defects.

  • Recognize clinical signs of congenital oronasal fistula and diagnose the condition.

  • Discuss medical management for primary and secondary cleft palate; recognize when surgery is warranted.

  • Understand the concepts and techniques for surgical repair of primary and secondary cleft palate.

  • Identify complications associated with primary and secondary cleft palate and understand their causes.

  • Recognize and comprehend the causes of lip avulsions and the surgical management of these conditions.

  • Discuss the procedures of cheiloplasty and cheilopexy, and understand the differences between them.

  • Explore types of lip disorders and conditions for primary repair versus glossectomy.

  • Understand the definition and pathophysiology of salivary mucoceles (sialoceles).

  • Discuss the diagnosis and clinical presentation of salivary mucoceles based on the affected area.

  • Recognize the aspiration of fluids in salivary mucoceles for diagnostic purposes.

  • Understand the surgical treatment requirements for salivary mucoceles, including the need for removing certain glands.

  • Discuss postoperative management, potential complications, and prognosis related to salivary mucoceles.

Congenital Oronasal Fistula

  • Definition: An abnormal communication between oral and nasal cavities encompassing the soft and hard palate, premaxilla, and/or lip.

  • Primary Palate: Involves the lip and premaxilla; results from incomplete closure, termed primary cleft or cleft lip.

  • Secondary Palate: Pertains to the hard and soft palates; incomplete closure results in secondary cleft or cleft palate.

Pathophysiology of Congenital Fistula

  • Caused by the failure of fusion of two palatine shelves during fetal development.

  • Fetal palate closure occurs at approximately 25-28 days of gestation.

  • Inherited conditions can be recessive, irregularly dominant, or polygenic traits.

  • Nutritional causes include inadequate folic acid intake.

  • Hormonal factors, such as steroids, may influence development.

  • Mechanical factors, including in utero trauma, can contribute.

  • Toxic or viral agents may play a role as well.

Signalment and History

  • Affects primarily brachycephalic breeds:

    • Boston Terriers

    • Pekingese

    • Bulldogs

    • Miniature Schnauzers

    • Siamese cats (Females outnumber males)

  • Clinical signs include:

    • Difficulty nursing

    • Nasal regurgitation/discharge

    • Failure to thrive

    • Rhinitis and aspiration pneumonia

Medical Management of Cleft Palate

  • Tube feeding: To maintain nutritional status and minimize aspiration incidences until the animal is old enough for surgery.

  • Esophagostomy: Considered when tube feeding is necessary.

Surgical Management of Cleft Palate

  • Surgery is typically delayed until at least 8-12 weeks of age.

  • Surgical techniques include:

    • Sliding bipedicle flaps

    • Overlapping flap techniques

    • Reference: Tobias and Johnston, Veterinary Surgery: Small Animal, 2012, Saunders, Elsevier Inc.

Closure of Primary Cleft

  • Technique involves a mucosal flap to create separation between the nasal and oral cavity.

  • Employing modified Z-plasty may be necessary.

  • Resection of the rostral maxilla might be required as well.

Acquired Oronasal Fistula

  • Definition: Abnormal communication between nasal and oral cavities.

  • Causes include:

    • Trauma (e.g., bite wounds, gunshot wounds, electrical burns)

    • Dental disease

    • History of chronic rhinitis

Surgical Management of Acquired Fistulas

  • Successful repairs require methods that are:

    • Well-supported

    • Airtight

    • Tension-free

  • Surgical techniques may include direct closure and flap techniques, both of which can be successful.

  • Key complications to monitor for include dehiscence and recurrence.

Lip Avulsions

  • Typically due to:

    • Trauma from being struck by a car (common in cats)

    • Animal bites (common in dogs)

  • Involves the avulsion of the rostral mandibular lip and associated labial mucosa from adjacent gingiva.

Surgical Management of Lip Avulsions

  • Procedures referenced in Front Vet Sci, 06 July 2018, Veterinary Dentistry and Oromaxillofacial Surgery Volume 5 - 2018.

Cheiloplasty (Lip Fold Resection)

  • Purpose: Address lip fold dermatitis resulting from excessive mandibular labial tissue.

  • Reference: Fossum, Small Animal Surgery, 2013, Mosby, Elsevier.

Antidrool Cheiloplasty - Cheilopexy

  • Indication: To reduce loss of food and saliva due to excessive lower lip eversion or denervation.

  • While this maintains oral function, it may lead to postoperative inflammation and infection at the site.

  • The procedure results in permanent flap adhesion and cheek scarring.

Disorders of the Tongue

  • Common causes include:

    • Trauma (e.g., entrapment in paper shredders, cage grates, chain link fences, bite wounds).

    • Treatment involves apposition of deep muscular tissue followed by epithelium, using fine, absorbable monofilament sutures (sizes 3-0 to 4-0).

  • Neoplasia: Clinical signs include halitosis, hypersalivation, oral hemorrhage, and difficulty in prehension and swallowing.

  • Surgical treatment: Glossectomy may be required for neoplasia.

Sialoceles/Salivary Mucoceles

  • Definition: Accumulation of saliva that leaks from a damaged salivary gland or duct.

  • Common locations include:

    • Cervical

    • Sublingual (Ranula)

    • Pharyngeal

    • Zygomatic

Pathophysiology of Salivary Mucoceles

  • Caused by the tearing of a salivary gland or duct, leading to leakage.

  • Distinction: Salivary mucoceles are not cysts; cysts are lined by epithelium, while mucoceles have granulation tissue due to inflammation.

  • The cause is often not identifiable; though foreign body, trauma, and sialoliths are suspected contributing factors.

  • The sublingual salivary gland is the most commonly affected.

Diagnosis of Salivary Mucoceles

  • More common in dogs than cats.

  • All breeds can be affected.

  • Presentation is dependent on the location of the mucocele:

    • Asymptomatic for cervical sialoceles

    • Abnormal prehension and bleeding in the case of ranulas

    • Respiratory distress and dysphagia for pharyngeal sialoceles

    • Orbital issues (exophthalmos, protrusion of the third eyelid, painless orbital swelling) for zygomatic sialoceles

  • Diagnostic aspiration may yield clear, yellowish, or blood-tinged viscous mucoid fluid with a low cell count indicating the presence of saliva.

Medical Management of Salivary Mucoceles

  • Emergency drainage may be necessary for animals with respiratory distress.

  • Palliative and repeated drainage can complicate surgical outcomes.

Surgical Treatment of Salivary Mucoceles

  • Complete excision of the gland and duct complex along with the draining mucocele is the curative approach.

  • Determining the side of origin requires thorough oral examination, palpation, or exploration of the mucocele.

Mandibular and Sublingual Salivary Gland Excision

  • Cervical, Sublingual, Pharyngeal Mucoceles:

    • Excision of the originating gland and duct complex is necessary via lateral or ventral incision; subsequent drainage of the mucocele follows.

    • For ranula, marsupialization is the preferred approach.

Postoperative Care for Salivary Mucoceles

  • Histopathology of the excised gland is essential.

  • Bandage changes are necessary along with placement of a Penrose drain for cervical mucoceles.

  • Soft food should be provided for 3-5 days following ranula marsupialization or drainage of pharyngeal mucoceles.

Complications and Prognosis

  • Potential complications include:

    • Seroma formation

    • Infection

    • Recurrence of mucocele

  • Misdiagnosis or inadequate gland excision can lead to recurrence.

  • Careful attention to anatomy during surgery can minimize recurrence rates.

  • Prognosis is generally excellent if the disease is accurately diagnosed and excision is complete.