Cleft lip

A cleft lip (CL) is a defect involving the primary palate structures and might be an isolated defect or be associated with a cleft palate (CP). The primary palate is the lip and palate rostral to the palatine fissures, including the lip and alveolar process.
A CL results from a failure of fusion of the two ossification centers of the incisive bone. The cleft extends from the border of the upper labia at the muzzle and continues dorsally into the upper portion of the lip toward the nostril.
An incomplete cleft does not involve the nostril, whereas a complete cleft includes all the lip and continues into the nostril.
A complete cleft is usually, but not always, accompanied by a cleft of the alveolar process, which may be partial or through-and-through.

A CL may be unilateral or bilateral. Unilateral clefts more commonly affect the left side. The actual morphology of the defect/abnormality will depend on the type of cleft.

Orofacial clefts affect ~3% of puppies (CL 26%, CP 59%, and CLP 15%). The incidence of orofacial clefts and the incidence of specific cleft phenotype varies across breeds. Brachycephalic breeds and mastiff/terrier breeds are predisposed to orofacial clefts. Clefts occur in 41.7% of offspring produced by phenotypically cleft parents, but the clefts' severity does not relate to the clefts' severity in parents.

Etiopathogenesis is complex and includes genetic and environmental factors (incl. teratogenic factors, nutritional factors, mechanical trauma, and geographic region).

A complete physical examination of the patient is needed to evaluate general health and possible concurrent congenital anomalies (cranial and extracranial). Animals with CL are presented due to sneezing and difficulty drinking. Only rarely with poor body condition/growth, inability to nurse with drainage of milk from the nares during or after nursing, and respiratory infections such as rhinitis and/or aspiration pneumonia.

Oral examination findings may include malocclusion, and abnormal number and/or shape of teeth, mostly associated with maxillary incisor teeth.

Complete blood count and serum biochemistry are recommended, although the results are usually within normal limits.

Thoracic radiographs are indicated, although aspiration pneumonia is not common in CL cases. If aspiration pneumonia is confirmed, a tracheal wash is suggested to determine appropriate antibiotic therapy based on culture and sensitivity testing.

In assessing patients for a palatal surgery, the size and shape of the defect are evaluated under general anesthesia. CT imaging is recommended, and dental extractions, if needed, are done before cleft repair.

A CL defect is a clinical diagnosis facilitated by radiographs, including occlusal intraoral radiograph and two (left and right rostral maxilla) lateral intraoral views obtained by a bisecting angle technique. A CT and 3D reconstruction are recommended and performed to evaluate better the relationship between soft and hard tissues and to diagnose any coexisting craniofacial abnormalities.