Case Study – The Inappetent Rabbit

History

A 4 year old male neutered rabbit presented with lethargy, inappetence and hypersalivation. The body condition score of the rabbit was a 3/9 and a large swelling was noted on the lateral right maxilla. The skin overlying the swelling had hair loss and inflammation secondary to the constant salivation.

On clinical examination, the patient was subdued and sensitive to handling of the head. The mass present on the right side of the head measured 3cm by 2.5cm and was firm on palpation. There was an additional, smaller mass present at the level of the upper left cheek teeth. Although a thorough conscious oral examination was not possible due to discomfort, the incisors could be assessed and were markedly overgrown. The upper incisors curved backwards and pierced the rostral maxillary soft tissues, which appeared swollen. There was mild submandibular lymphadenopathy. Thoracic auscultation and abdominal palpation were unremarkable, apart from poor body condition, and the patient was normothermic.

Severe dental disease with secondary abcessation was suspected as the cause of the rabbit’s inappetence and weight loss. For this reason, plain radiography was performed to assess the extent of the dental disease.

Radiographic Technique and Findings

Three radiographic views of the head are required when assessing dental disease in rabbits. These include a dorsoventral or ventrodorsal projection, two obliques and a laterolateral projection.

General anaesthesia was induced in order to facilitate positioning for radiography.

When positioning rabbits for radiographic assessment of the head, the dorsoventral view is acquired first. In this case, the patient was positioned in sternal recumbency with the head extended forward and secured with tape parallel to the x-ray detector. When acquiring this view, the primary beam is centered on the midline of the skull at the level of the mid-orbital rim. The collimation should include the entire skull, from the nose rostrally to the mid neck caudally.

To acquire a laterolateral view of the patient’s head, the patient was placed in right lateral recumbency, ensuring the head was horizontal with the philtrum parallel to the x-ray detector. Radiolucent foam wedges can be used to raise or position the head as necessary. The primary beam was centered rostrally in front of the orbit at the level of the zygomatic arch.

Oblique projections of the skull are useful for separating the individual cheek teeth which are otherwise superimposed in the laterolateral view. The oblique views of the head are acquired as two separate projections. The patient is positioned in left and then right lateral recumbency, with the head tilted 10-20° anti-clockwise from the true lateral position. The primary beam is centered rostrally in front of the orbit at the level of the maxilla.

 

Image 1:

Dorsoventral view of the patient’s head. A large, round, soft tissue opacity mass is seen lateral to the right maxilla (red arrow) at the level of the cheek teeth, with osseous destruction of the right zygomatic bone (yellow arrow). A smaller soft tissue opacity mass is present lateral to the left zygomatic bone (green arrow). There is evidence of upper incisor overgrowth with both teeth appearing to curl backwards. The overgrowth of the right upper incisor (blue arrow head) appears more severe than that of the left upper incisor. There is also overgrowth of the pre-molar roots on the right hand side, although superimposition makes this difficult to identify.

 

Picture1-3

Image 2:

Laterolateral view of the head. Severe overgrowth of the upper incisors can be seen (blue arrow head). There is malocclusion between the upper and lower pre-molars and molars (blue brace), with abnormally long roots present in all four sets of teeth. A calcified dental spur (green arrow) can be seen originating from the lower right premolars. A soft tissue mass (red arrow) can be seen on the mid-cranium at the level of the zygomatic process of the frontal bone.

Picture2-2

 

Image 3

Left 10-20˚ dorsal – right ventral oblique view of the head. In this image, severe overgrowth of the upper and lower arcade of dental roots can be seen. The soft tissue mass (red arrow) can be visualized dorsally at the level of the upper molars. There is reduced radiopacity of the right maxillary bone adjacent to the mass (yellow arrow).

Picture3

Image 4:

Right 10-20˚ dorsal – left ventral oblique view of the head. Severe overgrowth of the upper incisors is present (blue arrow head). Elongated abnormal roots are visible in both the upper (red brace) and lower arcade teeth. Malocclusion between the dental arcades can be noted with unequal growth affecting the first premolar and the last molar (blue brace). This uneven growth has contributed to the deviation of the normal alignment of the teeth. The calcified dental spur originating from 407 is visible (green arrow) and appears to be directed rostrally. A second dental spur can also be seen extending ventrally from the upper first pre-molar tooth (orange arrow).

Picture4-1

 

From the radiographs and clinical signs, it can be concluded that there is severe dental disease affecting the oral cavity, with suspected bilateral dental abscesses, and osseous destruction affecting the right zygomatic bone.

Discussion

Dental disease is one of the most common reasons for pet rabbits to require veterinary treatment1. The underlying causes of dental disease are still subject to debate but can be divided into congenital and acquired conditions. Congenital dental disease is usually limited to malocclusion of the incisors and sometimes cheek teeth, especially in dwarf or brachycephalic breeds. Acquired dental disease is often associated with nutrition, trauma or age-related attrition2.

The clinical signs associated with dental disease in rabbits include:

  • Emaciation and general loss of condition
  • Decreased food intake
  • Dysphagia
  • Changes in faecal output
  • Excessive grooming
  • Excessive salivation
  • Exophthalmos
  • Facial masses or swellings
  • Epiphora and purulent nasal discharge
  • Restricted or painful mandibular movements

Secondary conditions relating to dental disease include systemic disease due to emaciation, dermatitis, ocular disease including dacryocystitis, conjunctivitis and corneal ulceration2.

Therefore, when dental disease is suspected based on history or preliminary oral examination, a thorough examination of the rabbit under general anaesthesia is essential. The examination should include radiography at a minimum, and endoscopy if available.

Although radiography is commonly the first opinion diagnostic imaging modality of choice, there are limitations due to superimposition of the skull and dentition. In these circumstances, computed tomography (CT) is superior as it overcomes many of the limitations of plain radiography through its ability to acquire cross-sectional images of the rabbit’s head in multiple planes. In addition, it provides more detail on the extent of osseous changes and dental pathology3.

In general, the treatment of dental disease in rabbits consists of restoring normal tooth length, restoration of the occlusal plane to as near normal as possible, extraction of diseased teeth and treatment of any associated abscessation2. With many cases of dental disease in this species, cure is impossible and owners must understand that treatment must be followed up by ongoing management.

References

  1. Harcourt-Brown FM. (2007) The Progressive Syndrome of Acquired Dental Disease in Rabbits. Journal of Exotic Pet Medicine. 16:146–157.
  2. Lennox AM. (2008) Diagnosis and Treatment of Dental Disease in Pet Rabbits. Journal of Exotic Pet Medicine. 17:107–113.
  3. Riggs GG., Arzi B., Cissell DD., et al. (2016) Clinical Application of Cone-Beam Computed Tomography of the Rabbit Head: Part 1 – Normal Dentition. Frontiers in Veterinary Science. 17;3.

 

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