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Facial abscesses

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Abstract

Facial abscesses are a common problem in pet rabbits, and rapid advances have been made in their successful treatment in recent years. This chapter covers the aetiology of abscesses; clinical features; differential diagnosis; types of abscess; diagnostic procedures; antibiotic therapy; surgical management; non-surgical management; prognosis; and retrobulbar abscesses. : Treating a dental abscess with marsupialization.

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Figures

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29.1 An abscess capsule is composed of fibroblasts and inflammatory cells, with an inner layer of degenerating neutrophils. In rabbits, the capsule can become very thick, forming an effective barrier between infection and surrounding tissue. Live bacteria are most likely to be present on the inner aspect of the capsule, which is the best site for taking samples for culture.
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29.3 Some abscesses contain anaerobic bacteria that form gas. In the abscess shown here, a circle of gas can be seen in the centre of the abscess cavity.
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29.4 A simple but informative diagnostic procedure is to squeeze an abscess to see if, and where, pus can be expressed into the oral cavity. This is not easy to photograph in rabbits with abscesses involving the cheek teeth, but the rabbit shown here had a submandibular abscess involving the lower incisor and the first lower cheek tooth. Copious quantities of pus could be expressed from the incisor socket.
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29.5 Clinical signs and prognosis of facial abscesses at different sites.
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29.6 A large retrobulbar venous plexus is situated between the alveolar bulla and the globe (see Chapter 17). Erosion of this plexus by periapical infection can result in sudden haemorrhage behind the eye and marked exophthalmos.
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29.7 Rictus is a manifestation of nerve damage to the facial nerve, affecting the left side of this rabbit’s face. Problems with mastication may arise if food becomes trapped between the maxillary cheek teeth and the inside of the cheek.
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29.8 Lateral view of the skull of a 7-year-old rabbit with no previous history of dental problems. There was a hard, fast-growing mass on the mandible, which grew to be so large that it prevented the rabbit eating only 2 weeks after this radiograph was taken. Chest radiography confirmed metastases to the lungs and the rabbit was euthanased with a presumed malignant bone tumour.
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29.9 A typical cyst. These cysts are an intermediate stage in the life cycle of , a tapeworm found in dogs and foxes. Fresh herbage that has been contaminated by dog or fox faeces containing eggs is the source of infection. The cysts can be found in the subcutis around the face or on other parts of the body, such as the axilla or retrobulbar space. The swellings they cause can be mistaken for abscesses. The cysts are thin-walled fluctuating structures from which clear fluid is aspirated. Ultrasonography shows the presence of multiple scolices in the fluid-filled cavity.
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29.10 Occlusal view of a mandible of a rabbit that was euthanased because of a large mandibular abscess. The rabbit was in the initial stages of PSADD and there was alveolar bone loss resulting in wide periodontal spaces. A splinter of wood (arrowed) was discovered wedged in the socket of the 1st mandibular cheek tooth.
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29.11 Periapical infections can be the result of trauma to the teeth from rabbits chewing on hard substances. This lateral view of the mandible shows a split 1st mandibular cheek tooth (arrowed) that led to the development of an abscess in the soft tissue at its apex.
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29.12 Dorsoventral view of the skull of a rabbit with a retrobulbar abscess. The elongated root of the 5th maxillary cheek tooth has penetrated the bone and continued to grow into the abscess cavity in the orbit (arrowed). Although this radiograph shows a true DV view of the maxilla, the mandible was deliberately pushed away from the side of the lesion to reduce superimposition of right upper and lower arcade so that the maxillary cheek teeth could be seen. (Reproduced from with permission from .)
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29.13 Lateral view of the skull with a localized bony swelling along the ventral border of the mandible. The swelling extended to the deformed apex of the lower 4th cheek tooth, which was the source of infection.
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29.14 This prepared skull, from a rabbit that was euthanased because of bilateral mandibular abscesses, shows proliferation of the thin bone that enclosed an abscess capsule during life. Infection involved the apices of both the 1st and 2nd mandibular cheek teeth. If the rabbit had undergone surgery, it is probable that the root of the lower incisor would have been removed as its apex is immediately adjacent to the lower 1st cheek tooth on the medial aspect of the hemimandible and is often infected in abscesses at this site.
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29.15 Some abscesses form subcutaneous tracks that branch out of the main capsule and extend into surrounding soft tissue (arrows). Pus may burst out of the track at a distant site. In the case of dental abscesses, the distant abscess is often under the chin or in the dewlap, where they form a discrete swelling that can be removed. Careful dissection will expose the track, which can be followed back to the infected tooth. The fibrous track can either be removed or opened and marsupialized. The decision depends on the extent of the fibrous track and how adherent it is to neighbouring tissues.
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29.16 Lateral view of the skull of a rabbit with generalized mandibular abscesses. In the past, this rabbit had had extensive coronal reduction of the cheek teeth using dental burrs. Whether the infection was secondary to generalized pulp necrosis because of thermal injury, or whether it was due to spread of infection between teeth affected by PSADD, is difficult to prove. Thermal injury causes haemostasis, inflammation and thrombosis in the pulp. It is thought that exposure of the pulp cavity during burring was the cause of the mandibular abscesses in this rabbit. One author (FHB) has seen several similar cases.
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29.17 Lateral view of the skull of a rabbit with abscesses involving both mandibular arcades and one maxillary arcade. Her incisors had been removed on a previous occasion due to acquired malocclusion. The rabbit was of good bodyweight and appeared to enjoy life, although she could only eat softened food. Pus was discharging into the mouth from both mandibular arcades. Periodically, loose crowns could be pulled out via the oral cavity during her regular dental check-ups under anaesthesia. She would also have a 14-day course of parenteral penicillin/streptomycin on these occasions. This radiograph was taken when she presented with unilateral exophthalmos. Several loose crowns were easily removed from the upper arcade and the eye became less protuberant. The rabbit lived for a further 2 years with oral meloxicam each day. (Reproduced from with permission from .)
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29.18 This cheek abscess developed rapidly. There was skin necrosis over the abscess and the rabbit was inappetent. The position of the abscess does not identify any particular cheek tooth as a source of infection (see Figure 29.5 ) although the rabbit was suffering from advanced PSADD. The abscess was not identifiable on skull radiographs. Surgical exploration revealed a large quantity of liquid foul-smelling pus containing a large piece of hay that presumably had been caught around a deformed tooth and penetrated the oral mucosa. The rabbit made a complete recovery after opening the abscess, removing the necrotic skin, draining all the pus and leaving the cavity open. A 10-day course of penicillin/streptomycin by subcutaneous injection was also given.
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29.19 Lateral and DV views of the skull of a rabbit with a swollen nose, stridor and a nasal discharge. He was a rescue rabbit that had been adopted one year previously, with his incisors already extracted. One upper incisor had regrown to form a dysplastic remnant that was occluding the nasal cavity. There was severe osteomyelitis of the incisive bone and infection in the ethmoturbinates. The rabbit was eventually euthanased, despite extensive surgery to remove the tooth remnants and infected bone with prolonged courses of antibiotics. Recalcitrant infection had spread into the nasal passages and sinuses.
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29.20 This lateral view of the skull shows an abscess at the apex of a mandibular incisor that was maloccluded. This was a rescue rabbit with no clinical history but the most plausible explanation for an abscess in that site was that infection had tracked through a pulp cavity that had been exposed during incisor clipping.
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29.21 Important anatomical structures of the face. Drawn by S.J. Elmhurst BA Hons (www.livingart.org.uk) and reproduced with her permission.
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29.22 A gauze-packed abscess cavity. (Courtesy of A Melillo)
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29.23 This lateral view of the skull was taken because the rabbit was suffering from epiphora. It was taken 3 years after the rabbit had undergone surgery for a mandibular abscess involving the lower 4th cheek tooth. The jaw had fractured during the surgical procedure, and the site of the healed abscess and fracture can be seen (arrow).
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29.24 Lateral view of the skull of FHB’s 7-year-old Dutch rabbit that had fractured a lower 4th cheek tooth by chewing on something hard in the garden. An abscess on the cheek developed and was cured by removing the fractured tooth in addition to the 5th mandibular cheek tooth which was displaced. Subsequently, the rabbit required dentistry every 6–8 weeks to shorten the opposing maxillary crowns that grew into a point that penetrated the mucosa (arrow). The rabbit was euthanased because of an intestinal lymphoma 18 months later.
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29.25 Maggots placed in an abscess cavity can be seen through the translucent semipermeable plastic sheet that will be sutured over the wound. As this cavity must be kept dark and damp, a gauze sheet is sutured over the plastic and impregnated daily with sterile saline. (© John Chitty)
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29.26 Lateral view of a rabbit with a walled-off abscess that never required treatment. This is a rare case. The pus has calcified granules in it. (Reproduced from with permission from .)
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29.27 An example of an abscess with a good prognosis. Despite the evidence of advanced dental disease that can be seen on this lateral radiograph of the skull, the mandibular abscess that was present carried a good prognosis. The abscess was contained in a bony capsule. The calcified granules indicate that it was a longstanding chronic abscess. There is lucency around a single tooth fragment (arrow) that was easily accessible surgically. The tooth fragment was removed and the cavity marsupialized. The abscess did not recur, although the rabbit continued to have some dental problems. The fractured crown on an upper incisor was removed at the time of abscess surgery.
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29.28 An example of an abscess with a bad prognosis. This 10-month-old rabbit was presented with a swollen nose, a purulent nasal discharge, salivation and anorexia. His incisors had been removed by the referring veterinary surgeon 2 months previously. Oral examination showed a spur on the 6th maxillary cheek tooth, curling round and penetrating the hard palate. The eye on the affected side was slightly exophthalmic. The lateral radiograph of the skull shows a generalized osteopenia. There is regrowth of a maxillary incisor, sinusitis and turbinate loss. The cheek teeth are grossly deformed (though some still have a central enamel fold) and they were still growing. The presence of a retrobulbar abscess was confirmed by aspirating pus from the retrobulbar space. The retrobulbar abscess and the abscess on the nose were treated at the owner’s request but reappeared some weeks later. The rabbit was euthanased.
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29.29 Mandibular abscess in a rabbit with chronic renal failure. This lateral view of the skull is well exposed, with good bone contrast. This is often a feature of rabbits with renal disease because they are unable to excrete excess calcium through their kidneys, and ectopic and dystrophic mineralization can be the result. The hyoid bone is calcified. Blood tests showed raised urea, creatinine, calcium and phosphorus levels but the owner still opted for surgery. The rabbit died postoperatively.
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29.30 Retrobulbar abscess. The left eye of this rabbit had suddenly become grossly exophthalmic. A retrobulbar swelling was visible and palpable between the eye and the zygomatic arch . Blood was aspirated from the swelling, as it was suspected that haemorrhage from the ophthalmic venous sinus behind the eye was responsible for the sudden marked exophthalmos and that infection from the abscess had eroded into the blood vessel. The globe of the eye looked normal. A discharging sinus adjacent to a maxillary cheek tooth was evident on oral examination and radiography confirmed the presence of elongated, deformed tooth roots in the retrobulbar space. Exploratory surgery via an incision between the globe and the zygoma revealed the abscess capsule, which was opened to remove the pus. Two maxillary teeth were removed and the rabbit recovered without enucleation of the eye.
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29.31 This exophthalmic eye would never be visual again and could only be a source of pain and discomfort for the rabbit. The eye was enucleated and the retrobulbar abscess treated by identifying and removing the infected teeth.
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Image of Appearance of an infected tooth within an abscess cavity (arrow).
Appearance of an infected tooth within an abscess cavity (arrow). Appearance of an infected tooth within an abscess cavity (arrow).
Image of Sectioning the infected tooth root with bone cutters.
Sectioning the infected tooth root with bone cutters. Sectioning the infected tooth root with bone cutters.
Image of Appearance of an infected root that has been sectioned with bone cutters.
Appearance of an infected root that has been sectioned with bone cutters. Appearance of an infected root that has been sectioned with bone cutters.
Image of Removing the distal fragment of an infected tooth root with adapted needle-holders.
Removing the distal fragment of an infected tooth root with adapted needle-holders. Removing the distal fragment of an infected tooth root with adapted needle-holders.
Image of Appearance of distal fragment after removal.
Appearance of distal fragment after removal. Appearance of distal fragment after removal.
Image of Appearance of cavity after removal of distal fragment.
Appearance of cavity after removal of distal fragment. Appearance of cavity after removal of distal fragment.
Image of Elevating rostral tooth fragment with a scalpel blade.
Elevating rostral tooth fragment with a scalpel blade. Elevating rostral tooth fragment with a scalpel blade.
Image of Appearance of rostral fragment after removal through abscess cavity.
Appearance of rostral fragment after removal through abscess cavity. Appearance of rostral fragment after removal through abscess cavity.
Image of Appearance of abscess cavity after cleaning with cotton buds.
Appearance of abscess cavity after cleaning with cotton buds. Appearance of abscess cavity after cleaning with cotton buds.
Image of Suturing abscess capsule to skin.
Suturing abscess capsule to skin. Suturing abscess capsule to skin.
Image of Appearance of marsupialized abscess at the end of surgery.
Appearance of marsupialized abscess at the end of surgery. Appearance of marsupialized abscess at the end of surgery.
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