Caroline Fina DEDV DipECVDI MRCVS European Specialist in Veterinary Diagnostic Imaging Rosario Vallefuoco DVM MRCVS Crystal White BVetMed (Hons) MRCVS
History
A 5-year-old female Labrador dog was referred to Pride Veterinary Centre for investigation and treatment of a ventral mid-cervical swelling. Eleven days prior to presentation the owners report the dog had cried out in pain, and blood had been seen coming from the mouth whilst playing with a wooden stick. Physical examination performed by a referring veterinary surgeon under general anaesthetic revealed a small bleed on the dorsal aspect of her tongue. This was probed, flushed and closed. No foreign body was found at that time and the dog was prescribed a course of antibiotics and non-steroidal anti-inflammatory drugs. At the end of the antibiotic course a swelling formed at the ventral aspect of her mid-cervical region. Concurrently she developed signs of dysphagia and odynophagia and the owners reported halitosis. At this stage the dog was referred to our surgery department.
Clinical examination
On clinical examination, the patient was reluctant and uncomfortable on opening her mouth. The swelling on her ventral mid-cervical region was inflamed, elicited pain on palpation and had a fibrous-like core. The skin directly overlying the swelling was particularly inflamed and exudative. The rest of her general examination was largely unremarkable. The history and subsequent clinical examinations were highly suspicious of oropharyngeal penetrating stick injury associated with secondary abscess formation. Therefore, it was elected to perform an oropharyngeal inspection and a computed tomography examination under sedation to identify and localise the potential foreign body and to aid in surgical planning.
Oropharyngeal inspection
A healed 1cm-long wound was noticed on the right dorsolateral aspect of thetongue. The rest of the oral and pharyngeal cavities were within normal limits.
Computed Tomography (CT) findings
On CT, a long (6.5cm (L) x 1.4cm (H) x 0.9cm (W)) irregular-shaped space-occupying structure corresponding to a foreign body was present within the ventral aspect of the corpus linguae and geniohyoideus muscle. The foreign body was markedly heterogeneous with a density of -200 Hounsfield units (HU) at the centre (consistent with air) and +120HU at its peripheral. It was encapsulated within an irregular heterogeneous soft tissue attenuating region displaying a marked rim enhancement on the postcontrast images, suggestive of an abscess. There was secondary distortion and asymmetry of the tongue, marked dorsolateral displacement of the deep lingual artery and vein, and mild lateral displacement of the right sublingual vein. The hyoid apparatus and larynx were slightly tilted to the right side but intact. A severe adjacent subcutaneous soft tissue swelling and cellulitis and a mild enlargement of the right mandibular lymph node were also noted. The CT diagnosis was an abscess encapsulated retained foreign object within the tongue and surrounding ventral musculature, associated with secondary adjacent cellulitis and reactive right mandibular lymphadenopathy. Given the heterogeneous density of the foreign body, this was likely to be wood material and air, consistent with the recent history of a stick injury.
Surgery
Exploratory surgery was discussed and offered for the treatment of this kind of condition. With the assistance of the images obtained by the computed tomography multi-planar reconstruction, amid-cervical neck exploration by a ventral midline approach was performed. The abscess was debrided and a 7x2cm wooden stick was removed from the corpus linguae. A bacteriological sampling was performed to target the most appropriate post-operative antibiotic treatment. The surgical site was copiously rinsed and a Penrose drain was placed. The closure of the surgical site was performed as routine in two layers.
Outcome
The patient was discharged the day after the surgery with anti-inflammatory and antibiotic course according to the bacteriological examination. She was much more comfortable than before the surgery and able to eat, drink and swallow without issue. The drain was removed a few days after the surgery. A small area of necrosis of the skin directly involved in the abscess occurred within 10 days, but it was easily managed with subsequent complete healing of the wound and no recurrence of the clinical signs.
Discussion
Detecting retained wooden foreign bodies can be very challenging in practice. Radiography, sonography, ultrasonography, computed tomography (CT) and magnetic resonance imaging (MRI) have been used in dogs to diagnose penetrating or migrating foreign bodies. The choice of imaging modality depends on multiple factors including site of injury, type of foreignbody and availability. Radiography can aid in the detection of wooden foreign bodies but generally is more useful in the acute cases as it allows detection of soft tissue disruption and subcutaneous air introduced at the time of the initial trauma. In chronic cases of retained wooden stick injuries, radiography tends to be less sensitive as the radio-opacity of the wood is not too dissimilar to that of the surrounding soft tissues. CT is often preferred as it enables a fast, cross-sectional examination of any part of the body with relatively high spatial resolution. In a recent retrospective study in dogs with suspected wooden foreign bodies, [1] the sensitivity of CT in the detection of wooden foreign bodies was moderate (79%) but its specificity was high (93%). The clinical and imaging findings could be divided into two groups, reflecting acute and chronic presentations respectively. Presence of gas in soft tissues on CT was significantly associated with acute cases, usually resulting from a penetrating trauma. Conversely, chronic cases often result from ingestion of the foreign body, and subsequent development of an abscess and draining tract, as illustrated in our patient. The presence of suspected foreign body material, cavitary lesions, fat stranding and periosteal reactions on adjacent bones on CT were associated with these chronic cases in the same study. Wooden foreign bodies most often appear as rectangular or linear structures with a wide range of attenuation on CT. In the acute cases, they can be particularly challenging to identify due to the difficulty distinguishing low-density wood material from gas introduced by a penetrating injury. CT multiplanar reconstructions aid identification of foreign bodies and allow better surgical planning and approach of these stick injuries.
References [1] Lamb CR, Pope EH, Lee KC. Results of computed tomography in dogs with suspected wooden foreign bodies. Vet Radiol Ultrasound, 2017, 58(2), 144-150.