Oropharyngeal penetrating stick injury is a traumatic injury to the oropharynx caused by impact with a stick. It is frequently a consequence of chasing behaviour when a stick is thrown by the owner, but is also reported following stick carrying. Medium sized dog breeds (Border collies, retrievers) are over-represented, presumably due to innate retrieving behaviour. Impact with the stick causes trauma to local structures and may penetrate the oropharynx leading to inoculation of bacteria into the cervical tissue planes; fragments of wood or large pieces of stick may break off and remain embedded within cervical tissues.

Clinical Presentation and Physical Examination

Owners commonly observe the traumatic incident, hear a cry or notice a degree of oral haemorrhage. Following the incident the majority of dogs display only non-specific clinical signs of lethargy and pain. More specific findings on physical examination are identified in some dogs, including the presence of cervical swelling and palpable subcutaneous emphysema, hypersalivation, coughing, gagging and retching. Some dogs present with dyspnoea or severe oropharyngeal haemorrhage. Tetraparesis following penetration of the stick into the spinal canal has also been described.

Dogs that have not been presented to a veterinary surgeon or have not undergone appropriate management may develop signs of sepsis, associated with a descending septic mediastinitis or pyothorax. Alternatively, the grossly contaminated embedded material may form a nidus for persisting infection and abscessation within the cervical tissues, often resulting in a recurrent discharging sinus.

Initial Management

When a dog is presented with a history consistent with a stick injury the following investigations are considered mandatory:

 Thorough oropharyngeal examination under sedation or general anaesthesia.

 Radiography of the cervical soft tissues and thoracic cavity.

Oropharyngeal examination under heavy sedation or general anaesthesia is essential to allow thorough examination and assessment of penetrating injuries. It is important to inspect the sublingual region, caudal oropharynx, soft palate and hard palate. Lesions may not be penetrating, causing only superficial abrasion to the sublingual region or oropharynx. Be very cautious in making this assessment; if there is any perforation of the sublingual or pharyngeal mucosa then further exploration must be performed. It is important to remember that in the majority of cases the dog impacts upon the stick at speed and therefore deep penetration through the cervical tissues and even into the mediastinum or pleural cavity may have occurred. Oesophageal perforation is most common near the pharyngo-oesophageal junction and this may not be possible to appreciate on oropharyngeal examination or with flexible endoscopy. Rigid endoscopy may be more rewarding for assessment of this very proximal region of the oesophagus; however the author does not routinely use endoscopy for investigation in these cases.

Cervical and thoracic radiography is performed in the sedated or anaesthetised patient primarily to look for the presence of free gas within the cervical tissue planes. The cervical tissue planes and the mediastinum are one continuous space; if gas is seen in the cervical tissue planes a pneumomediastinum may also be observed and this does not necessarily indicate that stick penetration has occurred to the depth of the mediastinum. Radiography is a far more sensitive method for detection of gas within cervical tissue planes when compared to physical examination alone. It is unlikely that a foreign body will be identified, unless outlined by gas.

Surgical Exploration

If a penetrating oropharyngeal lesion is identified and/or gas is observed within the cervical tissue planes then prompt ventral midline cervical exploration is essential. The patient should be clipped adequately to allow surgical exploration to be extended to a cranial median sternotomy and thoracotomy depending upon surgical findings. Appropriate preparation should be made for ventilation of the patient during anaesthesia. Familiarity with the complex anatomy of this region is essential prior to embarking upon surgery; referral to a specialist surgical practice is recommended to those without appropriate experience.

Where a penetrating oropharyngeal injury is present a sterile instrument (e.g., Carmalt forceps) is placed through the lesion to serve as a probe, guiding surgical exploration of the cervical tissues. A midline approach for exploration should be maintained initially to avoid damage to cervical structures; however the tract and foreign material will frequently be lateralised. Wooden foreign material is identified and carefully removed; multiple fragments may be present. Exploration is continued caudally towards the thoracic cavity if a tract can be traced from the site of oropharyngeal penetration. If an oesophageal laceration is identified debridement and primary repair are performed. Following removal of pieces of foreign material, copious lavage is performed to reduce the level of wound contamination. The use of suction apparatus facilitates thorough lavage. A bacteriology swab should be obtained from the cervical tissues post-lavage and submitted, together with a piece of retrieved material, for aerobic and anaerobic culture. Empirical antibiosis should be started, initially via the intravenous route (a second generation cephalosporin or potentiated amoxicillin may be an appropriate choice), while awaiting culture results. Prior to wound closure a surgical drain should be placed in the wound. A Penrose drain or Jackson Pratt active suction drain would be appropriate. If the oropharyngeal wound is large or if an active suction drain is selected, closure of the oropharyngeal wound using an absorbable suture material is recommended. The oropharyngeal mucosa will heal rapidly and some surgeons would choose not to perform a primary repair of this site.

Post-Operative Care

The level of post-operative care will be dictated by the injury sustained and the extent of exploratory surgery required. Careful attention is paid to ensure the patient is receiving adequate post-operative analgesia, including a non-steroidal anti-inflammatory medication and opioid agents post-operatively. Most patients can be fed orally immediately post-operatively, but soft food only is recommended. In cases of oesophageal laceration, depending upon the degree of oesophageal injury the use of a surgically placed gastrostomy tube for feeding may be necessary to protect the oesophageal repair. Penrose drains should ideally be dressed and the dressing should be changed once or twice per day to assess the level of fluid production. Patients with dressings involving the head and neck require careful monitoring during hospitalisation. The reservoir of active suction drains should be checked at least twice per day for the volume of fluid collected and for ongoing efficacy of the drain. Removal of the drain is routinely performed 2 to 5 days post-operatively when a steady low amount of fluid production has been reached.

Prognosis

Oropharyngeal penetrating stick injury is a potentially life threatening disease. However, the rate of mortality or ongoing morbidity is low following prompt appropriate management. In cases where a chronic discharging sinus has formed there is a more guarded prognosis for resolution of clinical signs. Recent use of computed tomography of the neck to guide surgical management of these cases may result in a more favourable outcome.

References

1.  White RAS, Lane JG. Pharyngeal stick penetration injuries in the dog. Journal of Small Animal Practice (1988) 29, 13-35

2.  Griffiths LG, Tiruneh R, Sullivan M, Reid SWJ. Oropharyngeal Penetrating Injuries in 50 dogs: A retrospective study. Veterinary Surgery (2000) 29, 383-388

3.  Rayward RM. Acute onset quadriparesis as a sequela to an oropharyngeal stick injury. Journal of Small Animal Practice (2002) 43, 295-298