Retropharyngeal abscess revealing a migrant foreign body complicated by mediastinitis: a case report

Pharyngeal foreign bodies are quite common. Their diagnosis is usually easy. The risk of complications including retropharyngeal abscess and mediastinitis is rare and it depends mainly on the nature of the foreign body and the period of the therapeutic management. The occurrence of these complications darkens the prognosis of this affection usually benign. We report a 21 years old patient, without any significant history, admitted to the emergency for a high painful dysphagia and impaired general condition with fever 20 days after trauma in the posterior pharyngeal wall following a meal. The radiological assessment including cervico-thoracic CT scan had objectified the presence of a metallic foreign body in the retropharyngeal space associated with a retropharyngeal abscess and aggravated by a mediastinitis following the migration of the foreign body to the chest. Biological markers of infection were very increased. The therapeutic management consisted of a surgical drainage of the collections by a cervicotomy with removal of the foreign body. The outcome was favorable clinically and biologically. Pharyngeal foreign bodies are common and favorable when the diagnosis and extraction are made on time. The occurrence of complications, especially retropharyngeal abscess and mediastinitis is rare and burdened with a high morbidity and mortality.


Introduction
Pharyngeal foreign bodies are quite common. Their diagnosis is usually easy. The risk of loco-regional complications, including retropharyngeal abscess is rare and depends essentially on the nature of the foreign body and the delay of the therapeutic management. The retropharyngeal abscess may progress to mediastinitis, which is life-threatening to a patient who initially consulted for a benign prognosis disease. The recent observation of a case of unknown retropharyngeal foreign body gave us the opportunity to make a review of these rare complications.

Patient and observation
A 21 years old patient with no individual pathological history was presented 20 days after a posterior pharyngeal wall trauma produced when taking a meal. The chief complains were a very painful dysphagia, impaired general condition with fever. The general examination revealed a temperature of 39.5°C, a blood pressure 130/70 mmHg, an impaired general condition with asthenia, anorexia and a non quantified weight loss. The examination of the oral cavity revealed a bulge in the posterior wall of the oropharynx. The rest of the examination was without particularity.
Radiography of the cervical spine showed an aspect of a retropharyngeal collection associated with a radio -opaque foreign body (Figure 1), and a cervical CT scan had objectified a retropharyngeal abscess without disco-vertebral lysis confirming the presence of the foreign body (Figure 2). An oral needle aspiration of the collection brought a frankly purulent fluid which was drained under general anesthesia. The patient had received a triple parenteral antibiotics therapy consisting of a combination of amoxicillin-clavulanic acid (1g every six hours), metronidazole (500 mg every eight hours) and aminoglycoside (160mg per day). After healing of the retropharyngeal infection on the tenth day of hospitalization, the patient was operated externally by a lateralcervical incision to remove the foreign body, since the intraoperative X-ray intensifier control had not objectified it in the cervical region.
A nasogastric tube was put in place to enable feeding and healing of the pharynx.

Discussion
Ingestion of foreign bodies was observed in 80% of cases of children in oral phase, usually between six months and three years [1,2]. In adults, the ingestion of foreign bodies are mainly observed in patients with dental prosthesis, prisoners, psychotics or patients with mental retardation and alcoholics [3,4]. In our case, the metallic foreign body was hidden in the meat which the patient accidentally  [5]. A large number of differential diagnoses must then be discussed [6]. CT scan is an important contributing factor for diagnosis, but its limit is the fact that it can't Page number not for citation purposes 3 differentiate a cellulitis from an abcess in the retropharyngeal space [7]. Plain radiography, in lateral view, is very specific when it shows air in the retropharyngeal space [6]. The implementation of radiological assessment should not delay medical support. In case of any suspicion of retropharyngeal abscess, the doctor must prescribe empiric antibiotic therapy that subsequently adapted to the results of antibiogram to prevent it from moving towards infection with a worse prognosis: mediastinitis. Acute mediastinitis is an infectious disease, life-threatening in many cases (20-40 % mortality), that extends from the oropharynx, cervical or esophageal region [8]. The extension of the cervical infection to the mediastinum is due to the continuity of cervico-mediastinal fascia [9].The infection may spread along three anatomical distribution routes: 1-the pretracheal space 2-perivascular space 3-the retropharyngeal space: the elective communication channel between the cervical region and the posterior mediastinum explaining 70% of mediastinitis [10]. The spread of infection can range from the skull base to the diaphragm and below, since there is continuity between the retropharyngeal, retroperitoneal and retro-esophageal space.
Early diagnosis of mediastinitis and therapeutic management are essential for optimal patient survival. The cervico-thoracic CT scan is essential for the diagnosis and follow-up. This infection of the mediastinum is extremely serious and suspected from clinical and radiological arguments. It must be confirmed by surgical exploration and the positive culture of per-operative microbiological samples [8]. The therapy is based on broad spectrum antibiotics, surgery, drainage and treatment of any organ failure. There is currently no standardized surgical therapeutic conduct. A minimally invasive surgical approach may be recommended when the diagnosis is made early and the thoracic drainage is effective. The clinical, laboratory and CT monitoring may indicate a thoracotomy [8].

Conclusion
Pharyngeal foreign bodies are common and favorable when the diagnosis and extraction are made on time. The occurrence of complications, particularly retropharyngeal abscess and mediastinitis is rare and burdened with a high morbidity and mortality.

Competing interests
The authors declare no competing interests.

Authors' contributions
Tarik Ziad contributed substantially in the study design, drafting,