Retropharyngeal Abscess

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Diagnosis and reasoning

This young boy has presented with a high fever, severe dysphagia (as indicated by drooling of saliva), odynophagia, and restriction of neck movements. These symptoms are suggestive of a severe pathology of the throat. Important diagnoses to consider include acute epiglottitis; a retropharyngeal, peritonsillar or parapharyngeal abscess; or a residual foreign body. In addition, cervical lymphadenopathy complicated by neck muscle spasms may present in this manner. Examination shows that no foreign bodies are present; that the epiglottis is normal; and that the tonsils are also normal. In addition, note the bulging posterior pharyngeal wall - this is suggestive of a retropharyngeal abscess (RPA). This fits in with the history of impaction of a fish bone, as RPAs are well known to occur following penetrating trauma. Note that parapharyngeal abscesses typically cause a bulge in the lateral pharyngeal wall and lateralization of the tonsils - features which are absent in this child. A soft tissue x-ray of the neck is a good first-line investigation, and in this patient shows a widened retropharyngeal space. Along with the clinical findings, this is sufficient to diagnose a RPA. A throat swab is best avoided, as cultures are usually negative and there is a risk of rupture of the abscess. In these patients, the first priority is to assess the state of the airway. As this child's airway appears to be stable, urgent intubation is unnecessary - although he should be kept under close observation. Empirical IV antibiotic therapy (i.e. with Clindamycin) should be commenced simultaneously. While immediate surgical drainage is not essential (as he is clinically stable, and as the RPA may resolve with antibiotic therapy alone), he should still be kept nil orally, as emergency surgery may be required if his condition deteriorates. Antispasmodics are not indicated in this patient.


Discussion

A retropharyngeal abscess (RPA) is a severe infection of the deep neck space. It is an otolaryngological emergency, with potential for life-threatening airway obstruction. RPAs are the most common deep neck infection in children, occurring mainly between 6 months to 6 years of age, with a slight male predominance. There are two main mechanisms via which the retropharyngeal space can become infected - local spread of infection and direct inoculation from penetrating trauma. In children below 5 years, RPAs are usually secondary to infection of lymph nodes in the retropharyngeal space (following upper respiratory tract infections, dental infections or cervical lymphadenitis). Beyond this age, the retropharyngeal lymph nodes regress, and direct inoculation due to penetrating trauma becomes the primary source of infection. Penetrating pharyngeal trauma is usually caused by foreign bodies (such as fishbones); falling with a sharp object in the mouth; or iatrogenic injuries. The offending pathogens vary based on the origin of the infection, and frequently include multiple aerobic and anaerobic organisms. The most common infections are due to group A beta-haemolytic Streptococci, anaerobic organisms and Staphylococcus aureus. Affected patients typically present with constitutional complaints such as fever, chills, malaise, decreased appetite, muffled “hot potato” voice and irritability. Other signs and symptoms include a sore throat, dysphagia, odynophagia, trismus and torticollis. Examination may reveal bulging of the posterior pharyngeal wall, cervical lymphadenopathy (usually unilateral) and painful restricted neck movements. Children with severe infections may position themselves to maintain a patent airway (for example, by mouth breathing, tongue protrusion or mandibular protrusion). If a RPA is suspected clinically, and the child is stable, a lateral soft tissue neck radiograph is a good first-line investigation. This should be performed during inspiration with the neck held in normal extension. In a normal x-ray, the soft tissue plane between the anterior surface of the vertebrae to the posterior border of the airway is less than one half the width of the corresponding vertebral body. Widening of this retropharyngeal space is the usual radiographic finding in a RPA. In addition, the cervical spine may also be straightened with loss of the normal lordosis ("Ram Rod spine") and an air or fluid level may be noted. However, x-rays have a limited sensitivity and specificity - thus contrast CT imaging of the neck is being increasingly used now. Typical CT findings include a hypodense lesion in the retropharyngeal space, and ring enhancement or scalloping of the walls of a lymph node. CT scans are also helpful in demarcating the lesion and determining if vascular involvement is present. MRI is unnecessary and is rarely used. Ultrasonography is another alternative but it is of limited value in surgical planning. Routine laboratory investigations are nonspecific. Full blood counts usually shows a neutrophil leukocytosis. Blood cultures should be obtained to guide antibiotic therapy. Note that if the child is clinically unstable, the above investigations should be postponed until after stabilization. In the management, the first priority is to determine the stability of the airway. If impending obstruction is suspected, the airway should be secured emergently. Stable patients should be allowed to remain in a comfortable position and monitored continuously. Empirical IV antibiotic therapy should be commenced as soon as possible, and changed as appropriate once blood culture results are available. Clindamycin is one of the first-line antibiotics recommended, and should be given in combination with a beta-lactamase inhibitor (such as clavulanic acid) or cefoxitin, cefuroxime, or imipenem, to cover beta-lactamase-resistant organisms. IV antibiotics should be continued until the patient improves clinically and is afebrile for at least 48 hours, following which they may be switched to oral therapy. Surgical incision and drainage is indicated in patients with progressive airway obstruction and in those who fail to improve within 24 to 36 hours of antibiotic therapy. This can be done either through an intraoral incision or via an external cervical approach. Note that the airway may be distorted in these patients (due to the mass effect of the abscess), and intubation can be complex - thus an experienced anesthetist should be involved, and equipment required for difficult airway management should be kept close at hand. Important complications of RPA include airway compromise, rupture of the abscess with inhalation of contents leading to aspiration pneumonia (or rarely, asphyxiation), spread of infection to adjacent structures in the neck (including the carotid sheath), osteomyelitis of the cervical spine, and mediastinitis. Necrotizing fasciitis is another rare, but serious complication. In previously healthy individuals, uncomplicated RPAs usually carry a good prognosis, with complete recovery.


Take home messages

  1. When a child presents with profound throat symptoms, the possibility of an RPA should be kept in mind.
  2. An undue delay in removing foreign bodies in the pharynx may result in an RPA down the line.
  3. The first priority in patients with a RPA is to ensure a patent airway.
  4. Many such patients have a difficult airway - expert anesthetic assistance should be sought prior to intervention.

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  1. Anaesthetic management of difficult airway due to retropharyngeal abscess - Indian Journal of Anaesthesia (2010)
  2. Anaesthetic management of retropharyngeal abscess in children: Anaesthesia tutorial of the week - World Federation of Societies of Anaesthesiologists (2011)
  3. Retropharyngeal abscess - Diagnosis - Best Practice - BMJ (2011)
  4. Retropharyngeal abscess: Archives of Disease in Childhood (1991)