Retropharyngeal Cellulitis

Retropharyngeal cellulitis is infection of the loose connective tissue between the posterior pharyngeal wall and the prevertebral fascia, before it collects into an abscess. It is polymicrobial: group A streptococci, Staphylococcus aureus (including MRSA) and oral anaerobes.

• Commonest in children under 5 years because the retropharyngeal lymph nodes are present and regress with age.
• In adults it follows penetrating throat trauma, fish bone or instrumentation, dental sepsis, or spread from the vertebrae.
• It can obstruct the airway, erode into vessels and descend into the mediastinum.

Fever, severe sore throat, painful or refused swallowing, drooling, muffled "hot potato" voice, neck stiffness or torticollis, reluctance to extend the neck, and sometimes noisy breathing.

• Bulging of the posterior pharyngeal wall may be seen, but the throat is hard to examine in a distressed child.
• Differential diagnosis: peritonsillar abscess, epiglottitis, croup, bacterial tracheitis, meningitis, cervical lymphadenitis, foreign body, vertebral osteomyelitis, Kawasaki disease, dystonic drug reaction.
• Complications: airway obstruction, parapharyngeal extension, mediastinitis, jugular vein thrombosis (Lemierre syndrome), carotid artery erosion, aspiration pneumonia, sepsis, epidural abscess.

Diagnosis rests on clinical suspicion and imaging; do not distress a child with an airway at risk.

• Contrast enhanced CT of the neck distinguishes cellulitis from abscess and shows extent.
• Lateral soft tissue neck radiograph in extension: prevertebral space wider than 7 mm at C2 or wider than 14 mm in children (22 mm in adults) at C6.
• Full blood count, CRP, blood cultures, and swab or pus culture if drained.

Secure the airway first, then treat with intravenous antibiotics and drain if an abscess forms.

• Supportive: nil by mouth, intravenous fluids, humidified oxygen if hypoxic, keep the child calm with a parent present, head up position, analgesia with paracetamol 15 mg/kg every 6 hours (adults 1 g).
• Pharmacological: ampicillin sulbactam 3 g IV every 6 hours (children 50 mg/kg of ampicillin every 6 hours, maximum 2 g per dose); or ceftriaxone 2 g IV daily (children 50 to 100 mg/kg daily) with metronidazole 500 mg IV every 8 hours (children 7.5 mg/kg every 8 hours). Add clindamycin 600 mg IV every 8 hours (children 10 mg/kg every 8 hours) or vancomycin 15 to 20 mg/kg IV every 8 to 12 hours where MRSA is likely. Switch to oral amoxicillin clavulanate 625 mg three times daily to complete 10 to 14 days once afebrile and swallowing.
• Procedures: surgical drainage if an abscess is larger than 2 cm on CT, if the airway is threatened, or if there is no improvement within 24 to 48 hours; intubation or tracheostomy by an experienced operator for impending obstruction.
• Special groups: infants, weight based dosing and close airway observation; diabetes, tight glucose control; penicillin allergy, clindamycin with ciprofloxacin in adults; HIV, culture and consider tuberculosis.
• Red flags: stridor, drooling with inability to swallow, trismus, torticollis with fever, chest pain or widened mediastinum, neck swelling with persistent fever.
• Follow-up: review in 48 to 72 hours after discharge; repeat imaging if symptoms return.