How can I detect or rule out a retropharyngeal abscess?

Detection and Diagnosis of Retropharyngeal Abscess

Contrast-enhanced CT scan of the neck is the most effective diagnostic tool for detecting or ruling out retropharyngeal abscess, with sensitivity of 90-100% and specificity of 93.7-100%. 1

Clinical Presentation and Initial Assessment

• Patients with retropharyngeal abscess typically present with acute onset of dysphagia, inability to swallow saliva, odynophagia, neck tenderness, retrosternal pain, sore throat, foreign body sensation, retching, vomiting, and drooling 1
• Airway-related symptoms such as choking, stridor, and dyspnea may indicate airway obstruction or aspiration 1
• Physical examination findings may include fever, cervical subcutaneous emphysema, erythema, and neck tenderness 1
• In children, common presenting signs include fever, dysphagia, neck swelling, and torticollis; respiratory compromise may be present in approximately 29% of pediatric cases 2
• Be vigilant for atypical presentations, especially in infants, as retropharyngeal abscess can masquerade as meningitis 3

Diagnostic Approach

Laboratory Tests

• Complete blood count (CBC), C-reactive protein (CRP), blood gas analysis for base excess, and lactate are recommended biochemical investigations 1
• Blood cultures should be obtained in all patients, as they are positive in approximately 28% of cases 1

Imaging Studies

1. Plain Radiography

   • Lateral neck radiographs showing widening of the prevertebral space are an important initial diagnostic tool 4
   • However, plain radiography has a high false-negative rate (up to 47%), making it insufficient as a standalone test 1

2. Contrast-Enhanced CT Scan

   • Contrast-enhanced CT of the neck is the gold standard for diagnosis with sensitivity of 90-100% and specificity of 93.7-100% 1
   • CT can accurately assess the presence, location, size, shape of the abscess and possible signs of perforation 1
   • CT is superior for evaluating the extent of deep neck inflammation and can help identify dental sources of infection 1
   • CT is essential if there is suspicion of complications such as perforation, abscess, mediastinitis, or fistulas 1

3. MRI

   • MRI offers excellent spatial and contrast resolution for detecting and evaluating the extent of both superficial and deep soft tissue infections 1
   • MRI is particularly useful for evaluating inflammation in bones, joints, muscles, and other soft tissues 1
   • Contrast-enhanced MRI increases diagnostic sensitivity for abscesses, fistulas, and vascular complications 1

4. Ultrasound

   • Ultrasound can be useful for detecting fluid collections but has limitations for deeper structures and evaluation of adjacent bone involvement 1
   • Cervical ultrasonography may be used to evaluate the extension of cervical nodes in obese patients with no palpable lymphadenopathy 1

Special Considerations

• In patients with suspected airway compromise, preparation for securing the airway should be prioritized before any other interventions 5
• Pediatric patients with multiple abscess sites have a significantly greater chance of requiring multiple procedures to clear the infections 6
• Patients presenting with signs of airway obstruction are more likely to have a complicated clinical course requiring PICU admission and/or intubation 6
• Contrast swallow studies are not recommended and should not delay other investigations or interventions 1

Differential Diagnosis

• Consider other deep neck space infections, foreign body ingestion, trauma, or complications of dental infections 4
• In adults, retropharyngeal abscesses are often secondary to trauma, foreign bodies, or complications of dental infections 4
• In children under five years, abscesses are typically secondary to upper respiratory infections, particularly oropharyngeal infections 4

Management Approach

• Once diagnosed, prompt surgical drainage is typically required, with approaches including transoral (most common), external cervical approach, or a combined approach 2
• Appropriate antibiotic therapy should be initiated based on culture results, with Streptococcus pyogenes being a commonly isolated pathogen 4

By following this systematic approach to diagnosis, retropharyngeal abscesses can be detected early, allowing for prompt treatment and prevention of potentially fatal complications such as airway obstruction and mediastinitis.