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Retropharyngeal abscess aetiology, diagnosis and management

Retropharyngeal abscess is a type of deep neck space infection, which can be a life-threatening infection if not detected early.

Potential threat to airways should always be considered.

Symptoms may be non-specific (e.g., fever, dysphagia), especially in children under 2 years old. CT scan of neck is the definitive investigation.
Retropharyngeal abscess


Treatment includes use of intravenous antibiotics and surgical or radiologically guided drainage. Type of surgical drainage depends on the size and extent of the abscess; this can be endo-oral or external.

Epidemiology

Although rare, RPAs are serious, with the potential for significant morbidity and mortality if not detected early. They account for 12% to 22% of all deep space infections in the neck. The peak incidence in children is at 3 to 5 years of age. 

The condition is increasing in incidence in adults. Children are more frequently affected by the condition because they have an increased frequency of upper respiratory tract infections and oropharyngeal trauma, as well as the tendency towards suppuration in the retropharyngeal lymph nodes. These nodes tend to regress after the age of 4 years. RPAs are more common in males than in females, with 53% to 62% of cases occurring in males.

In a 10-year review of RPA cases in the US, 70% of patients were African-American, 25% were white, and 5% were Hispanic. However, a 2004 study found 43% of cases in African-American people, 54% in white people, 1% in Hispanic people, and 1% in biracial people.

Clinical picture

Although history and examination are key to identifying an RPA, imaging or the spontaneous or surgical drainage of the abscess confirms the diagnosis.

History

A careful history is important, as other serious conditions are part of the differential diagnoses. RPAs are most commonly the sequelae of an upper respiratory tract infection (e.g., pharyngitis, tonsillitis, sinusitis, dental infections). They occur more commonly in children; therefore, a history of foreign body ingestion should be noted.

In children, presentation may be vague and depends on the stage of disease, but characteristic symptoms include spiking fever, neck pain (especially on movement) or torticollis, and dysphagia. Other common symptoms include irritability, malaise, mild photophobia, and odynophagia (painful swallowing). Odynophagia causes drooling, poor oral intake, and anorexia. Less common symptoms include trismus (lockjaw), dysphonia (hoarseness), stridor, or sleep apnoea. The child may also be seen to pull at their ears or throat, which indicates pain.

In adults, the presentation may be more specific with drooling and dysphagia, but is usually more insidious in onset. It is important to enquire about comorbidities such as diabetes mellitus and optimise glycaemic control if present. Up to one third of patients with a deep neck abscess have diabetes mellitus.

Airway compromise usually presents with symptoms of dyspnoea, distress, and fatigue. Patients with a more complicated clinical course are more likely than those with a smooth clinical course to present with airway obstruction or multiple abscesses.

Physical examination

An attempt should be made to examine the oral cavity and neck to look for tonsillar swelling, oropharyngeal swelling, and lymphadenopathy. Other important observations may be made such as drooling, dyspnoea, torticollis, and neck swelling/mass. In children the examination may be limited depending on the age and co-operation of the child (and parents).

Airway compromise usually presents as tachypnoea, cyanosis, tracheal tug, or intercostal recession. High respiratory rate and oxygen saturations aid diagnosis of a compromised airway. In cases where there is a concern of airway compromise in the form of partial airway obstruction, stridor, or stertor, oropharyngeal examination may be best performed in a controlled setting (i.e., in the operating theatre where an emergency surgical airway can be established if required).

Laboratory investigations

A full blood count with differential should be ordered initially to confirm neutrophilia. The erythrocyte sedimentation rate can be measured to establish the degree of inflammatory disease in the absence of a significant neutrophilia. Blood cultures are not usually taken, unless sepsis is suspected. In unusual presentations consider testing for Epstein-Barr virus, cytomegalovirus, and toxoplasmosis titers in addition to C-reactive protein.

Imaging

Radiological investigations are required to confirm diagnosis. The selected investigation depends on the degree of suspicion and access to the different imaging modalities, as well as the severity of the case. Nonetheless, a CT scan is the definitive investigation and will demonstrate a ring-enhancing lesion in the retropharyngeal tissues when performed with contrast.

If there is an airway concern or a likelihood of surgical drainage, then sedating and intubating a child before CT scanning with a view to proceeding to the operating theatre should be considered.

Ultrasonography and plain x-ray of the neck will provide some evidence of an RPA, but these modalities are less sensitive and less specific than a CT scan. They should only be used when a CT scanner is not available.

MRI is not used to diagnose this condition, as CT gives such a clear result in most cases and is usually more readily available and cheaper as a resource.

Retropharyngeal abscess CT scan
CT scan of neck demonstrating ring-enhancing lesionPhilpott CM, Selvadurai D, Banerjee AR. Paediatric retropharyngeal abscess. J Laryngol Otol. 2004;118:919-926

Surgery

Examination under anaesthetic (EUA) should be performed if diagnosis of RPA is strongly suspected and the airway is compromised or if a CT scanner is not available. 

EUA should also be performed if CT scan (or other imaging investigations if CT is not available) has been performed and the result is consistent with RPA. In cases where CT does not show well defined ring-enhancing lesions, trial of intravenous antibiotics can be tried before considering surgical drainage.

EUA allows confirmation of diagnosis and allows transoral incision and drainage. A well circumscribed, uniloculated RPA may, in selected adults, be adequately treated with ultrasound guided drainage.  A specimen of pus should be taken for culture and sensitivity at the time of drainage.

Aetiology

Around 45% of RPAs are the sequelae of an upper respiratory tract infection (e.g., pharyngitis, tonsillitis, sinusitis, dental infections). Most of the time RPAs are polymicrobial irrespective of age of presentation. 

The most common microorganisms implicated are Streptococcus viridans, Staphylococcus aureus, Streptococcus epidermidis, and beta-haemolytic streptococci. 

Less common causes include Veillonella species, Bacteroides melaninogenicus, Haemophilus parainfluenzae, and Klebsiella pneumoniae. Infections with both methicillin-resistant Staphylococcus aureus and Mycobacterium tuberculosis have also been reported.

Normal commensals of the upper respiratory tract can become pathologically offending organisms in an RPA. 

Approximately 27% of RPAs are associated with accidental trauma to the retropharyngeal area from, for example, foreign body ingestion, a child running along with a lollipop in their mouth and falling, or swallowing sharp objects such as chicken bones. The remaining 28% are idiopathic.

Pathophysiology

The retropharyngeal space is immediately anterior to the prevertebral fascia that continues inferiorly from the skull base for the length of the pharynx.  It is in continuity with the parapharyngeal space and the infratemporal fossa. 

The retro- and parapharyngeal spaces are separated by the alar fascia, which seems to be an ineffectual barrier to the spread of infection. As the retropharyngeal space is in continuity with the superior and posterior mediastinum, it is a potential pathway for spread of infection into the chest.

The retropharyngeal space contains loose areolar tissue and lymphatic chains, the former allowing movement of the pharynx and oesophagus on swallowing. 

The lymph flowing through the space originates from tissues in the nose, paranasal sinuses, eustachian tubes, and adjacent pharyngeal tissues. 

Pus formation in the retropharyngeal nodes is often well contained, and therefore vertical spread of infection can occur late in the progression of the condition, although this rarely occurs in practice.

Most of the symptoms and signs of RPA relate to the increasing obstruction of the upper aerodigestive tract and irritation of local muscle groups (e.g., sternomastoid and pterygoids).

Differential Diagnosis

  • Acute epiglottitis
  • Laryngotracheobronchitis
  • Meningitis
  • Tonsillitis
  • Peritonsillar abscess
  • Retropharyngeal lymphadenopathy
  • Nasopharyngeal carcinoma
  • Epstein-Barr virus infection
  • Retropharyngeal calcific tendonitis
  • Branchial cyst
  • Kawasaki disease (KD)

Management

Management is initially medical. If this fails, surgical intervention is required, with the consultation of an otolaryngologist. All patients should be admitted to hospital. Safe and appropriate management of the airway is paramount. This is usually achieved through conservative or surgical means. Treatment primarily depends on the severity of respiratory distress.

Airway compromise

If there is a strong suspicion of an RPA and the airway is compromised (indicated by stridor, tachypnoea, and decreased oxygen saturation as the patient becomes fatigued), the patient should be admitted to hospital immediately. Initial medical management includes the use of corticosteroids, nebulised adrenaline (epinephrine), and antibiotics. 

If this is not rapidly effective, the patient should be taken to theatre promptly for examination under anaesthesic (EUA) with a view to surgical drainage. 

Intubation or a surgical airway such as a tracheostomy will be required and should be performed by an experienced paediatric or adult anaesthetist. Fibre-optic intubation is sometimes favoured in these cases to prevent bursting of the abscess and to gain a good view of the airway. 

If the tube is uncuffed, it is helpful to insert a pack allowing a view of the posterior pharyngeal wall for surgical access. 

If an RPA is confirmed on surgical examination (bulging of posterior oropharyngeal wall seen and/or by aspiration of purulent fluid), the surgeon should perform a transoral incision and drainage. Cultures are taken and sent to the laboratory. 

In cases where there is extension to the posterior mediastinum, drainage of purulent discharge and debridement of necrotic material from the pericardial area and pleural space may be required, possibly in conjunction with a cardiothoracic team.

If the airway is still unstable, the patient should be monitored closely in an intensive care unit and started on empirical intravenous antibiotics; prolonged intubation or tracheostomy may be required. Patients with a stable airway after surgery should also be started on empirical intravenous antibiotics.

No airway compromise

Even in the absence of airway compromise, the patient should still be admitted to hospital and carefully observed. 

If the airway is not an immediate concern and there is no evidence of mediastinal extension of the abscess, treatment with empirical intravenous antibiotics for 24 to 48 hours should be initiated promptly. 

Corticosteroids may also be used in conjunction with the intravenous antibiotics.

Prompt treatment with antibiotics, with or without corticosteroids, can cause resolution or prevention of disease progression, in some patients with an early presentation (where there is only cellulitis rather than true abscess formation), thereby avoiding the need for surgical drainage.

Failure of initial medical treatment (i.e., no symptomatic improvement, continuing swinging pyrexia, deterioration of vital signs), and/or the presence of a defined abscess on imaging should prompt the need for EUA with a view to peroral surgical drainage. 

Although the general rule of thumb is to consider drainage for abscesses over the size of 2 cm, it is important to value clinical presentation and initial response to intravenous antibiotics even in larger abscesses. 

Repeat CT imaging may be necessary to precisely locate the abscess. 
In paediatric patients, it is usually preferable to anaesthetise prior to the CT scan, whereas adults can generally undergo imaging without the need for anaesthesia. Intravenous antibiotics are continued after surgical drainage, either as an empirical regimen or according to sensitivities when available.

The presence of a defined abscess on imaging is typically an indication for drainage. However, the efficacy of medical management for CT-confirmed, deep neck abscesses in children was evaluated in a 2012 systematic review. The authors found that medical therapy alone might be an effective alternative to surgery in some patients, although the evidence was weak. 

Delaying surgery in favour of medical management for confirmed abscesses remains controversial, given the risk of disease progression and subsequent airway compromise. Additionally, a lack of microbiology samples may hamper the ability to tailor antibiotic therapy.

Empirical antibiotic therapy

Antibiotics should cover the most commonly implicated organisms: Streptococcus viridans, Staphylococcus aureus, Streptococcus epidermidis, and beta-haemolytic streptococci. 

Less common causes include Veillonella species, Bacteroides melaninogenicus, Haemophilus parainfluenzae, and Klebsiella pneumoniae. Normal commensals of the upper respiratory tract can become pathologically offending organisms in an RPA. 

Typical antibiotic regimens include ampicillin/sulbactam, clindamycin, cefuroxime, ceftriaxone, metronidazole, and amoxicillin/clavulanic acid. Combination regimens of these antibiotics may be necessary to adequately cover likely organisms (e.g., ceftriaxone plus metronidazole or clindamycin plus cefuroxime). 

Metronidazole would cover for anaerobic bacteria as there may be a connection with the parapharyngeal space and therefore the oral cavity.

Clinical improvement should be seen within 24 to 48 hours; if this is not the case, the patient should be re-evaluated. The antibiotic spectrum may need to be broadened. In refractory cases, atypical mycobacteria or MRSA should be suspected. 

Empirical antibiotics should be continued until the patient is afebrile or able to tolerate oral medications to complete a 14-day course. Patients may be switched to targeted therapy based on cultures if drainage is performed.

Supportive care

Patients should have their airway monitored throughout treatment, and patients with an unstable airway after surgery should be monitored closely in an intensive care unit. 

Adequate intravenous hydration and nutrition should be given until oral intake of food and drink is tolerated. 

Some patients may require analgesia. Patients should be monitored closely for development of complications.

Treatment algorithm

Please note that formulations/routes and doses may differ between drug names and brands, drug formularies, or locations. Treatment recommendations are specific to patient groups.

1st line


Intravenous corticosteroid + nebulised adrenaline (epinephrine)

If there is a strong suspicion of RPA and the airway is compromised, the patient should be admitted to hospital immediately. 

Initial medical management includes the use of intravenous corticosteroids and nebulised adrenaline (epinephrine). If this is not rapidly effective, the patient should be taken to theatre promptly for examination under anaesthesic with a view to surgical drainage. 

Fibre-optic intubation is sometimes favoured in these cases to prevent bursting of the abscess and to gain a good view of the airway

Primary options
dexamethasone: children and adults: 0.5 to 2 mg/kg/day intravenously given in divided doses every 6 hours

and:

adrenaline inhaled: consult local protocols for guidance on dose.

Plus 

surgery

Treatment recommended for ALL patients in selected patient group

If intravenous corticosteroids + nebulised adrenaline (epinephrine) are not rapidly effective, the patient should be taken to theatre promptly for examination under anaesthesic with a view to surgical drainage.

Intubation (by an experienced paediatric or adult anaesthetist) or a surgical airway such as a tracheostomy will be required. 

Fibre-optic intubation is sometimes favoured in these cases to prevent bursting of the abscess and to gain a good view of the airway. 

If the tube is uncuffed, it is helpful to insert a pack allowing a view of the posterior pharyngeal wall for surgical access.

If an RPA is confirmed on surgical examination, the patient should undergo transoral incision and drainage.

Cultures are taken and sent to the laboratory.

In cases where there is extension to the posterior mediastinum, drainage of purulent discharge and debridement of necrotic material from the pericardial area and pleural space may be required, possibly in conjunction with a cardiothoracic team.

Plus: 

empirical antibiotic therapy

Treatment recommended for ALL patients in selected patient group

Antibiotics should be started after surgery and should cover the most common organisms: Streptococcus viridans, Staphylococcus aureus (including MRSA), Streptococcus epidermidis, and beta-haemolytic streptococci. Less common causes include Veillonella species, Bacteroides melaninogenicus, Haemophilus parainfluenzae, and Klebsiella pneumoniae. 

Normal commensals of the upper respiratory tract can become pathologically offending organisms in an RPA.

Metronidazole provides necessary cover for anaerobic bacteria (there may be a connection with the parapharyngeal space and therefore the oral cavity).

Clinical improvement should be seen within 24 to 48 hours; if this is not the case, the patient should be re-evaluated. The antibiotic spectrum may need to be broadened. In refractory cases, atypical mycobacteria or MRSA should be suspected.

Intravenous treatment should be continued until the patient is afebrile or is able to tolerate an oral antibiotic (e.g., amoxicillin/clavulanate), to complete a 14-day course.

Patients may be switched to targeted therapy based on cultures from incision and drainage if performed.

Primary options
ampicillin/sulbactam: children >1 month of age: 100-200 mg/kg/day intravenously given in divided doses every 6 hours; adults: 1-2 g intravenously every 6-8 hours, maximum 12 g/day.

OR

ceftriaxone: children >1 month of age: 50-80 mg/kg/day intravenously given in divided doses every 12-24 hours; adults: 1-2 g intravenously every 12-24 hours

and

clindamycin: children >1 month of age: 25-40 mg/kg/day intravenously given in divided doses every 6-8 hours; adults: 1.2 to 2.7 g/day intravenously given in divided doses every 6-12 hours

OR

cefuroxime: children >1 month of age: 75-150 mg/kg/day intravenously given in divided doses every 8 hours; adults: 750-1500 mg intravenously every 8 hours

and

metronidazole: children >1 month of age: 22.5 mg/kg/day intravenously given in divided doses every 6 hours; adults: 500 mg intravenously every 8 hours.

Plus 

supportive care + analgesia

Treatment recommended for ALL patients in selected patient group

Patients who still have an unstable airway after surgery should be monitored closely in an intensive care unit. These patients may require prolonged intubation or tracheostomy.

Adequate intravenous hydration and nutrition should be given until the patient is able to tolerate oral intake of food and drink.

Some patients may require analgesia.

Patients should be monitored closely for development of complications.

Primary options
paracetamol: children: 10-15 mg/kg orally every 4-6 hours when required, maximum 75 mg/kg/day; adults: 500-1000 mg orally every 4-6 hours when required, maximum 4000 mg/day.

OR

ibuprofen: children: 5-10 mg/kg orally every 4-6 hours when required, maximum 40 mg/kg/day; adults: 300-400 mg orally every 6-8 hours when required, maximum 2400 mg/day.
Retropharyngeal abscess aetiology, diagnosis and management
Dr.Tamer Mobarak

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