Sandbox:Retropharyngeal abscess

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]Associate Editor(s)-in-Chief: Vishal Devarkonda, M.B.B.S[2]

Overview

Retropharyngeal space is a deep space in neck extending from the base of skull to the posterior mediastinum. Microorganisms can be introduced into this space either through lymphatic or direct or traumatic spread leading to cellulitis. Cellulitis may progress to form phlegmon, which in-turn progress to form mature abscess. Most common causes of retropharyngeal abscess are polymicrobial infections, beta-hemolytic streptococcus, Streptococcus pyogenes (group A streptococcus [GAS]), Staphylococcus aureus (including methicillin-resistant S. aureus [MRSA]), and respiratory anaerobes. Retropharyngeal abscess commonly affects children, median age being 4 years for children. Common complications of retropharyngeal abscess are life-threatening descending necrotizing mediastinitis, sepsis, internal jugular vein thrombophlebitis, and mediastinitis. Patients with retropharyngeal abscess may present with pain in neck, fever, sore throat, and mass in neck . Diagnosis of retropharyngeal abscess is based on clinical presentation supported by radio-graphic imaging. Management predominantly consists of empiric intravenous antibiotics or combination of surgical drainage and intravenous antibiotics.

Historical Perspective

• The exact origins of the disease is not clearly known. The term abscess is derived from latin term abscessus(meaning: act of going away)
• In 1926, Guthrie described a case of retropharyngeal abscess in childhood.
• In 1946, Davidson described a case of retropharyngeal abscess in adults.

Classification

There is no established classification system for retropharyngeal abscess.

Pathophysiology

The pathophysiology of retropharyngeal abscess can be discussed in following headings:

Anatomy of retropharyngeal space

Retropharyngeal space is a deep space of neck extending from the base of skull to the posterior mediastinum. Space is bordered anteriorly by middle layer of deep cervical fascia(buccopharyngeal fascia), posteriorly by deep layer of deep cervical fascia, laterally by carotid sheath containing carotid artery and jugular vein.

Transmission

Transmission of microorganisms into the retropharyngeal space could be through trauma or direct or lymphatic spread.

Mode of transmission of infection to retropharyngeal space
Lymphatic spread	Retropharyngeal space consists two pair of lymph nodes, which drains nasopharynx, adenoids, posterior paranasal sinuses, middle ear, and eustachian tube. Draining lymph nodes may get inflamed/infected following an upper respiratory tract infection. Lymph node may undergo liquefaction necrosis, which my progress into retropharyngeal cellulitis, which left untreated can progress to abscess formation. However by age 4 years, these lymph nodes undergo spontaneous atrophy.
Direct spread/ Trauma	Adults In adults, retropharyngeal space can be contaminated by direct trauma(eg, penetrating foreign trauma, endoscopy, dental procedures) or extension of local infection such as odontogenic infection, ludwig's angina, osteomyelitis of cervical spine. Children In children, retropharyngeal space can be contaminated by direct trauma to oropharynx(swallowing a foreign body or running and falling with an object in mouth).

Immune response

Introduction of infections into retropharyngeal space either through lymphatic or direct or traumatic spread may lead to suppurative adenitis of retropharyngeal lymph nodes or cellulitis of retropharyngeal space. Cellulitis may progress to form phlegmon, which inturn progress to form mature abscess.

Causes

Polymicrobial infection is often responsible for retropharyngeal abscess. The other organisms involved in causing retropharyngeal abscess include:

Most common causes

• Poly-microbial infections
• Beta-hemolytic streptococcus
• Streptococcus pyogenes (group A streptococcus [GAS])
• Staphylococcus aureus (including methicillin-resistant S. aureus [MRSA])
• Prevotella

• Veillonella

Less common causes

• Haemophilus Influenzae
• Haemophilus parainfluenzae
• Neisseria species
• Bacteroides
• Fusobacterium
• Salmonella
• Mycobacterium
• Bartonella henselae
• Porphyromonas species

Epidemiology and Demographics

There are no comprehensive studies studying the epidemiology and demographics of retropharyngeal abscess worldwide.

Incidence

In United states, incidence of retropharyngeal abscess in kids under age 20 years is 4.10 per 100,000 population for year 2012.

Case Fatality Rate

Case fatality rate for retropharyngeal abscess varies from study to study, it ranges from low of zero case fatalities(after reviewing the data from 1321 pediatric admissions with retropharyngeal abscess in year 2003) to high of 2.6% case fatalities(234 adults with deep space neck infections in adults).

Age

Retropharyngeal abscess commonly affects children, with median age being 4 years for children.

Gender

Retropharyngeal abscess is more commonly affects in males than in females. The gender ratio is approximately 1.63.

Race

In year 2015, a comprehensive study analysed 6233 patients admitted to US hospitals with retropharyngeal abscess from year 2003 to 2012 and reported that for year 2012, 49.5% of the admitted patients were white, 19.2% were black, 21.9 % were hispanic and 9.5% were other race.

Screening

There are no established screening guidelines to screen patients for retropharyngeal abscess.

Natural History, Complications, and Prognosis

Natural history

If left untreated or appropriate medial or surgical interventions are delayed, patients with retropharyngeal abscess may develop life threatening complications which include mediastinitis, sepsis and internal jugular vein thrombophlebitis.

Complications

Complications of retropharyngeal abscess include:

• Epidural abscess
• Mediastinitis
• Carotid artery aneurysm or erosion
• Internal jugular vein thrombophlebitis
• Septic pulmonary embolism
• Cranial nerve dysfunction (IX–XII)
• Cavernous sinus thrombosis
• Aspiration pneumonia
• Life-threatening descending necrotizing mediastinitis
• Sepsis

Prognosis

The prognosis of retropharyngeal abscess is good when detected early and appropriately treated. Relapse may occur in 1 to 5 percent of cases.

Diagnosis

Diagnosis is based on the clinical presentation supported by radiographic imaging:

History and symptoms

Patients with retropharyngeal abscess may present with:

• Pain in neck
• Fever
• Sore throat
• Mass in neck
• Respiratory distress(stridor)
• Difficulty swallowing (dysphagia)
• Pain with swallowing (odynophagia)
• Unwillingness to move the neck(torticollis)
• Change in voice
• reduced opening of the jaws(Trismus)
• Chest pain

Physical examination

Role of physical examination in diagnosing retropharyngeal abscess is limited, as most of the patients aren't able to open the mouth widely.

Patients with suspected retropharyngeal abscess should be examined in a head-down position(trendelenburg) position. It is recommended to perform examination in an operation room as it permits to place an artificial airway, if necessary. A midline or unilateral swelling of the posterior pharyngeal wall can be appreciated.

Other physical examination findings include

• Tender anterior cervical lymphadenopathy
• Palpable neck mass

Laboratory findings

Laboratory findings may show non-specific leukocytosis.

Imaging

Diagnosis of retropharyngeal abscess should be ultimately supported by radio-graphic imaging. In suspected patients, an initial lateral and anterio-posterior X-ray of neck should be ordered, which is usually followed with CT scan of the neck with IV contrast. CT scan not only helps in diagnosing the retropharyngeal abscess but also helps in identifying the position of carotid artery and internal jugular vein in relation to the infectious process.

Plain X-ray

Lateral neck X ray demonstrate thickening of soft tissue with possible gas-fluid levels in the pre-vertebral cervical space.

Pathological widening of retropharyngeal space should be considered, if it is greater than 22 mm at C6 in adults and 7 mm at C2 or 14 mm at C6 in children.

Other X ray findings include:

• Reversal of normal cervical lordosis
• Radiopaque foreign body
• Soft-tissue mass

CT scan

Patients with retropharyngeal abscess, abscess may appear as

• Mass impinging on the posterior pharyngeal wall
• Complete rim enhancement with scalloping is indicative of an abscess
• Low density core, soft tissue swelling, obliterated fat planes are other common CT scan associated findings with retropharyngeal abscess

Retropharyngeal abscess CT-axial CT of the neck demonstrates an extensive multi-loculated collection located posterior and to the right of the pharynx. The oropharynx and hypopharynx are both distorted, narrowed and displaced anteriorly and towards the left.

Management

There are no comprehensive randomized controlled studies evaluating the management of retropharyngeal infections. Patients should be ideally hospitalized in a setting where intubation or tracheotomy are easily accessible, in case if there is any respiratory compromise. Management predominantly consists of empiric intravenous antibiotics or combination of surgical drainage and intravenous antibiotics. During hospitalization patient should be regularly monitored for airway patency, hydration status, and potential complications.

Management of retropharyngeal abscess in children and adults follows:

Children

Combination of surgical drainage and intravenous antibiotics

Widely accepted indications for surgical drainage of abscess include: airway compromise, or failure to response after 24-24 hrs of administration of empiric anti microbial therapy, or CT scan showing large (>3 cm2) hypodense area(indicative of mature abscess) or life-threatening complications. Drainage fluid should be sent for culture and sensitivity, for choosing appropriate antibiotics for further management.

Medical therapy

Trail of antimicrobial therapy for initial 24 to 48 hours without surgical drainage should be considered in patients who do not have airway compromise, CT scan showing cross-sectional hypodense area between <2 to 3 cm2 and no life-threatening complications.

Empiric intravenous antibiotic include:

• Ampicillin-sulbactam (50 mg/kg 6 h iv) or Clindamycin (15 mg/kg per dose [maximum single dose 900 mg]every 8 h IV).
• In patients with moderate or severe disease who do not respond to empiric therapy, additional intravenous Vancomycin (40 to 60 mg/kg per day divided in three to four doses; maximum daily dose 2 to 4 g or Linezolid (<12 years: 30 mg/kg per day divided in three doses; ≥12 years: 20 mg/kg per day in two doses; maximum daily dose 1200 mg) should be considered to optimize the coverage against Gram-positive cocci.
• Once the patients is afebrile and shows signs of clinical improvement a 14 day oral antimicrobial therapy with either Amoxicillin-clavulanate (45 mg/kg per dose 12 h oral), or Clindamycin (13 mg/kg 8 h oral) should be prescribed.
• Antimicrobial therapy should be adequately supplemented with analgesics, antipyretics and intravenous fluids.

Adults

Combination of surgical drainage and intravenous antibiotics

Widely accepted indications for surgical drainage of abscess include: airway compromise, or failure to response after 24-24 hrs of administration of empiric antimicrobial therapy, or CT scan showing large volume abscess or life-threatening complication. Drainage fluid should be sent for culture and sensitivity, for choosing appropriate antibiotics for further management.

Medical therapy

Trail of antimicrobial therapy for initial 24 to 48 hours without surgical drainage should be considered in patients who do not have airway compromise, CT scan showing small volume abscess and no life-threatening complications.

Antibiotics regimen coverage for deep neck space infections
Antibiotics regimen	Coverage rate (%)
Ceftriaxone, clindamycin	76.40%
Ceftriaxone, metronidazole	70.79%
Cefuroxime, clindamycin	61.80%
Penicillin G, metronidazole	16.85%
Penicillin, gentamicin, clindamycin	67.42%

Preferred medical therapies

Preferred regimen

Ampicillin-sulbactam 3 g/6h IV

Alternative regimens

• Penicillin G 2 to 4 MU/6h IV every four to six hours plus metronidazole  500 mg/6h IV OR
• Clindamycin  600 mg/6h IV OR
• Ceftriaxone 1 g/24 h plus metronidazole 500 mg/6 h IV OR
• Ciprofloxacin 400 mg/12 h IV plus clindamycin 600 mg/6h IV

In patients with moderate or severe disease or having MRSA risk factors(higher incidence of MRSA in hospital and community, IV drug abuse or co-morbid conditions like diabetes mellitus, living in crowed places) or who do not respond to empiric therapy, additional intravenous vancomycin (15 to 20 mg/kg/12 h IV) or linezolid (600 mg/12 h IV) should be considered to optimize the coverage against gram-positive cocci.

Antimicrobial therapy should be adequately supplemented with analgesics, antipyretics and intravenous fluids.

Duration

Once the patients is afebrile and shows signs of clinical improvement IV antibiotics can be replaced with oral antibiotics. Oral antibiotics should be continued for 2-3 weeks after discharge to prevent recurrence or complications.

Discharge instructions

Patients should be asked to report to the health care provider if they notice any new onset of enlarging mass, difficulty in breathing, worsening pain, fever and any stiffness in neck.

Prevention

Primary Prevention

There are no established primary preventive measures for preventing retropharyngeal abscess.

Secondary prevention

There are no established secondary prevention measures, but early detection and appropriate medical and surgical intervention can help in early recovery and prevention of complications.