Retropharyngeal and peritonsillar abscess

By the end of this page you should be able to:

1. Explain why the same upper respiratory infection produces retropharyngeal abscess in a toddler and peritonsillar abscess in an adolescent.
2. Recognise RPA and PTA from their history and examination, and distinguish each from the other deep neck infections and from meningitis.
3. Interpret a lateral soft-tissue neck radiograph and a contrast CT of the neck, including the thresholds that suggest (or refute) an abscess.
4. Choose initial intravenous antibiotics and adjunctive corticosteroids, and say when drainage is required.
5. Describe the complications of deep neck infection, including Lemierre syndrome and how its risk of jugular thrombosis changes management.
6. Adapt the assessment to a low-resource setting where CT or drainage may not be available.

The retropharyngeal space lies between the buccopharyngeal fascia in front and the alar fascia behind, extending from the skull base to the mediastinum at the level of the tracheal bifurcation. The peritonsillar space is between the tonsillar capsule and the superior constrictor muscle. These two spaces define the two conditions on this page.

A useful bedside distinction is which structures are involved. Retropharyngeal infection is a node-driven process in young children; peritonsillar infection arises in and around the tonsil. The two are compared side by side in the table below.

Deep neck infections are uncommon in children but potentially lethal; in one multi-centre Taiwanese series of 1,743 paediatric patients with deep neck infection, no tracheostomy was required, mediastinal complications fell from 0.6% to 0% between earlier (2006 to 2014) and later (2015 to 2023) periods, and mortality stayed at 0.1%. ^[10]

Retropharyngeal abscesses are rare but potentially life-threatening infections of children, primarily affecting those 5 years old or younger and, occasionally, adults. ^[1] Over 95% of retropharyngeal abscesses occur in children under six years of age. ^[6] They typically follow an upper respiratory tract infection in the younger child and trauma to the posterior pharynx (foreign body, sharp food, intubation) in the older child or adult. ^[1]

Peritonsillar abscess is the most common deep neck space infection in adolescents and young adults. ^[3] It peaks between 15 and 35 years of age in one guideline, while another places the highest incidence in adults aged 20 to 40 years. ^{[3] [5]} The overall incidence in individuals aged 5 to 59 years is 14 to 30 cases per 100,000 per year, rising as high as 167 per 100,000 in adolescents (StatPearls); one United States series cites 30 per 100,000, and a Danish paediatric cohort peaked at 78.4 per 100,000 in 16- to 17-year-olds. ^{[3] [5] [12]} Peritonsillar abscess is uncommon in children younger than 5 years, who are instead more susceptible to retropharyngeal abscess. ^[3] In children, incidence is low (2.3 to 8.4 per 100,000 at ages 2 to 9 in one cohort) and mean age at diagnosis is about 13.6 to 13.9 years. ^{[11] [12] [9][10]}

In peritonsillar abscess, girls are affected more often than boys in those younger than 14 years, and males more often than females over 14 years. ^[3] In retrospective series of retropharyngeal and parapharyngeal infection, roughly three out of five patients are male. ^[9]

Retropharyngeal infection begins in the lymph nodes. In the young child, retropharyngeal nodes (the nodes of Rouviere) drain the nose, nasopharynx, oropharynx and middle ear. They respond to an upper respiratory tract infection by becoming inflamed, then suppurative, and finally abscessed. These nodes normally regress by about 5 years of age, which is why the disease is a disease of toddlers. ^[2]

Peritonsillar infection begins in the tonsil or the tissue around it. It is thought to follow acute tonsillitis, or infection of the Weber salivary glands in the peritonsillar space. Polymicrobial flora dominate: peritonsillar abscess is generally polymicrobial, the organisms being the normal flora of the oral cavity and tonsillar area (group A streptococcus, Staphylococcus aureus, Haemophilus influenzae, viridans streptococci, and anaerobes such as Bacteroides, Fusobacterium and Peptostreptococcus). ^[11] Retropharyngeal abscess is likewise polymicrobial, with facultative anaerobes such as streptococci and staphylococci alongside true anaerobes such as Prevotella, Peptostreptococcus and Veillonella. ^[10] Group A streptococcus, Staphylococcus aureus and anaerobes are the classic triad for deep neck infection. ^[2]

Risk factors for retropharyngeal infection include a recent upper respiratory tract infection, trauma to the posterior pharynx (food, foreign body, instrumentation), dental infection and spinal discitis or osteomyelitis (rare). Risk factors for peritonsillar abscess include chronic or recurrent tonsillitis, multiple courses of oral antibiotics for tonsillitis, smoking in young adults, and immunocompromise. ^[5]

The illness runs through several stages, and each stage explains a symptom.

1. Lymph node or tonsillar infection. The process starts as cellulitis or phlegmon: redness, oedema, fever.
2. Suppuration. Pus forms in a node (RPA) or in the peritonsillar space (PTA). The abscess may be small and early.
3. Expansion. The abscess enlarges and shifts the surrounding tissues. In the retropharyngeal space this pushes the airway forward and may cause stridor or, at worst, asphyxiation; an abscess in the prevertebral region can descend through the fascial planes to the mediastinum. ^[1]
4. Septic spread. Bacteraemia and septic emboli can occur, giving metastatic abscesses or septic thrombophlebitis of the internal jugular vein (Lemierre syndrome). Inflammatory cytokines drive fever, tachycardia and raised acute-phase markers. The abscess may rupture or extend into the adjacent deep spaces, explaining a peritonsillar abscess that becomes a parapharyngeal or retropharyngeal infection.

The physical signs are the body's report of these stages. In RPA the neck is stiff because the child splints the inflamed retropharyngeal tissues: they refuse to extend the neck, prefer to sit upright, and may drool because swallowing hurts. In PTA the inflamed pterygoid and pharyngeal muscles produce trismus, and the swollen tonsil pushes the uvula to the other side.

History: the child usually has a prodrome of upper respiratory infection, then fever, sore throat, neck pain, drooling, refusal to feed and restricted neck movement, sometimes with cough or breathing difficulty. ^[1]

Examination: fever, a "bull neck" or boggy swelling, cervical lymphadenopathy, limited neck extension or torticollis, possible stridor, and in the severe case respiratory distress. Some patients present with neurological deficits or numbness if the abscess is large enough to compress. A lateral neck radiograph or CT is needed to confirm.

History: severe, usually one-sided, sore throat that is worse when swallowing; fever, malaise, otalgia (referred to the ear on the affected side), drooling and difficulty eating. ^[5][11]

Examination: a toxic-looking patient, trismus (inability to open the mouth more than a couple of centimetres), a muffled "hot potato" voice, erythematous swollen soft palate, inferior and medial displacement of the affected tonsil, deviation of the uvula to the contralateral side, and tender jugulodigastric lymphadenopathy on the affected side. ^[5][11] Uvular deviation is found in roughly half of cases in one series. ^[3] The diagnosis is often clinical.

A stiff neck with fever in a child has a wider differential than meningitis, and missing RPA among these patients is a common pitfall. The clues are where the pain is and how the child holds the neck.

The airway comes before any test. If the child is stridulous, drooling, in the sniffing position or toxic-looking, obtain intravenous access, keep them in a position of comfort, call anaesthesia and ENT urgently and take radiographs only if they can be tolerated without distress. Mouth examination and tongue depression should be avoided when airway compromise is possible. ^[1]

This is the usual first image in a young child, because it involves little radiation and the child can be held upright in a position of comfort. Obtain it during inspiration with the neck in normal extension (flexion or expiration can falsely widen the prevertebral shadow). ^[1][6]

Normal prevertebral thickness in children is under 7 mm at the level of C2 and under 14 mm at C6 (under 15 years); adult cut-offs reported differ (about 20 to 22 mm at C6), so local radiology guidance should be used. ^[1][2][6] An air-fluid level, loss of the normal cervical lordosis, or gas in the tissues also suggests infection. ^[1] The reported sensitivity and specificity of the plain film are 80% and 100% respectively, but abscesses high in the nasopharynx can be missed, so a normal film in a child with convincing symptoms does not exclude RPA and a CT is needed. ^[1][6]

White cell counts are typically elevated: values above 12,000 per microlitre are reported in 91% of cases in one review. ^[1] Inflammatory markers and blood cultures add information in the septic or deteriorating child.

Contrast CT of the neck (often of the chest too) is the definitive imaging study. It separates cellulitis from abscess, shows the extent and the relation to vessels, and allows drainage planning. ^[1][2] Figures from one paediatric series show: infections are retropharyngeal in 84.8% of cases versus parapharyngeal, 16.7% have a concurrent peritonsillar infection, the CT diagnosis is abscess in 53.3% (48 of 90), oedema in 21.1% (19 of 90), suppurative lymph node in 13.3% (12 of 90), phlegmon in 7.8% (7 of 90) and cellulitis in 4.4% (4 of 90). ^[9]

Imaging does not predict treatment alone: cross-sectional area greater than 2.5 square centimetres and younger age predict the need for drainage in one cohort, but no single feature is reliable. ^[9]

There is no bedside criteria score for RPA or PTA. The working diagnosis is clinical, and imaging describes rather than defines the disease. Points that change management:

• Abscess versus cellulitis/phlegmon. CT with rim enhancement supports an abscess; cellulitis and phlegmon may be treated with antibiotics alone. ^[9]
• Size. A cross-sectional area greater than 2.5 square centimetres separates medical from surgical cases across a small series (p 0.0225), and cross-sectional area greater than 3 square centimetres and fever (over 38 degrees Celsius) were independent predictors of surgical intervention. ^{[9] [10]}
• No evidence that mature abscesses greater than about 3 square centimetres benefit from surgical drainage before 24 to 48 hours of antibiotics, in stable patients. ^[1]
• Hospital course. Most cases respond to antibiotics alone (51.1% in one series), with a median hospital stay of about 4 days; 48.9% need surgery initially or after a medical trial. ^[9]

• Airway vigilance is the first treatment: all patients need meticulous airway monitoring, particularly during the first 24 to 48 hours, and anxious children can decompensate suddenly. ^[1]
• Intravenous access, rehydration, analgesia, nothing by mouth until a drainage decision is made, and high-flow oxygen if indicated.
• Ear, nose and throat (and where available infectious diseases and paediatric anaesthesia) should be involved early; many children with RPA need a guarded airway plan even if they are not intubated immediately.
• Dexamethasone: for peritonsillar abscess the PCH ED guideline recommends a single dose of intravenous dexamethasone 0.6 mg per kg (maximum 10 mg); for retropharyngeal infection, steroids are used variably (steroids were given to 42.9% of patients in one paediatric series) and the body of evidence for adjunctive steroid in deep neck infection is thin. ^[4][9]

The flora is polymicrobial (group A streptococcus, Staphylococcus aureus and anaerobes), so initial therapy is broad and intravenous. ^[2]

One standard initial choice is ampicillin-sulbactam (50 mg per kg every 6 hours) or clindamycin (15 mg per kg every 8 hours). ^[1] Add vancomycin or linezolid if there are signs of sepsis or no response to initial therapy, or where MRSA carriage is plausible. ^[1] Alternative regimens include amoxicillin-clavulanate, cefotaxime with rifampin (for uncomplicated disease), and ceftriaxone with or without metronidazole. ^[1][9] Anaerobic coverage is required in every case. ^{[1] [10]}

Initial therapy with ampicillin-sulbactam is given as 50 mg per kg per dose every 6 hours. ^[1] Follow your own hospital antimicrobial guideline and check local age, severity and culture results.

Continue parenteral antibiotics until there is clinical improvement and the child has been afebrile for at least 24 hours, then step down to oral (amoxicillin-clavulanate or clindamycin), with deep-neck infection usually treated for 2 to 3 weeks, longer if complicated, and peritonsillar abscess regimens continued for 10 to 14 days in one guideline. ^[1][2][5]

The route depends on the space. A retropharyngeal abscess medial to the great vessels can be drained intraorally; a parapharyngeal or lateral collection needs a transcervical approach. ^[11]

Most children can be tried on antibiotics alone for 24 to 48 hours. Surgical drainage is indicated for failure of medical therapy (fever beyond 48 hours or no clinical improvement), clinical deterioration, an airway that is difficult to secure, or a large collection (cross-sectional area greater than about 2.5 square centimetres, especially in younger children). ^[1][9] In one paediatric series, 92.7% of operations were transoral. ^[9]

Small peritonsillar abscesses (less than 1 cm) without muffled voice, drooling or trismus can be treated without drainage; all others need needle aspiration or incision and drainage, and immediate tonsillectomy ("quinsy tonsillectomy") is reserved for selected cases such as airway compromise, recurrence or previous deep neck abscess. ^[5]

Recurrent peritonsillar abscess is common after a first episode. Persistent swelling or a non-healing cavity after 2 weeks warrants imaging.

• Upper airway obstruction, which is the most common fatal complication, and can occur at presentation or during treatment. ^[1]
• Mediastinitis from downward spread through the fascial planes, particularly from the retropharyngeal "danger space"; it occurs in less than 1% of paediatric deep neck infection cases in large series. ^[10]
• Aspiration pneumonitis or lung abscess if a peritonsillar abscess ruptures. ^[5]
• Internal jugular vein thrombophlebitis and Lemierre syndrome: an oropharyngeal or deep neck infection extends to the internal jugular vein, causing septic thrombophlebitis with pulmonary and other metastatic infection. Mortality can be as high as 60% when jugular vein thrombosis or mediastinitis occur. ^[6]
• Lemierre syndrome itself: classically follows pharyngitis, with Fusobacterium necrophorum in most cases (over 80% of paediatric cases in some series; 78.3% in a 2026 systematic review of 143 children). ^[8][7] Mean age is about 15.2 years in that 2026 systematic review and about 20 to 21 years in a broader 2024 review. ^[7][8] Fever occurs in 92% of paediatric cases in the 2026 review, CT is used in 89.5%, anticoagulation in 62.2% (2026 review) to 63.7% (2024 review) (controversial), surgery in 6%, long-term complications in 4.2% (2026 review) to about 10% (2024 review), and mortality 1.4% in the systematic review (older series report 2 to 4%, up to 4 to 6%). ^[7][8] Reported incidence is about 3.6 cases per million, rising to about 1 per 100,000 among children and young adults. ^[8] The gold standard imaging is contrast CT of neck and chest (internal jugular vein filling defect with rim-enhancing pulmonary emboli); duration of antibiotics is 3 to 6 weeks. ^[8]
• Other metastatic foci: septic arthritis, osteomyelitis, liver and splenic abscess, endocarditis, pericarditis, meningitis and brain abscess (CNS complications in 10 to 16%). ^[8]
• Post-treatment complications: recurrence, scarring causing dysphagia, and after surgery, pharyngeal fistula or stenosis (rare).

With modern antibiotics most children recover. Hospital stays are short (median 4 days) and surgery is needed in about half. ^[9] Even small abscesses can resolve on antibiotics alone. Lemierre syndrome aside, death is rare (0.1% in a large paediatric series), and the main residual risk is recurrence and scarring from the incision. ^[10] A child with a first episode has no excess mortality, but surveillance for recurrence is wise. ^{[9] [8]}

• Younger than 5. The retropharyngeal space is where infection occurs; the diagnosis is harder because the child cannot describe symptoms and the lateral film is taken with the child upright. Under-2-year-olds with Lemierre syndrome present with non-specific signs (irritability, poor feeding, respiratory distress) rather than the adolescent sore throat-neck pain triad, in one review. ^[8]
• Children with Down syndrome, immunodeficiency or diabetes have more severe or recurrent disease and more complications; involve infectious diseases.
• Neonates rarely develop deep neck infection; the differential includes congenital cysts and branchial anomalies.
• Immunocompromised and HIV-positive children should get wider antibacterial and antifungal cover and imaging of the chest at the same time; ID consultation is recommended. ^[4]
• Pregnancy and older adults are outside the usual age range for these conditions, but the same principles apply, with dose adjustments and antimicrobial review.

• A good-quality lateral neck radiograph with the neck extended and the film taken in inspiration, plus a careful clinical examination, is usually enough to recognise RPA. ^[1]
• Contrast CT, if available, is the test that tells abscess from cellulitis and guides surgery. ^[1] Where it is unavailable, surgical decision-making rests on airway status and failure to improve after 24 to 48 hours of intravenous antibiotics. ^[1]
• Ampicillin-sulbactam and clindamycin are widely available and inexpensive; metronidazole covers anaerobes when ampicillin-sulbactam is not.
• Anaesthesia for airway management and surgical drainage are harder to obtain; early transfer to a centre with paediatric anaesthesia is preferable to an attempted heroic local drainage in a poorly equipped setting.
• The same airway precautions (upright posture, no agitated examination, no removal of toys or forcing of mouth opening) apply everywhere.

• Retropharyngeal abscess (RPA) is the infection of toddlers (6 months to 6 years, over 95% under 6); peritonsillar abscess (PTA) is the infection of adolescents and young adults (peak 15 to 35 years, or 20 to 40 years in one review, rare under 5). ^[1][3][5][6]
• RPA presents with fever, sore throat, drooling and refusal to extend the neck; PTA with a one-sided sore throat, "hot potato" voice, trismus and uvula deviation. ^[3][5]
• Lateral soft-tissue neck film in a child: widened prevertebral shadow above 7 mm at C2 or above 14 mm at C6 (or above half the adjacent vertebral body from C1 to C4, or the whole body from C5 to C7) suggests infection; sensitivity 80% and specificity 100% (abscesses high in the nasopharynx may be missed on the film). ^[1][2][6]
• Normal prevertebral thickness: under 7 mm at C2 and under 14 mm at C6 in children. ^[1][2]
• CT with intravenous contrast is the definitive study and separates abscess from cellulitis. ^[1][2]
• Polymicrobial flora dominate: group A streptococcus, Staphylococcus aureus and anaerobes. ^[2][11]
• Airway comes first; monitor closely for 24 to 48 hours. ^[1]
• Initial IV antibiotics: ampicillin-sulbactam 50 mg per kg every 6 hours, or clindamycin 15 mg per kg every 8 hours; add vancomycin or linezolid for sepsis, non-response or MRSA risk. ^[1]
• Continue parenteral therapy until afebrile for 24 hours; typical total duration 2 to 3 weeks for deep neck infection. ^[1][2]
• Drainage is indicated for failure after 24 to 48 hours, for airway concerns, or for a large (greater than 2.5 square centimetres cross-sectional area) collection; most small PTA (under 1 cm) without red-flag features do not need drainage. ^[1][5][9]
• Mediastinitis and internal jugular vein thrombosis can raise mortality to roughly 60% in the small group in which they occur; Lemierre syndrome occurs mainly in adolescents. ^[6][8]
• Most children recover with median hospital stay around 4 days; paediatric mortality overall is low (about 0.1% in large series). ^[9][10]

Plain text (no links on this page): meningitis; acute tonsillitis/pharyngitis; airway obstruction in children; Lemierre syndrome; mediastinitis; safe swallowing and dysphagia; paediatric emergency assessment; low-resource paediatric airway care; orbital and deep-space infections of the head and neck.