What is the differential diagnosis for a pediatric patient presenting with unilateral tonsillar opacity?

Differential Diagnosis for Unilateral Tonsillar Opacity in Children

The most critical diagnosis to exclude in a child with unilateral tonsillar opacity is peritonsillar abscess (PTA), followed by intratonsillar abscess, with malignancy being a rare but important consideration that must not be missed.

Primary Infectious Etiologies

Peritonsillar Abscess (Most Common Deep Neck Infection)

• PTA is the most common deep neck infection in both adults and children, presenting with unilateral tonsillar fullness, asymmetric tonsillar hypertrophy, and peritonsillar swelling 1
• Classic presentation includes severe sore throat, fever, odynophagia, trismus, and "hot potato" voice 2, 3
• Asymmetric tonsillar hypertrophy is present in approximately 82% of pediatric PTA cases, with peritonsillar fullness in about 27% 3
• Transcutaneous ultrasound has emerged as the preferred diagnostic modality to avoid radiation exposure from CT, showing high accuracy in distinguishing abscess from cellulitis 4

Intratonsillar Abscess (Less Common but Important)

• Presents with unilateral tonsillar swelling but abscess is contained within the tonsillar capsule rather than in the peritonsillar space 3
• May show asymmetric tonsil hypertrophy (82% of cases) with tonsillar erythema (100% of cases) but less peritonsillar fullness compared to PTA 3
• CT imaging reveals unilateral intratonsillar abscess in 82% of cases, with parapharyngeal space inflammatory changes common 3
• Clinically stable children with isolated intratonsillar abscess typically respond to IV antibiotic therapy alone without surgical drainage 3

Peritonsillar Cellulitis/Phlegmon

• Represents the inflammatory stage before frank abscess formation 4
• Ultrasound can differentiate cellulitis (hyperechoic, heterogeneous tonsillar tissue without fluid collection) from abscess (hypoechoic or anechoic fluid collection) 4
• May progress to abscess if untreated, but responds well to antibiotics alone 3

Malignant Considerations (Red Flag Diagnosis)

Lymphoma

• Any persistent unilateral tonsillar enlargement, especially painless and progressive, warrants consideration of lymphoma
• Typically presents with firm, non-tender unilateral tonsillar mass without acute infectious symptoms
• Requires tissue diagnosis via biopsy if suspected

Other Malignancies

• Rhabdomyosarcoma and other soft tissue sarcomas can rarely present as unilateral tonsillar masses in children
• Squamous cell carcinoma is exceedingly rare in pediatric populations but possible in adolescents

Treatment Algorithm Based on Diagnosis

For Suspected PTA or Intratonsillar Abscess:

• Immediate IV antibiotics are the cornerstone of initial management: ampicillin-sulbactam (80-90 mg/kg/day) or clindamycin are first-line agents based on typical polymicrobial flora 2, 3
• Aggressive pain management with acetaminophen or ibuprofen should be initiated immediately 5
• Transcutaneous ultrasound should be performed to confirm diagnosis and guide management 4

Surgical Intervention Criteria:

• PTA requires incision and drainage or needle aspiration, with approximately 50% of pediatric patients requiring treatment in the operating room due to inability to cooperate 1
• Intratonsillar abscess with respiratory compromise requires emergency surgical drainage 3
• Combined intra- and peritonsillar abscess requires surgical drainage of the peritonsillar component 3
• Quinsy tonsillectomy (immediate tonsillectomy) should be considered in 31% of cases, particularly with history of recurrent tonsillitis, inability to cooperate with drainage, or respiratory compromise 1

Critical Pitfalls to Avoid

Diagnostic Errors:

• Do not rely solely on clinical examination in uncooperative children—imaging is essential for accurate diagnosis 4, 1
• Prior antibiotic treatment does not prevent abscess development, as 33-81% of mastoiditis patients (similar deep space infection) had received antibiotics before diagnosis 6
• Failure to consider malignancy in painless, progressive unilateral tonsillar enlargement can lead to delayed cancer diagnosis

Management Errors:

• Antibiotics alone have only 10% success rate for established PTA—do not delay surgical consultation 6
• Outpatient management is appropriate only for older, cooperative children with confirmed cellulitis or small abscesses without respiratory compromise 7
• Recurrence occurs in up to 15% of PTA cases and is associated with older age and history of recurrent tonsillitis 7

Age-Specific Considerations:

• Younger children and those with smaller anatomy often require operating room management due to inability to cooperate with bedside procedures 1
• Children under 3 years have higher complication rates from any tonsillar surgery 8