A 28-year-old woman presents with severe throat pain, dysphagia, fever (39.5°C), and trismus for 3 days. On examination, the right tonsil is enlarged with deviation of the uvula to the left. Intraoral palpation reveals a fluctuant swelling in the right lateral pharyngeal wall. Which investigation is most appropriate to confirm the diagnosis and guide management?

Explanation

## Investigation of Choice for Peritonsillar Abscess **Key Point:** While intraoral ultrasound is a useful bedside tool, **Contrast-Enhanced CT (CECT) of the neck** is the investigation of choice when the clinical picture suggests a mature peritonsillar abscess with complications, as it provides comprehensive anatomical detail, confirms the diagnosis, and guides definitive management. ### Comparative Analysis of Investigations | Feature | CECT Neck | Intraoral USG | Plain X-ray | Culture & Sensitivity | |---------|-----------|---------------|-------------|----------------------| | **Sensitivity for abscess** | 95–100% | 80–90% | Poor | Not diagnostic | | **Differentiates abscess vs. cellulitis** | Yes, reliably | Yes, but operator-dependent | No | No | | **Assesses airway compromise** | Excellent | Limited | Poor | N/A | | **Detects deep space extension** | Yes | No | No | N/A | | **Detects complications** | Yes (Lemierre's, mediastinitis) | Limited | No | N/A | | **Guides surgical planning** | Yes | Partially | No | N/A | | **Availability** | High (most centers) | Operator-dependent | High | Days for results | ### Why CECT Neck is the Answer Here In this patient with **trismus, uvular deviation, fluctuant swelling, and high fever**, the clinical diagnosis of peritonsillar abscess is strongly suspected. CECT neck is preferred because: 1. **Confirms abscess cavity:** Shows a well-defined, low-attenuation (10–30 HU) fluid collection with peripheral rim enhancement — distinguishing abscess from peritonsillar cellulitis. 2. **Delineates anatomical relationships:** Critically shows proximity to the **internal carotid artery** and jugular vein — essential before any drainage procedure. 3. **Detects life-threatening complications:** Lemierre's syndrome (septic thrombophlebitis of the internal jugular vein), parapharyngeal/retropharyngeal extension, and descending necrotizing mediastinitis. 4. **Guides intervention:** Determines whether needle aspiration, incision & drainage, or quinsy tonsillectomy is appropriate. 5. **Assesses airway:** Identifies degree of airway compromise requiring urgent intervention. ### Role of Intraoral Ultrasound **Clinical Pearl:** Intraoral ultrasound (using a high-frequency endocavitary probe) is a valuable **bedside, radiation-free** tool that can differentiate abscess from cellulitis and guide aspiration in resource-limited or emergency settings. However, it is **operator-dependent**, has a **limited field of view**, and **cannot assess deep neck spaces or detect complications** such as Lemierre's syndrome or mediastinitis. In a patient with trismus and suspected deep extension, CECT is superior. ### CECT Findings in Peritonsillar Abscess - **Abscess cavity:** Low-density (10–30 HU) collection with well-defined walls - **Rim enhancement:** Peripheral enhancement post-contrast - **Uvular deviation:** Displacement contralateral to the abscess - **Parapharyngeal fat stranding:** Inflammatory edema in adjacent spaces - **Carotid sheath assessment:** Rules out vascular involvement **High-Yield Mnemonic:** **CECT = C**onfirms cavity, **E**xtent of spread, **C**arotid proximity, **T**hreat to airway *[Reference: Scott-Brown's Otorhinolaryngology, Head and Neck Surgery, 8th Ed., Ch. 13; Cummings Otolaryngology, 7th Ed., Ch. 11]*