Retrospective Observational Study of Computed Tomography-Based Vascular Risk Assessment During Needle Drainage of Peritonsillar Abscess.

Peritonsillar abscess (PTA) is a common deep neck infection in which bedside drainage is performed close to major cervical vessels. Although catastrophic vascular complications are rare, clinicians have limited quantitative information on how far the internal carotid artery (ICA), external carotid artery (ECA), and internal jugular vein (IJV) lie from the abscess in individual patients. This protocol describes a contrast-enhanced computed tomography (CT)-based workflow to confirm unilateral PTA, acquire neck CT images under standard clinical settings, measure linear distances from the anterior and posterior abscess capsule to the ipsilateral ICA, ECA, and IJV, compare these distances with the contralateral healthy side as an internal control, and classify the theoretical risk of ICA injury during needle drainage using a modified Pfeiffer system. The procedure includes patient selection, safety screening for iodinated contrast, contrast-enhanced CT acquisition, standardized axial image review by a head and neck radiologist, and structured data recording and analysis. In a retrospective cohort of 94 adult patients, PTA consistently displaced the ICA, ECA, and IJV away from the tonsillar space, increasing both anterior and posterior distances compared with the healthy side. The mean posterior PTA-ICA distance was approximately 14 mm, whereas the contralateral tonsil-ICA distance was about 9 mm. ICA course anomalies (tortuosity or coiling) were detected in a minority of patients, and roughly one in seven cases met moderate-risk criteria because of shorter distances and/or aberrant ICA anatomy. Age, sex, and abscess volume did not significantly alter these relationships. This CT-based protocol provides a reproducible method to quantify PTA-vessel distances and identify patients with potentially higher vascular risk anatomy prior to drainage. It supports cautious, controlled-depth needle aspiration in most cases and highlights scenarios in which image-guided or operating-room drainage may be preferable.