Two questions that outrank the diagnosis: is the AIRWAY threatened, and has it reached the mediastinum or a vessel.
Orient first
- The neck is compartmentalised by fascial layers, and the SPACE the collection occupies predicts where it will spread. Retropharyngeal and danger-space collections track into the mediastinum; parapharyngeal collections abut the carotid sheath.
- AIRWAY COMPROMISE is the finding that changes the next hour, and it must be communicated before the report is finished.
- Descending mediastinitis is the complication that kills. Any retropharyngeal collection needs the scan extended to the carina, and if it was not, that limitation must be stated.
- Distinguish a drainable COLLECTION from PHLEGMON — non-drainable inflammatory tissue. Reporting phlegmon as an abscess sends a patient for a drain that finds nothing.
- Lemierre syndrome — internal jugular thrombophlebitis with septic emboli — is the vascular complication to look for specifically.
Acquire the study
- Contrast-enhanced CT from the skull base THROUGH TO THE CARINA. Stopping at the thoracic inlet misses descending mediastinitis, which is the reason this study is urgent.
- Portal venous or a dedicated neck phase; a non-contrast study cannot separate collection from phlegmon and cannot show vessel thrombosis.
- Thin slices with coronal and sagittal reformats — the craniocaudal extent of a retropharyngeal collection is a sagittal finding.
- If the airway looks threatened, communicate BEFORE completing the report.
The manoeuvre
- Assess the AIRWAY first: patency, degree of narrowing, and displacement.
- Identify the SPACE involved: peritonsillar, parapharyngeal, retropharyngeal, danger space, submandibular, masticator, or visceral.
- Decide collection versus phlegmon — a rim-enhancing low-attenuation centre is drainable; homogeneous inflammatory infiltration is not.
- Measure the collection in three planes and describe a drainage route.
- Follow the process CAUDALLY to its lowest extent, and state whether it crosses the thoracic inlet.
- Assess the carotid sheath: internal jugular vein patency, thrombus, and any arterial irregularity or pseudoaneurysm.
- Look for gas within the soft tissues, which suggests a gas-forming organism and escalates urgency.
- Identify the SOURCE: odontogenic, tonsillar, salivary, or a foreign body.
What confirms it
- A rim-enhancing low-attenuation collection within a named fascial space, with surrounding inflammatory change.
- Gas within the collection, outside the immediate post-operative window, confirms infection.
What licenses you to exclude it
- ⚠️ A study that stopped at the thoracic inlet does NOT exclude descending mediastinitis. Report the limitation explicitly and recommend extension.
- Absence of a drainable collection does not exclude a serious infection — phlegmon can still obstruct an airway.
- A non-contrast study cannot separate collection from phlegmon or assess the vessels; say so rather than reporting an appearance.
The classic misread
- Reporting the collection and not the airway.
- Calling phlegmon an abscess and sending the patient for a fruitless drain.
- Not scanning to the carina.
- Missing jugular thrombosis by not looking at the carotid sheath.