How to read nasapharynx xray
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how to read nasopharynx lateral X-ray radiology interpretation
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how to read nasopharynx lateral X-ray adenoid nasopharyngeal ratio A/N ratio
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I now have enough information from authoritative textbook sources (Scott-Brown's Otorhinolaryngology and Cummings Otolaryngology) to give a comprehensive answer. Let me compose the full response.
Reading a Nasopharynx X-ray (Lateral Soft Tissue Radiograph)
The lateral soft-tissue radiograph of the nasopharynx is the standard plain-film view used to assess this region. It is most commonly ordered in children to evaluate adenoid hypertrophy and airway obstruction, and in adults to investigate soft tissue masses.
1. Positioning & Technical Requirements
- Patient is placed in a true lateral position, neck extended, midsagittal plane parallel to the image receptor
- Exposed during quiet inspiration (not expiration or phonation) with the patient upright
- Soft tissue technique is used (lower kV, ~50-60 kV) to maximize air-soft tissue contrast
- Critical: If taken during expiration or with neck flexed, the normal retropharyngeal soft tissue in children bulges anteriorly and can mimic a retropharyngeal mass - always ensure neck extension and inspiration
2. Anatomy to Identify on the Lateral View
On a properly exposed lateral nasopharynx X-ray, you should be able to identify (from superior to inferior):
| Structure | What to Look For |
|---|---|
| Adenoids | Soft tissue mass on the posterior nasopharyngeal wall |
| Nasopharyngeal airway | Lucent (black) air column between adenoids and hard palate |
| Hard palate | Bony floor of the nasal cavity |
| Soft palate | Soft tissue extending posteriorly from hard palate |
| Posterior pharyngeal wall | Retropharyngeal soft tissue stripe |
| Skull base / clivus | Posterior bony limit of nasopharynx |
| Tongue base and tonsils | More inferiorly visible |
The lateral view also shows: tongue, epiglottis, aryepiglottic folds, pyriform sinuses, laryngeal ventricle, and subglottic trachea.
- Cummings Otolaryngology Head and Neck Surgery, p. 1955
3. The A/N Ratio - Key Measurement for Adenoid Hypertrophy
The most important measurement on a nasopharynx X-ray is the Adenoid-to-Nasopharyngeal (A/N) ratio:
- A = vertical thickness of the adenoid (measured from the lowest point of adenoid tissue to the lateral cranial tangent line of the occipital slope)
- N = width of the nasopharyngeal cavity (measured from the posterior end of the hard palate to the base of the pterygoid plate)
- A/N ratio > 0.73 = pathologic adenoid hypertrophy (Elwany's criteria)
- A/N ratio ≤ 0.73 = normal
This ratio is the standard quantitative tool used by radiologists worldwide to assess adenoid obstruction.
4. Adenoid Grading (Clinical Correlation)
Based on radiograph findings correlated with endoscopy, adenoids are graded:
| Grade | Description |
|---|---|
| Grade I | Adenoid tissue filling one-third of the vertical choanae |
| Grade II | One-third to two-thirds of the choanae |
| Grade III | Two-thirds to nearly complete obstruction |
| Grade IV | Complete obstruction |
- Scott-Brown's Otorhinolaryngology Head & Neck Surgery, Vol. 2
5. Systematic Approach to Reading the Film
- Check quality: Is it a true lateral? Is the neck extended? Was it taken during inspiration?
- Assess the nasopharyngeal airway: Is the air column present, narrowed, or obliterated?
- Measure the adenoid (A measurement): Look for a soft tissue bulge on the posterior/superior wall
- Measure the nasopharyngeal space (N measurement)
- Calculate A/N ratio
- Assess posterior pharyngeal wall: Retropharyngeal soft tissue should be thin (<7 mm at C2, <22 mm at C6 in children as general references)
- Look for masses: Any asymmetric soft tissue fullness, erosion of skull base, or encroachment from lateral walls should raise concern for neoplasm
6. Key Pathologies to Recognize
| Finding | Likely Diagnosis |
|---|---|
| A/N ratio > 0.73 | Adenoid hypertrophy |
| Thickened posterior wall + narrowed airway | Adenoid hypertrophy / retropharyngeal abscess |
| Asymmetric soft tissue mass + skull base erosion | Nasopharyngeal carcinoma |
| Tonsils and adenoids encroaching on airway | Can simulate pathologic mass - normal variant in 6-10 year olds |
| Anterior bulging of posterior pharyngeal wall (neck flexed film) | Normal variant - do not misinterpret as retropharyngeal abscess |
7. Important Clinical Notes
- Adenoids are largest between ages 7-10 years, then regress by the seventh decade
- Enlarging tonsils/adenoids after 6 months of age can encroach on the nasopharynx and simulate a pathologic soft tissue mass - clinical correlation is essential
- If the plain film is inconclusive, CT or MRI is preferred for detailed assessment of masses, deep structures, and skull base involvement
- For endoscopy-intolerant children, the lateral nasopharynx X-ray correlates well with endoscopic adenoid assessment
- Scott-Brown's Otorhinolaryngology Head & Neck Surgery, Vol. 2; Cummings Otolaryngology Head and Neck Surgery, p. 1954-1955
In summary: The key steps are - verify patient positioning/technique, identify the air column and soft tissue boundaries, measure the A/N ratio (>0.73 = pathologic), grade adenoid obstruction, and look for asymmetric masses or retropharyngeal thickening that would warrant further cross-sectional imaging.
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