A 6-week-old infant presents with non-bilious, projectile vomiting. Ultrasound shows a pyloric muscle thickness of 4.5 mm and pyloric channel length of 18 mm. Which is the most accurate cut-off for pyloric muscle thickness diagnostic of hypertrophic pyloric stenosis?
- A ≥4 mm (commonly cited 3–4 mm) ✓
- B ≥2 mm
- C ≥3 mm
- D ≥6 mm
Correct answer: A. ≥4 mm (commonly cited 3–4 mm)
Explanation
The diagnostic ultrasound criteria for hypertrophic pyloric stenosis (HPS) are pyloric muscle wall thickness ≥3–4 mm (most widely used cut-off is ≥3 mm in neonates or ≥4 mm in older infants) and pyloric channel length ≥16–18 mm. In this case, a thickness of 4.5 mm and length of 18 mm are diagnostic. US has replaced barium meal as the gold standard for HPS diagnosis. The 'target sign' or 'doughnut sign' is seen on transverse view.
Reference: Grainger & Allison's Diagnostic Radiology, 7th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.