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Findings: Longitudinal ultrasonographic images of the pyloric region in this symptomatic infant demonstrate characteristic findings for the disorder, with pyloric muscle thickness of 4 mm, and pyloric channel length of 17 mm.

Diagnosis:: Hypertrophic pyloric stenosis.

Discussion: The diagnosis of pyloric stenosis can often be rendered on clinical grounds, without supporting data from imaging studies such as ultrasound or fluoroscopy (UGI). In an infant who presents with non-bilious, post-prandial vomiting, failure to thrive, and a palpable mass ("olive") in the epigastric region, hypertrophic pyloric stenosis is a presumptive diagnosis. Demographic factors have been clarified regarding this entity, and are as follows:

• Age at presentation: majority between 2-6 weeks of live
• Sex predilection: males > females (radio of approximately 5:1)
• Race predilection: uncommon in blacks
• Inheritance pattern: dominant polygenic

The value of imaging studies to assist in the diagnosis of pyloric stenosis has, however, been clearly elucidated. Ultrasound is presently the imaging modality-of-choice at most institutions. The currently accepted parameters (longitudinal images) necessary for diagnosis are as follows:

• Pyloric muscle thickness: > 4 mm
• Pyloric channel length: > 17 mm
• Pyloric muscle length: > 19 mm

References:
1. Haller JO, and Cohen HL. Hypertrophic pyloric stenosis:
Diagnosis using US. Radiology 161:335-339, 1986.

2. Hilton, SvW. The Child with Vomiting. In: Practical Pediatric Imaging,
2nd edition, pages 297-333. SvW Hilton
and DK Edwards, eds. WB Saunders Company, 1994.

3. Teele RL and Smith EH. Ultrasound in the diagnosis of
idiopathic hypertrophic pyloric stenosis. N Engl J Med 296: 1149-1150, 1977.

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