December 9, 2010

Infantile Hypertrophic Pyloric Stenosis

Longitudinal scan of the stomach (as labeled) shows a thickened (5 mm) wall of the pylorus and elongation of the pyloric canal. Labe

Facts: Pyloric Stenosis
  • Most common surgical etiology for young infant presenting emergently with nonbillous vomiting
  • Incidence: 2 to 5 of every 1,000 infants
  • Multifactorial etiology: genetic, biochemical and environmental association
  • Hypertrophy of the pyloric muscle, leading to gastric outlet obstruction (vomiting, dehydration, poor weight gain and hypochloremic metabolic alkalosis)
  • Average age of presentation = 3 weeks old (rare before 1 week, or after 3-4 months)
  • US is now the imaging modality of choice for diagnosis of this condition. It can directly show the pyloric muscle
  • Elongation of the pyloric canal
  • Persistent spasm of pyloric canal with little, if any, fluid passing into the duodenum
  • Persistent thickening of the circular muscle in the canal
  • Pyloric muscle thickness (one wall) greater than 4 mm, or pyloric length greater than 16 mm (cutoff values vary depending on the sensitivity, specificity needed to make the diagnosis)
  • Imaging differential diagnosis is pylorospasm. In pylorospasm, there is usually no thickening of the pylorus (can be up to 2-3 mm) and when visualized in real time the pylorus can open
  • If ultrasound is negative, UGI series or nuclear medicine to evaluate for reflux may be necessary.
1. Swischuk LE. Imaging of the newborn, infant and young child, 5th edition.
2. Hernanz-Schulman M, Berch BR, Neblett WW. Imaging of infantile hypertrophic pyloric stenosis (IHPS). Evidence-based Imaging in Pediatrics 2010; 5:447-457.

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