Hypertrophic Pyloric Stenosis

  • Etiology: idiopathic hypertrophy of circular pylorus muscle leading to gastric outlet obstruction
  • AXR: caterpillar sign of peristaltic waves in stomach due to hyperperistalsis
  • US: pyloric muscle > 3.5 mm thick, pyloric channel > 17 mm long, minimal passage of fluid through pylorus
  • UGI: antral shouldering + pyloric beak / teat + tram track through pylorus all secondary to thickened pylorus
  • DDX: prostaglandin E induced gastritis, pylorospasm
  • Note: lower esophageal sphincter can mimic appearance of normal pylorus

Radiology Cases of Hypertrophic Pyloric Stenosis

Upper GI and US of hypertrophic pyloric stenosis
Lateral images from an upper GI exam (above) show delayed passage of barium out of the stomach due to a thickened and elongated pylorus. A tram track sign of barium in the pyloric channel was seen (upper left) along with pyloric muscle shouldering on the antrum along with a pyloric beak (upper right). Sagittal (lower left) and transverse (lower right) US of the pylorus shows marked thickening of the peripheral hypoechoic pyloric muscle which measures 4.5 mm thick, as compared to the thin central hyperechoic pyloric mucosa. Elongation of the pyloric channel was also noted, measuring 25 mm in length.
AXR and US of hypertrophic pyloric stenosis
AXR (above) shows an extremely distended stomach with peristaltic waves (caterpillar sign). Sagittal (below left) and transverse (below right) US of the pylorus shows the pylorus muscle to be thickened and elongated in length, measuring 3.9 mm thick and 20 mm in length.
US of hypertrophic pyloric stenosis
Sagittal US of the pylorus (middle) shows the calipers on the hypoechoic pyloric muscle which is thickened and elongated, measuring 3.7 mm thick and 20 mm in length. Transverse US of the pylorus (right) shows the circumferentially thickened and hypoechoic pyloric muscle whose boundaries are marked by the calipers surrounding the echogenic mucosa in the center of it.
US of hypertrophic pyloric stenosis
Sagittal (left) and transverse (right) US of the pylorus shows the pyloric muscle to be lengthened and thickened, measuring 21 mm in length and 5 mm thick.

Surgery Cases of Hypertrophic Pyloric Stenosis

Surgical image of hypertrophic pyloric stenosis
Surgical image shows delivery of the pylorus which is thickened, firm and blanched as opposed to its normal small, soft and pink consistency.