Hypertrophic Pyloric Stenosis

  • Etiology: Idiopathic hypertrophy of circular pylorus muscle leading to gastric outlet obstruction
  • Imaging AXR: Caterpillar sign of peristaltic waves in air-filled stomach due to hyperperistalsis
  • Imaging US:
    — Directly images hypertrophied pyloric muscle
    — Pyloric muscle greater than 3.5 millimeters thick
    — Pyloric channel greater than 17 millimeters long
    — Minimal to no passage of fluid through pylorus
  • Note: Remember pi for diagnosis of hypertrophic pyloric stenosis: greater than 3 millimeters single wall thickness and greater than 14 millimeters for pyloric channel length
  • Note: It is normal for fluid to pass through thickened pylorus in patients with hypertrophic pyloric stenosis – remember “tram track” or “string sign” when an UpperGI was used to diagnose hypertrophic pyloric stenosis
  • Note: Gastroesophageal junction can mimic appearance of normal pylorus on US so check for portal vein and gallbladder to be on same image as pylorus to confirm image is of pylorus
    — Confluence of hepatic veins and heart will be on same image of gastroesophageal junction
  • Imaging UpperGI:
    — Indirectly images effect of hypertrophied pyloric muscle
    — Elongated pyloric channel
    — Thin track (tram track or string sign) of contrast passing through the stomach
    — Impression on antrum and duodenal bulb (shouldering)
    — Pyloric beak or teat
  • DDX:
    — Pylorospasm which resolves over a few minutes while hypertrophic pyloric stenosis does not resolve
    — Prostaglandin E induced gastritis
  • Complications:
  • Treatment: Pyloromyotomy
  • Clinical: Present with projectile vomiting

Radiology Cases of Hypertrophic Pyloric Stenosis

Radiology Cases of Normal Pylorus Muscle

US of a normal pylorus muscle
Sagittal US of the pylorus shows the pylorus muscle is not thickened (above left) and is not lengthened (below left) while transverse US of the pylorus (right) again shows the pylorus muscle to not be thickened.

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.
AXR and US of hypertrophic pyloric stenosis
AXR AP (left) shows a hugely distended air-filled stomach with distal bowel gas. Sagittal US of a posteriorly positioned pylorus (right) shows the pyloric channel to be lengthened (25 mm) and the pyloric muscle to be thickened (4 mm). The anechoic gallbladder is positioned anteriorly to the pylorus.
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 Case of a Pyloromyotomy in 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.
Surgical image of pyloromyotomy
Surgical image shows that while stabilizing the pylorus between the thumb and forefinger, a shallow incision is made and then the musculature of the pylorus is bluntly split.
Surgical image of pyloromyotomy
Surgical image shows the pyloric muscle being spread, exposing the mucosa.
Surgery image of pyloromyotomy
Surgical image shows the pylorus muscle split with bulging exposed mucosa.