Hypertrophic pyloric stenosis
 Discussion of Hypertrophic pyloric stenosis
- Hypertrophic pyloric stenosis (HPS): antropyloric portion of the stomach becomes abnormally thickened and manifests as obstruction to gastric emptying.
- Infants with HPS are clinically normal at birth; during the first few weeks of postnatal life, they develop nonbilious forceful vomiting described as "projectile."
- Gastric outlet obstruction leads to emaciation and, if left untreated, may result in death.
- Surgical treatment is curative.
- Incidence of HPS is approximately two to five per 1,000 births per year in most white populations,
- HPS is less common in India and among black and Asian populations
- Male-to-female ratio is approximately 4:1
 Imaging Findings for Hypertrophic pyloric stenosis
 Upper GI Series
- The pyloric canal is outlined by a string of contrast material coursing through the mucosal interstices, termed the string sign; or by several linear tracts of contrast material separated by the intervening mucosa. The latter is termed the double-track sign. This sign demonstrates the intervening redundant mucosa outlined as a filling defect by the contrast material.
- UGI is performed with the infant in the right anterior oblique position, to facilitate gastric emptying.
- Fluoroscopic observations include vigorous active peristalsis resembling a caterpillar and coming to an abrupt stop at the pyloric antrum, outlining the external thickened muscle as an extrinsic impression, termed the shoulder sign.
- Luminal barium may be transiently trapped between the peristaltic wave and the muscle, and this is termed the tit sign.
- Eventual success of gastric peristaltic activity will propel contrast material through the pyloric mucosal interstices, with the appearance as either the string sign or the double-track sign, although at times more than one layer of contrast material may be appreciated in the mucosal filling defect.
- US demonstrates the thickened prepyloric antrum bridging the duodenal bulb and distended stomach.
- Demonstration of the pylorus is achieved by identifying the duodenal cap, distended stomach, and intervening pyloric channel.
- In patients with IHPS, the muscle is hypertrophied to a variable degree, and the intervening mucosa is crowded, thickened to a variable degree, and protrudes into the distended portion of the antrum (nipple sign) and can be seen filling the lumen on transverse sections.
- The length of the hypertrophied canal is variable and may range from as little as 14 mm to more than 20 mm.
- The numeric value for the lower limit of muscle thickness has varied in reports in the literature, ranging between 3.0 and 4.5 mm.
- The actual numeric value is less important than the overall morphology of the canal and the real-time observations.
 See Also
 External Links
 References for Hypertrophic pyloric stenosis
- Marta Hernanz-Schulman. Infantile Hypertrophic Pyloric Stenosis. Radiology 2003 227: 319-331.