Congenital Hypertrophic Pyloric Stenosis
Hypertrophic pyloric stenosis (HPS) is commonly encountered in pediatric practice. The typical infant presents with nonbilious projectile vomiting and dehydration (with hypochloremic metabolic alkalosis) if the diagnosis is delayed. HPS accounts for one third of nonbilious vomiting occurrences in infants and is the most common reason for laparotomy before age 1 year.
Hypertrophic pyloric stenosis (HPS) is commonly encountered in pediatric practice. The typical infant presents with nonbilious projectile vomiting and dehydration (with hypochloremic metabolic alkalosis) if the diagnosis is delayed. HPS accounts for one third of nonbilious vomiting occurrences in infants and is the most common reason for laparotomy before age 1 year.
Ultrasonography (US) is important in the diagnosis of HPS and has likely contributed to the changing face of the disease, because this modality results in earlier diagnosis and treatment.
USG Findings :
. US is the method of choice for both the diagnosis and exclusion of HPS because this modality has a sensitivity and specificity of approximately 100%.
US is performed with a 7.5- to 13.5-MHz linear transducer in the supine child. Transverse images at the epigastrium identify the pylorus to the left of the gallbladder and anteromedial to the right kidney. A distended stomach, however, displaces and distorts the pylorus and may require the placement of a nasogastric tube to withdraw the stomach\'s contents. A gastric aspirate of more than 5 mL in a baby who has been without oral intake (NPO) for several hours indicates gastric outlet obstruction. Right posterior oblique positioning and scanning from a posterior approach may help to improve visualization of the pylorus.
US signs of HPS are as follows:
- MT (serosa to mucosa) greater than 3 mm .
- Target sign on transverse images of the pylorus.
- Pyloric channel length greater than 17 mm
- Pyloric thickness (serosa to serosa) of 15 mm or greater
- Failure of the channel to open during a minimum of 15 minutes of scanning Retrograde or hyperperistaltic contractions
- Antral nipple sign (ie, a prolapse of redundant mucosa into the antrum, which creates a pseudomass)
- US double-track sign (ie, redundant mucosa in the narrowed lumen, which creates 2 mucosal outlines)
- Other findings - Reversible portal venous gas; nonuniform echogenicity of the pyloric muscle.
Radiograph/Contrast studies
Abdominal radiographs may show a fluid-filled or air-distended stomach, suggesting the presence of gastric outlet obstruction. A markedly dilated stomach with exaggerated incisura may be seen, which represents increased gastric peristalsis in these patients.
- Delayed gastric emptying (if severe, this may prevent barium from passing into the pylorus and severely limit the study)
- Cephalic orientation of the pylorus
- Shouldering (ie, filling defect at the antrum created by prolapse of the hypertrophic muscle)
- Mushroom or umbrella sign (ie, thickened muscle that indents the duodenal bulb; the name refers to the impression made by the hypertrophic pylorus on the duodenum)
- Double-track sign (ie, redundant mucosa in the narrowed pyloric lumen, which results in separation of the barium column into 2 channels)