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Pyloric stenosis

Hypertrophic pyloric stenosis (HPS) refers to idiopathic thickening of gastric py­loric musculature which then results in progressive gastric outlet obstruction.


Pyloric stenosis is relatively common and has a male predilection (M:F ~4:1), and is more commonly seen in Caucasians 4. It typically occurs between first week to 3 months of age. There may be a positive family history. Incidence of hypertrophic pyloric stenosis is approximately 2-5 per 1,000 births per year in most white populations. HPS is less common in India and among black and Asian populations.

Clinical presentation

Clinical presentation is typically with non-bilious projectile vomiting. The hypertro­phied pylorus can be palpated as an olive sized mass in the right upper quadrant. A succussion splash may be audible, and although common, is only relevant if heard hours after the last meal 6

Radiographic features

Children with hypertrophic pyloric stenosis may show gastric distension, prominent peristaltic waves (caterpillar sign), and mottled retained gastric content.

A upper gastrointestinal series (barium meal) excludes other, more serious causes of pathology, but the findings of a UGI series infer rather than directly visualise the hypertrophied muscle.

Plain film - abdominal radiograph

Non specific and may show a distended stomach with minimal distal intestinal bowel gas.


Ultrasound is the  modality of choice in right clinical setting because of its advantages over a barium meal are that it directly visualises the pyloric muscle and does not use ionising radiation. Unfortunately it is incapable of excluding other diagnoses such as midgut volvu­lus. Easy ultrasound technique is to find gallbladder then turn the probe obliquely sagittal to the body in an attempt to find pylorus longitudinally.7

The hypertrophied muscle is hypoechoic, and the central mucosa is hyperechoic. Normal measurements include:

  • pyloric muscle thickness, i.e. diame­ter of a single muscular wall on a transverse image: <3 mm (most accurate 3)
  • length, i.e. longitudinal measurement: <15 mm

With the patient right side down the pylorus should be watched and should not be seen to open.

Described sonographic signs include:

Fluoroscopy (barium meal)
  • delayed gastric emptying
  • elongated  pylorus with a narrow lumen (string sign) which may appear  duplicated due to puckering of the mucosa (double-track sign)
  • the pylorus indents the contrast-filled antrum (shoulder sign) or base of the duodenal bulb (mushroom sign)
  • the entrance to the pylorus may be beak-shaped ("beak sign")

Described barium signs include:

Treatment and prognosis

Initial medical management is essential with rehydration and correction of electrolyte imbalances. This should be completed prior to surgical intervention.

Treatment is surgical with a pyloromyotomy in which the pyloric muscle is divided down to the submucosa. This can be performed both open and laparoscopically. The operation is curative and has very low morbidity 4-5.

Differential diagnosis

There is usually little differential when imaging findings are appropriate. Of course clinically it is important to consider other causes of vomiting in infancy.

A degree of pylorospasm is common in infancy and is responsible for some delay in gastric emptying. The pylorus, however, appears normal.

Gastroesophageal (GE) reflux which represents the cause of vomiting in 2/3 of infants referred to radiology 8.

Other causes of proximal gastrointestinal obstruction e.g.8

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