Hypertrophic pyloric stenosis (HPS) pediatric

HPS is a condition occurring in newborn infants commonly about 6 weeks of age when the pyloric muscle becomes hypertrophied and elongated, restricting the passage of gastric contents, causing projectile vomiting. Most infants with HPS are found to have a hypochloraemic alkalosis and, when seen in association with a palpable epigastric mass the size of an olive on test feeding, the diagnosis is clear without the need for ultrasonic imaging.
However, ultrasound is very successful in demonstrating HPS in approximately 20% of infants in whom the pyloric olive cannot be palpated. The baby should be positioned comfortably right side down and the stomach and pylorus identified usually just to the right of the midline in the low epigastric region. A small feed, of approximately 20–30 ml of sugared water (preferable to milk as it does not contain echoes which may obscure vital detail), may be used to aid visualization of the gastric antrum if the stomach is empty. A nasogastric tube may also be used to administer clear fluid in a controlled way providing that the gastric position of the tube is confirmed prior to injection of the fluid. A small, highfrequency linear or curved linear transducer is best. The pylorus projects into gastric lumen and is outlined by the fluid. HPS can be confirmed by the demonstration of:
● thickened and elongated pyloric muscle
● increased but ineffective peristalsis
● failure of the pylorus to relax and open Various figures have been quoted for muscle thickness in hypertrophic pyloric stenosis ranging from 2.5 to 5 mm but 3 mm is most com accepted.

It must be stressed that the examination is dynamic and measurements of muscle thickness must be interpreted in conjunction with the observations of gastric peristalsis and failure of the pylorus to relax normally. Sensitivity and specificity of 97% and 99% for the diagnosis of HPS have been reported in expert hands (Fig. 9.14). If clinical suspicion persists after a negative ultrasound, a repeat examination after 1 or 2 days may be performed to exclude an evolving pyloric stenosis.

jurnal radiology Tags: Hypertrophic pyloric stenosis (HPS)
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