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Hypertrophic Pyloric Stenosis
1
What is hypertrophic pyloric stenosis (HPS)?
HPS is the most common cause of gastric outlet obstruction in infants resulting in nonbilious vomiting. The pathogenesis of HPS is unknown; it is not thought to be a developmental defect. Hypotheses include nitric oxide deficiency, decreased neurotrophins, and alterations in growth factors and gastrointestinal peptides. It is more common in boys than girls (2:1). Offspring of an affected parent have an increased risk of HPS (10%); the highest rate (20%) occurs in boys born to affected mothers. The pylorus muscle grossly and histologically appears thickened and hypertrophied.
2
Describe the typical presentation of an infant with HPS
Typically, an otherwise healthy infant who was feeding without issue develops nonbilious emesis at 2–8 weeks of age. Initially, the emesis is not frequent or forceful. Over a period of days, the infant develops projectile vomiting with most feeds. The emesis may have a coffee-ground appearance as a result of gastritis or esophagitis. The infant remains hungry after emesis. In premature infants, the diagnosis often presents 2 weeks later. As HPS goes unrecognized, the infant becomes dehydrated.
3
What are the physical findings?
The infant may appear normal, especially if the diagnosis is made early. Some infants are dehydrated, malnourished, or lethargic. The abdomen is nondistended and soft. A palpable “olive” confirms the diagnosis. The pylorus can be palpated in a relaxed infant in the epigastrium. This is becoming a lost skill in the era of ultrasonography.
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