Hypertrophic pyloric stenosis vs Neonatal proximal obstruction patterns
How to tell Hypertrophic pyloric stenosis and Neonatal proximal obstruction patterns apart when a board question makes them look alike.
Pyloric stenosis is weeks-later nonbilious outlet obstruction; duodenal atresia/annular pancreas are neonatal bilious duodenal obstruction patterns.
Side by side
Weeks-old infant with progressive nonbilious projectile vomiting, hungry after feeds, olive mass, and hypochloremic hypokalemic metabolic alkalosis.
Duodenal atresia causes early bilious vomiting with double bubble; annular pancreas causes duodenal obstruction from encircling pancreatic tissue.
Hypertrophied pyloric smooth muscle narrows the gastric outlet proximal to the ampulla of Vater.
Duodenal atresia reflects failed recanalization; annular pancreas encircles and narrows the duodenum.
Ultrasound showing thickened elongated pylorus supports pyloric stenosis.
Double-bubble sign and bilious vomiting support duodenal obstruction distal to the ampulla.
The trap
All can cause vomiting in infants, so bilious status, timing, and anatomy are decisive.
The repair move
For infant vomiting, first ask bilious versus nonbilious, then match timing and obstruction level.
Try a free question
CoreA 4-week-old has progressive nonbilious projectile vomiting after feeds, visible peristalsis, hypochloremic hypokalemic metabolic alkalosis, and an olive-like epigastric mass. Which diagnosis is most likely?
Show answer and explanation
Answer: A. Hypertrophic pyloric stenosis. Pyloric stenosis causes nonbilious projectile vomiting after the first weeks of life because obstruction is proximal to the ampulla.
Why the other choices are tempting
- B. Duodenal atresia usually causes bilious vomiting soon after birth with a double-bubble sign.
- C. Annular pancreas can obstruct the duodenum and may mimic duodenal obstruction.
- D. Midgut volvulus causes acute bilious vomiting and ischemia risk.
- E. Hirschsprung causes delayed meconium and distal obstruction.
Flashcards
Tap a card to flip it.
Why is pyloric stenosis vomiting nonbilious?
The obstruction is proximal to the ampulla, so bile does not enter the vomitus.
What lab pattern fits pyloric stenosis?
Hypochloremic hypokalemic metabolic alkalosis can result from repeated gastric acid loss and volume depletion.
Quick answers
What is the fastest way to tell Hypertrophic pyloric stenosis from Neonatal proximal obstruction patterns?
Pyloric stenosis is weeks-later nonbilious outlet obstruction; duodenal atresia/annular pancreas are neonatal bilious duodenal obstruction patterns.
What is the key clue for Hypertrophic pyloric stenosis?
Weeks-old infant with progressive nonbilious projectile vomiting, hungry after feeds, olive mass, and hypochloremic hypokalemic metabolic alkalosis.
What is the key clue for Neonatal proximal obstruction patterns?
Duodenal atresia causes early bilious vomiting with double bubble; annular pancreas causes duodenal obstruction from encircling pancreatic tissue.
What is the common trap with Hypertrophic pyloric stenosis vs Neonatal proximal obstruction patterns?
All can cause vomiting in infants, so bilious status, timing, and anatomy are decisive.