Review Question - QID 104287

This patient is presenting with vomiting and an ultrasound with a thickened and elongated pylorus suggesting a diagnosis of pyloric stenosis. Increased vomiting causes a low potassium, metabolic alkalosis (high bicarbonate), and low chloride.

Pyloric stenosis is classically seen in male infants who feed well for the first few weeks of life and subsequently have episodes of vomiting after feeds or episodes of projectile vomiting at 2 weeks to 2 months of age. A palpable epigastric olive-shaped mass is pathognomonic for this condition and the diagnosis can be confirmed with an ultrasound. The metabolic profile represents a hypokalemic, hypochloremic, metabolic alkalosis (secondary to the loss of acid in recurrent vomiting). The treatment of this condition is to first administer IV fluids and correct any electrolyte derangements followed by surgical correction.

Figure/Illustration A demonstrates a thickened and elongated pylorus (red circle) which is classically seen in pyloric stenosis.

Incorrect Answers:
Answer 1: A low bicarbonate would not be seen in this condition as vomiting causes a loss of acid resulting in an increased bicarbonate.

Answer 3: A high chloride would not be seen in this condition since profuse vomiting leads to chloride loss.

Answers 4-5: A high potassium would not be seen in this condition. Chronic vomiting and dehydration activate the renin-angiotensin-aldosterone system which retains fluid and causes loss of hydrogen ions and potassium in the urine.

Bullet Summary:
Pyloric stenosis can cause a metabolic alkalosis with hypokalemia and hypochloremia.