Gastroenterology · Pediatric GI
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Presents in a first-born male aged 3-6 weeks with non-bilious, projectile vomiting and a palpable olive-shaped mass in the right upper quadrant.
Abdominal ultrasound is first-line and gold standard, showing muscle thickness >= 4 mm and channel length >= 14 mm.
The mandatory first step is IV fluid resuscitation with normal saline to correct the hypochloremic, hypokalemic metabolic alkalosis.
Definitive treatment is the surgical Ramstedt pyloromyotomy, performed only after electrolytes are normalized.
The infant is classically a hungry vomiter who eagerly wants to feed again right after emesis.
Add potassium to fluids only after adequate urine output is confirmed to avoid fatal arrhythmias.
Distinguish from duodenal atresia and midgut volvulus, which present with bilious vomiting (a double-bubble sign in atresia).
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A 4-week-old first-born boy is brought in for two weeks of progressively worsening vomiting that now shoots forcefully across the room immediately after each feed. The emesis is non-bilious, and the infant eagerly feeds again afterward. On exam he appears dehydrated with a firm, mobile olive-shaped mass palpable in the right upper quadrant. Labs reveal hypochloremic, hypokalemic metabolic alkalosis.
Which of the following is the most appropriate next step in management?
IV fluid resuscitation with normal saline to correct electrolyte abnormalities.
Non-bilious projectile vomiting, a palpable olive, and hypochloremic hypokalemic metabolic alkalosis in a first-born male confirm pyloric stenosis. Fluid and electrolyte correction must precede the definitive Ramstedt pyloromyotomy, since operating on an alkalotic, dehydrated infant risks perioperative apnea and arrhythmia.
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Etiology / Epidemiology
Most common in first-born males aged 3-6 weeks; strongly associated with early neonatal or maternal macrolide exposure.
Clinical Manifestations
Presents with immediate post-prandial, non-bilious, projectile vomiting and a palpable olive-shaped mass in the right upper quadrant.
Diagnosis
Abdominal ultrasound is first-line, demonstrating a muscle thickness ≥ 4 mm and length ≥ 14 mm.
Treatment
IV fluid resuscitation is the mandatory first step to correct hypochloremic, hypokalemic metabolic alkalosis, followed by definitive Ramstedt pyloromyotomy.
Prognosis
Excellent post-surgical outcomes; severe dehydration and cardiovascular collapse are the primary acute threats if delayed.
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Epidemiology & Etiology
Occurs in 2-3 per 1000 live births, classically affecting first-born males between 3 to 6 weeks of age. Risk factors include early infant or maternal use of erythromycin or azithromycin for pertussis or chlamydia. Genetic predisposition exists, but the exact environmental trigger causing the hypertrophy remains heavily tested but incompletely understood, risking severe dehydration in affected infants.
Pertinent Anatomy
The pylorus is the muscular sphincter connecting the gastric antrum to the proximal duodenum. Hypertrophy specifically of the circular muscle layer creates a rigid, elongated canal that acts as a functional gastric outlet obstruction.
Pathophysiology
Progressive hypertrophy and hyperplasia of the pyloric sphincter lead to severe mechanical narrowing of the antral-duodenal junction. This obstruction prevents gastric emptying, causing the stomach to distend and violently contract, resulting in projectile vomiting that expels massive amounts of hydrochloric acid (HCl). The resulting volume depletion activates the RAAS pathway, forcing the kidneys to paradoxically excrete potassium and hydrogen ions to retain sodium, culminating in the classic hypochloremic, hypokalemic metabolic alkalosis.
Clinical Manifestations
Infants present with progressive, non-bilious, projectile vomiting that occurs immediately after feeding. The infant is classically described as a hungry vomiter who eagerly desires to feed again despite the emesis. Physical exam reveals a firm, mobile olive-shaped mass in the right upper quadrant and visible gastric peristaltic waves moving left-to-right across the upper abdomen. Severe dehydration, sunken fontanelles, and failure to thrive develop rapidly if unrecognized.
Diagnosis
Abdominal ultrasound is the first-line and gold-standard imaging modality. Diagnostic thresholds on ultrasound are a pyloric muscle thickness ≥ 4 mm and a pyloric channel length ≥ 14 mm. If ultrasound is equivocal, an upper GI series will show delayed gastric emptying and the classic string sign or double-track sign representing barium trickling through the narrowed channel.
Treatment
The absolute first step is IV fluid resuscitation with normal saline to correct the hypochloremic, hypokalemic metabolic alkalosis before any surgical intervention is attempted. Potassium is added to the maintenance fluids only after adequate urine output is confirmed to avoid fatal arrhythmias. Once electrolytes are normalized, the definitive gold-standard treatment is surgical Ramstedt pyloromyotomy, which longitudinally splits the hypertrophied muscle down to the submucosa.
Prognosis
Prognosis is excellent following successful pyloromyotomy, with normal feeding usually resuming within 12 to 24 hours. The main risks are preoperative cardiovascular collapse from fluid depletion or postoperative mucosal perforation during the surgical myotomy.
Differential Diagnosis
1. Gastroesophageal Reflux Disease (GERD): Presents with frequent regurgitation but lacks projectile vomiting or an olive-shaped mass.
2. Duodenal Atresia: Presents on day 1 of life with bilious vomiting and a classic double-bubble sign on abdominal X-ray.
3. Malrotation with Midgut Volvulus: A surgical emergency presenting with sudden onset bilious vomiting and rapid hemodynamic instability.
4. Gastroenteritis: Usually accompanied by diarrhea and fever, without an anatomical mass or metabolic alkalosis.