Definition (Pediatr Rev 2000;21:249; Adv Pediatr 2011;58:195)
• Gastric outlet obstruction 2/2 hypertrophy and edema of pyloric canal, and antropyloric distension and muscle spasm → vomiting, dehydration, and hypochloremic, hypokalemic, metabolic alkalosis; thought to be an acquired condition
Epidemiology
• Incidence of 1 in 250–1,000, M 4–8× > F, Caucasian predilection
Clinical Manifestations
• Mean age 3 wk, but anytime birth to 5 mo; begins w/ regurgitation → nonbilious vomiting +/− projectile vomiting
• Classically w/ “olive-like” mass palpated in epigastric region, pathognomonic; not always appreciable; exam enhanced by NGT decomp and prone positioning
Diagnostic Studies
• U/S is study of choice, pyloric thickness >4 mm, length >16 mm w/ sens 89%, spec 100%; may need repeat U/S given operator variability
• Most common cause of metabolic alkalosis in infancy; hypochloremic metabolic alkalosis 2/2 acid loss from vomiting and decreased HCO3 secretion
• Excess bicarb can be excreted in urine w/ obligate Na loss, followed by H2O, also 2° hyperaldo 2/2 inc renin release causes distal H+ secretion and paradoxic aciduria
• Can have low or nml K but usually total body K depletion
Treatment
• Reverse metabolic derangements and volume status
• Pyloromyotomy is curative, incision through serosa and mucosal layer. Essentially 100% success rate