Hypertrophic Pyloric Stenosis Diagnosis and Management

Clinical Presentation and Diagnosis

The American Academy of Pediatrics suggests that forceful projectile vomiting in a neonate with epigastric swelling strongly suggests Hypertrophic Pyloric Stenosis (HPS), which typically presents between 2-8 weeks of age with progressive non-bilious vomiting that becomes increasingly forceful 2, 3
The presence of an epigastric fullness or swelling, representing the classic palpable "olive" mass in the right upper quadrant, is pathognomonic for HPS when present 2
Decreased urine output results from progressive dehydration due to persistent vomiting and inability to retain fluids 2
The vomiting is characteristically non-bilious because the obstruction is proximal to the ampulla of Vater 3

Ultrasound of the abdomen is the imaging modality of choice for suspected HPS, with high sensitivity and specificity for detecting the thickened pyloric muscle 2, 3
Diagnostic criteria on ultrasound include a pyloric muscle thickness >3-4 mm 2, a pyloric channel length >15-17 mm 1, and a target sign on transverse view 2
The American College of Radiology recommends that plain abdominal radiograph may show a distended stomach with minimal distal bowel gas, but ultrasound provides definitive diagnosis 4

If vomiting becomes bilious at any point, this represents a surgical emergency requiring immediate evaluation for malrotation with midgut volvulus, which can cause intestinal necrosis within hours 1, 3
Malrotation with volvulus accounts for 20% of bilious vomiting cases in the first 72 hours of life and requires urgent upper GI series if suspected 3
Duodenal atresia presents with bilious vomiting and "double bubble" sign on radiograph, with epigastric distention 3, 4

The American Academy of Pediatrics recommends assessing and correcting dehydration immediately with IV fluid resuscitation, as HPS typically causes hypochloremic, hypokalemic metabolic alkalosis from persistent vomiting 2
Immediate pediatric surgery consultation is mandatory once HPS is confirmed or strongly suspected, as pyloromyotomy is the definitive treatment 2

Do not dismiss non-bilious vomiting as benign reflux when it is forceful/projectile and associated with poor weight gain or dehydration 2, 3
Do not delay imaging if clinical suspicion is high—the "olive" mass is palpable in only 60-80% of cases 2
Always reassess for bilious vomiting, as this changes the diagnosis to a more urgent surgical emergency like malrotation 1, 3