What are the typical physical exam findings in pyloric stenosis?

Physical Examination Findings in Pyloric Stenosis

The most characteristic physical examination finding in pyloric stenosis is palpation of an olive-shaped pyloric mass in the right upper quadrant, though this is only detectable in approximately 50-70% of cases.

Key Physical Examination Findings

Abdominal Examination

• Pyloric olive: A firm, mobile, olive-shaped mass approximately 1-2 cm in size, palpable in the right upper quadrant or epigastrium, best felt during feeding when the stomach is empty or immediately after vomiting
• Visible gastric peristaltic waves: Moving from left to right across the upper abdomen, particularly visible after feeding
• Abdominal distention: Upper abdomen may appear distended due to gastric dilation

Vomiting Characteristics

• Projectile, non-bilious vomiting (occurs in approximately 67% of cases) 1
• Vomiting typically occurs 30-60 minutes after feeding
• Despite vomiting, the infant often remains hungry and eager to feed again

Signs of Dehydration and Metabolic Abnormalities

• Decreased skin turgor
• Dry mucous membranes
• Sunken fontanelles
• Lethargy or irritability
• Signs of weight loss or failure to thrive

Diagnostic Challenges

The physical examination findings in pyloric stenosis have evolved over time due to earlier diagnosis and increased reliance on imaging:

1. Declining palpation skills: The percentage of cases where a pyloric mass is palpated has decreased significantly, with studies showing it is not detected in approximately 50% of confirmed cases 1

2. Variable presentation: The classic presentation of projectile vomiting is absent in about one-third of patients 1

3. Metabolic abnormalities: While classic teaching emphasizes hypochloremic, hypokalemic metabolic alkalosis, these findings are present in only about 20-30% of cases in modern practice due to earlier diagnosis 1

Special Considerations

• Timing of examination: The pyloric olive is best palpated when the stomach is empty, such as immediately after vomiting
• Examination technique: Palpate with fingertips in the right upper quadrant while the infant is calm, possibly during feeding
• Experience matters: Detection rates of the pyloric olive vary significantly based on examiner experience 2

When Physical Examination is Inconclusive

When physical examination findings are equivocal or the pyloric olive cannot be palpated, point-of-care ultrasound (POCUS) is highly accurate:

• Sensitivity of 97.7% and specificity of 94.1% 3
• The "ultrasonic cervix sign" - visualization of the hypertrophied pyloric muscle in longitudinal section - is pathognomonic 4

Pitfalls to Avoid

1. Overreliance on imaging: Unnecessary imaging studies can delay diagnosis and potentially lead to adverse outcomes 2

2. Missing the diagnosis in atypical presentations: Not all infants present with the complete classic triad of projectile vomiting, visible peristalsis, and palpable olive

3. Failure to recognize dehydration: Metabolic derangements require correction before surgical intervention

4. Confusing with other conditions: Gastroesophageal reflux, overfeeding, and other causes of vomiting may present similarly but without the physical finding of a pyloric mass

Physical examination remains a crucial component in the diagnosis of pyloric stenosis, though the detection of classic findings has decreased with earlier presentation and increased use of imaging studies.