What are the clinical symptoms of pyloric stenosis?

Clinical Symptoms of Pyloric Stenosis

Pyloric stenosis classically presents with non-bilious projectile vomiting in infants between 3-8 weeks of age, accompanied by a palpable mid-epigastric "olive-shaped" mass, visible gastric peristaltic waves after feeding, and hypochloremic hypokalemic metabolic alkalosis 1, 2.

Key Clinical Features

Primary Symptoms

• Non-bilious projectile vomiting: The hallmark symptom, though notably absent in one-third of cases 1
• Age of presentation: Typically 3-6 weeks of life, with mean diagnosis at 40 days 1
• Preserved appetite: Infants remain hungry and eager to feed despite vomiting 1
• Duration of symptoms: Average 8 days before diagnosis 1

Physical Examination Findings

• Palpable pyloric "olive": A firm, mobile, olive-shaped mass in the mid-epigastrium, though this is not palpated in approximately 50% of cases 1
• Visible gastric peristaltic waves: Observable after feeding as the stomach attempts to empty against the obstruction
• Signs of dehydration: Due to persistent vomiting 3

Laboratory Abnormalities

The classic metabolic derangement includes:

• Hypochloremic metabolic alkalosis: Present in only 20-33% of cases 1
• Elevated bicarbonate (>28 mEq/L): Found in only 20% 1
• Elevated pH (>7.45): Present in 25% 1
• Hypokalemia: Part of the classic triad but not universally present

Important Clinical Pitfalls

The "Non-Classical" Presentation

A critical caveat is that the textbook presentation is increasingly uncommon 1. Modern imaging accessibility has led to earlier diagnosis before the full constellation of classic findings develops. Specifically:

• Projectile vomiting may be absent in 33% of patients
• The pyloric tumor is not palpable in 50% of cases
• Classic electrolyte abnormalities are present in only 20-33% of patients

Age Considerations

While typical presentation is 3-8 weeks, late-onset cases can occur up to 14 weeks of age 3. The diagnosis should not be excluded based on age alone if clinical suspicion exists.

Diagnostic Confirmation

When clinical presentation is atypical, pyloric ultrasonography is the diagnostic test of choice 4. Upper GI series should be reserved for equivocal ultrasound results 4. Ultrasound findings include:

• Pyloric length ≥18-20 mm
• Pyloric muscle thickness measurements
• Pyloric length ≥24 mm correlates with longer symptom duration 1

Gender and Birth Order

• 81% male predominance 1
• 43% are firstborn children 1

Clinical Algorithm

When evaluating an infant with persistent vomiting:

1. Assess vomiting characteristics: Non-bilious and projectile pattern
2. Check age: Most common 3-8 weeks, but can occur later
3. Perform careful abdominal examination: Palpate for pyloric mass (though absence doesn't exclude diagnosis)
4. Obtain electrolytes: Look for alkalosis, but normal values don't exclude diagnosis
5. Proceed to pyloric ultrasound if clinical suspicion exists, regardless of whether classic findings are present 4

The key message is that pyloric stenosis should remain in the differential for any infant presenting with non-bilious vomiting, even without the classic physical examination or laboratory findings 1, 3.