Hypertrophic pyloric stenosis (HPS) is one of the most common causes of gastric outlet obstruction in infants. It occurs when the muscle at the pylorus (the opening between the stomach and small intestine) becomes abnormally thickened, narrowing the passage of food into the duodenum. The condition typically presents within the first few weeks of life and is a leading cause of persistent projectile vomiting in infants.
Pathophysiology of Hypertrophic Pyloric Stenosis
The pylorus is a muscular valve that controls the flow of stomach contents into the duodenum. In HPS:
1. Hypertrophy of the pyloric muscle – The circular muscle of the pylorus thickens abnormally.Pathological hallmark: A pyloric muscle thickness >4 mm or length >16 mm on ultrasound confirms the diagnosis.
Causes and Risk Factors
The exact cause of HPS is not fully understood, but multiple risk factors are known:
- Genetic Predisposition – Strong familial tendency.
- Gender – More common in males, especially first-born boys.
- Race/Ethnicity – Higher incidence in Caucasian infants.
- Feeding Practices – Bottle feeding is considered a risk factor in some studies.
- Environmental Influences – Maternal smoking during pregnancy increases risk.
Signs and Symptoms of Hypertrophic Pyloric Stenosis
The clinical features of HPS usually appear between 2–8 weeks of life. Key signs include:
- Projectile vomiting – Forceful vomiting after feeds, often non-bilious (since the obstruction is proximal to the bile duct).
- Non-bilious emesis – Vomit does not contain bile.
- Palpable Olive-Shaped Mass – On abdominal examination, a firm, movable, olive-sized mass is felt in the right upper quadrant.
- Persistent Hunger – Infants remain hungry despite frequent feeds, leading to irritability.
- Weight Loss and Poor Growth – Due to inadequate nutrition.
- Signs of Dehydration – Sunken fontanelles, decreased urine output, dry mucous membranes.
Biochemical Features
Due to recurrent vomiting of gastric acid:
- Metabolic Alkalosis – Increased pH and bicarbonate (HCO₃⁻).
- Hypochloremia – Low chloride levels.
- Hemoconcentration – Elevated hematocrit and blood urea nitrogen (BUN).
Diagnosis of Hypertrophic Pyloric Stenosis
Diagnosis involves clinical suspicion plus confirmatory tests:
- Physical Examination – Detection of the classic "olive-shaped" mass in the epigastrium.
- Ultrasound Abdomen – First-line imaging; shows thickened pyloric muscle and elongated canal.
- Upper GI Contrast Study – May be used when ultrasound findings are inconclusive, showing delayed gastric emptying and a "string sign."
- Blood Tests – Reveal metabolic alkalosis, hypokalemia, and hypochloremia.
Treatment of Hypertrophic Pyloric Stenosis
Management includes stabilization followed by definitive surgery:
Initial Stabilization
- IV Fluids – To correct dehydration and electrolyte imbalances.
- Electrolyte Correction – Potassium and chloride supplementation as needed.
- Monitoring – Input/output charting, vomiting episodes, stool pattern, daily weights.
Definitive Treatment – Pyloromyotomy
- Ramstedt’s Pyloromyotomy – The standard surgical procedure where the hypertrophied pyloric muscle is cut (without entering the mucosa), relieving the gastric outlet obstruction.
- Prognosis – Excellent, with rapid return to normal feeding within 24–48 hours post-surgery.
Nursing and Supportive Care
- Monitor fluid balance and electrolytes.
- Provide Comfort and Emotional Support to parents coping with an infant requiring surgery.
- Educate families about pre- and post-operative care.
- Post-Surgery Care – Gradual reintroduction of feeds, wound care, and monitoring for complications.
Complications of Untreated Hypertrophic Pyloric Stenosis
If not diagnosed and treated early, HPS can lead to:
- Severe dehydration
- Failure to thrive
- Electrolyte imbalance
- Metabolic alkalosis
- Hypovolemic shock
- Death in extreme cases
Hypertrophic Pyloric Stenosis: Key Points in a Table
| Feature | Description |
|---|---|
| Definition | Narrowing of the pyloric canal due to muscle hypertrophy |
| Typical Age | 2–8 weeks of life |
| Key Symptom | Projectile, non-bilious vomiting |
| Classic Sign | Olive-shaped mass in right upper quadrant |
| Biochemical Abnormality | Hypochloremic metabolic alkalosis |
| First-line Diagnosis | Ultrasound abdomen |
| Definitive Treatment | Ramstedt’s Pyloromyotomy |
| Prognosis | Excellent after surgery |
Frequently Asked Questions (FAQ)
Q1. What is the hallmark sign of hypertrophic pyloric stenosis?
The hallmark is projectile, non-bilious vomiting in infants along with a palpable olive-shaped mass in the abdomen.
Q2. At what age does pyloric stenosis usually present?
Most cases present between 2–8 weeks of age.
Q3. How is hypertrophic pyloric stenosis different from gastroesophageal reflux?
In gastroesophageal reflux, vomiting is effortless and non-projectile, while in HPS, vomiting is forceful and projectile due to mechanical obstruction.
Q4. Can hypertrophic pyloric stenosis resolve without surgery?
No, surgery (pyloromyotomy) is the definitive treatment. Medical management only stabilizes the infant preoperatively.
Q5. What electrolyte imbalance is commonly seen in HPS?
Hypochloremic metabolic alkalosis is the classic biochemical abnormality.
