Overview
Definition:
Pyloric stenosis is a condition characterized by progressive, concentric hypertrophy of the circular muscle of the pylorus, leading to gastric outlet obstruction in infants
It is the most common cause of non-bilious projectile vomiting in this age group.
Epidemiology:
It typically affects infants between 2 to 8 weeks of age, with a peak incidence around 3 to 6 weeks
It is more common in males (4:1 male:female ratio) and in first-born infants
A familial predisposition exists, and associations with certain blood groups (e.g., non-O blood types) and maternal smoking during pregnancy have been noted
Incidence is estimated to be 1-3 per 1000 live births in Western populations, with variations in other regions.
Clinical Significance:
Prompt diagnosis and appropriate management of pyloric stenosis are crucial to prevent severe dehydration, electrolyte abnormalities, and malnutrition
Early recognition and intervention significantly improve patient outcomes and reduce morbidity
Understanding its pathophysiology, diagnostic modalities, and resuscitation strategies is a cornerstone for pediatricians and pediatric surgeons preparing for DNB and NEET SS examinations.
Clinical Presentation
Symptoms:
Onset typically between 2-8 weeks of age
Non-bilious projectile vomiting, often forceful, occurring after most feeds
Vomiting may increase in frequency and severity
Infant may appear hungry shortly after vomiting and may try to feed again
Poor weight gain or weight loss
Decreased urine output due to dehydration
Constipation may also be present.
Signs:
Dehydration: decreased skin turgor, dry mucous membranes, sunken fontanelle, lethargy
Palpable pyloric mass ("olive") in the epigastrium, more easily felt after vomiting or during feeding, located in the RUQ
Gastric peristaltic waves may be visible progressing from left to right across the abdomen
Emesis: characteristically non-bilious and projectile
Bradycardia and hypotension can occur in severe dehydration.
Diagnostic Criteria:
No universally defined diagnostic criteria exist as it is primarily a clinical and radiological diagnosis
The constellation of projectile vomiting, palpable olive, and characteristic ultrasound findings is considered diagnostic
Laboratory findings like hypochloremic metabolic alkalosis support the diagnosis and assess severity of dehydration.
Diagnostic Approach
History Taking:
Detailed history of feeding pattern, frequency and character of vomiting (bilious vs
non-bilious, projectile vs
regurgitation)
Onset of symptoms and progression
Weight gain pattern
Urine output
Any recent illnesses or antibiotic use
Family history of pyloric stenosis.
Physical Examination:
Assess hydration status thoroughly: check skin turgor, mucous membranes, fontanelle, and capillary refill time
Carefully palpate the abdomen, especially the right upper quadrant, for a pyloric mass ("olive")
Observe for gastric peristalsis
Auscultate bowel sounds
Check for any signs of other congenital anomalies.
Investigations:
Ultrasound of the abdomen: This is the investigation of choice, highly sensitive and specific
Look for a thickened pyloric muscle (wall thickness > 3 mm) and an elongated pyloric canal (> 15 mm)
Gastric distension may be noted
Barium swallow: Historically used, now largely replaced by ultrasound
Shows a narrowed, elongated pyloric channel with a "string sign" or "beak sign"
Not recommended in cases of severe dehydration or electrolyte imbalance due to risk of aspiration
Serum electrolytes and blood gas: To assess for dehydration and acid-base status
Typically shows hypochloremia, hyponatremia, hypokalemia, and metabolic alkalosis (elevated pH and bicarbonate).
Differential Diagnosis:
Gastroesophageal reflux (GER) with secondary vomiting
Food allergies or intolerances
Gastroenteritis
Intestinal obstruction (e.g., malrotation with volvulus, intussusception – often presents with bilious vomiting)
Neurological causes of vomiting (e.g., increased intracranial pressure)
Pylorospasm (usually transient and less severe than HPS).
Management
Initial Management:
Immediate fluid resuscitation is paramount in dehydrated infants
Intravenous access should be secured
Correction of electrolyte imbalances and acid-base disorders is critical before surgical intervention
Nasogastric tube (NGT) decompression may be considered for comfort and to reduce vomiting, especially if significant gastric distension is present, but it is not a definitive treatment.
Medical Management:
Correction of dehydration and electrolyte abnormalities
Intravenous fluids typically start with normal saline (0.9% NaCl) and then maintenance fluids with potassium supplementation
For metabolic alkalosis, correction of hypochloremia is key
Slow infusion of isotonic saline with potassium chloride is often used
Once electrolytes are corrected and the infant is euvolemic, they are usually ready for surgery
Pylorospasm might be managed medically with antispasmodics, but true HPS requires surgery.
Surgical Management:
The definitive treatment for hypertrophic pyloric stenosis (HPS) is a pyloromyotomy
This involves surgically dividing the hypertrophied muscle fibers of the pylorus to relieve the obstruction
Options include: Laparoscopic pyloromyotomy: Currently the preferred method, offering minimally invasive approach, faster recovery, and reduced pain
Open pyloromyotomy (Ramstedt procedure): A classic surgical technique involving a small abdominal incision to perform the muscle division
The procedure is generally safe and highly effective with low complication rates.
Supportive Care:
Frequent monitoring of vital signs, fluid input and output, and electrolyte levels is essential
Gradual reintroduction of oral feeds post-operatively, typically starting with clear liquids and progressing as tolerated
Monitoring for signs of complications such as wound infection, wound dehiscence, or persistent vomiting
Pain management post-operatively.
Ultrasound Criteria
Muscle Thickness:
Pyloric muscle wall thickness > 3 mm is considered abnormal.
Canal Length:
Pyloric canal length > 15 mm is considered abnormal
Some sources use a threshold of >16 mm.
Gastric Peristalsis:
Abnormal, visible peristaltic waves moving from the stomach into the narrowed pyloric channel can be a helpful secondary sign.
Gastric Distension:
Moderate to severe gastric distension may be present proximal to the stenosed pylorus.
Pre Operative Resuscitation
Fluid Therapy:
Initial resuscitation with intravenous isotonic crystalloids (e.g., 0.9% NaCl)
Aim to restore euvolemia and adequate urine output
Maintenance fluids with 5% dextrose are added once hydration is achieved.
Electrolyte Correction:
Crucial for metabolic alkalosis
Hypochloremia is corrected with saline
Hypokalemia is corrected with potassium chloride (KCl) supplementation (typically 20-40 mEq/L in maintenance fluids) once urine output is adequate
Monitor serum sodium, potassium, chloride, and bicarbonate levels closely.
Acid Base Balance:
Correction of hypochloremic metabolic alkalosis
This is primarily achieved by providing chloride and volume
Avoid routine bicarbonate administration unless severe and refractory to chloride repletion, as it can worsen intracellular acidosis and shift potassium intracellularly
Surgery should be postponed until metabolic derangements are corrected.
Nutritional Support:
While awaiting surgery, parenteral nutrition may be considered in infants with severe malnutrition or prolonged pre-operative course, though typically not required for routine cases where surgery is imminent after resuscitation
The focus remains on fluid and electrolyte balance.
Key Points
Exam Focus:
Ultrasound findings: muscle thickness > 3mm, canal length > 15mm
Electrolyte disturbance: hypochloremic metabolic alkalosis
Treatment: fluid resuscitation followed by pyloromyotomy (laparoscopic preferred)
Recognize the "olive" sign.
Clinical Pearls:
Always examine infants with projectile vomiting for the pyloric mass
Palpation is easier after vomiting or during feeding
Prioritize resuscitation and electrolyte correction before surgery, as it significantly improves outcomes and reduces anesthetic risks.
Common Mistakes:
Misdiagnosing pyloric stenosis as simple reflux or gastroenteritis
Delaying surgery due to inadequate pre-operative resuscitation
Overlooking electrolyte abnormalities
Performing unnecessary investigations like barium swallow in unstable infants.