Overview
Definition:
Pyloric stenosis is a condition characterized by the progressive hypertrophy of the pyloric smooth muscle, leading to gastric outlet obstruction in infants
This obstruction impedes the passage of gastric contents into the duodenum
It is the most common cause of non-bilious vomiting in the first few months of life.
Epidemiology:
It typically presents between 2 and 8 weeks of age, with a peak incidence at 3-6 weeks
The condition is more common in males (4:1 male:female ratio) and first-born infants
There is a familial predisposition, and certain genetic factors may be involved
Caucasian infants are more commonly affected than those of other ethnicities.
Clinical Significance:
Pyloric stenosis is a critical surgical emergency in infants
Delayed diagnosis or management can lead to severe dehydration, electrolyte disturbances (particularly hypochloremic metabolic alkalosis), malnutrition, and failure to thrive
Prompt recognition and surgical intervention are crucial for optimal outcomes and to prevent serious complications
Understanding the associated metabolic derangements is vital for perioperative management and is a key area of focus for DNB and NEET SS examinations.
Clinical Presentation
Symptoms:
Typically presents with progressive, non-bilious, projectile vomiting, often starting after the first week of life
Vomiting may occur after most feedings
Infants often remain hungry and eager to feed immediately after vomiting
Poor weight gain or weight loss is common
Constipation may be present due to decreased stool output.
Signs:
Physical examination may reveal dehydration and poor turgor
A palpable "olive-shaped" mass in the epigastrium, representing the hypertrophied pyloric muscle, is a pathognomonic sign and can be felt during abdominal palpation, especially after the infant has vomited
Peristaltic waves may be visible moving across the abdomen from left to right
Vital signs might show tachycardia due to dehydration.
Diagnostic Criteria:
Diagnosis is primarily clinical, confirmed by imaging
The presence of projectile vomiting, a palpable pyloric mass, and characteristic findings on ultrasonography are sufficient for diagnosis
Laboratory investigations are important to assess the degree of dehydration and metabolic disturbance.
Diagnostic Approach
History Taking:
Focus on the onset, frequency, character (non-bilious, projectile), and timing of vomiting
Inquire about feeding patterns, weight gain, stooling habits, and signs of dehydration
A family history of pyloric stenosis is also important
Red flags include bilious vomiting (suggesting a more distal obstruction), poor feeding despite a good suck, and lethargy.
Physical Examination:
A thorough abdominal examination is essential
Palpate for the pyloric olive, observe for peristaltic waves, and assess for signs of dehydration (sunken fontanelle, dry mucous membranes, poor skin turgor, decreased urine output).
Investigations:
Laboratory investigations: Serum electrolytes (sodium, potassium, chloride, bicarbonate), blood urea nitrogen (BUN), creatinine, and arterial blood gas (ABG) or venous blood gas (VBG) analysis are crucial to assess for hypochloremic metabolic alkalosis
Typical findings include low serum chloride (<90 mEq/L), elevated bicarbonate (>30 mEq/L), and a normal or slightly elevated BUN/creatinine ratio
Imaging: Ultrasound of the abdomen is the investigation of choice
It can visualize the hypertrophied pyloric muscle, measure wall thickness (>3 mm), and canal length (>15 mm)
A gastric fluid level may also be seen
Contrast radiography (barium swallow) can be used if ultrasound is equivocal, showing a "string sign" or "beak sign" due to narrowing of the pyloric canal.
Differential Diagnosis:
Other causes of vomiting in infants include gastroesophageal reflux, feeding intolerance, infectious gastroenteritis, milk protein allergy, intestinal malrotation with volvulus, intussusception, and CNS causes of increased intracranial pressure
Bilious vomiting necessitates immediate exclusion of intestinal obstruction.
Management
Initial Management:
The immediate goal is to correct dehydration and electrolyte imbalances
This involves intravenous fluid resuscitation with normal saline and potassium supplementation as per electrolyte levels
Gastric decompression via an nasogastric (NG) tube is often initiated to relieve vomiting and reduce gastric distension, especially if surgical correction is delayed
Correction of hypochloremic metabolic alkalosis is paramount before surgery.
Medical Management:
Medical management is primarily supportive and focuses on fluid and electrolyte correction
Pharmacological agents are not used to treat the hypertrophy itself
Careful monitoring of electrolytes is required throughout the management period
Nasogastric tube decompression is often continued until after surgery to allow the stomach to recover.
Surgical Management:
The definitive treatment is surgical correction via a pyloromyotomy, most commonly the Ramstedt procedure
This involves incising the hypertrophied muscle of the pylorus down to, but not through, the mucosa
It can be performed laparoscopically or via an open approach (e.g., umbilical or right upper quadrant incision)
The timing of surgery is critical
It should be performed once the infant is adequately resuscitated, dehydrated, and the electrolyte imbalances, particularly the hypochloremic alkalosis, are corrected
Delaying surgery until metabolic derangements are resolved is crucial to minimize perioperative risks.
Supportive Care:
Postoperatively, infants are monitored for pain, feeding tolerance, and wound healing
Oral feeds are usually started cautiously 4-6 hours after surgery, with progression from clear liquids to full feeds
Recurrent vomiting in the early postoperative period can occur and is usually managed conservatively with NG tube decompression
Nutritional support is maintained via IV fluids until adequate oral intake is established.
Hypochloremic Alkalosis
Pathophysiology:
Vomiting leads to loss of gastric acid (hydrochloric acid), resulting in a decrease in serum chloride and an increase in serum bicarbonate
The body compensates by retaining bicarbonate and excreting potassium and hydrogen ions in the urine, leading to a paradoxical aciduria and contributing to the alkalosis
This metabolic derangement can impair cellular function and complicate anesthetic management.
Clinical Manifestations:
Symptoms can include lethargy, muscle weakness, hyporeflexia, tetany, and cardiac arrhythmias due to associated hypokalemia
The degree of alkalosis can range from mild to severe, impacting overall well-being and recovery.
Correction And Timing Of Surgery:
Correction involves intravenous fluid administration with normal saline to provide chloride and a source of sodium, and potassium supplementation to replace urinary losses
Bicarbonate levels typically normalize as chloride is replaced
Surgery should ideally be postponed until serum chloride levels are >90-100 mEq/L and bicarbonate levels are <30 mEq/L, and the infant is clinically stable
This pre-operative metabolic optimization is crucial for patient safety and reducing perioperative complications, a key learning point for DNB and NEET SS candidates.
Monitoring:
Close monitoring of electrolytes, acid-base status, and fluid balance is essential during the correction phase
Serial electrolyte measurements guide the repletion strategy.
Pyloromyotomy Timing
Indications For Surgery:
The definitive indication for surgery is the diagnosis of hypertrophic pyloric stenosis causing significant gastric outlet obstruction, leading to dehydration, weight loss, and electrolyte disturbances
The presence of a palpable pyloric mass and characteristic imaging findings confirms the diagnosis.
Optimal Timing Factors:
The optimal timing for pyloromyotomy is determined by the infant's metabolic status and overall condition, rather than a fixed time after diagnosis
The surgery should be performed once the infant is adequately resuscitated, dehydrated, and critically, once the hypochloremic metabolic alkalosis is corrected
This typically requires at least 24-48 hours of aggressive fluid and electrolyte management
Avoiding surgery in a severely acidotic or alkalotic, dehydrated infant is paramount for surgical safety and anesthetic management.
Risks Of Delay:
Delaying surgery beyond metabolic correction can lead to prolonged hospitalization, increased risk of complications related to severe dehydration and malnutrition, and potential for postoperative feeding difficulties
Conversely, rushing surgery before metabolic stabilization increases perioperative risks such as anesthetic complications, wound infections, and delayed gastric emptying.
Laparoscopic Vs Open:
Both laparoscopic and open pyloromyotomy are effective
Laparoscopic surgery offers smaller incisions, potentially faster recovery, and reduced pain
However, it requires specialized equipment and expertise
The choice often depends on surgeon preference and available resources
The timing principles remain the same for both approaches.
Complications
Early Complications:
Bleeding (from incision or gastric mucosa), perforation of the gastric mucosa during the myotomy, wound infection, residual or recurrent obstruction (due to incomplete myotomy or technical error), postoperative ileus, and feeding intolerance leading to persistent vomiting.
Late Complications:
Scarring, adhesions leading to bowel obstruction (rare), and long-term effects on gastric emptying are generally uncommon
Most infants recover fully with minimal long-term sequelae.
Prevention Strategies:
Meticulous surgical technique to ensure complete but mucosa-sparing myotomy, prompt and adequate correction of metabolic derangements preoperatively, careful postoperative feeding protocols, and vigilant monitoring for signs of complications are key prevention strategies.
Key Points
Exam Focus:
Understand the pathophysiology of hypochloremic metabolic alkalosis in pyloric stenosis
Know the typical electrolyte derangements (low chloride, high bicarbonate)
Master the indications and contraindications for immediate surgery
Recognize the signs of pyloric stenosis and the diagnostic utility of ultrasound
Recall the steps of the Ramstedt pyloromyotomy and its potential complications.
Clinical Pearls:
Always palpate for the pyloric olive after the infant vomits
Remember that "projectile" vomiting is key
distinguish it from simple regurgitation
Electrolyte correction is often the bottleneck before surgery
prioritize it
Laparoscopic pyloromyotomy is increasingly common but open surgery is still widely performed.
Common Mistakes:
Mistake: Rushing to surgery before correcting severe metabolic alkalosis
Mistake: Misdiagnosing pyloric stenosis as simple reflux or gastroenteritis
Mistake: Incomplete pyloric muscle division leading to residual obstruction
Mistake: Aggressive postoperative feeding too soon, leading to persistent vomiting.