Pyloric stenosis

Question 1

You are asked to see a 6-week-old male baby who presents with non-bilious vomiting. This always occurs after feeding and the parents describe it as ‘explosive’. After vomiting, the baby remains hungry and is still eager to feed. What is the diagnosis?

Answer 1

Pyloric stenosis

Question 2

What is the sex ratio for pyloric stenosis?

Answer 2

7:1 M:F and more common in first born boys

Question 3

When does pyloric stenosis commonly present?

Answer 3

4-6 weeks but can be up to 4 months

Question 4

Why does pyloric stenosis present at 3-6 weeks ?

Answer 4

The pylorus is normal at birth and hypertrophies as time progresses.

Question 5

What are the risk factors for pyloric stenosis?

Answer 5

• Age at presentation: majority between 3-6 weeks of life
• Sex predilection: males > females (ratio of approximately 4:1)
• Race predilection: More common in Caucasian people
• Family history
• Most common in first-borns

Question 6

How common is pyloric stenosis?

Answer 6

• incidence of 4 per 1,000 live births (~0.4%)
• 4 times more common in males

Question 7

How does pyloric stenosis present?

Answer 7

• ‘projectile’ vomiting, typically 30 minutes after a feed
• constipation and dehydration may also be present
• a palpable mass may be present in the upper abdomen

hypochloraemic, hypokalaemic alkalosis due to persistent vomiting

Question 8

Which three signs might be seen on examination in a patient with pyloric stenosis?

Answer 8

• Jaundice - in approximately 5% of infants
• After feeding a wave of gastric peristalsis may be seen traversing the abdomen from left to right, representing intense contractions against an obstruction.
• Abdominal distension - late finding
• Hypertrophied pylorus palpable - it is firm, mobile and olive-shaped and is located in the right upper quadrant of the abdomen, beneath the liver edge.
• Fontanelle may be depressed - if malnourished and dehydrated

Question 9

What metabolic profile is seen in pyloric stenosis?

Answer 9

hypochloraemic, hypokalaemic metabolic alkalosis

Question 10

When would you see each of these results?

Answer 10

Pattern 1 is a classic early vomiting picture often seen with pyloric stenosis.

Pattern 2 is typical of adrenal crisis (low Na, high K).

Pattern 3 is a picture of vomiting resulting in dehydration and lactic acidosis and can also be seen later in the clinical course of pyloric stenosis as the dehydration worsens.

Pattern 4 is typical of hypernatraemic dehydration.

Question 11

What imaging investigations would you do for pyloric stenosis?

Answer 11

Abdominal US - diagnostic with 90% sensitivity. Measures pyloric muscle thickness (arrow) and the length of the pyloric canal; if the patient is fed it is possible to visualise the feed within the distended gastric antrum (arrow) and show that the stenosed pyloric canal (arrow) does not open

Barium meal - if US results are equivokal

Question 12

What is the definitive management of pyloric stenosis?

Answer 12

Ramstedt’s pyloromyotomy - easily performed with minimal complications. Right upper-quadrant incision made and the pyloric muscle is split longitudinally down to the mucosa.

Question 13

What is the conservative management before surgery for pyloric stenosis?

Answer 13

Fluid bolus prior to maintenance fluids

Correction of any electrolye abnormalities e.g. KCl