GI - Pyloric Stenosis

Question 1

Definition

Answer 1

Congenital hypertrophy of the pyloric smooth muscle = non-bilious vomiting after feeding.
Typical findings = HYPOCHLORAEMIC HYPOKALEMIC METABOLIC ALKALOSIS

Question 2

Epidemiology

Answer 2

Neonates and younger children: 2-6 weeks of age (can present as late as 4 months)
Male ( x4 more common)
First born
Family history
Caucasian ethnicity

Question 3

Pathophysiology

Answer 3

Vomiting of stomach acid leads to hypochloraemic metabolic alkalosis. Hypokalaemia occurs for two reasons:
- potassium is lost in the vomit as KCl
- dehydration activates the renin-aldosterone system which stimulates potassium excretion in the distal nephron

Question 4

Bilious vs non-bilious vomiting

Answer 4

Obstruction proximal to the ampulla of Vater = non-bilious vomiting
Obstruction distal to AoV = bilious vomiting
(Because bile enters the small intestines at AoV)

Question 5

Causes of bilious (green) vomiting

Answer 5

• Intestinal obstruction: volvulus, intussuception, Hirschsprung’s disease
• Necrotising enterocolitis
• Severe gastroenteritis

Question 6

Causes of non-bilious vomiting

Answer 6

Pyloric stenosis
GORD
Gastroenteritis

Question 7

Signs

Answer 7

• Visible peristalsis in abdo
• Olive-shaped mass in upper abdo
• Evidence of dehydration
  = tachycardic or hypotensive
  = sunken fontanelle
  = dry mucous membranes
  = mottled skin

Question 8

Symptoms

Answer 8

• Projectile, non-bilious vomiting: 30 minutes after feeding
• Poor feeding
• Dehydration: reduced: reduced wet nappies

Question 9

Diagnosis

Answer 9

Test feed: feed baby and observe projectile vomit
Capillary blood gas: hypochloremic, hypokalaemic, metabolic alkalosis with elevated lactate due to dehydration
U + E’s: AKI due to dehydration + hypoK+
Abdo USS: the diagnostic investigation of choice:
- Hypertrophied and lengthened pylorus with ‘ target sign ’ and ‘ antral nipple sign ’
- Muscle wall thickness >3 mm and pyloric channel length >15 mm are diagnostic in infants < 30 days old

Question 10

Treatment

Answer 10

FIRST LINE =
- Nil-by-mouth + NG tube insertion: decompress the stomach to prevent aspiration.
- IV fluids: rehydration with surgery only taking place until electrolyte imbalances and hypovolaemia are addressed

Ramstedt pyloromyotomy:
- Definitive surgical management usually performed laparoscopically
- Almost all cases are managed surgically
- Involves an incision in the longitudinal and circular muscles of the pylorus

Question 11

Complications

Answer 11

Hypovolaemia and electrolyte imbalance : due to profuse vomiting
Acute kidney injury : due to dehydration secondary to profuse vomiting