Congenital Abnormalities Within GI Tract

Question 1

Atresia vs fistula vs duplications

Answer 1

Atresia

• congenital narrowing of blood vessels/GI tract
• agenesis = complete absence

Fistulae
- congenital abnormal connection between two hollow spaces (usually blood vessels, intestines or other hollow organs)

Duplications
- congenital splitting/coupling of two hollow organs/blood vessels and/or intestines

generally, require prompt surgical repair and are incompatible with life

Question 2

Secondary causes from fistula of esophagus

Answer 2

Usually fistula results in connection of esophagus to the trachea which causes

• aspiration
• suffocation
• pneumonia
• fluid/electrolyte

Question 3

Development abnormalities of the esophagus are also associated with what kind of congenital diseases?

Answer 3

Heart defects

Genitourinary malformations

Neurologic genetic disorders

Question 4

Where in the intestines does atresia occur at the most often?

Answer 4

Duodenum

Question 5

Imperforate anus

Answer 5

Most common form of congenital intestinal atresia

- is due to the cloacal diaphragm to involute

Question 6

Stenosis

Answer 6

Incomplete atresia in which the lumen is markedly reduced as a result of fibrosis thickening of the lumen wall
- can result in partial or complete obstruction

Can involve any part of the GI tract, but most commonly hits the esophagus and small intestine

Question 7

Diaphragmatic hernia

Answer 7

Incomplete formation of the diaphragm which allows for the abdominal viscera to herniate into the thoracic cavity
- often causes pulmonary hypoplasia and in severe cases, incompatible with life

Question 8

Omphalocele

Answer 8

Abdominal musculature incompletely closes, which results in the abdominal viscera to herniate into a ventral membranous sac

Requires surgical repairment and roughly 40% of infants that have this also have other compounding birth defects

Question 9

Gastroschisis

Answer 9

Similar to omphalocele except that all layers of the abdominal wall including peritoneum and skin are affected
- not just abdominal viscera

Is more dangerous and is surgically correctable

Question 10

Ectopic tissues

Answer 10

Developmental arrest and movement of site specific tissues outside of normal site area specific.
- most frequent ectopic gastric mucosa = upper third of the esophagus (causes “inlet patch”)

Other areas are

• pancreatic tissues in the esophagus or stomach
• gastric heterotopia mucosa in the small bowel or colon

gastric heterotopia often causes occult blood less due to peptic ulcerations due to acid secretion

Question 11

Meckel diverticulum

Answer 11

A blind outpouching of the alimentary (GI) tract in the ileum
- contains all layers of bowel wall and the lumen of the bowel

Results from failed involution of the Vitelline duct (connects developing duct to yolk sac)

*most common type of diverticulum

Question 12

“Rules of 2’s” for meckel diverticulum

Answer 12

2% occurrence rates

Generally present within 2 feet of ileocecal valve

Are approximately 2 inches long

2x as common in males

Most often symptomatic by age 2 (if they ever become symptomatic)

Question 13

What does meckel diverticulum often mimic if it becomes symptomatic?

Answer 13

Acute pancreatitis

- this is because the ileum is in the same region as the pancreas

Question 14

Congenital hypertrophic pyloric stenosis epidemiology

Answer 14

Occurs in 1:300-900 live births

3-5x more common in males

Is highly genetic (monozygotic twins have a 200x increase in risk; dizygotic = 20x)

Is correlated with Turner syndrome (trisomy 18)

Antibiotics erythromycin and azithromycin exposure in newborns increases risk as well

Question 15

Congenital hypertrophic pyloric stenosis pathogenesis

Answer 15

Occlusion of the pyloric sphincter preventing food to leave stomach due to extreme hypertrophy of the pyloric muscularis PROPRIA layer -> small intestines
- looks like a firm ovoid abdominal mass on imaging

Appears between 3-6 weeks old as new-onset regurgitation projectile nonbilious vomiting with dehydration and weight loss
- may also show left -> right visible hyperperistalsis (can see the stomach trying to push the food through the pyloric stenosis)

Treatment = surgical intervention cures

Question 16

Hirschsprung disease

Congenital aganglionic megacolon

Answer 16

tremendous distention and hypertrophy of the sigmoid and descending colon

Epidemiology

• 1:5000 live births
• often presents with confounding developmental abnormalities
• very well linked to Down syndrome (trisomy 21)

Symptoms:

• failure to pass meconium (first bowel movement)
• constipation and abdominal distention
• may see bilious vomiting

Treatment: surgical resection of dead area

Question 17

Hirschsprung disease pathogenesis

Answer 17

Normal migration of neural crest cells from cecum -> rectum arrests prematurely OR when the ganglion cells of the enteric neuronal plexus undergo premature death.
- both result in a distal intestinal segment that lacks both Meissener Submucosa and Auerbach myenteric plexus

ultimately makes the rectum and distal intestinal segment (sigmoid) NOT be able to coordinate any peristalsis. Functional obstruction occurs and results in dilation of the descending colon and some of the sigmoid

Question 18

What is the most common genetic mutation that results in hirschsprung disease?

Answer 18

Heterozygous loss of function in the receptor tyrosine kinase (RET) enzymes

Question 19

How do you diagnose hirschsprung disease

Answer 19

Requires:

• biopsy of affected intestines and notice an absence of ganglion cells
• also usually need to see IHC staining for acetylcholinesterase enzymes (will be negative)

Question 20

Where do ruptures of the intestines most commonly occur in hirschsprung disease?

Answer 20

The cecum

- only occurs when it gets super large (roughly 20cm)