Embryology

Question 1

What are the specific transcription factors expressed for early development of the:

Esophagus and Stomach

Duodenum

Small Intestine

Large Intestine and Rectum

Answer 1

Esophagus and Stomach: SOX2

Duodenum: PDX1

Small Intestine: CDXC

Large Intestine and Rectum: CDXA

Question 2

What is the function of sonic hedgehog?

Answer 2

To initiate epithelial-mesenchymal interaction throughout the gut tube.

SHH expression upregulates factors in the mesoderm that then determine the type of structure that forms the gut tube. (i.e. SOX2, PDX1, CDXC, CDXA, HOX, etc)

Question 3

What are clinical features of tracheoesophageal atresia?

Answer 3

Symptoms: Feedings produce coughing, choking, and cyanosis

Incidence of 1 in 3000 live births

Maternal polyhydramnios is often present b/c amniotic fluid is unable to pass through the intestinal tract due to atresia

Question 4

What are the types of tracheoesophageal atresia and fistulas?

Answer 4

• Esophageal atresia (EA) with distal Tracheoesophageal fistula (TEF)
• EA without TEF
• TEF without EA: “H” type (often discovered later in life)
• EA with TEF to proximal esophageal segment
• EA with TEF to both proximal and distal segments

Question 5

What are the anomalies associated with Tracheoesophageal Fistulas?

Answer 5

VACTERL Association:

Vertebral Defects

Anal atresia

Cardiovascular anomalies

TrachEoesophageal fistula

Renal Anomalies

Limb Defects

Question 6

What kind of congenital malformations can occur in the GI tract?

Answer 6

• Duplication
• Hypertrophic Pyloric Stenosis
• Intestinal Atresia
• Meckel Diverticulum
• Hirschsprung Disease
• Omphalocele
• Imperforate Anus

Question 7

What are clinical features of hypertophic pyloric stenosis?

Answer 7

• *Symptoms:
• Seen at 2-6 weeks as progressive, nonbilious* vomiting
• Visible peristaltic waves
• Almond-sized mass to right of midline**
• Male predominance (1 in 200 boys)

*Nonbilious b/c bile cannot get into the stomach from the Ampulla of Vater due to pyloric stenosis

Question 8

What is the treatment of Hypertrophic Pyloric Stenosis?

Answer 8

• Longitudinal incision of hypertophied muscle down to mucosa
• Most common cause of abdominal operation in first 6 months of life

Question 9

What are the clinical features of Intestinal Atresia?

Answer 9

Symptoms:
- Presents as obstruction:
Bilious vomiting
Abdominal Distention

• Maternal polyhydramnios: 25%
• Associated with Downs Syndrome and Cystic Fibrosis
• Equally in duodenum, jejunum, and ileum (infreq. in colon)

Question 10

What are clinical features of Hirschsprung Disease?

Answer 10

• Congenital absence of intramural parasympathetic ganglion cells in distal GI tract
• *Symptoms:
• Abdominla distension
• vomiting
• Diarrhea
• Necrotizing entercolitis
• Perforation
• Chronic constipation (older patients)**

Ultra short segment disease may not present until later childhood or even adulthood (by chronic constipation)

Question 11

What is Malrotation?

Answer 11

When the bowel returns to abdomen at end of 1st trimester, counterclockwise rotation of midgut occurs that puts colon anterior to duodenum and descending colon on left

In Malrotation, Nonrotation can occur that puts small bowel on right and colon on left
Reverse rotation puts colon posterior to duodenum

It is due to failure of fixture of mesentary to posterior wall of abdomen

Question 12

What are clinical features of Malrotation?

Answer 12

Symptoms:
- Obstruction from volvulus
Vomiting
Abdominal Pain
Bleeding

• Associated with Downs Syndrome (trisomy 13 and 18)
• Resection of bowel may be required if infarcted

Question 13

What is an omphalocele?

Answer 13

Abdominal wall defect in which abdominal organs protrude from the abdomen wrapped by amnion

Question 14

What is gastroschisis?

Answer 14

Abdominal wall defect in which abdominal organs protrude from the abdomen not wrapped by amnion

Question 15

What is Meckel Diverticulum?

Answer 15

• Remnant of vitelline duct that may connect to umbilicus
• Located on antimesenteric border, 1-3 feet from ileocecal valve
• Lined by intestinal or gastric mucosa

Question 16

What are clinical features of an Imperforate Anus?

Answer 16

Lack of anus, obvious on physical examination
–> May be low (ano-vestibular or ano-cutaneous)
or High (recto-vaginal or recto-urethral fistula)

VATER association