Gastrointestinal- Embriology, Flashcards
Normal gastrointestinal embryology
- Foregut
- Midgut
- Hindgut
esophagus to upper duodenum
lower duodenum to proximal 2/3 of transverse colon.
distal 1/3 of transverse colon to anal canal above pectinate line.
Midgut development:
6th week—physiologic midgut herniates through umbilical ring
10th week—returns to abdominal cavity + rotates around superior mesenteric artery (SMA), total 270° counterclockwise.
Ventral wall defects
Failure of rostral fold closure (eg, sternal defects [ectopia cordis]),
Lateral fold closure (eg, omphalocele, gastroschisis)
Caudal fold closure (eg, bladder exstrophy)
Gastroschisis
- Etiology
- Covered
- Associations
Extrusion of abdominal contents through abdominal folds (typically right of umbilicus).
Not covered by peritoneum or amnion;
Not associated with chromosome abnormalities
Omphalocele
- Etiology
- Covered
- Associations
Failure of lateral walls to migrate at umbilical ring persistent midline herniation of abdominal contents into umbilical cord.
Surrounded by peritoneum
Associated with congenital anomalies (eg, trisomies 13 and 18, Beckwith-Wiedemann syndrome) and other structural abnormalities (eg, cardiac, GU, neural tube)
Congenital umbilical hernia
Failure of umbilical ring to close after physiologic herniation of the intestines. Small defects usually close spontaneously
Tracheoesophageal anomalies
- Clinical features
- Diagnosis
Neonates drool, choke, and vomit with first feeding. TEFs allow air to enter stomach (visible on CXR). Cyanosis is 2° to laryngospasm (to avoid reflux-related aspiration).
Clinical test: failure to pass nasogastric tube into stomach.
Tracheoesophageal anomalies
- Types
In H-type, the fistula resembles the letter H. In pure EA, CXR shows gasless abdomen.
Esophageal atresia (EA) with distal tracheoesophageal fistula (TEF) is the most common (85%) and often presents as polyhydramnios in utero.
Intestinal atresia
- Clinical features
Presents with bilious vomiting and abdominal distension within first 1–2 days of life.
Intestinal atresia
- Duodenal atresia
failure to recanalize. Associated with “double bubble” (dilated stomach, proximal duodenum) on x-ray ). Associated with Down syndrome
Intestinal atresia
- Jejunal and ileal atresia
disruption of mesenteric vessels ischemic necrosis segmental resorption (bowel discontinuity or “apple peel”).
Hypertrophic pyloric stenosis
- Clinical features
Most common cause of gastric outlet obstruction in infants (1:600). Palpable olive-shaped mass in
epigastric region, visible peristaltic waves, and nonbilious projectile vomiting at ∼ 2–6 weeks old.
Hypertrophic pyloric stenosis
- Associations
- Diagnosis
- Treatment
associated with exposure to macrolides. Results in hypokalemic hypochloremic metabolic alkalosis.
Ultrasound shows thickened and lengthened pylorus
Treatment is surgical incision (pyloromyotomy).
Pancreas embriology
Derived from foregut.
Ventral pancreatic buds contribute to uncinate process and main pancreatic duct.
The dorsal pancreatic bud alone becomes the body, tail, isthmus, and accessory pancreatic duct.
Both the ventral and dorsal buds contribute to pancreatic head
Annular pancreas
Abnormal rotation of ventral pancreatic bud forms a ring of pancreatic tissue encircles 2nd part of duodenum; may cause duodenal narrowing and vomiting.
