GI Embryology Flashcards
development of the GI tract - overview
*formed during the 4th week of gestation
*appears as 4mm hollow tube
*buccopharyngeal and cloacal membranes rupture during 3rd and 7th weeks
*well formed & early function by end of 2nd trimester
foregut
*esophagus
*stomach
*duodenum
*liver
*gallbladder
*pancreas
midgut
*jejunum
*ileum
*ascending colon
*transverse colon
hindgut
*descending colon
*rectosigmoid colon
esophageal atresia & tracheoesophageal fistula
*often occur together
*50% of infants have associated anomalies (VACTERL or CHARGE)
*many different types
embryology of esophageal atresia & tracheoesophageal fistula
*normally, foregut is partitioned by a septum into 2 separate tubes:
1. anterior trachea develops cartilaginous rings and lung buds
2. posterior esophagus stretches from pharynx to stomach
*INCOMPLETE TUBULAR SEPARATION may occur, leading to esophageal atresia & tracheoesophageal fistula
esophageal atresia & tracheoesophageal fistula - associated anomalies
*polyhydramnios in 50% of mothers
*cardio: PDA, VSD, ASD
*GI: imperforate anus, duodenal atresia
*skeletal: vertebral anomalies
*GU: hypospadias
*other: trisomy
most common type of esophageal atresia & tracheoesophageal fistula
type C: esophageal atresia with DISTAL tracheoesophageal fistula
esophageal atresia with DISTAL tracheoesophageal fistula (type C)
*85% of total esophageal defects
*esophageal gap 1 to 2 cm
*distal TEF joins trachea at carina
*diagnosis made by placing nasogastric tube (does not go in)
*cough, choking, aspiration with first feed
esophageal atresia without tracheoesophageal fistula (type A)
*8% of congenital esophageal defects
*absence of gas within the GI tract
*20% will have Down’s syndrome
*if the gap between the esophageal pouches is > 4 cm, primary anastomosis is difficult
H-type tracheoesophageal fistula
*TEF without esophageal atresia
*3-5% of cases
*rarely have other anomalies
*repeated episodes of pneumonia
*esophagus & trachea otherwise normal
pyloric stenosis - overview
*sx: non-bilious vomiting
*hypokalemic, hypochloremic metabolic alkalosis
*typically presents between 3-5 weeks of age
*pyloric mass on PE
pyloric stenosis - incidence and heredity
*most frequent surgical disorder of the stomach
*1.5x increased risk in first-born children
*MALES to females 4-6:1
*possible positive family hx
*premature infants > full term
*increased risk due to maternal smoking
*possible increased risk with bottle feeding vs. breastfeeding
*significant increased risk with use of macrolide antibiotics (esp < 2 weeks of age)
pyloric stenosis - pathogenesis
*pyloric muscle hypertrophy from gastric peristalsis against closed pyloric canal
*hypergastrinemia with hyperacidity
*elevations of prostaglandins leading to smooth muscle constriction
pyloric stenosis - clinical presentation
*non-bilious, progressive projectile vomiting
*dehydration
*failure to thrive
*classically presents between 3-6 weeks of age
*elevated serum bicarbonate, decrease in serum chloride and potassium
pyloric stenosis - diagnosis
*physical exam reveals pyloric mass or “olive”
*UGI (upper GI series)
*sonography! (ultrasound - gold standard)
pyloric stenosis - treatment
*fluid & electrolyte management!! (first step)
*surgical correction: pyloromyotomy
duodenal atresia - overview
*thought to arise from failure of recanalization of duodenal lumina (normally occurs during weeks 8-10 of gestation)
*incidence: 1 in 10,000
*associated with prematurity
*F to M 2:1
*ASSOCIATED WITH DOWN’S SYNDROME
*presents with BILIOUS vomiting
duodenal atresia - clinical presentation
*BILIOUS vomiting
*abdominal distension
*“double bubble” on x-ray (dilated stomach & proximal duodenum)
which disorders classically present with non-bilious vomiting in infancy
*esophageal atresia with tracheoesophageal fistula
*pyloric stenosis
which disorder classically presents with non-bilious vomiting in infants with Down syndrome
*duodenal atresia
duodenal atresia - treatment
*fluid & electrolyte management
*feeding tube for decompression
*antibiotics
*surgical correction = duodenoduodenostomy
*prognosis dependent on associated anomalies
jejunal/ileal atresias
*bilious emesis
*failure to pass meconium
*can be associated with cystic fibrosis
*jejunal atresia can be associated with other malformations
duplications of the GI tract
*rare anomalies consisting of well-developed tubular or spherical structures
*located on the MESENTERIC BORDER
*50% contain gastric mucosa
*presents in infancy if symptomatic
*sx related to obstruction, intussusception, volvulus, perforation, or hemorrhage
malrotation
*failure of the midgut to achieve normal position
*predisposes to volvulus of midgut
*acute bowel obstruction
*bilious emesis
*symptomatic -> surgical emergency
malrotation - treatment
*if asymptomatic - controversial
*if symptomatic - surgical
*Ladd’s procedure:
-reduction of volvulus
-evaluation of intestinal viability
-division of Ladd’s bands
-broadening base of mesenteric peduncle
-appendectomy
-return of SMALL INTESTINE TO RIGHT ABDOMEN
-return of LARGE INTESTINE TO LEFT ABDOMEN
Meckel’s Diverticulum - overview
*remnant of the omphalomesenteric (vitelline) duct due to its incomplete obliteration
*ANTIMESENTERIC border of ileum
*TRUE diverticulum (contains all 3 layers of bowel wall)
*rules of 2’s:
-presents before 2 years of age
-within 2 feet of ileocecal valve
-2 inches long
-2% of population
-2 types of ectopic tissue (gastric or pancreatic)
Meckel’s Diverticulum - clinical presentation
*bowel obstruction
*GI bleeding (usually painless)!!
*intussusception
Meckel’s Diverticulum - diagnosis
*Meckel’s scan (99m-Tc pertechnetate scintigraphy)
*needs presence of ectopic gastric mucosa
*pre-treatment with H2 blocker
Meckel’s Diverticulum - treatment
surgical
Hirschsprung’s disease - overview
*absence of intramural ganglion cells
*1 in 5000 live births
*4:1 MALE to female
*20% of cases are familial
*associated with Down’s syndrome
*85% limited to rectosigmoid colon
*aganglionic segment permanently contracted
*loss of rectosphincteric reflex (relaxation of anal sphincter during defecation)
Hirschsprung’s disease - symptoms
*delayed passage of meconium (within 48 hours of birth)!!
*majority have symptoms within first month to year of life
*failure to thrive
*vomiting
*intermittent diarrhea
*abdominal distension
-complication = Hirschsprung’s disease-associated enterocolitis:
-acute diarrheal illness
-severe dehydration, sepsis
Hirschsprung’s disease - diagnosis
*barium enema (unprepared)
*rectal mucosal suction biopsy (highest sensitivity/specificity - gold standard)
*anorectal manometry (absent RAIR)
Hirschsprung’s disease - treatment & prognosis
*tx: surgical removal of aganglionic segment of colon
*creation of neo rectum using proximal ganglionic bowel
*low mortality today
Hirschsprung’s disease - common post-op complications
*persistent constipation
*anastomotic strictures
*toilet training issues
*recurrent enterocolitis
*fecal incontinence
omphalocele
*ventral wall defect
*location: umbilical ring
*size: 4-10 cm
*umbilical cord inserts onto sac
*sac present (amnion & peritoneum)
*includes stomach, small bowel, colon, liver, etc
*normal bowel appearance
*malrotation present
*associated anomalies common
gastroschisis
*ventral wall defect
*location: lateral to cord
*size: 3-4 cm
*normal insertion of umbilical cord
*sac absent
*includes only small bowel typically
*bowel is abnormal (poor motility, absorption, etc)
*malrotation present
*associated anomalies rare
