Week 1: embryonic and developmental disorders of the GI tract

Question 1

Omphalocele

Answer 1

When midgut doesn’t return to abdominal cavity

-associated with other abnormalities: cardiac, skeletal, kidney

Question 2

Meckel’s diverticulum-overview

Answer 2

• partial persistence of the omphalomesenteric duct with proximal patency
• 2-3% of population
• located 2 feet from ileocecal valve on the anti mesenteric border
• 30-50% may contain ectopic gastric mucosa capable of producing acid and gastric enzymes

Question 3

Meckel’s diverticulum: clinical presentation

Answer 3

1. Rectal bleeding
   - hemorrhage due to peptic ulceration of mucosa
   - common in first 2 years of life
   - asymptomatic passage of red stool
2. vomiting-bowel obstruction
   - may invaginate and serve as lead point that will pull ileum inside in a telescope fashion (intussusception)
   - sudden onset ab pain, emesis-bile stained, distention
3. acute abdominal pain
   - inflammation, may be similar to acute appendicitis including perforation, peritonitis, intra abdominal abscess formation

Question 4

Diagnosis of Meckel’s diverticulum

Answer 4

• hx of sudden onset painless rectal bleeding with soft non distended abdomen
• radionuclide imaging with 99tecnetium pertechnetate may confirm diagnosis. isotope is taken up and secreted by gastric mucosa
• sensitivity improved by PPI
• Rx is surgical resection

Question 5

Intestinal obstruction in the newborn: pathophysiology

Answer 5

• obstruction of fecal stream
• continued secretion with increased intraluminal pressure of GI tract leads to decreased venous return followed by decreased arterial blood flow
• leads to necrosis, perforation, peritonitis
• complete obstruction: early symptoms within 24-48hrs
• incomplete obstruction: variable time of onset

Question 6

Clinical findings of intestinal obstruction of newborn

Answer 6

• polyhydramnios: excess amniotic fluid because infants cannot swallow it in utero
• material hx of toxemia, bleeding, viral infection, DM
• family hx of CF
• signs/symptoms: bilious vomiting, distention, delayed or absent passage of meconium, increased gastric aspirate
• high obstructions: early symptoms, vomiting before distention, mild distention, small number of distended air filled loops of bowel
• low obstruction: onset after 24hr, distention before vomiting, multiple air filled loops of bowel on plain film, micro colon

Question 7

malrotation and midgut volvulus

Answer 7

• failure of normal rotation of intestine results in arrest of cecum in abnormal site with formation of adhesions (ladd’s bands) to posterior peritoneal wall–>obstruction
• short horizontal small bowel mesentery can twist and occlude the SMA (volvulus) causing ischemic necrosis of small bowel. EMERGENCY.
• major cause of short bowel
• sx: bilious emesis, rectal bleeding
• dx: plain film

Question 8

duodenal atresia and stenosis

Answer 8

• complete (atresia) or incomplete (stenosis, web, diaphragm) obstruction
• often seen with Down syndrome and other abnormalities e.g. Trachea esophageal fistula, congenital heart disease, imperforate anus
• sx: 80% distal to ampulla of Vater, bilious vomiting
• plain film: double bubble sign: 2 loops of distended bowel, absent distal gas

Question 9

Jejunal and high ileal atresia and stenosis

Answer 9

• often associated with CF and intrauterine volvulus of loop of bowel with thick meconium
• from intrauterine vascular accidents during late fetal life
• necrosis and eventual resorption of involved segment produces a mesenteric defect/gap
• sx: early onset distention and bilious emesis
• dx: plain film shows limited number of dilated loops of small bowel with absent distal gas. micro colon in contrast enemas.

Question 10

Pyloric stenosis

Answer 10

• post natal development defect
• hypertrophy and hyperplasia of circular and longitudinal muscle layers
• etiology unclear but several factors suggested, i.e. decreased nerve cell bodies, decrease in ICC, ganglion cells, lack of C-KIT, decreased NOS gene, infantile hypergastrinemia
• sx: 3-12 weeks of age, non bilious projectile emesis, weight loss, dehydration, hyper peristaltic waves, palpable pyloric olive (the hypertrophied pylorus), some have jaundice, hypokalemia, hypochloremia, metabolic alkalosis
• dx: clinical findings, upper GI series, abdominal ultrasound-elongated and thickened pylorus seen