Gastroenterology Flashcards
Pancreatic amylase
Present at 22 weeks gestation
Adequate amounts produced
Decreased secretion at birth
Glucoamylase
Normal action at birth
Located in intestinal brush border Removes glucose from end of starch
Intestinal disaccharidases
All except lactase reach adult levels at 28 weeks
Glucosidases - sucrase, maltase, isomaltase
Colonic bacteria
Helps ferment malabsorbed carbs to acids
Colonics salvage pathway
Lactase
Adult levels at 36 weeks gestation
Colonic salvage pathway helps limit carb malabsorption
Benefits to enteral feeding
Mucosal development/growth depends on enteral nutrients
Increases concentration of G.I. hormones
Improves gut barrier function
Increases G.I. blood cell
How much of the immune system does the intestinal tract make up?
70%
Nonspecific intestinal barrier defenses
Mucus layer Digestive enzymes, bile salts IgA Peristalsis Tight junctions Antimicrobial peptides
Epithelial cell G.I. immune function
Goblet cell Enterocytes Enteroendocrine cells M cells Intraepithelial lymphocytes Paneth cells Gut associated lymphoid tissue (GALT)
Two major pancreatic proteases
Trypsin
Chymotrypsin
Decreased in preterm and term infants compared to older children (PT more)
Peptidase levels
Well developed early in life
Amino acid transport in the newborn
Well developed
Protein digestion
Proteins are broken down to peptides in the stomach and duodenum by pepsin and pancreatic proteases
Peptides are broken down to amino acids by peptidases
Fat digestion
Fats form micelles after bile acid emulsification
Hydrolyzed by lipase
Fatty acids are transferred across intestinal mucosa
Triglyceride re-synthesized from FA and enterocytes then forms a chylomicron which is secreted into blood
Breastmilk lipases help
What does a triglyceride become after it’s broken down?
2 free fatty acids and 1 glyceride molecule
Digestion of short and medium chain FA
Absorbed directly into the blood
Travel through portal vein
Bile acids are not required
<14 carbons
Salivary and pancreatic amylase
Hydrolyze starch, glycogen, dextrin -> glucose, maltose, limit-dextrins
Decreased in newborns
Carbohydrate digestion
Starch and glycogen are broken down by amylase
Polysaccharides and disaccharides are broken down to monosaccharides
Glucose and galactose Transport/absorption
Active transport via SGLT1 transporter into the cell
- Needs Na/K pump
- Inefficient in the newborn especially pre-term
Crosses into circulation via GLUT2 transporter
Fructose Transport/absorption
Facilitated/passive transport via GLUT5 transporter
Crosses into circulation via GLUT2 transporter
What is absorbed in the stomach?
Water
Copper
Iodide
Fluoride
What is absorbed in the duodenum?
Calcium/Phos/Mag Iron Copper and selenium Vitamins B1, B2, B3 Biotin, folate Vitamin A, D, E, K
What is absorbed in the jejunum?
Lipids Monosaccharides Amino acids/small peptides Vitamins B1,B2,B3,B5,B6 Biotin/folate Vitamin C Vitamins A, D, E, K Ca/Phos/Mag Iron Zinc Chromium and manganese
What is absorbed in the ileum?
Vitamin C Folate Vitamin B12 Vitamin D and K Magnesium Bile salts and acids 
What is absorbed in the large intestine?
Water Electrolytes Vitamin K Biotin Short chain fatty acids
Risks for Spontaneous gastric perforation
Perinatal stress
Postnatal steroids
Etiology of spontaneous gastric perforation
Mechanical overdistention versus ischemia
Symptoms of spontaneous gastric perforation
Typically large and proximal
2-7 days of life
Abrupt abdominal distention, respiratory distress, shock
Spontaneous intestinal perforation Epidemiology
5% of extremely low birthweight infants
Compared to general population - more likely to have a PDA treated with indomethacin, more likely to receive vasopressor support
SIP vs NEC
SIP: Smaller/more immature Earlier postnatal age Unlikely to be fed PDA treated with indomethacin Vasopressor support Received surfactant and ventilation Maternal chorio
Pathophysiology of SIP
MC involves terminal ileum
Intestinal mucosa is robust and viable
Hypothesis
- meds and other exposures -> skewed trophism (mucosal hyperplasia, submucosal thinning, smooth muscle necrosis) -> bowel wall fragility
Symptoms of SIP
First week of life Abdominal distention Black/blue discoloration Hypotension X-ray with pneumoperitoneum, no pneumatosis or portal venous gas
Prognosis of SIP
Increased mortality compared to controls
Decreased mortality compared to NEC
Neurodevelopmental impairment but less when compared with NC
Risks of pyloric stenosis
Mother with PS: 19% son, 7% daughter
Father with PS: 5% son, 2.4% daughter
One child with PS: 3% chance next child (4% male, 2.4% female)
Males>females 5:1
Symptoms of pyloric stenosis
1-5 weeks
Non-bilious projectile vomiting, dehydration
Hypochloremia, hypokalemic metabolic alkalosis
Bilious emesis
Due to obstruction beyond the outlet of the common bile duct (beyond sphincter of Oddi)
Bile produced in the liver, stored in gallbladder
Etiology of duodenal atresia
Failure of recanalization during 8-10th week after obliteration of lumen
Usually in second part of duodenum past sphincter of Oddi
What is associated with duodenal atresia?
T21 81% Malrotation 20% Congenital heart disease 30% Esophageal atresia 10% Genitourinary anomalies 11% Annular pancreas 20%
Symptoms of duodenal atresia
In utero - polyhydramnios, distended duodenum Bilious emesis in the first 24 hours of life Can have meconium passage Abdominal distension (upper abdomen)
Symptoms can also be due to an annular pancreas which usually presents later
What does duodenal atresia look like on x-ray?
Double bubble
Air fluid level
No distal intestinal air
Jejunal/ileal atresia epidemiology
Overall incidence greater than duodenal or colonic atresias Usually a single atresia Distal ileum 36% Proximal jejunum 31% Distal jejunum on 20% Proximal ileum 13%
Etiology of jejunal/ileal atresia
In utero mesenteric vascular occlusion
Symptoms of jejunal/ileal atresia
Polyhydramnios in 1/3 patients with jejunal atresia, more rare for distal
Often SGA
Bilious emesis
Abdominal distention worse with more distal atresias
Can fail to pass meconium
What does jejunal/ileal atresia look like an x-ray?
X-ray: triple bubble, air fluid levels
Greater the amount of air = lower the obstruction
Peritoneal calcifications = In utero perforation and meconium peritonitis
What is malrotation associated with?
CDH Abdominal wall defects Intestinal atresias Beckwith Wiedemann Heterotaxy/situs inversus
Etiology of malrotation
Failure of normal rotation
Abnormal fixation - Ladd’s bands (fibrous bands between the cecum and right posterior retroduodenal peritoneum)
If volvulus occurs can lead to intestinal ischemia
What does malrotation look like on x-ray?
If complete obstruction- dilated bowel loops, air fluid levels, decreased air distal to the obstruction
Etiology of meconium ileus
Obstruction of the terminal ileum due to hyperviscous secretions from mucous glands of small intestine
Meconium with decreased water -> adheres to intestinal lining
How many patients with CF have meconium ileus?
10-15%
How many patients with meconium ileus have CF?
90%
Symptoms of meconium ileus
24 to 48 hours Usually no passage of meconium Abdominal distention at birth Bilious emesis Palpable bowel loops
What does an x-ray of meconium ileus look like?
Descendent intestinal loops without air fluid levels
Can appear granular or bubbly
What does malrotation look like on barium enema?
Cecum seen in RUQ instead of RLQ
Corkscrew appearance of proximal jejunum
Management of meconium ileus
Uncomplicated treat with enema (hypertonic barium, gastrografin, or Hypaque)
Draws fluid into the intestines and allows for disimpaction
Successful in 60%
Etiology of meconium peritonitis
In utero intestinal perforation with meconium spillage into peritoneal cavity
Usually secondary to meconium ileus, intestinal atresia, volvulus, gastroschisis
Meconium pseudocysts
Type of meconium peritonitis
Wall of fibrous tissue surrounds meconium
Meconium present for many weeks
Adhesive meconium peritonitis
Widespread contamination of peritoneal cavity
Days-weeks before birth
X-ray with calcifications
Vascular adhesion seen in surgery
Often associated with intestinal obstruction
Meconium ascites
Type of meconium peritonitis
Perforation only a few days before birth
No calcifications on x-ray
Infected meconium peritonitis
Intestinal perforation that does not seal
Seating of micro organisms into peritoneal cavity
Etiology of microcolon
Functional immaturity of ganglion cells
Affects descending and rectosigmoid colon
Transient functional obstruction
What is microcolon associated with?
Maternal diabetes*
Maternal hypothyroidism
Maternal magnesium exposure
Symptoms of microcolon
Abdominal distention
Failure to pass meconium
What does microcolon look like on x-ray?
Multiple dilated loops of bowel
What does microcolon look like on a barium enema?
Small colon segment with dilated bowel proximal, rectum is normal
Epidemiology of Hirschsprung’s
If one child has Hirschsprung’s = 3-5% risk to next child
80% male
What is Hirschsprung’s associated with?
T 21 Heterochromia Cartilage-hair hypoplasia Goldberg-Shprintzen syndrome Hirschsprung’s disease with limb anomalies MEN 2 Waardenburg syndrome Congenital deafness 13q deletion Pheochromocytoma Neurofibromatosis Neuroblastoma Congenital hypoventilation syndrome Riley-Day syndrome
Etiology of Hirschsprung’s
Failure of cranial to caudal migration of neural crest cells
8-10 weeks gestation
Aganglionic = no parasympathetic innervation to distal colon
Symptoms of Hirschsprung’s
No meconium in first 24 hours
Abdominal distention, failure to thrive
Constipation or foul smelling liquid stool seepage
Can have urinary obstruction due to large colon
Can be complicated by acute bacterial enterocolitis (25-30% mortality rate)
What does Hirschsprung’s look like on x-ray?
Large colon with absence of air in rectum
What does Hirschsprung’s look like on barium enema?
Assesses for transition zone - Area between end of normal proximal zone and beginning of abnormal distal zone
Definitive diagnosis of Hirschsprung’s
Biopsy to detect the absence or presence of ganglion cells with acetylcholinesterase staining
Treatment of Hirschsprung’s
Diverting colostomy
Definitive treatment at 1-1.5 years
Final repair is a pull through
Meconium plug
Colonic obstruction 2/2 a viscous, congealed mass of meconium
Associated with CF, maternal diabetes, and prematurity
Symptoms of meconium plug
Abdominal distension
No meconium in first two days
Can have bilious vomiting
What does a meconium plug look like on x-ray?
Multiple dilated loops of bowel
No rectal gas
What does a meconium plug look like on a barium enema?
Empty distal colon
Dilated proximal bowel
Filling defects caused by plugs
Treatment of meconium plugs
Abdominal decompression
Contrast enemas can be therapeutic
Consider Hirschsprung’s if no improvement after repeated enemas
Epidemiology of imperforate anus
Includes wide spectrum of anorectal abnormalities
Usually no familial pattern
Etiology of imperforate anus
Anorectum derives from cloaca
Failure of normal separation and division of cloaca into anterior urogenital sinus and posterior intestinal canal
Symptoms of imperforate anus
High and intermediate lesions often without an anal opening
If rectal atresia anal opening will appear normal
Rocker bottom perineum suggest sacral agenesis
If the lesion is high 10% have a tethered cord
Etiology of gastroschisis
Controversial, several mechanisms proposed
- Involution of right umbilical vein creates a weak spot
- Teratogenic exposures might be vasoconstrictive agents
- Genetic influences
Prenatal findings with gastroschisis
Elevated AFP, oligohydramnios, fetal growth restriction, MSAF
If intestinal atresia is present may develop polyhydramnios
Dilated loops of bowel correlate with bowel edema, longer repair time, higher rate of post operative complications
Defects associated with gastroschisis
All infants have malrotation
16% have other G.I. anomalies
Chromosomal or non-G.I. anomalies are very rare

Management of gastroschisis
Cover bowel loops with a plastic wrap
Silo placement or immediate surgical repair
Prognosis of gastroschisis
Survival 90%
Most have good long-term health and growth
Prematurity, low birthweight, stage silo repair, intestinal atresia -> all a/w longer time to full feedings and prolonged hospital stays
Epidemiology of omphalocele
3:1 male to female
Higher incidence of prematurity and FGR
Defects associated with omphalocele
As many as 80% Chromosomal 50% (T13,T18,T21) Cardiac 28% Genitourinary 20% Craniofacial 20%
Syndromes associated with omphalocele
Pentalogy of Cantrell
Beckwith-Wiedemann syndrome
OEIS complex (omphalocele, bladder exstrophy, imperforate anus, spinal deformity)
Etiology of omphalocele
Intestinal loops fail to return to abdominal cavity at 11 weeks
OR somatic folds failed to complete formation of abdominal wall at 18 weeks
Prenatal findings of omphalocele
Elevated AFP
Can be seen in second trimester
Amniocentesis recommended to rule out chromosomal abnormalities
Symptoms of omphalocele
Amniotic/peritoneum membrane protects intestinal loops
Covering sac may be ruptured
Abdominal wall musculature is normal
All have malrotation
Prognosis of omphalocele
Mortality is high is 30-40%
Large defect, ruptured sac, low birthweight, additional congenital anomalies, early respiratory failure -> all effect survival
Survival rate 90% with isolated omphalocele
Complications of omphalocele
Decreased G.I. motility Bowel obstruction Perforated viscous GE reflux Sepsis
Etiology of cholestasis
Increased direct fraction of bilirubin caused by abnormal bilirubin excretion
Conjugated should be <15% of total bilirubin
Symptoms of cholestasis
Conjugated hyperbili
Jaundice
Hepatomegaly
Acholic stools (2wks)
Causes of intrahepatic cholestasis
Neonatal idiopathic hepatitis
Alagille syndrome
Non-syndromic paucity of bile ducts
Causes of extrahepatic cholestasis
Biliary atresia Sclerosing cholangitis Bile duct stenosis Choledochal cyst Bile plug syndrome
What to etiologies cause 60-70% of cases of cholestasis?
Biliary atresia and idiopathic neonatal hepatitis
Biliary atresia
Obstruction of biliary tree 2/2 progressive sclerosis of extrahepatic bile ducts (possibly after viral infection)
On histology will see bile duct proliferation
Idiopathic neonatal hepatitis
Inflammatory condition of neonatal liver
Histology: multinucleated giant cella
PN associated liver disease
Inversely related to birthweight
Related to duration of PN use (>2 wks)
Initiate enteral feedings as soon as possible (stimulus for bile flow, gallbladder contraction, intestinal motility)
What are choledochal cysts?
Congenital bile duct anomalies
Cystic dilations of biliary tree
Symptoms of choledochal cysts
Jaundice
Acholic stools
Palpable mass in RUQ
Hepatomegaly
Diagnosis of choledochal cysts
Ultrasound
Management of choledochal cysts
Complete excision
Construction of biliary-enteric anastomosis
Causes of term NEC
Cocaine
Congenital heart disease
Things that decrease perfusion to the gut
Most common location of NEC?
Terminal ileum and proximal colon
Timing of NEC
PMA 31 to 32 weeks, preterm infants can get it later compared to full-term
Pathophysiology of NEC
Prematurity Formula Abnormal bacterial colonization Reduced commensal organisms Final pathway to injury seems to be activation of inflammatory cascade
Esophageal sphincter tone
Preterm 4mmHg
Term 18mmHg
Gastroesophageal reflux
Physiological event
Gastric contents move into the esophagus
Gastroesophageal reflux disease
Pathologic state, complications arise from GER
Pain
Mucosal damage
Potential for aspiration
Risk factors for GERD
Prematurity
Caffeine
Sepsis
Neurologic impairment
Which comes first - apnea or reflux?
Apnea preceeds reflux more often
Desaturation with leads to relaxation of sphincter
Histamine antagonists
Reduce gastric acidity
Does not stop reflux
Increased levels of NEC
PPIs
Reduce acidity and reflux episodes
No improvement in clinical symptoms
No evidence for efficacy or safety in neonates
Prokinetics
Erythromycin - increased risk of pyloric stenosis, sepsis, cardiac dysrhythmias
Metoclopramide - Tardive dyskinesia, extrapyramidal symptoms, bradykinesia, tremor, rigidity
When is the esophageal lumen reestablished?
10 weeks
When is swallowing seen in utero?
16 weeks
When does nonnutritive sucking appear?
20 weeks
When does nutritive sucking appear?
32-34 weeks
When does stomach start secreting things?
16 weeks Hydrochloric acid Intrinsic factor Pepcid Gastrin Mucus
What does caudal portion of foregut give rise to?
Upper duodenum
What does midgut give rise to?
Lower duodenum Jejunum Ileum Appendix Ascending colon Proximal 2/3 of transverse colon
What does hindgut give rise to?
1/3 of transverse colon Descending colon Sigmoid colon Rectum Superior anal canal
When does midgut loop herniate through umbilical ring?
Six weeks
Esophageal duplication cysts
Can lead to esophageal obstruction
Can present with respiratory or digestive issues
Neonatal intussusception
Very rare, often confused with NEC
Present with abdominal distention, feeding intolerance, vomiting, bloody stools
Diagnosis with Ultrasound
Congenital sucrase-isomaltase deficiency
Chromosome 3
Appears at 3-6 months - introduced to foods containing sucrose
Severe watery diarrhea, acidosis, abdominal extension, cramping, FTT
Stool pH <7
Reducing substances negative
Congenital lactase deficiency
Very rare
Autosomal recessive, most in Finland
Seen when starting to feed
Severe watery diarrhea, vomiting, FTT, lactosuria, aminoaciduria, lethargy
Endoscopy with biopsy for disaccharidase activity
Maltase-glucoamylase deficiency
Very rare
Presents with diarrhea and distention after starch introduced to diet
Glucose-galactose malabsorption
Very rare, autosomal recessive Chromosome 22
Defect in SGLT protein
Severe watery diarrhea when infant is fed breastmilk or glucose containing formula
Stools positive for reducing substances
Hypobetalipoproteinemia and abetalipoproteinemia
Autosomal dominant
Low or absent apolipoprotein B and LDL cholesterol
Fat malabsorption, acanthocytosis, retinitis pigmentosa, neuromuscular degeneration
Congenital chloride diarrhea genetics
Autosomal recessive
Defect in brush border Cl/HCO3 exchange
Electrolyte abnormalities in congenital chloride diarrhea
Hyponatremia
hypokalemia
hypochloremia
metabolic alkalosis
Congenital sodium diarrhea genetics
Autosomal recessive
Defect in Na/H exchanger in jejunal brush border
Electrolyte abnormalities in congenital sodium diarrhea
Hyponatremia
Hypokalemia
Metabolic acidosis
Neonatal hemachromatosis diagnosis
Biopsy parotid gland
Gastric pH in neonates is higher or lower than adults?
Higher
More alkalotic

Symptoms of congenital chloride diarrhea
Severe watery diarrhea high in chloride immediately after birth
Persist when NPO
Symptoms of congenital sodium diarrhea
High sodium content in severe watery diarrhea immediately after birth
Neonatal hemachromatosis
Alloimmune process
Can lead to IUFD
Liver failure at birth
Treatment of neonatal hemachromatosis
IVIG
Exchange transfusion
Liver transplant
Recurrence risk of neonatal hemachromatosis
Up to 90%
Symptoms of neonatal hemachromatosis/GALD
Refractory hypoglycemia Severe coagulopathy Hypoalbuminemia Elevated ferritin >1000 LFTs near normal Extrahepatic iron deposition Elevated AFP >80,000 Elevated transferrin saturation
What is another, newer term for neonatal hemachromatosis?
Gestational alloimmune liver disease (GALD)
This is to distinguish it from juvenile hemachromatosis which is a genetic disease
Secretory IgA plays a role in ___
Immunity
Uptake of proteins in GI system
How many carbons do short chain fatty acids have?
<6
How many carbons do medium chain fatty acids have?
6-12
What are Fatty acids with double bonds known as?
Unsaturated
What are fatty acids without double bonds known as?
Saturated
How many carbons do long chain fatty acids have?
13-21
How many carbons do very long chain fatty acids have?
> 22
