B. Week 4. Intestine is present; esophagus and trachea separate and are distinct; stomach becomes obvious; liver is present.

C. Week 5. Esophagus, stomach, proximal duodenum present; intestine elongates into a loop and begins to rotate.

D. Week 6. Stomach rotates into adult position; distal duodenum, jejunum, ileum, cecum, ascending colon, and proximal two thirds of transverse colon present; rapidly developing midgut herniates into umbilical cord.

E. Week 7. Rapid endothelial proliferation results in temporary duodenal occlusion; intestinal loops herniate into umbilical cord, lengthen, and rotate; and urorectal septum fuses with cloacal membrane, separating rectum from the developing urinary bladder.

F. Week 8. Small intestine recanalizes; intestinal villi develop; diaphragm complete.

G. Weeks 9 and 10. Intestines begin to reenter abdominal cavity and continue counterclockwise rotation around the axis of the superior mesenteric artery.

H. Week 12. Muscular layers of intestine are present; active transport of amino acids begins; pancreatic islet cells appear; bile appears; lactase appears.

I. Week 16. Meconium is present; swallowing is observed.

J. Week 24. Ganglion cells are detected in the rectum.

K. Week 26. Random peristalsis begins.

L. Weeks 34 to 36. Sucking and swallowing become coordinated.

M. Weeks 36 to 38. Maturity of GI system completed.

N. Weeks 5 to 40. Intestine elongates approximately 100-fold (small intestine is 6 times the length of the colon).

B. Elimination of waste products.

C. Maintenance of fluid and electrolyte balance.

D. Protection of host from toxins and pathogens.

b. Beckwith–Wiedemann syndrome: umbilical defects, diastasis recti, posterior diaphragmatic eventration, pancreatic hyperplasia resulting in hypoglycemia.

c. Fetal hydantoin syndrome: umbilical hernia, duodenal atresia.

d. Meckel–Gruber syndrome: liver defects (bile duct proliferation, fibrosis, cysts), single umbilical artery, patent urachus, omphalocele, intestinal malrotation, imperforate anus.

e. Sirenomelia: imperforate anus, anal agenesis.

f. Trisomy 13: umbilical defects, intestinal malrotation, CDH.

g. Trisomy 18: umbilical defects, pyloric stenosis, intestinal malrotation, TEF/EA, CDH, single umbilical artery.

h. Trisomy 21: Hirschsprung’s disease, pyloric stenosis, duodenal atresia, intestinal malrotation.

i. VATERR association (vertebral defects, imperforate anus, tracheoesophageal fistula and/or esophageal atresia, and radial and renal dysplasia). Additional: single umbilical artery.

j. VACTERL association (vertebral defects, anal atresia, cardiac abnormalities, tracheoesophageal fistula and/or esophageal atresia, renal agenesis or dysplasia, and limb defects).

3. History of present illness.

(2) Abdomen can be assessed for intactness of abdominal wall, umbilical cord insertion, stomach as fluid-filled chamber, bowel dilation, or indication of obstruction.

(3) Polyhydramnios (> 2000 mL) may indicate interference with fetal swallowing or intestinal obstruction.

(4) Oligohydramnios (< 500 mL) may indicate renal agenesis or dysgenesis.

(2) Abnormal: erythematous, dusky, mottled.

(3) Distended: intestinal obstruction, infection, organomegaly, ascites.

(4) Scaphoid: associated with CDH.

(5) Asymmetrical: mass, organomegaly, intestinal obstruction.

b. Muscular development.

(2) Gap between rectus muscles: diastasis recti.

(3) Externalization of abdominal contents: omphalocele, gastroschisis, bladder exstrophy.

(4) Hernias: protrusions of an organ or tissue through an abnormal opening. Common in three areas:

(b) Inguinal.

(ii) Frequently bilateral.

(iii) May not be evident until second or third month of life.

(iv) Usually readily reducible.

(c) Femoral.

(ii) Located just below inguinal ligament on anterior aspect of thigh.

c. Umbilicus/umbilical cord.

(2) Normally three vessels: two ventrally situated arteries, one dorsally situated vein.

(3) Usually dries and spontaneously detaches in 10 to 14 days.

(4) Green or yellow staining suggests in-utero meconium passage.

(5) Wet, foul-smelling cord, or periumbilical redness: omphalitis.

(6) Persistent clear drainage: patent urachus.

(7) Ileal fluid drainage: omphalomesenteric duct.

(8) Serous or serosanguineous drainage: granuloma.

(9) Abnormally thick: single herniated loop of intestine.

(10) Thick, gelatinous: large for gestational age.

(11) Thin, small: intrauterine growth restriction.

d. Bowel loops.

(2) Presence: obstruction.

e. Movements.

(2) Movements not in synchrony may represent respiratory distress, peritoneal irritation, or central nervous system (CNS) disease.

(3) Peristalsis: not normally seen.

(b) Presence: associated with hypertrophic pyloric stenosis.

f. Veins.

(2) Dilated veins: venous obstruction.

g. Perineum: inspected for patency of anus and presence of fistulas.

2. Auscultation.

b. Bowel sounds.

(b) Hirschsprung’s disease.

(c) Diarrhea.

(5) Decreased or absent sounds.

(b) Starvation.

(c) Medication administration: opiates, magnesium, anesthesia.

c. Vascular sounds: bruit, similar to murmur. Caused by turbulent blood flow through an artery, especially if heard despite position change of infant. Bruits may indicate partial vascular obstruction.

d. Friction rub: peritoneal inflammation, splenic involvement, hepatic tumor, abscess.

3. Percussion.

b. Two main sounds to listen for:

(2) Dullness: high-pitched, short, heard over dense or solid organs (liver, spleen).

4. Palpation.

(2) Organ position.

(b) Spleen rarely palpable. Tip should not be more than 1 cm below left costal margin.

(c) Kidneys are about 4 to 5 cm in length. Right kidney is easier to palpate and is lower than left.

(3) Organomegaly.

(4) Masses.

(5) Pulsations.

(6) Fluid.

b. Technique: start in lower quadrants and progress to upper quadrants using a bimanual approach. Place one hand under infant’s back; using free hand, start with light palpation, then progress to deep palpation.

c. Hints to relax infant.

(2) Flex legs.

(3) Use gentle circular motion.

(4) Slowly increase depth of palpation.

(5) Palpate any known areas of tenderness last.

C. Diagnostic tests.

b. Apt test.

(2) Can be done on gastric fluid or stool.

2. Stool examination.

b. Examined for color, consistency, odor, blood, mucus, pus, tissue fragments, bacteria, and parasites.

c. Color may be influenced by diet, dyes, drugs, pathology.

(2) Greenish black: iron, meconium.

(3) Black: iron, swallowed blood, blood from high GI tract lesion.

(4) Pale: biliary atresia.

(5) White: antacids, barium.

(6) Red: bright red indicates blood from low GI tract lesion or anal fissure; currant jelly indicates intussusception.

d. Odor.

(2) Purulent odor suggests colitis.

e. CHO malabsorption.

3. pH probe test: 24-hour pH probe study to diagnose GI reflux. Detects acid reflux only; does not detect nonacid (milk) or gas reflux.

4. Radiologic studies.

(b) Within 30 minutes, gas should be in stomach.

(c) By 3 to 4 hours, gas should be in small intestine.

(d) After 6 to 8 hours, gas should be in entire intestine.

(2) Absence of gas below pylorus: possible indication of obstruction.

b. Upper GI series: done to assess structure and function of esophagus and evaluate for pyloric stenosis, malrotation, and strictures.

(2) Water-soluble products are preferred in cases of suspected perforation.

c. Lower GI series: may be used to detect presence of malrotation, Hirschsprung’s disease, meconium ileus, and meconium plug syndrome. May be therapeutic in meconium ileus and meconium plug syndrome.

5. Ultrasonography: may be used to diagnose suspected cases of pyloric stenosis, duplications, gastroesophageal reflux (GER), or biliary atresia.

6. Scintigraphy (nuclear scan): used to evaluate gastric emptying, aspiration with swallowing, reflux with aspiration, and liver excretory function. Radionuclide-tagged formula is fed to the infant and recorded by a gamma camera.

7. Endoscopy: used to directly visualize the upper or lower GI mucosa. Endoscopic retrograde cholangiopancreatography (ERCP) visualizes the biliary pancreatic ducts.

8. Fecal fat: used to diagnosis malabsorption syndromes. Fecal fat content greater than 6 g/24 hours is associated with malabsorption syndrome.

9. Culture: helpful in differentiating bloody diarrhea caused by infection versus hypoxic insult to intestine.

b. Decreased levels occur in hepatocellular injury; usually a late finding.

2. Alkaline phosphatase (ALP).

b. Elevated levels occur in obstructive liver disease (e.g., biliary atresia) and hepatitis, as well as in bone disease.

3. Aminotransferase activity.

b. Aspartate aminotransferase (AST) catabolizes the reversible transfer of the α-amino group of aspartic acid to the α-keto group of α-ketoglutaric acid, leading to the formation of oxaloacetic acid.

c. ALT and AST are the most sensitive tests of hepatocyte necrosis. ALT is more specific than AST because it is not found in high concentrations in other tissues.

d. High elevations occur in hepatocellular injury. Slight elevations occur in cholestasis. Serum ALT greater than 300 units coupled with jaundice signals a liver disorder and not a hemolytic disorder.

e. ALT-to-AST ratio is often performed to help differentiate types of liver disease.

4. Ammonia.

b. Elevated in liver failure.

c. Elevations occur in acute or chronic liver disease.

5. Bilirubin.

b. Increased indirect bilirubin occurs when liver function is reduced (prematurity, injury) or when there is an excessive load of unconjugated bilirubin (hemolysis).

c. Increased direct bilirubin occurs when the liver cannot excrete conjugated bilirubin into the bile ducts or biliary tract (biliary atresia, cholestasis).

6. Prothrombin time (PT).

b. In cases of obstructive liver disease in which bile acids do not reach the intestine, fat-soluble vitamins are not absorbed (required for coagulation factors).

c. Prolonged PT occurs in patients with hepatocellular injury and biliary obstruction.

7. International Normalized Ratio (INR): ratio of a patient sample PT to a normal PT.

8. Serum bile acids.

b. Elevations occur in acute and chronic liver disease.

b. Cardiac defects (50%).

c. Intestinal malrotation and/or atresia.

d. Pentalogy of Cantrell: upper abdominal omphalocele above the umbilical cord, diaphragmatic hernia, sternal cleft, pericardial defect, ectopia cardiac defect.

e. Neurologic anomalies, neural tube (40%).

f. Genitourinary anomalies.

g. Skeletal anomalies.

h. Chromosomal anomalies (50% to 65%). Common anomalies include trisomy 13, 18, and 21, with 18 being the most frequent. Frequent in infants with Beckwith–Wiedemann syndrome (chromosome 11).

5. Diagnosis.

b. High-resolution prenatal ultrasound.

c. Amniocentesis: chromosome analysis for associated defects; amniotic fluid α-fetoprotein and acetylcholinesterase levels to evaluate for defects associated with abnormal values.

d. Inspection at birth.

(2) Large defect: may contain intestines, stomach, liver, spleen, bladder, uterus and ovaries, testicles; deficient upper musculature of umbilical ring.

(3) The thin, avascular membranous sac may rupture before or at time of delivery; must be differentiated from gastroschisis because of the high rate of associated anomalies with omphalocele.

6. Prognosis.