Anemia of Prematurity - Portal Neonatal

condition characterized by abnormalities in cellular membrane physiology and chloride ion transport
that contribute to progressive respiratory failure, derangements in cellular secretory patterns, and
diminished mucosal motility.
Incidence of cystic fibrosis is 1 case per 3000 live births. Of newborns with cystic fibrosis, 10-20%
present with meconium ileus. The gene for cystic fibrosis is carried by 3.3% of whites. Identified in
1985, the cystic fibrosis gene localized to the DF508 locus on chromosome 7 codes for a protein that
acts as a cystic fibrosis transmembrane conductance regulator (CFTCR). Abnormalities in the CFTCR
disrupt membrane function. In the GI mucosa of the newborn, this defect manifests as poor motility.
Meconium may build up and obstruct the lumen of the distal small bowel and colon.
Because meconium does not pass readily into the distal GI tract, distal small-bowel obstruction may
develop in utero. The involved segment of bowel may dilate and even perforate. A pseudocyst may
wall off around the perforation. Prenatal ultrasonography or neonatal plain radiography may identify a
soap bubble or ground glass appearance of inspissated meconium. Adhesions may develop from the
perforation. The functional picture of tenacious thick meconium that does not pass is termed
meconium ileus. Segmental obstruction of the small bowel from meconium ileus can also precipitate
volvulus of the bowel upstream from the obstruction.
Treatment of meconium ileus involves evacuation of the meconium. In more than 50% of patients,
nonsurgical management relieves the obstruction successfully. A contrast enema may be both
diagnostic and therapeutic. For the enema to evacuate the meconium, fluid must be refluxed into the
terminal ileum. Multiple enemas may be administered. Dilute Gastrografin with N-acetylcysteine may
be administered by nasogastric tube from above to help loosen the meconium. Hyperosmolar
solutions (1% acylcysteine) may be effective in drawing more fluid into the lumen of the bowel, thereby
enhancing the ability to loosen the thick meconium. Hyperosmolar enemas may increase the risk of
perforation. The risk of perforation reportedly is 3-10%.
Calcification on scout radiography suggests intrauterine perforation. Do not administer therapeutic
contrast enemas in the presence of bowel perforation or compromise. A pseudocyst may develop
around a bowel perforation during development. In these patients or in those who underwent
unsuccessful initial management with enemas, postnatal laparotomy is indicated. An enterotomy with
irrigation of the bowel contents may move the meconium through successfully. In some patients, an
ostomy for diversion and access for proximal irrigation may be necessary. Long-term outcome
depends upon management of the underlying cystic fibrosis.
Meconium plug syndrome
Some newborns present with bowel obstruction from plugs of meconium isolated to the colon. Most of
these newborns are otherwise healthy babies, but all should undergo a contrast enema, which almost
always is diagnostic (no pathology) as well as therapeutic (successful in loosening the meconium plug
and resolving the obstruction). A plug of meconium isolated to the colon is usually unrelated to cystic
fibrosis. Conditions that predispose to dysmotility of the neonatal bowel, such as maternal
preeclampsia, maternal diabetes mellitus, maternal administration of magnesium sulfate, prematurity,
sepsis, and hypothyroidism, may be responsible for the formation of the meconium plug.
In each of these conditions, the colon distal to the obstruction is narrowed and small in caliber.
Because of the frequent association between maternal diabetes mellitus and colonic obstruction with a
small left colon, this association is termed small left colon syndrome.
As with meconium ileus, a nonoperative approach with administration of enemas is favored to relieve
the obstruction. The enemas can also serve to dilate the small-caliber distal colon. A need for
laparotomy to evacuate the meconium suggests a diagnosis other than simple meconium plug
syndrome. Hirschsprung disease can be associated with meconium plug syndrome in 4% of patients;
therefore, a suction rectal biopsy may be indicated.