Meconium ileus, other name, Neonatal intestinal obstruction
Neonatal bowel obstruction (NBO) or neonatal intestinal obstruction is the most common surgical emergency in the neonatal period.
Meconium ileus is a neonatal intestinal obstruction caused by the inspissation of thick, sticky meconium in the ileum.
It is often the earliest clinical manifestation of cystic fibrosis (CF), occurring in approximately 15-20% of neonates with CF.
The pathophysiology involves mutations in the CF transmembrane conductance regulator (CFTR) gene, leading to abnormally thick secretions that obstruct the bowel.
Clinically, meconium ileus presents with abdominal distension, bilious vomiting, and failure to pass meconium within the first 24-48 hours of life.
Diagnosis is typically made through prenatal ultrasound showing hyperechoic bowel or postnatal imaging such as abdominal radiographs, which may reveal dilated bowel loops.
Management of meconium ileus can be nonoperative or operative.
Nonoperative management includes the use of hyperosmolar contrast enemas, such as Gastrografin, which can relieve the obstruction in some cases.
If nonoperative measures fail or if there are complications like volvulus, atresia, or perforation, surgical intervention is required.
Surgical options include enterostomy, resection with primary anastomosis, or other procedures tailored to the specific complications present.
Long-term prognosis for neonates with meconium ileus has improved significantly with advances in neonatal care.
The neonatal bowel obstruction is suspected based on polyhydramnios in utero, bilious vomiting, failure to pass meconium in the first day of life, and abdominal distension.
The presentations of meconium ileus varies from subtle and easily overlooked, to involve massive abdominal distension, respiratory distress and cardiovascular collapse.
Neonatal bowel obstruction is grouped into two general categories: high, or proximal, obstruction and low, or distal obstruction.
Neonatal bowel obstruction is suspected by failure to pass meconium at birth.
High obstruction can be suspected based on the double bubble sign.
Cases without distal gas are usually related to duodenal atresia, while high obstruction with distal gas need an upper gastrointestinal series because of the need to distinguish duodenal web, duodenal stenosis and annular pancreas from midgut volvulus, the latter being a surgical emergency.
Confirmation is ultimately by surgical intervention.
The differential for low obstruction is ileal atresia, meconium ileus, meconium plug syndrome and Hirschsprung disease.
In cases of meconium ileus or ileal atresia, the colon distal to the obstruction is hypoplastic, usually less than 1 cm in caliber, as development of normal colonic caliber in utero is due to the passage of meconium, which does not occur in either of these conditions.
When diffusely small caliber is seen, it is referred to as microcolon.
X-rays in meconium ileus demonstrate a bubbly appearance in the right lower quadrant due to a combination of ingested air and meconium.
If, on contrast enema, reflux into the dilated distal small bowel loops can be achieved, the study is both diagnostic and therapeutic, as the ionic contrast medium can dissolve the meconium to allow passage of enteric content into the unused colon.
If contrast cannot be refluxed into the distal small bowel, ileal atresia remains a diagnostic possibility.
Treatment;
Jejunal and ileal atresia are caused by in utero vascular insults, leading to poor recanalization of distal small bowel segments, a condition in which surgical resection and reanastamosis are mandatory.
Hirschsprung disease is due to an arrest in neural cell ganglia, leading to absent innervation of a segment distal bowel, and appears as a massively dilated segment of distal bowel on contrast enema: Surgical resection is necessary for this condition.
Imperforate anus also requires surgical management, with the diagnosis made by inability to pass the rectal tube through the anal sphincter.
With early intervention, morbidity and mortality of cases of intestinal obstruction is low.