Intestinal atresia and intestinal stenosis are congenital malformations of intestinal development and are among the common causes of intestinal obstruction in the neonatal period. The most frequent sites are the jejunum and ileum, followed by the duodenum, with the colon and rectum being the least commonly affected.
Etiology and Pathology
These conditions generally result from developmental abnormalities during the recanalization phase of the embryonic intestinal tract.
Intestinal atresia is typically classified into the following three types:
- Presence of a membranous structure within the intestinal lumen, completely obstructing the lumen.
- Discontinuity of the intestinal tract, where the two segments are connected by a thin fibrous band.
- Complete interruption of the intestinal tract with the ends forming blind pouches, accompanied by a V-shaped mesenteric defect.
Single-site atresia is more common, though multiple sites of atresia may occur, sometimes resembling a string of sausages.
As for intestinal stenosis, the membranous type is the most commonly observed. Milder cases involve only a narrow ring of stenosis, while short-segment stenosis is less frequently encountered.
Clinical Manifestations
Regardless of the location, intestinal atresia leads to complete intestinal obstruction, with the major symptoms being:
Vomiting
In cases of high-intestinal atresia, newborns experience vomiting immediately after their first feeding, with symptoms gradually worsening and becoming more frequent. Vomitus contains fed water, milk, and bile, leading to rapid dehydration, electrolyte imbalances, and acidosis. In ileal and colonic atresia, vomiting typically begins 2 to 3 days after birth, with the presence of bile and fecal material, but occurs less frequently compared to high-atresia cases.
Abdominal Distension
In cases of high-atresia, the upper abdomen distends, and a visible gastric outline may appear; severe vomiting can reduce the distension. In lower-intestinal atresia, generalized abdominal distension occurs, often accompanied by hyperactive bowel sounds and visible intestinal loops. Late-stage complications may include perforation and subsequent peritonitis.
Bowel Movements
Newborns with atresia do not pass meconium or may pass only small amounts of gray-green mucus-like material.
For intestinal stenosis, the timing of vomiting and degree of abdominal distension depend on the location and severity of the narrowing. Symptoms may include chronic, incomplete intestinal obstruction. Severe stenosis can present similarly to intestinal atresia.
Diagnosis
In addition to clinical manifestations, radiographic imaging provides diagnostic evidence. In high-intestinal atresia, abdominal X-rays typically reveal a "double bubble" or "triple bubble" sign. Iodine-based contrast studies of the upper gastrointestinal tract can help localize the site of atresia. Lower-intestinal atresia is associated with multiple dilated bowel loops and fluid-air levels on X-ray, while barium enema X-rays may reveal a narrow colon. Prenatal ultrasonography may detect multiple hypoechoic areas in the fetal abdomen, aiding in early diagnosis. Intestinal stenosis can be diagnosed with barium-meal contrast studies to confirm the location of the narrowing.
Treatment
Once intestinal atresia is confirmed, surgical intervention is required after correcting water, electrolyte, and acid-base imbalances.
For duodenal atresia, duodeno-duodenostomy or duodeno-jejunostomy may be performed. In jejunal and ileal atresia, resection of the blind ends followed by end-to-end anastomosis is typically required. During surgery, resection is recommended for the dilated, hypertrophic proximal segment with poor blood supply.
For colonic atresia, surgical resection of the dilated proximal bowel may be followed by one-stage ileocolonic or colocolonic anastomosis. In cases where the patient's condition is poor, a temporary colostomy may be performed before a second-stage procedure to close the stoma and complete intestinal anastomosis.
For intestinal stenosis, resection of the narrowed segment followed by end-to-end anastomosis generally produces favorable outcomes.