Pathogenesis and classification: ileal atresia results from late intrauterine mesenteric vascular accident (volvulus, intussusception, internal hernia, gastroschisis-related compression) causing segmental ischemic necrosis. Grosfeld-Martin classification - Type I: mucosal/membranous web with intact bowel wall; Type II: fibrous cord between blind ends; Type IIIa: V-shaped mesenteric defect with proximal blind end; Type IIIb: apple-peel/Christmas tree (distal bowel coiled around marginal artery from ileocolic; associated with malrotation and short bowel); Type IV: multiple atresias (string of beads). Associated anomalies in 10-30% - Down syndrome, cystic fibrosis (meconium ileus), gastroschisis, malrotation, biliary atresia.
Clinical presentation and workup: prenatal ultrasound - polyhydramnios, dilated bowel loops, hyperechogenic bowel (may suggest CF). Postnatal - bilious vomiting (within 24 hours), abdominal distention (lower atresia more pronounced), failure to pass meconium, dehydration, electrolyte imbalance. Diagnostic workup - abdominal X-ray (dilated loops with air-fluid levels, distal bowel paucity), upper GI series with water-soluble contrast (rules out malrotation), contrast enema (microcolon distally; rules out Hirschsprung, distal small bowel obstruction), sweat chloride/IRT (CF screen if meconium ileus suspected), echocardiography (cardiac anomalies). Preoperative resuscitation - IV fluids, NG decompression, antibiotics, correction of electrolyte abnormalities.
Surgical technique and outcomes: timing - within 24-48 hours of stable resuscitation. Open or laparoscopy-assisted approach. Standard procedure - 1) midline or transverse supraumbilical incision; 2) eviscerate bowel and identify atresia; 3) check for additional atresias (multiple atresias up to 20%); 4) check for malrotation, midgut volvulus; 5) resection of dilated proximal segment (5-10 cm of dilated bowel) and a few cm of distal microcolon; 6) end-to-back/end-to-side anastomosis (proximal to distal) with single-layer interrupted sutures; 7) tapering enteroplasty (Kimura or longitudinal imbrication) if extreme proximal dilation prevents primary anastomosis; 8) Bishop-Koop or Mikulicz enterostomy in unstable patients with sepsis/peritonitis. Postoperative care - TPN until oral feeds tolerated (5-14 days), gradual enteral feeds with breast milk or hypoallergenic formula. Complications - anastomotic leak (3-5%), stricture (5-10%), short bowel syndrome (10-20%, especially type IIIb), motility disorder. Survival >90%; mortality from associated anomalies, sepsis, or short bowel.