8.1 Congenital and Acquired GI Abnormalities

8.1 Congenital and Acquired GI Abnormalities

Quick Answer: Treat green or bilious emesis as malrotation with midgut volvulus until imaging and surgery say otherwise. For abdominal wall defects, decide first whether a covering sac is present (omphalocele) or bowel is free in the air (gastroschisis), then protect viscera, temperature, and circulating volume while you search for associated anomalies.

Congenital and acquired gastrointestinal abnormalities are a high-stakes slice of the endocrine–hematology–GI–renal–integumentary domain on AACN Certification Corporation's current Neonatal CCRN Test Plan. Independent OpenExamPrep teaching for this leaf focuses on pattern recognition the bedside nurse can act on in minutes: what the abdomen looks like at delivery, whether emesis is bilious, whether meconium has passed, and whether the infant is still perfusing bowel. Many of these infants are transferred from a birth hospital to a surgical NICU; your first hour of covering, decompressing, warming, and documenting associated findings often determines whether bowel is salvageable.

/practice/ccrn-neonatalPractice questions with detailed explanations

Abdominal wall defects: start with the sac

Omphalocele is a midline herniation of abdominal viscera through the umbilical ring. The viscera are covered by a membrane of peritoneum and amnion; the umbilical cord inserts into the sac. Contents may include bowel only (small omphalocele) or liver and bowel (giant omphalocele). Because the defect is an embryologic failure of the lateral folds to close, associated anomalies are common: congenital heart disease, chromosomal differences (especially trisomy 13, 18, and 21), Beckwith–Wiedemann spectrum (macrosomia, macroglossia, visceromegaly, neonatal hypoglycemia), and pulmonary hypoplasia when the abdomen never contained the viscera in fetal life. Do not clamp the cord flush with a sac; leave a generous cord length so the membrane is not torn.

Gastroschisis is typically a full-thickness defect to the right of an intact umbilicus. There is no covering sac. Bowel has been exposed to amniotic fluid and is often edematous, matted, and exudative. Extra-intestinal anomalies are less common than with omphalocele, but intestinal atresia, stenosis, and necrosis occur because of vascular compromise at the defect or volvulus of the eviscerated loops. Fluid and heat losses are larger than with an intact omphalocele sac because serosa is open to the room.

Bedside priorities shared by both defects

Place the infant in a radiant warmer or a controlled thermal environment immediately. Exposed viscera are a massive evaporative surface: expected findings include hypothermia, tachycardia, and rising lactate if under-resuscitated. Cover bowel or an intact sac with a sterile bowel bag or warm saline-moistened nonadherent gauze plus plastic wrap; never use dry gauze that adheres and desiccates serosa. Position the infant side-lying or supine with viscera supported at the level of the abdomen so the mesentery is not stretched over the flank. Insert a large-bore orogastric tube to continuous low suction. Start intravenous isotonic crystalloid; gastroschisis infants often need substantially more than maintenance because of third-spacing into edematous bowel. Monitor glucose closely in omphalocele (Beckwith–Wiedemann) and in any cold, stressed neonate. Obtain blood culture and start antibiotics when bowel is exposed or the sac is ruptured, following unit surgical protocol. Vascular access, blood type, and a chest radiograph looking for heart size and pulmonary volume should proceed in parallel with surgical notification.

Silo reduction is used when bowel will not reduce without tension. A preformed silo is placed over eviscerated intestine and suspended; gravity and serial tightening return bowel over hours to days. Nursing watch-outs: dusky or black loops, increasing abdominal firmness, oliguria, lower-extremity mottling, and rising ventilator pressures—signs of abdominal compartment syndrome or mesenteric ischemia. Do not celebrate a tight-looking abdomen. If reduction is forced, vena cava return falls, urine output drops, and remaining bowel infarcts. Giant omphalocele may be managed with topical agents that promote epithelialization and delayed reconstructive closure when pulmonary reserve allows; that is a weeks-to-months strategy, not a delivery-room race.

Bilious emesis: malrotation and midgut volvulus

Malrotation is a failure of the midgut to complete its 270-degree counterclockwise rotation, leaving a narrow mesenteric pedicle and peritoneal Ladd bands that can obstruct the duodenum. Midgut volvulus is twisting of that narrow pedicle with acute ischemia of the entire midgut from duodenum to mid-transverse colon. The classic presentation is a previously feeding neonate who suddenly produces bilious (green) emesis. The abdomen may still be soft in early volvulus; waiting for a rigid, silent abdomen means bowel is already dying.

Nursing actions are simultaneous, not sequential: NPO, gastric decompression, intravenous access, volume to restore pulses and capillary refill, broad-spectrum antibiotics if perforation or necrosis is suspected, and immediate pediatric surgical presence. Upper gastrointestinal contrast series is the usual diagnostic study for malrotation (abnormal duodenal-jejunal junction, corkscrew of volvulus). Do not delay surgery in a deteriorating infant to complete a perfect imaging package. The Ladd procedure divides bands, widens the mesentery, and appendectomizes; necrotic bowel is resected, and a second-look operation may be planned. Families need an honest description that surviving volvulus can still leave short-bowel syndrome, which is taught with nutritional conditions in section 8.3.

Other causes of bilious emesis (atresia, Hirschsprung, meconium ileus, NEC) remain on the differential, but they do not demote volvulus. The exam trap is reassuring a parent that green spit-up is swallowed meconium or that a benign abdominal exam rules out ischemia.

Intestinal atresias and the double-bubble

Duodenal atresia presents with polyhydramnios, early vomiting that may be bilious or nonbilious depending on whether the atresia is distal or proximal to the ampulla, and the radiographic double-bubble: air in the stomach and in a dilated proximal duodenum with little distal gas. Association with trisomy 21 is high enough that you assess for the other findings of Down syndrome and involve genetics as the surgical plan proceeds; full trisomy teaching lives in chapter 15. Annular pancreas and malrotation can coexist. Preoperative care is decompression, fluids, and evaluation for cardiac disease before anesthesia.

Jejunoileal atresias more often reflect an intrauterine vascular accident. Radiographs show several dilated loops rather than a clean double-bubble, and a contrast enema may show microcolon from unused distal bowel. Multiple atresias and apple-peel deformity increase the chance of short gut after reconstruction. Colonic atresia is less common. Any atresia infant stays NPO with gastric suction until an operating plan exists.

Imperforate anus and Hirschsprung disease

Imperforate anus ranges from a thin anal membrane to a high anomaly with a fistula to the urinary tract or vagina. Inspect the perineum in the delivery room; do not assume a normal anus because stool later appears in the diaper (that stool may be fistula drainage). These infants belong on a VACTERL search: vertebral, anorectal, cardiac, tracheoesophageal, renal, and limb findings. Tracheoesophageal fistula and esophageal atresia are covered in the respiratory anomaly chapter; here, your job is NPO, gastric decompression, no rectal temperatures, and a surgical plan that may include a diverting colostomy for high lesions. Cross-check the renal and spinal workup so associated defects are not missed during the GI rush.

Hirschsprung disease is failed craniocaudal migration of neural crest cells, leaving an aganglionic distal bowel that cannot relax. Term infants may fail to pass meconium in the first 24–48 hours, develop abdominal distention and bilious vomiting, and show explosive stool after digital rectal exam. Contrast enema can show a transition zone; suction rectal biopsy showing absent ganglia (and often hypertrophic nerve trunks) is the tissue diagnosis. The feared complication is Hirschsprung-associated enterocolitis: fever, explosive diarrhea or stasis with sepsis physiology. Treat as a GI emergency with decompression, irrigations per surgical protocol, antibiotics, and fluid resuscitation. Pull-through surgery is definitive; enterocolitis can still recur and is an exam-favorite reason a postoperative infant crashes.

Intussusception and pyloric stenosis

Intussusception (telescoping of bowel, usually ileocolic) is more common in older infants (classically 3–24 months) than in the first days of life, but it is listed among acquired GI abnormalities and does occur in neonates, often with a pathologic lead point such as Meckel diverticulum or polyp. Intermittent pain, drawing up the legs, currant-jelly stool, and a sausage-shaped mass are textbook; lethargy may dominate in young infants. Ultrasound shows a target or doughnut sign. Stable children without peritonitis may undergo air or hydrostatic enema reduction; peritonitis, perforation, or failed reduction go to the operating room. In a neonate, do not assume idiopathic viral lead-point disease; think structural lead point and surgical consultation early.

Hypertrophic pyloric stenosis is acquired hypertrophy of the pyloric muscle. It is not a first-day-of-life diagnosis. Typical age is 3–6 weeks (occasionally later in preterm infants by postmenstrual age). Emesis is nonbilious and becomes projectile. The infant remains hungry. An olive mass may be palpable after a feed, but ultrasound is the usual confirmation (pyloric muscle thickness often ≥3 mm with an elongated channel, commonly cited around 14–16 mm in term infants). The metabolic signature of prolonged vomiting is hypochloremic, hypokalemic metabolic alkalosis with dehydration. Correct volume, chloride, and potassium before pyloromyotomy; anesthesia in an uncorrected alkalotic infant risks apnea and arrhythmia. This is a medical-then-surgical sequence, unlike volvulus. Double-bubble does not diagnose pyloric stenosis; that pattern is duodenal obstruction.

Worked scenario and exam traps

A 2.1 kg infant is born with uncovered bowel to the right of the umbilicus. The cord is intact. You place a bowel bag, orogastric suction, and a hat, start isotonic boluses, and call surgery for expected silo placement. You do not launch a full chromosomal emergency panel as the first action (that priority belongs more to omphalocele), and you do not force bowel into a tight abdomen in the delivery room.

A 4-day-old who was feeding well now has green emesis and a still-soft abdomen. The wrong move is a trial of oral electrolyte solution. The right move is NPO, gastric tube, intravenous volume, and surgical evaluation for volvulus.

Traps: mixing up sac versus no-sac; treating pyloric stenosis as a newborn bilious emergency; delaying volvulus care because the abdomen is not yet rigid; forgetting hypoglycemia screening in omphalocele; clamping the cord on an omphalocele sac; using dry gauze on gastroschisis; and assuming intussusception cannot appear on a neonatal exam because it is statistically more common later.