8.2 Necrotizing Enterocolitis

8.2 Necrotizing Enterocolitis

Quick Answer: If a preterm infant develops feeding intolerance, a looping distended abdomen, and pneumatosis, stop feeds, decompress the stomach, culture, start antibiotics, and serially examine for perforation. Free air is a surgical emergency. A peritoneal drain may temporize an unstable micro-preterm infant, but it is not a promise that laparotomy will be avoided.

Necrotizing enterocolitis (NEC) is inflammatory necrosis of the neonatal intestine, most often the terminal ileum and proximal colon. It is the gastrointestinal emergency that most clearly links the test plan's nutritional and congenital/acquired GI leaves. Incidence rises as gestational age and birth weight fall; term NEC exists but usually rides on a different risk profile (congenital heart disease, perinatal asphyxia, gastroschisis, or formula exposure in a structurally abnormal gut). For the CCRN Neonatal exam, think preterm first.

Why the preterm gut necrotizes

Three overlapping injuries set the stage. First, the epithelial barrier, mucus layer, and secretory IgA are immature; tight junctions leak, and peristalsis is poorly coordinated. Second, the microbiome is easily pushed into dysbiosis by cesarean birth, empirical antibiotics, H2 blockers, and formula, with overgrowth of gas-forming gram-negative organisms. Third, ischemic or hypoperfusion hits—PDA steal, anemia, polycythemia, shock, intrauterine growth restriction, or a cold, under-resuscitated transition—damage mucosa so that bacteria and their products translocate. Human milk supplies oligosaccharides, antibodies, and growth factors that feed a less pathogenic flora; formula does not. Rapid volume advancement, hyperosmolar additives, and some thickeners have been implicated as additional hits. None of these factors is required in every case, which is why NEC still occurs in infants who were fed cautiously with milk. The exam still expects you to name prematurity, enteral feeding (especially formula), and dysbiosis as the dominant cluster.

Spontaneous intestinal perforation (SIP) is a related but distinct entity: an isolated hole, often in the terminal ileum of an extremely preterm infant in the first 1–2 weeks, sometimes associated with early postnatal steroids plus indomethacin, and usually without pneumatosis. Management overlaps (NPO, antibiotics, drain or laparotomy), but pathology and counseling differ. If a question stem shows pneumatosis, portal gas, and a mottled looping abdomen in a 3-week-old who was advancing feeds, think NEC, not SIP.

Clinical recognition

Early signs are easy to rationalize as ordinary prematurity: increased gastric residuals, emesis, subtle abdominal fullness, temperature instability, apnea, and glucose swings. Bloody stool may be occult or frank. As disease progresses, the abdomen becomes shiny, distended, and tender; bowel loops may be visible; the infant looks gray, mottled, or poorly perfused; and laboratory drift includes thrombocytopenia, hyponatremia, metabolic acidosis, neutropenia or a rising immature-to-total neutrophil ratio, and coagulopathy. A sudden need for more respiratory support in a previously stable feeder is a GI clue, not only a lung clue.

Examine the abdomen the same way every time: color, circumference, firmness, erythema or bluish discoloration of the wall (suggesting full-thickness injury or perforation with tracking), and the presence of a mass. Measure girth at the same landmark. Blue or black discoloration, a doughy silent abdomen, and refractory shock are late.

Imaging that changes management

A two-view abdominal series (supine plus left lateral decubitus or cross-table lateral) is the workhorse. Pneumatosis intestinalis—linear or cystic gas in the bowel wall—is the radiographic finding that moves the infant from suspected to definite NEC in modified Bell staging. Portal venous gas is air tracking into the portal venous system; it indicates more extensive disease and should not be dismissed as artifact. Pneumoperitoneum (free air over the liver on left-lateral decubitus, football sign, or air outlining the falciform ligament) means perforation until proven otherwise and is the most straightforward indication for a surgical procedure. Fixed, dilated loops that do not change on serial films suggest a dead segment even without free air; only about half of perforations show obvious pneumoperitoneum, so clinical deterioration still drives the operating-room call.

Ultrasound, where available, can show bowel-wall thickening, absent perfusion, and free fluid, and it may help when radiographs are equivocal. It does not replace serial bedside exams. Contrast studies are not first-line in acute NEC because of perforation risk.

Modified Bell staging: a nursing view

Staging is a shared language, not a reason to delay treatment while you argue about a number. Use it to communicate how sick the gut and the infant are.

Stage I infants can still have another diagnosis (milk-protein colitis, septic ileus, isolated feeding intolerance). Treat them as NEC until a safer explanation is proven. Stage II is medical NEC until a surgical indication appears. Stage III is where the ventilator, vasoactive infusions, blood products, and the surgeon share the bedside.

Medical management you will be tested on

Stop enteral feeds immediately and place a large-bore gastric tube to low intermittent or continuous suction. Do not continue trophic milk through pneumatosis. Secure intravenous nutrition; these infants catabolize fast and third-space into bowel. Obtain a blood culture before antibiotics when it does not delay the first dose. Antibiotic selection follows unit protocol but must cover gram-negative enteric organisms, gram-positive organisms (including possibilities such as coagulase-negative staphylococcus in a NICU infant), and anaerobes once NEC is definite or perforation is in play. Typical durations are on the order of 7–14 days of NPO and antibiotics for definite medical NEC, longer if surgical, always individualized.

Support is full critical-care nursing: thermoregulation, blood-pressure and perfusion targets, treatment of DIC, platelet and plasma support, avoidance of abdominal crowding from overly aggressive bag-mask ventilation, and careful line care because these infants often need prolonged parenteral nutrition. Re-examine the abdomen and review films on a schedule the team names out loud (often every 6–8 hours while unstable, and immediately with any change). Pain and developmental care still matter; a rigid, ignored abdomen is both inhumane and diagnostically sloppy.

When can you feed again? After clinical and radiographic recovery, surgeons and neonatologists restart slowly, preferably with human milk. Recurrence is real. Do not equate a single normal film with a green light if the infant still looks septic.

Peritoneal drain versus laparotomy

Pneumoperitoneum is the classic absolute indication for a procedure. Relative indications include progressive clinical deterioration, a fixed loop, abdominal wall cellulitis, and refractory acidosis or shock despite medical therapy. Two procedures dominate the first intervention:

Primary laparotomy allows inspection, resection of frankly necrotic bowel, ostomy or anastomosis depending on the infant and the amount of remaining intestine, and peritoneal washout. The surgical goal is source control while preserving every viable centimeter, because the aftermath is short gut.

Peritoneal drainage is a bedside or NICU procedure that places a drain (often in the lower quadrants) to decompress air and contaminated fluid. It is used most in extremely low-birth-weight, unstable infants who may not tolerate an immediate trip to the operating room. Randomized and observational evidence has not shown a consistent survival winner between initial drain and initial laparotomy for perforated NEC. Many drained infants later require laparotomy if they fail to improve. Counsel families that a drain can be a bridge, not a cure. SIP versus NEC at the time of the decision may influence which infants do well with drainage alone, but you will not have histology at the moment of collapse.

Postoperatively, watch stoma perfusion, abdominal compartment physiology after tight closure, third-space losses, and glucose. A second-look operation may be planned when viability was uncertain.

Short-gut aftermath

Surgical NEC is a leading cause of neonatal short-bowel syndrome. Loss of ileum impairs bile-acid reabsorption and vitamin B12 uptake; loss of the ileocecal valve worsens small-bowel bacterial overgrowth and rapid transit. The infant may leave the acute NEC episode only to enter months of parenteral nutrition, central-line infections, intestinal failure–associated liver disease, high-output stoma losses, D-lactic acidosis from malabsorbed carbohydrate, and growth failure. Nursing implications start before the first postoperative feed: meticulous line care, stoma output replacement, early human-milk exposure when the surgeon allows, and honest family teaching that survival of perforation is not the end of GI critical care. Full malabsorption and TPN cholestasis detail continues in sections 8.3 and 8.4.

Worked scenario and traps

A 26-week infant at 16 days of life develops 8 mL residuals, a 2 cm girth increase, and a mottled loop. You stop feeds, decompress, culture, start antibiotics, and obtain a left-lateral decubitus film. Pneumatosis is present without free air: Bell stage II medical NEC, not a feed-through-and-watch plan. Six hours later the infant is gray with free air: that is now surgical disease.

Traps: calling every residual NEC (but also dismissing residuals in a distended preterm); treating pneumatosis as an automatic laparotomy; treating free air as a medical-only finding; confusing SIP (early, no pneumatosis) with classic NEC; advancing formula rapidly as a preventive strategy; and using xanthan-gum thickeners in preterms. Prevention language that belongs on the exam is mother's own milk, careful feeding, infection-prevention hygiene, and avoiding unnecessary broad-spectrum antibiotics and acid blockade—not a claim that any protocol abolishes NEC.