Intussusception, malrotation and necrotising enterocolitis

Overview

Three conditions cause most dangerous intestinal obstruction or gut ischaemia in infants:

• Intussusception: commonest cause of obstruction from about 2 months to 2 years.
• Malrotation with midgut volvulus: can infarct the whole midgut within hours.
• Necrotising enterocolitis (NEC): the commonest gut emergency in premature babies.

Other causes of neonatal obstruction (atresias, Hirschsprung disease, anorectal malformations including imperforate anus, meconium ileus) are summarised at the end and covered in more detail in their own chapters.

Intussusception

Definition and pathology

One segment of bowel (the intussusceptum) telescopes into the next segment (the intussuscipiens). The mesentery is dragged in, so venous return is blocked, the bowel swells, then arterial supply fails: a strangulating obstruction that can progress to gangrene and perforation.

Adults almost always have a lead point (often a tumour). Rotavirus vaccine carries a very small increased risk.

Clinical features

• A previously well infant with sudden episodes of colicky pain: screaming, pallor, drawing the legs up, lasting a few minutes, then quiet or lethargic between attacks.
• Vomiting: milk at first, then bile.
• Redcurrant jelly stool (blood and mucus): a late sign.
• A sausage-shaped mass, usually in the right upper quadrant, with an empty right iliac fossa (Dance sign).
• Rectal examination may show blood; rarely the apex is felt.
• Late: dehydration, distension, fever, shock, peritonitis.

Investigations

Management

Resuscitation first: IV fluids (boluses as needed), nasogastric tube, broad-spectrum antibiotics, analgesia.

Non-operative reduction:

• Air (pneumatic) enema under fluoroscopy is the usual first-line method. Hydrostatic (saline or contrast) enema under ultrasound is an alternative.
• Success: air passes freely into the terminal ileum and symptoms settle.
• More than 70% reduce non-operatively (sources quote a wide range). Repeat attempts are possible in a stable child.
• Risk: colonic perforation (rare); a surgeon must be available.
• Recurrence after enema reduction is up to about 5–10%.

Contraindications to enema reduction:

• Peritonitis
• Perforation (pneumoperitoneum on X-ray)
• Shock not responding to resuscitation

Surgery (open or laparoscopic) is needed if:

• enema is contraindicated or fails;
• there is a pathological lead point;
• there are multiple recurrences.

At operation the intussusception is squeezed back from the apex (pushed, not pulled). Non-viable bowel, an irreducible mass or a lead point needs resection and primary anastomosis.

Malrotation and midgut volvulus

Embryology

• The midgut herniates into the umbilical cord in early fetal life and returns to the abdomen by about the 10th–12th week.
• During this it rotates 270° anticlockwise around the superior mesenteric artery (SMA).
• Normal result: duodenojejunal (DJ) flexure on the left of the spine (at the ligament of Treitz), caecum in the right iliac fossa, and a broad mesenteric base running diagonally between them.

In malrotation the rotation is incomplete:

• the DJ flexure lies to the right of the midline;
• the caecum lies high and central;
• the small bowel mesentery has a very narrow base, so the midgut can twist around the SMA (midgut volvulus);
• Ladd bands (peritoneal bands from the high caecum to the right abdominal wall) cross and compress the second part of the duodenum.

Clinical features

• Most present in the first month of life, but can occur at any age (even adults).
• Sudden bilious vomiting in a previously well baby.
• Early on the abdomen may be soft and not distended (high obstruction). Do not be reassured.
• With ischaemia: blood per rectum, distension, tenderness, shock, acidosis.
• Older children: intermittent pain and vomiting, failure to thrive.

Investigations

Management

• Resuscitation (fluids, NG tube, antibiotics) and emergency laparotomy. Volvulus can kill the entire midgut in hours, causing short bowel syndrome or death.
• Ladd procedure:

1. Untwist the volvulus anticlockwise (counter-clockwise). 2. Divide Ladd bands to release the duodenum. 3. Widen the mesenteric base (separate the duodenum and caecum). 4. Place the bowel in a non-rotated position: small bowel on the right, colon on the left. 5. Appendicectomy, because the appendix will lie in an abnormal site and later appendicitis would be confusing.

• Clearly dead bowel is resected; doubtful bowel may be left and checked at a second-look laparotomy.

Necrotising enterocolitis (NEC)

Definition and risk factors

An acquired inflammatory necrosis of the bowel wall in newborns, mainly premature babies.

The terminal ileum and colon are most often affected. Onset is later in more premature babies (often in the second week or later); in term babies it comes within the first days.

Clinical features

• Feeding intolerance, increasing gastric bile-stained aspirates, vomiting.
• Abdominal distension and tenderness.
• Blood in stools (occult or fresh).
• Systemic sepsis: lethargy, apnoea, bradycardia, temperature instability, poor perfusion, shock.
• Late: abdominal wall redness, fixed mass, peritonitis.

Investigations

Staging (modified Bell staging, in outline)

Management

Medical (most cases):

• Stop feeds (nil by mouth), NG decompression.
• Broad-spectrum IV antibiotics (covering gut organisms and anaerobes).
• IV fluids / TPN (gut rest usually for 1–2 weeks in established NEC).
• Correct acidosis, clotting and platelets; ventilatory and inotropic support; remove umbilical catheters.
• Serial X-rays, girth, bloods.

Surgery for:

• Perforation (pneumoperitoneum): the absolute indication.
• Clinical deterioration despite maximal medical care, fixed loop, abdominal wall erythema, mass.

Options: laparotomy with resection of dead bowel and stoma formation; in very small, unstable babies a peritoneal drain may be placed first.

Complications and outcome

• Strictures (often colonic), presenting weeks later with obstruction: a common late complication.
• Short bowel syndrome / intestinal failure after big resections.
• Neurodevelopmental delay.
• Mortality remains around 30% or more, highest in the most premature babies.

Other causes of intestinal obstruction in the newborn

Quick revision

• Intussusception: 2 months–2 years, ileocolic, Peyer patches; colic, vomiting, sausage mass, redcurrant jelly.
• Ultrasound target sign; air enema reduction; no enema if peritonitis, perforation or shock.
• Lead point more likely over 2 years or with recurrence (Meckel, polyp, lymphoma, HSP).
• Bilious vomiting = malrotation/volvulus until proven otherwise.
• Malrotation: DJ flexure right of midline on contrast; Ladd bands compress D2.
• Ladd procedure: untwist anticlockwise, divide bands, widen base, appendicectomy.
• NEC: premature, formula-fed, terminal ileum/colon; pneumatosis; nil by mouth, antibiotics, TPN; operate for perforation.
• NEC late complication: stricture.

Written by The House Job from standard references (Bailey & Love; Basis of Paediatrics).

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