Meconium Disease

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CHAPTER 17 Meconium Disease

Mary L. Brandt

Meconium Ileus

Step 1: Surgical Anatomy

♦ Meconium ileus is an obturator (intraluminal) obstruction caused by thick, viscous meconium, most commonly in patients with cystic fibrosis.
♦ Accurate prenatal diagnosis of meconium ileus is difficult.

image The most common ultrasound findings are echodense bowel and bowel dilatation.
image Fetal magnetic resonance imaging has been suggested as an additional tool for prenatal diagnosis of the underlying cause of echodense bowel because it can differentiate between meconium ileus, atresia, bowel duplication, and other pathologic conditions.
image Absence of the gallbladder may also be associated with cystic fibrosis.
image Maternal polyhydramnios may occur in some cases.

Step 2: Preoperative Considerations

♦ The passage of meconium in healthy term infants usually occurs within the first 24 hours, but this is prolonged by prematurity. In one study of infants weighing less than 1250 g and less than 32 weeks’ gestation, the mean time to first stool was 44 hours, and the 75th percentile was 10 days.
♦ Clinical presentation

image The presentation varies depending on whether the obstruction is simple (uncomplicated) or complex (complicated).
image Simple meconium ileus refers to an intraluminal obstruction of the bowel without complication, which is much more common than complicated meconium ileus.

• Soon after birth, these infants have failure to stool, bilious emesis, and abdominal distention.

image Complicated meconium ileus refers to meconium ileus with perforation, volvulus, or atresia.

• Perforation or volvulus with necrosis can cause peritonitis and the associated systemic changes.
• If a volvulus occurs antenatally, the bowel can absorb and at birth the patient will have a small bowel atresia.
• If there is a patent processus vaginalis, meconium may be visible in the scrotum, which can manifest as calcifications on radiographs.

♦ Provide intravenous fluid resuscitation, place an orogastric or nasogastric (NG) tube, and correct any electrolyte imbalance.

Step 3: Treatment

♦ All infants who are stable enough should undergo a contrast enema.

image If the patient has complicated meconium ileus, knowing that the colon is patent before surgery is important.
image The contrast enema may be therapeutic as well as diagnostic for simple meconium ileus.
image A KUB (kidneys, ureters, and bladder) examination should be performed 12 hours after the contrast enema; if obstruction is still present, the contrast enema can be repeated.

♦ The first use of a contrast enema to relieve the obstruction of meconium ileus was reported in 1969 by Noblett. He defined seven “requirements” that still hold true today:

image Rule out other causes of obstruction with an initial diagnostic enema.
image The patient must have uncomplicated meconium ileus.
image The procedure must be performed under careful fluoroscopic control.
image The patient should receive parenteral antibiotics before the procedure.
image A pediatric surgeon should be present during the procedure.
image The infant should be fully resuscitated.
image All preparations should be in place in case emergency surgery is needed.

Operative Considerations

♦ Indications for surgery

image All neonates with complicated meconium ileus
image Those with uncomplicated meconium ileus who have failed two or three therapeutic enemas

♦ Goal is to evacuate the inspissated, thick meconium from the bowel.
♦ The goal is accomplished in most cases by one of three simple measures: a needle enterostomy, an open enterostomy, or access through the appendix. This procedure can be tedious and can easily take an hour or longer.

image A needle enterostomy involves multiple injections slanted through the wall of the bowel with a small-gauge needle to deliver saline, dilute Gastrografin, and/or 2% to 4% N-acetylcysteine. Once the meconium is liquefied by one or all of these substances, it can be manually passed into the colon and out the rectum.
image Alternatively, a small enterotomy can be performed, usually just proximal to the junction of the dilated and nondilated bowel.
image An appendectomy can be performed and the open appendiceal stump used as an enterotomy.

♦ Removal of the meconium can be facilitated by judicious and gentle use of either a Foley or Fogarty catheter (Fig. 17-1

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