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).
♦ Using the appendix for removal of the meconium has a slight theoretical advantage in that it prevents future appendiceal pathology (Fig. 17-2).
♦ For most patients, once the meconium has been evacuated, the enterotomy or appendiceal stump can be closed primarily.

image If there is tenacious meconium that cannot be removed, or if there is a question of the ability of the enterotomy or appendiceal stump to heal, a T-tube (enterotomy) or Malecot (appendicostomy) can be placed to create a controlled fistula (Fig. 17-3). A 10 to 14 French T-tube is trimmed, and extra holes are cut before insertion. It is held in place by two pursestring sutures, and the bowel is sutured to the abdominal wall as well. In patients who have had a T-tube placed in the terminal ileum, daily irrigation with N-acetylcysteine is used to promote and maintain patency of the terminal ileum. Once pancreatic enzymes have been started and spontaneous defecation established, the tube can be removed 2 to 3 weeks after surgery. The fistula tract will then spontaneously close.

♦ In cases of complex meconium ileus or severely ischemic bowel in simple meconium ileus, bowel resection may be indicated.

image Primary anastomosis historically has been frowned on but can be done if the bowel is decompressed well distally and there is no evidence of ischemia.
image An end ileostomy and mucous fistula is the safest and most diverting ostomy.

♦ The Bishop-Koop and Santulli stomas were developed to make stoma closure easier and to give access to the bowel. The Bishop-Koop procedure (Fig. 17-4, A) involves resection of the segment of ileum obstructed by the meconium and anastomosing the end of the proximal bowel (ileum) to the side of the distal bowel. The end of the distal bowel (ileum) is brought out as a decompressive ileostomy that can also be used for irrigation. The Santulli (Fig. 17-4, B) refers to the formation of a proximal enterostomy, and the distal end is anastomosed to the side of the proximal bowel. These procedures are uncommonly performed today but can be useful in patients with densely adherent intraluminal meconium who are at risk for postoperative obstruction or with dramatically different caliber of proximal and distal bowel.
♦ Free-flowing meconium peritonitis, which occurs with a late-term in utero perforation, can be treated by evacuation and irrigation. In this setting, there is a chemical and minimally contaminated peritonitis. The bowel can usually be separated for inspection, and a decision of how to treat the perforation can be made, usually to resect and bring out stomas. Primary anastomosis is not indicated in the setting of meconium peritonitis.
♦ Meconium pseudocyst occurs when there is an in utero perforation weeks to months before birth. Calcification of the pseudocyst wall is often seen, and a bowel that is involved cannot be separated from this dense inflammatory response. These neonates are best treated with diversion and control of the perforation. The procedure should evacuate distal meconium and leave as much bowel length as possible. Surgery in the setting of a meconium pseudocyst may range from just placing a tube enterostomy into a well-formed perforation to an extensive resection of the pseudocyst and involved bowel.
image

Figure 17-1

image

Figure 17-2

image

Figure 17-3

image

Figure 17-4

Step 4: Postoperative Care

♦ Neonatology and pulmonary specialists are critical.
♦ If an enema was successful in evacuating the viscous meconium, N-acetylcysteine (Mucomyst) is started (5 mL per NG tube every 6 hours). Pancreatic enzymes are started when feeds are started beginning with a dose of 450 to 900 units of lipase per gram of fat. Breast milk or easily absorbed infant formulas such as Pregestimil are preferred.
♦ Residual meconium can be evacuated postoperatively by instilling N-acetylcysteine through the NG tube or, if a T-tube was placed, through the T-tube.
♦ As soon as spontaneous defecation is established, an elemental formula should be ordered and pancreatic enzymes started.

Step 5: Pearls and Pitfalls

♦ Meconium ileus occurs most commonly in patients with cystic fibrosis.
♦ This is one of very few diagnoses associated with abdominal distention at birth, before the infant swallows any air.
♦ On physical examination, the abdomen is nontender and may feel “doughy.” Dilated bowel loops and peristaltic waves may be visible. There may also be a “putty sign”; that is, an indentation made by a finger into the bowel loop filled with meconium may still be visible after pressure is released.
♦ Around 10% of infants with jejunal atresia will have cystic fibrosis.

Distal Intestinal Obstructive Syndrome

Step 1: Surgical Anatomy

♦ The term meconium ileus equivalent has now been replaced by the term distal intestinal obstructive syndrome (DIOS).
♦ The key distinction for these patients is between constipation and DIOS.
♦ The current, and most clinically relevant, definition of DIOS is fecal obstruction unresponsive to usual laxatives.
♦ Patients with DIOS are almost exclusively older than 5 years of age.
♦ Most patients develop DIOS because of a change in their routine, such as insufficient oral enzymes, noncompliance, or a recent change in enzymes.
♦ One of the most significant risk factors is a previous episode of DIOS; recurrence is reported in more than 80% of patients.
♦ Symptoms include chronic crampy abdominal pain, anorexia, early satiety, vomiting, weight loss, and change in stool pattern.
♦ On physical examination, the abdomen will be distended, and there is usually a palpable fecaloma in the right lower quadrant.
♦ Plain radiograph of the abdomen will show a copious amount of fecal material in the right colon, usually with a “soap bubble” appearance.

Step 2: Preoperative Considerations

♦ DIOS can lead to intussusception, with the heavy stool acting as a lead point; appendicitis, with the lumen of the appendix occluded by the inspissated stool; and volvulus.
♦ The differential diagnosis of DIOS includes these complications as well as adhesive small bowel obstruction, fibrosing colonopathy, Crohn disease, and small bowel fistula.
♦ Treatment of patients with DIOS begins with intravenous hydration and correction of electrolyte imbalances.
♦ An NG tube may be placed, initially for decompression and subsequently to deliver solubilizing agents.
♦ Rectal contrast enemas (Gastrografin, Hypaque or Omnipaque +/− Tween 80), and oral N-acetylcysteine are given to loosen and liquefy the inspissated stool.
♦ Once some stool begins to pass, Golytely can be used to complete evacuation of the stool.

Step 3: Surgery

♦ If surgery is necessary, the appendix should be removed and the stump used to flush the stool into the colon. If an appendectomy has already been performed, an enterotomy can be used instead to evacuate the stool.
♦ For patients with recalcitrant recurrence of DIOS, an appendicostomy or button cecostomy may be indicated.

Step 4: Postoperative Care

♦ Following resolution of the acute event, it is important to prevent recurrence by adjusting enzyme therapy, concentrating on good oral hydration and using stool softeners/hydrating agents such as MiraLax.

Step 5. Pearls and Pitfalls

♦ Other risk factors for DIOS include binge eating or other dietary indiscretions, medications that slow gut transit, fasting, respiratory infection, and fluid loss from warm weather or exercise.
♦ DIOS can also occur after surgery, and prophylaxis for patients with cystic fibrosis should be considered in the perioperative period after any procedure.

Other Meconium-Related Disorders

Meconium Plug Syndrome

♦ Meconium plug syndrome is an obstruction of the colon (rather than the terminal ileum) that occurs in 1:500 to 1:1000 live births and was classically described by Clatworthy in 1956 as a “transient form of distal colonic or rectal obstruction in newborn infants caused by inspissated, immobile meconium.”
♦ Meconium plug has a high association with cystic fibrosis and Hirschsprung disease. Up to 25% of patients with meconium plug will subsequently be shown to have cystic fibrosis.
♦ The risk factors for isolated meconium plug syndrome include prematurity, hypotonia, hypermagnesemia, respiratory distress, sepsis, maternal diabetes, and hypothyroidism.
♦ Patients with meconium plug syndrome are usually full-term infants whose symptoms include vomiting, distention, and failure to pass meconium.
♦ Contrast enemas are not only diagnostic but therapeutic as well. Only rarely is a second enema needed, and surgery is almost unheard of in this syndrome.

Meconium Disease of Prematurity

♦ Premature infants pass meconium later than term infants.
♦ On occasion, like meconium ileus or meconium plug syndrome, the meconium becomes obstructive, and these infants become symptomatic.
♦ The diagnosis of meconium disease of prematurity is usually made when the infant is between 5 and 30 days of age.
♦ These infants are often symptomatic before diagnosis. They have a distended but otherwise benign abdomen and are not systemically ill.
♦ Abdominal radiographs resemble those of meconium ileus, with dilated loops and a paucity or absence of air-fluid levels.
♦ Contrast enemas should be obtained for diagnostic as well as therapeutic reasons.
♦ Very dilute Gastrografin (1:5) or iso-osomolar contrast is recommended.
♦ In these tiny and vulnerable patients, a trip to radiology has risks.
♦ Although some physicians contend that these risks are worth the benefit of fluoroscopic guidance, others start with a bedside technique.
♦ Although some physicians have suggested the use of small-volume, frequent saline enemas to evacuate meconium in low-birth-weight infants, this method was shown to be ineffective in a prospective, randomized trial.
♦ Likewise, the use of N-acetylcysteine via NG tube is probably ill advised because of the risk of hypernatremia in these fragile patients.
♦ Unlike term infants with meconium plug syndrome, infants with meconium disease of prematurity have no increased risk of cystic fibrosis or Hirschsprung disease.

Bibliography

Clatworthy HW, Howard WH. The meconium plug syndrome. Surgery. 1956;39:131-142.

Dimmitt RA, Moss RL. Meconium diseases in infants with very low birth weight. Semin Pediatr Surg. 2000;9(2):79-83.

Docherty JG, Zaki A, Coutts JAP, et al. Meconium ileus: a review 1972-1990. Br J Surg. 1992;79(6):571-573.

Escobar MA, Grosfeld JL, Burdick JJ, et al. Surgical considerations in cystic fibrosis: a 32-year evaluation of outcomes. Surgery. 2005;138(4):560-571. discussion 571-572

Meetze WH, Palazzolo VL, Bowling D, et al. Meconium passage in very-low-birth-weight infants. JPEN J Parenter Enteral Nutr. 1993;17(6):537-540.

Noblett HR. Treatment of uncomplicated meconium ileus by Gastrografin enema: A preliminary report. J Pediatr Surg. 1969;4:190-197.

Rescorla FJ, Grosfeld JL. Contemporary management of meconium ileus. World J Surg. 1993;17(3):318-325.

Rubinstein S, Moss R, Lewiston N. Constipation and meconium ileus equivalent in patients with cystic fibrosis. Pediatrics. 1986;78(3):473-479.

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