Introduction
Background
Meconium is the material found in the intestine in a newborn. It consists of succus entericus that, in turn, is made up of bile salts, bile acids, and debris that is shed from the intestinal mucosa during intrauterine life. It is normally evacuated within 6 hours after birth or sooner in utero as a result of a vagal response to perinatal stress.
Normally, meconium is invisible on a radiograph. It occasionally has a mottled appearance on abdominal radiographs during the first 2 days of life. By convention, 4 GI conditions have the word meconium in their name: meconium ileus, meconium ileus–equivalent syndrome, meconium peritonitis, and meconium plug syndrome.
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Presentation
Demographics
- With meconium ileus–equivalent syndrome, the operative mortality and morbidity rates are high.
- More common in white populations.
- Meconium ileus affects males and females almost equally.
- Meconium ileus affects newborns.
Presentation
Meconium ileus
In meconium ileus, low or distal intestinal obstruction results from the impaction of thick, tenacious meconium in the distal small bowel. In addition, complications such as ileal atresia or stenosis, ileal perforation, meconium peritonitis, and volvulus with or without pseudocyst formation can occur in association with meconium ileus.
Infants with meconium ileus present with vomiting (usually bile stained), abdominal distention, and failure to pass meconium. Pulmonary manifestations due to cystic fibrosis are not usually present at birth and develop shortly thereafter, typically resulting in a bronchiolitis-like picture. Although meconium ileus in the absence of cystic fibrosis is considered rare, it occurred in 21.6% of newborns in 1 series; these infants had no laboratory or clinical evidence of cystic fibrosis.
Meconium peritonitis
Meconium peritonitis may be incidentally detected on abdominal radiographs. Clinically, patients may present because of bowel obstruction caused by fibroadhesive bands, which are the result of the inflammatory peritoneal reaction. The bowel itself may be intact, with the perforation having healed, but bowel atresias are often found in association. If the processus vaginalis is patent at the time the perforation occurs, calcification or hernias may involve the scrotum. Ascites may also be present.
Meconium ileus–equivalent syndrome
The condition is important, as it can be the presenting feature of cystic fibrosis in childhood and even in early adult life. Moreover, the operative mortality and morbidity rates are high. Recurrent bowel obstruction (which is often correlated with poor compliance with medication for cystic fibrosis) may manifest as recurrent colicky abdominal pain, often in the right upper quadrant. In the older infant or child, chronic constipation can be a problem, and intestinal obstruction can occur secondary to fecal impaction. These patients may also present with intussusceptions.
Other manifestations include benign pneumatosis cystoides intestinalis (resulting from chronic obstruction), decreased bile secretion with a poorly functioning gall bladder, bile concretions in the biliary system, cirrhosis of the liver with portal hypertension, and severe colitis.
Meconium plug syndrome
Functional colonic obstruction in the full-term neonate is another name for meconium plug syndrome. Although this abnormality is found mostly in term infants, Mees et al reported that 3 of their 4 patients were premature. Most infants with this form of colonic obstruction present within their first 24-36 hours of life. Findings include abdominal distention, bilious vomiting, and failure to initiate the normal passage of meconium.1
Meconium plug syndrome is especially common in infants delivered of diabetic mothers. This disease can also be seen in any infant who is depressed or hypotonic. In this regard, hypermagnesemia has been implicated as a cause of such hypotonia. In addition, sepsis can lead to bowel immotility, and as such, it can mimic meconium plug syndrome.
Differentiating Hirschsprung disease from meconium plug or small left-colon syndrome can be a problem, and one must completely exclude Hirschsprung disease before either of these diagnoses is confirmed.2
The initial clinical and radiologic findings may be similar, but infants with Hirschsprung disease invariably return with either constipation or diarrhea. Once treated, those with meconium plug or small left-colon syndrome remain healthy. Plain images in infants with Hirschsprung disease are more likely to show numerous air-fluid levels on the erect view. During an enema, abnormal contractions with bowel wall irregularity may be seen in the narrowed, aganglionic bowel of Hirschsprung disease, but the bowel wall typically has a smooth contour in the meconium plug setting.
Natural history
Meconium ileus
Meconium ileus occurs when the meconium becomes inspissated and obstructs the distal ileum. The condition is usually a manifestation of cystic fibrosis. Conversely, approximately 20% of infants with cystic fibrosis present with meconium ileus at birth. No other data have been reported regarding its incidence.3,4,5,6
Meconium ileus is usually taken to be synonymous with cystic fibrosis until proven otherwise, and meconium ileus is generally the earliest manifestation of the disease. Cystic fibrosis is the most common autosomal recessive disorder in white populations, with an incidence of 1 case in 2000 births. The condition also occurs in other individuals of other races.
Occasionally, meconium ileus may be seen in association with pancreatic atresia or stenosis of the pancreatic duct. In addition, meconium ileus can occur in the absence of any apparent abnormality of the pancreas in rare cases; in such cases, infants have a favorable outcome after decompression because they do not have cystic fibrosis. Instead, their problem is likely related to gut immaturity, resulting in decreased intestinal motility and impaired passage of meconium.
Meconium peritonitis
Meconium peritonitis usually results from intrauterine GI perforation. It can occur as early as the second trimester. Initially, it is a sterile chemical peritonitis, but if perforation of the GI tract persists after birth, complicating bacterial infection may supervene and the prognosis worsens. Perforation and subsequent meconium peritonitis can occur from many causes, but more often they result from obstruction and/or volvulus associated with meconium ileus (and cystic fibrosis). In other instances, perforation results from other causes of neonatal bowel obstruction (such as intestinal atresia).
Meconium ileus–equivalent syndrome
Meconium ileus–equivalent syndrome is a misnomer that is applied to a partial bowel obstruction seen in older patients known to have cystic fibrosis. Many prefer to call this the distal intestinal obstruction syndrome (DIOS). DIOS has nothing to do with meconium (as meconium is seen only in the newborn bowel), but on occasion the appearance of feces on the abdominal radiograph have been likened to that of meconium. In 15% of adolescents and adults with cystic fibrosis, abnormally viscid bowel contents become impacted in the distal small bowel. It is estimated that 37% of patients with cystic fibrosis experience meconium ileus–equivalent syndrome or DIOS sometime in their life.
Meconium plug syndrome
The terms small left-colon syndrome, colon immaturity, and functional colonic obstruction are now generally regarded as the same entity. All of these conditions refer to the same problem: functional immaturity of the ganglion cells of the colon, which simply manifests as failure to pass the first stool. The problem is probably more common than generally realized, and in most cases, the symptoms are so mild and transient that they pass unnoticed. However, if significant obstruction develops, symptoms become more profound, and complications such as perforation may even occur.
Treatment
The treatment of the meconium plug or small left-colon syndromes is conservative and consists of stimulation of the rectum or colon in some manner. In many cases, simple finger examination of the rectum or insertion of a rectal thermometer produces enough stimulation to induce peristalsis and promote evacuation of the meconium. In other cases, water-soluble contrast enema examination may induce meconium passage. If this or saline enemas fail, water-soluble contrast agents should be used. Examinations with contrast materials such as these require care regarding the patient's fluid and electrolyte balance.7,8,9
Balanced electrolyte solutions (eg, Golytely) given orally or contrast enemas can be used to treat meconium ileus-equivalent syndrome. If this disease can be diagnosed radiologically, conservative treatment should be pursued vigorously, and surgery is undertaken only if it is unavoidable.
With conservative treatment, complete decompression usually occurs within hours. However, in some infants, the process may take up to 2-3 days.
Differential Diagnoses
Other Problems to Be Considered
Cystic fibrosis
Infant of diabetic mother
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References
Mees WJ, Kramer PP, Bax NM. [The small left colon in newborn infants]. Tijdschr Kindergeneeskd. Oct 1986;54(5):143-7. [Medline].
Keckler SJ, St Peter SD, Spilde TL, Tsao K, Ostlie DJ, Holcomb GW 3rd, et al. Current significance of meconium plug syndrome. J Pediatr Surg. May 2008;43(5):896-8. [Medline].
Burge D, Drewett M. Meconium plug obstruction. Pediatr Surg Int. Feb 2004;20(2):108-10. [Medline].
Fakhoury K, Durie PR, Levison H. Meconium ileus in the absence of cystic fibrosis. Arch Dis Child. Oct 1992;67(10 Spec No):1204-6. [Medline].
Lang I, Daneman A, Cutz E, et al. Abdominal calcification in cystic fibrosis with meconium ileus: radiologic-pathologic correlation. Pediatr Radiol. Jun 1997;27(6):523-7. [Medline].
Lim CT, Yip CH, Chang KW. Meconium ileus--a rare cause of neonatal intestinal obstruction in Malaysia. Singapore Med J. Feb 1994;35(1):74-6. [Medline].
Rescorla FJ, Grosfeld JL. Contemporary management of meconium ileus. World J Surg. May-Jun 1993;17(3):318-25. [Medline].
Shinohara T, Tsuda M, Koyama N. Management of meconium-related ileus in very low-birthweight infants. Pediatr Int. Oct 2007;49(5):641-4. [Medline].
Khaitov S, Nissan A, Beglaibter N, Freund HR. Failure of medical treatment in an adult cystic fibrosis patient with meconium ileus equivalent. Tech Coloproctol. Apr 2005;9(1):42-4. [Medline].
Swischuk LE. Imaging of the newborn, infant, and young child. 4th ed. Philadelphia: Lippincott, Williams & Wilkins;. 1997.
O''Halloran SM, Gilbert J, McKendrick OM, et al. Gastrografin in acute meconium ileus equivalent. Arch Dis Child. Nov 1986;61(11):1128-30. [Medline].
Pilling DW, Steiner GM. The radiology of Meconium Ileus Equivalent. Br J Radiol. Jul 1981;54(643):562-5. [Medline].
Pelizzo G, Codrich D, Zennaro F, Dell'oste C, Maso G, D'Ottavio G, et al. Prenatal detection of the cystic form of meconium peritonitis: no issues for delayed postnatal surgery. Pediatr Surg Int. Sep 2008;24(9):1061-5. [Medline].
Further Reading
Meconium Ileus. American Pediatric Surgical Association, Deerfield, IL. Accessed November 12, 2008
Keywords
meconium ileus, succus entericus, perinatal stress, meconium plug syndrome, meconium ileus equivalent syndrome, meconium ileus–equivalent syndrome; meconium peritonitis, cystic fibrosis, pancreatic atresia, stenosis of the pancreatic duct, meconium impaction, distal intestinal obstruction syndrome, DIOS, small left-colon syndrome, colon immaturity, functional colonic obstruction, Hirschsprung disease, Hirschsprung's disease, functional colonic obstruction in the full-term neonate, soap-bubble effect, meconium thorax
