AUTHOR AND EDITOR INFORMATION

Section 1 of 11  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• MRI
• Ultrasound
• Angiography
• Intervention
• Multimedia
• References

INTRODUCTION

Section 2 of 11  

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• Introduction
• Differentials
• Radiograph
• CT SCAN
• MRI
• Ultrasound
• Angiography
• Intervention
• Multimedia
• References

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.

Meconium ileus

Meconium ileus occurs when 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.

Occasionally, however, 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. These last 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.

These cases not withstanding, 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.

In meconium ileus, low or distal intestinal obstruction in 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.

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, ie, 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.

Frequency

United States

No data are available.

International

No data are available.

Mortality/Morbidity

• With meconium ileus–equivalent syndrome, the operative mortality and morbidity rates are high.

Race

More common in white populations.

Sex

Meconium ileus affects both sexes almost equally.

Age

Meconium ileus affects newborns.

Clinical Details

Clinical signs of meconium ileus

Infants with meconium ileus present with vomiting (usually bile stained), abdominal distension, 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.

Clinical signs of 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.

Clinical signs of 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.

Clinical signs of 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 three of their four patients were premature. Most infants with this form of colonic obstruction present within their first 24-36 hours of life. Findings include abdominal distension, bilious vomiting, and failure to initiate the normal passage of meconium.

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.

Differentiation from Hirschsprung disease

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.

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.

Preferred Examination

Radiography is the preferred examination for evaluating cases of meconium ileus, meconium ileus–equivalent syndrome, meconium peritonitis, and meconium plug syndrome.

DIFFERENTIALS

Section 3 of 11  

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• Radiograph
• CT SCAN
• MRI
• Ultrasound
• Angiography
• Intervention
• Multimedia
• References

Other Problems to be Considered

Cystic fibrosis
Infant of diabetic mother

RADIOGRAPH

Section 4 of 11  

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• Ultrasound
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Findings

Meconium ileus

Plain abdominal radiographs frequently demonstrate a low small-bowel obstruction with numerous air-filled loops of bowel. Because of the tenacious meconium and the abnormality of mucous-gland secretion, air-fluid levels are often absent. However, images in some infants may demonstrate air-fluid levels, especially in those with complications such as volvulus and stenosis or atresia.

Although the absence of air-fluid levels strongly suggests meconium ileus, air-fluid levels do not exclude it. In some cases of meconium ileus, distension of the obstructed small bowel can be enormous, and the findings can be easily misinterpreted as distal colonic distension. In other cases, a so-called soap-bubble effect of gas mixed with meconium, may be seen.

Although the soap-bubble effect is not pathognomonic of the condition, it is commonly seen with meconium ileus. However, it can also be seen with ileal atresia, colonic atresia, Hirschsprung disease, and meconium plug syndrome. Although plain imaging findings may suggest the diagnosis, with or without a family history of cystic fibrosis, contrast enema examination of the colon is required to establish a diagnosis of meconium ileus.

Contrast enema study typically demonstrates microcolon, which is a reflection of underused bowel. A microcolon can be due to other etiologies besides cystic fibrosis such as ileal atresia or any other complete intrauterine obstruction of the distal small bowel. However, when contrast agent refluxes into the small bowel, meconium pellets distending the distal ileum are usually identified, and the diagnosis of meconium ileus is established.

Water-soluble contrast material is typically used and a variety of water-soluble contrast agents have been used. In the past, Gastrografin has been used, but this must be diluted to at least 3:1 (water to Gastrografin, as recommended by the manufacturer). However, the use of Gastrografin is now controversial, as deaths from fulminant colitis and dehydration have been reported.

Other nonionic contrast agents (eg, Hypaque, Omnipaque) are preferred by many radiologists and have less risk of dehydration or colitis. The Cystic Fibrosis Foundation Consensus Conference on GI disorders concluded that there is no scientific evidence that hyperosmolar Gastrografin enema is any better than an iso- or hypo-osmolar enema. However, opinion remains divided on this topic and Gastrografin is used safely by very experienced pediatric radiologists when diluted appropriately.

Because of potential fluid shifts, hypovolemia is a risk and therefore adequate hydration and electrolyte balance are essential before, during, and after the procedure. This monitoring should prevent significant fluid shifts. If perforation of bowel and leak of contrast or Gastrografin into the peritoneum occurs, more rapid fluid shifts may result and close monitoring by a neonatologist is recommended.

Acetylcysteine (a mucolytic) can be mixed with the enema to aid passage of the very sticky meconium, but the efficacy of this is not yet proven.

Meconium ileus–equivalent syndrome

Plain abdominal images show a mottled appearance (which may simulate meconium) in dilated loops of small bowel. Other plain imaging findings include a bubbly, granular appearance predominantly in the right side of the abdomen, with dilated small bowel and fluid levels due to small-bowel obstruction.

Water-soluble contrast enemas are often helpful in excluding the other possible causes of the symptoms and can be used to treat this condition and. If the diagnosis can be made radiologically, conservative medical treatment should be pursued vigorously, and surgery is undertaken only if it is unavoidable.

Meconium peritonitis

Meconium peritonitis may be incidentally detected on abdominal radiographs. The extruded meconium may or may not become calcified, and when no calcification is present, the radiograph may only suggest fluid in the abdomen. When calcification is seen, the diagnosis can usually be established. This calcification can be amorphous and irregular or curvilinear, with the latter suggesting cystic loculation or coating of the peritoneum. The term cystic or pseudocystic meconium peritonitis has been applied to this finding.

Eventually, most of the calcification in meconium peritonitis slowly disappears, and it is uncommon to encounter an older child with residual calcifications. In some cases, fluid and meconium can pass into the chest, presumably through congenital communications, resulting in meconium thorax.

Meconium plug syndrome

Meconium plug and small left-colon syndromes are diagnosed radiologically, and contrast enema examination is required. Plain images are nonspecific and usually show findings of a low small-bowel obstruction. Erect abdominal radiographs, albeit seldom necessary in the newborn, show a paucity of air-fluid levels, and in most cases, no gas is seen in the colon. If air is introduced into the rectum from below (eg, on rectal examination), rectal gas may be visualized. In this setting, meconium in the rectum can erroneously suggest a small presacral mass. However, if air entirely surrounds the meconium mass, it will outline the contour of the mass and suggests the correct diagnosis.

If peristalsis forces gas in from the small bowel into the colon and mixes with the meconium, a granular or bubbly appearance mimicking the findings of pneumatosis cystoides intestinalis and necrotizing enterocolitis (NEC) results. If a bubbly pattern is seen within the first 12 hours of life, meconium plug syndrome should be considered, but if it arises after 12-18 hours, NEC is more likely. NEC typically occurs in preterm infants.

In patients with intermediate findings, individual assessment is most important. . Contrast enema examination shows a characteristic appearance of the colon, with contrast material outlining the solid column of inspissated meconium and the wall of the colon for a double-contrast effect.

Water-soluble contrast enemas can be curative with passage of the meconium. After the meconium is passed, the part of the colon from which it was evacuated may appear narrowed, and a transition zone mimicking that seen in Hirschsprung disease may be noted. The small, contracted portion of the descending colon in these infants has led to the term neonatal small left-colon syndrome. In any of these cases, meconium proximal to the apparent transition zone may take the form of a solid, cylindrical mass extending to the cecum or lumps of solid meconium may be scattered throughout the colon.

False Positives/Negatives

Contrast enema examination can help in differentiating meconium plug syndrome from meconium ileus or ileal atresia. In these latter conditions, microcolon is seen, and only occasionally does an infant with meconium ileus have a picture similar to that seen in meconium plug syndrome.

CT SCAN

Section 5 of 11  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• MRI
• Ultrasound
• Angiography
• Intervention
• Multimedia
• References

Findings

CT scanning is not indicated in the evaluation of meconium ileus.

MRI

Section 6 of 11  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• MRI
• Ultrasound
• Angiography
• Intervention
• Multimedia
• References

Findings

MRI is not indicated in the evaluation of meconium ileus.

ULTRASOUND

Section 7 of 11  

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• Introduction
• Differentials
• Radiograph
• CT SCAN
• MRI
• Ultrasound
• Angiography
• Intervention
• Multimedia
• References

Findings

Meconium ileus

Radiologic signs of meconium ileus include enlarged bowel loops at 17-18 weeks' gestational age or a mass with proximal bowel distension, which is suggestive of cystic meconium peritonitis on prenatal sonography.

Meconium ileus–equivalent syndrome

Rare cases of intussusception as a complication of cystic fibrosis may be easily diagnosed with ultrasonography.

Meconium peritonitis

Sonography is seldom necessary, as the findings on plain radiographs are usually diagnostic.

Calcified meconium can be seen during in utero sonography. Ultrasonography may be useful after birth, when cystic masses are present and often appear circumscribed and heterogeneous.

Fluid (sonolucent areas) may be seen in the cyst, but usually, increased echogenicity resulting from debris and calcifications is seen. The wall of the cyst may be thin or thick, and one may note loops of fluid-filled bowel bound to the matrix of the associated adhesions.

With free-floating meconium in the abdomen, multiple speckled echoes are seen. These result in the snowstorm configuration.

Calcifications in the scrotum produce echogenic masses.

ANGIOGRAPHY

Section 8 of 11  

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• Introduction
• Differentials
• Radiograph
• CT SCAN
• MRI
• Ultrasound
• Angiography
• Intervention
• Multimedia
• References

Findings

Angiography is not indicated in the evaluation of meconium ileus.

INTERVENTION

Section 9 of 11  

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• Differentials
• Radiograph
• CT SCAN
• MRI
• Ultrasound
• Angiography
• Intervention
• Multimedia
• References

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.

Balanced electrolyte solutions (eg, Golytely) given orally or contrast enemas (see above) 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.

MULTIMEDIA

Section 10 of 11  

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• Radiograph
• CT SCAN
• MRI
• Ultrasound
• Angiography
• Intervention
• Multimedia
• References

Media file 1:  Abdominal radiograph shows low intestinal obstruction.
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Media type:  X-RAY

Media file 2:  Abdominal radiograph shows low intestinal obstruction.
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Media type:  X-RAY

Media file 3:  Gastrografin enema study shows filling defects in the terminal ileum and cecum. Also note the microcolon (transverse and descending colon).
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Media type:  X-RAY

Media file 4:  Enema study shows microcolon and contrast material outlining a terminal ileum packed with (meconium) filling defects.
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Media type:  CT

Media file 5:  Long, cylindrical filling defect in the descending and sigmoid colon.
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Media type:  X-RAY

REFERENCES

Section 11 of 11

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• MRI
• Ultrasound
• Angiography
• Intervention
• Multimedia
• References

• Burge D, Drewett M. Meconium plug obstruction. Pediatr Surg Int. 2004;20:108-10.
• 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].
• Mees WJ, Kramer PP, Bax NM. [The small left colon in newborn infants]. Tijdschr Kindergeneeskd. Oct 1986;54(5):143-7. [Medline].
• 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].
• Rescorla FJ, Grosfeld JL. Contemporary management of meconium ileus. World J Surg. May-Jun 1993;17(3):318-25. [Medline].
• Swischuk LE. Imaging of the newborn, infant, and young child. 4th ed. Philadelphia: Lippincott, Williams & Wilkins;. 1997.

Article Last Updated: Jul 21, 2005