AUTHOR AND EDITOR INFORMATION

Section 1 of 7  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• Intervention
• Multimedia
• References

INTRODUCTION

Section 2 of 7  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• Intervention
• Multimedia
• References

Background

Meconium plug syndrome, also termed functional immaturity of the colon, is a transient disorder of the newborn colon characterized by delayed passage (>24-48 h) of meconium and intestinal dilatation (see Image 1). Contrast enema demonstrates the retained meconium as a filling defect or plug (see Image 2) that produces a double-contrast effect. Small left colon syndrome is a subset of meconium plug syndrome in which an enema demonstrates an apparent transition zone between the dilated and the normal-to-decreased caliber distal colon at the splenic flexure (see Image 3).

Pathophysiology

Early descriptions of meconium plug syndrome emphasized the contrast-enema appearance and ascribed a possible etiologic role to the retained meconium, which is often dislodged after the enema study. Currently, meconium plug syndrome is understood as a transient functional disorder of the colon resulting from immaturity of the myenteric plexus nerve cells or their hormonal receptors. This distinguishes it from Hirschsprung disease, which may have identical clinical and radiographic findings in which nerve cells are absent in the distal diseased portion of the colon.

Frequency

United States

Since meconium plug syndrome is a clinical and radiographic disorder without pathologic or laboratory confirmation, incidence figures are not available.

Mortality/Morbidity

Typically, the clinical course is benign; however, serious complications may occur, primarily including intestinal perforation and electrolyte imbalance secondary to obstruction or hypertonic contrast enema.

Race

No racial predilection is apparent.

Sex

No sex predilection is known.

Age

By definition, the disorder is found only in newborns.

Anatomy

Anatomic changes in meconium plug syndrome vary. Usually, the colon is normal or may be mildly enlarged and filled with meconium. A change in the colon's diameter at the splenic flexure may be seen and is indistinguishable from that observed in Hirschsprung disease, although in the latter disorder the transition zone usually is in the rectosigmoid. In preterm infants weighing less than 1000 g, the entire colon may be small, producing an enema appearance similar to ileal atresia or meconium ileus.

Clinical Details

Clinically, the hallmarks of the disorder are abdominal distention and failure to pass significant meconium in the first 24 hours of life. Bilious vomiting may occur. Symptoms often are present before the first feeding, which helps distinguish the disorder clinically from necrotizing enterocolitis.

The incidence is increased in premature infants of diabetic mothers (especially the small left colon variant) and in infants whose mothers received magnesium sulfate for treatment of toxemia. Newborns with cystic fibrosis also may present with meconium plug syndrome, although meconium ileus is more frequent and characteristic in these patients. Despite these associations, many patients have no apparent risk factor.

Preferred Examination

The initial imaging modality is plain film, which includes supine and horizontal beam views (left lateral decubitus or cross-table lateral) of the abdomen. Follow plain films with contrast enema. Barium can be used but has been replaced by water-soluble contrast agents in most practices. Historically, Gastrografin was employed, which is a hypertonic solution containing both wetting and detergent agents. However, complications secondary to hyperosmolarity occurred that produced dehydration. Evidence exists that detergent and wetting additives may be toxic, and their possible therapeutic effect remains unproven.

Limitations of Techniques

Meconium plug syndrome is a diagnosis of exclusion. Contrast enema usually eliminates congenital small bowel obstruction and rare colon abnormalities such as atresia or duplication. The primary differential consideration is Hirschsprung disease, which is diagnosed eventually in approximately 10-30% of patients with apparent meconium plug syndrome (see Image 2).

Rare disorders that may partially simulate meconium plug syndrome include neuronal intestinal dysplasia, visceral neuropathies, and megacystis-microcolon-intestinal hypoperistalsis syndrome, also termed Berdon syndrome. However, radiographic and clinical features in these diseases usually are distinguished readily from meconium plug syndrome. A more common problem is an infant with sepsis or a metabolic disorder who presents with nonobstructive ileus.

DIFFERENTIALS

Section 3 of 7  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• Intervention
• Multimedia
• References

Other Problems to be Considered

Adynamic ileus
Imperforate anus
Inguinal hernia
Malrotation of the intestine with volvulus or Ladd bands
Megacystis-microcolon-intestinal hypoperistalsis (Berdon syndrome)
Neuronal intestinal dysplasia

RADIOGRAPH

Section 4 of 7  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• Intervention
• Multimedia
• References

Findings

Plain films usually demonstrate multiple dilated loops of bowel with absence of rectal gas. The presence or absence of air-fluid levels in the bowel is not helpful. Findings are similar to those of structural colonic or distal small bowel obstruction and help to exclude malrotation with volvulus or obstructing Ladd bands, in which the blockage usually occurs at the duodenum.

Contrast enema usually shows a moderately dilated colon filled with radiolucent material (the meconium plug). In the small left colon variant (see Image 3), a transition is seen from a relatively small to normal or increased caliber bowel in the region of the splenic flexure.

Degree of Confidence

Meconium plug syndrome is a diagnosis of exclusion. Contrast enema usually excludes congenital small bowel obstruction and rare colon abnormalities such as atresia or duplication. The main differential consideration is Hirschsprung disease, which is diagnosed eventually in approximately 10-30% of patients with apparent meconium plug syndrome (see Image 2).

Rare disorders that may partially simulate meconium plug syndrome include neuronal intestinal dysplasia, visceral neuropathies, and megacystis-microcolon-intestinal hypoperistalsis syndrome, also termed Berdon syndrome. However, radiographic and clinical features in these disorders usually are distinguished readily from meconium plug syndrome. A small (micro or mini) colon characterizes many of these diseases.

A more common problem is an infant with sepsis or metabolic disorder who presents with a nonobstructive ileus. In these patients, the intestinal dilatation resolves once the primary problem is treated.

The main problem in differential diagnosis, after the contrast enema has been performed, is Hirschsprung disease. The enema findings in neonatal Hirschsprung disease are not distinguishable from meconium plug syndrome. The most important point is the infant's response to supportive care and enemas.

Evaluate any infant with apparent meconium plug syndrome for Hirschsprung disease (rectal-suction biopsy) and other possible underlying disorders when findings persist after 1-2 enemas.

False Positives/Negatives

The normal infant's intestinal gas pattern often appears "gassy" by adult criteria. Typically, the width of a bowel loop does not exceed the width of one of the patient's lumbar vertebral bodies. Rectal gas often may be absent in the normal infant because the rectum is dependent and filled with meconium when the patient is supine. With the exception of the rectum, the colon and small bowel usually cannot be differentiated on plain film.

INTERVENTION

Section 5 of 7  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• Intervention
• Multimedia
• References

In addition to contributing to diagnosis, contrast enema may be therapeutic. In most patients, the enema probably speeds what otherwise may be a slower spontaneous recovery.

Historically, Gastrografin, a hypertonic solution containing both wetting and detergent agents, was employed for contrast. However, complications secondary to hyperosmolarity occurred that produced dehydration. Evidence exists that the detergent and wetting additives may be toxic, and their possible therapeutic effect remains unproven.

Current practice uses low-osmolar contrast, which is adequately radiopaque at iso-osmolar levels if a low-kV technique is used. No evidence exists that the newer low-osmolar agents are less therapeutic than hyperosmolar media.

Contrast enema technique

• Perform the enema with attention to the delicate temperature stability of the newborn infant. Use blankets and lamps and warm the contrast to body temperature.
• Advance a small-caliber soft, rubber catheter (10-14F) into the rectum using minimal lubricant. Hold the catheter in place primarily by taping the patient's buttocks tightly together.
• Some radiologists deploy a small Foley balloon (5 mL) to aid contrast retention. However, do not inflate the balloon until a preliminary injection of a small amount of contrast under fluoroscopy demonstrates adequate caliber of the rectum. Initial injection without an inflated balloon also assesses for a possible low-transition zone in patients with Hirschsprung disease.
• Because the internal volume of the colon may be low, at the author's institution, contrast is injected by hand using a syringe under careful and almost continuous fluoroscopic monitoring. Others use a low-capacity reservoir, such as an intravenous bag, and infuse via gravity drip.
• Opacify the entire colon both to maximize the therapeutic effect of the enema and to identify the position of the cecum.
• Carefully attempt to reflux contrast into the distal ileum in patients who may have meconium ileus.
• After the colon has been filled and the appropriate films obtained, remove the catheter without attempting to drain the colon. Allowing the patient to expel the contrast may help dislodge the meconium plug.

Response to the enema often is dramatic, with immediate passage of meconium and resolution of intestinal dilatation. In some patients, clinical findings persist and a second enema is performed for therapy. Since the plug is a symptom in this disorder, rather than its cause, little justification is found for multiple repeat procedures.

Special Concerns

• The primary complication of this disorder is intestinal perforation, which may be spontaneous or secondary to overdistension during an enema.
• Iatrogenic complications include fluid/electrolyte disorders resulting from hyperosmolar enema contrast and hypothermia from inadequate temperature control during the procedure.

MULTIMEDIA

Section 6 of 7  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• Intervention
• Multimedia
• References

Media file 1:  Supine frontal view of the abdomen in a newborn with meconium plug syndrome demonstrates multiple dilated loops of bowel but no rectal gas.
	View Full Size Image
Media type:  X-RAY

Media file 2:  A frontal view from contrast enema in a patient initially given a diagnosis of small left colon syndrome. A long filling defect is seen in the rectosigmoid with gradual transition to a more dilated proximal bowel. The infant failed to improve, and rectal biopsy confirmed Hirschsprung disease.
	View Full Size Image
Media type:  X-RAY

Media file 3:  A lateral view from contrast enema in a newborn demonstrates a normal-to-decreased caliber "empty" distal colon and dilated proximal bowel containing multiple plugs. The child responded clinically and radiographically to a single enema.
	View Full Size Image
Media type:  X-RAY

REFERENCES

Section 7 of 7

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• Intervention
• Multimedia
• References

• Burge D, Drewett M. Meconium plug obstruction. Pediatr SurgInternational. 2004;20(2):108-10. [Medline].
• Krasna IH, Rosenfeld D, Salerno P. Is it necrotizing enterocolitis, microcolon of prematurity, or delayed meconium plug? A dilemma in the tiny premature infant. J Pediatr Surg. Jun 1996;31(6):855-8. [Medline].
• McAlister WH, Kronemer KA. Emergency gastrointestinal radiology of the newborn. Radiol Clin North Am. Jul 1996;34(4):819-44. [Medline].
• Olsen MM, Luck SR, Lloyd-Still J. The spectrum of meconium disease in infancy. J Pediatr Surg. Oct 1982;17(5):479-81. [Medline].
• Sokal MM, Koenigsberger MR, Rose JS. Neonatal hypermagnesemia and the meconium-plug syndrome. N Engl J Med. Apr 13 1972;286(15):823-5. [Medline].
• Steves M, Ricketts RR. Pneumoperitoneum in the newborn infant. Am Surg. Apr 1987;53(4):226-30. [Medline].
• Swischuk LE. Meconium plug syndrome: a cause of neonatal intestinal obstruction. Am J Roentgenol Radium Ther Nucl Med. Jun 1968;103(2):339-46. [Medline].
• Wood BP, Katzberg RW. Tween 80/diatrizoate enemas in bowel obstruction. AJR Am J Roentgenol. Apr 1978;130(4):747-50. [Medline].

Article Last Updated: Mar 8, 2005