Introduction
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).
Supine frontal view of the abdomen in a newborn with meconium plug syndrome demonstrates multiple dilated loops of bowel but no rectal gas.
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.
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.
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. 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.1,2,3
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.
Presentation
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.4 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 radiography, 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).
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.
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.
Differential Diagnoses
| Hirschsprung Disease | Meconium Ileus |
| Ileal Atresia | Midgut Volvulus |
| Intussusception, Child | Necrotizing Enterocolitis |
| Meckel Diverticulum | Small-Bowel Obstruction |
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
More on Meconium Plug Syndrome |
 Overview: Meconium Plug Syndrome |
| Imaging: Meconium Plug Syndrome |
| Follow-up: Meconium Plug Syndrome |
| Multimedia: Meconium Plug Syndrome |
| References |
| Further Reading |
| Next Page » |
References
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].
American Pediatric Surgical Association. Meconium Plug/Small Left Colon Syndrome. American Pediatric Surgical Association. Available at http://www.eapsa.org/parents/resources/plug.cfm. Accessed May 11, 2009.
Burge D, Drewett M. Meconium plug obstruction. Pediatr SurgInternational. 2004;20(2):108-10. [Medline].
American College of Radiology ACR Appropriateness Criteria. Vomiting in Infants up to 3 Months of Age. American College of Radiology. Available at http://www.acr.org/SecondaryMainMenuCategories/quality_safety/app_criteria/pdf/ExpertPanelonPediatricImaging/VomitinginInfantsupto3MonthsofAgeDoc11.aspx. Accessed May 12, 2009.
American College of Radiology. ACR Practic Guideline for the Performance of Pediatric Fluoroscopic Contrast Enema Examinations. American College of Radiology. Available at http://www.acr.org/SecondaryMainMenuCategories/quality_safety/guidelines/pediatric/pediatric_contrast_enema.aspx. Accessed May 12, 2009.
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].
Further Reading
Related eMedicine topics
Meconium Ileus
Bowel Obstruction in the Newborn
Small Left Colon Syndrome
Atresia, Stenosis, and Other Obstruction of the Colon
Keywords
meconium plug syndrome, functional immaturity of the colon, small left colon syndrome, Hirschsprung disease
