Meconium plug + Meconium ileus. Current overview

Pediatric surgery

1. Meconium plug syndrome and meconium ileus GERALD LUMANYA, MD

2. Colonic obstruction caused by thick meconium. Meconium plug syndrome refers to a functional colonic obstruction in a newborn due to an obstructing meconium plug. It is usually transient and affects the left colon with meconium plugging the bowel distal to this segment. In this situation it is also termed the small left colon syndrome. = 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

3. Symptoms and Signs; Infants present in the first few days of life with failure to pass stools, abdominal distention, and vomiting. Thick, inspissated, rubbery meconium forms a cast of the colon, resulting in complete obstruction.

4. Pathology; More common among premature infants. Toxaemic mothers treated with Mg sulfate. May have a higher prevalence with maternal diabetes. Hirschsprung disease in ~15% May be associated with cystic fibrosis

5. Radiographic features; Radiograph = multiple dilated bowel loops = non specific finding. There may be a calibre change around the splenic flexure. No rectal gas. Barium can be used but has been replaced by water-soluble contrast agents in most practices.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.

6. Fluoroscopy: contrast enema small calibre to the left colon with multiple filling defects within due to retained meconium. Rectum is usually normal in size, unlike Hirschsprung disease. The use of high osmolar ionic contrast media for enema in a neonate or infant is controversial due the risks associated with fluid shift.   The enema can be both diagnostic as well as therapeutic and is usually accompanied by passage of meconium during or after the procedure. Contrast enema demonstrates the retained meconium as a filling defect or plug that produces a double-contrast effect.

7. Treatment and prognosis; Diagnosis of exclusion. Usually resolves with time. Initial nonsurgical management includes rectal stimulation and/or contrast enema. Treatment = Radiographic contrast enema = The water-soluble contrast enema can be therapeutic by separating the plug from the intestinal wall and expelling it. Occasionally, repeated enemas are required. Rarely, surgical decompression is required. Although most infants are healthy thereafter, diagnostic studies may be needed to rule out Hirschsprung disease or cystic fibrosis.

8. Differential diagnosis 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 calibre distal colon at the splenic flexure. Meconium ileus (right colon usually not dilated) = Unlike meconium ileus, in meconium plug syndrome; microcolon is not typically seen on x-ray with meconium plug syndrome. Long segment Hirschsprung disease (often has a reversed recto-sigmoid ratio) Ileal atresia (on contrast enema)

9. Meconium ileus;

10. Meconium is the material found in the intestine in a newborn. It consists of succus entericus that 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 term meconium in their name: Meconium ileus Meconium ileus–equivalent syndrome Meconium peritonitis, and Meconium plug syndrome.

11. 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. Unlike in the meconium plug syndrome, the meconium is abnormal in consistency. Epidemiology; Meconium ileus is more common in white populations and affects both sexes almost equally.

12. Pathology; Meconium found in the intestine of a neonate, consists of succus entericus (bile salts, bile acids, and debris from the intestinal mucosa) and is normally evacuated within 6 hours of birth (or earlier). Meconium ileus occurs when meconium becomes inspissated and obstructs the distal ileus. It is usually a manifestation of cystic fibrosis.  Approximately 20% of infants with cystic fibrosis present with meconium ileus at birth. Although it is usually understood as synonymous with cystic fibrosis until proven otherwise, it may also be seen with pancreatic atresia or stenosis of the pancreatic duct. Lack of trypsin enzyme…… in cystic fibrosis + pancreatic pathologies Only rarely does it occur without cystic fibrosis or pancreatic abnormality, and is thought to be related to gut immaturity (more favourable outcome).

13. Radiographic features; Plain radiograph; Non specific and may show dilated bowel loops proximal to the impaction. Classically, there is a paucity or absence of air-fluid levels and a "bubbly" appearance of the distended intestinal loops on radiographs.  Occasionally, has a mottled appearance on radiographs during the first 2 days of life.

14. Fluoroscopy Contrast enema will show a microcolon involving the entire large bowel and may show impacted meconium pellets particularly in the right colon or in the distal ileum.

15. Ultrasound Prenatal ultrasound findings associated with meconium ileus include echogenic bowel, which can be dilated and thick walled Polyhydramnios fetal ascites peritoneal wall calcifications intra-abdominal cysts

16. Treatment and prognosis; Water soluble contrast enema usually clears the impacted meconium. Complications Ileal atresia or stenosis ileal perforation resulting in meconium peritonitis volvulus with or without pseudocyst formation

17. Differential diagnosis; Total colonic Hirschsprung disease Meconium plug syndrome