**2. Detailed overview of meconium ileus**

An overview of meconium ileus in terms of etiology, pathophysiology, clinical features, investigations, and treatment will now be undertaken.

#### **2.1 Etiology**

Up to 20% of babies with cystic fibrosis are born with meconium ileus, and almost all babies with meconium ileus have cystic fibrosis [15, 16]. Cystic fibrosis is caused by gene mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) encoding gene [17–19]. The loss of CFTR-mediated Cl– and/or HCO3– transport by the intestinal epithelium and/or from pancreatic dysfunction is postulated as the pathogenesis of meconium ileus [20–24]. Cystic fibrosis is characterized by the triad of chronic obstruction and infection of the respiratory tract, exocrine pancreatic insufficiency, and elevated sweat chloride levels.

The pathogenesis of meconium ileus is due to hyperviscous mucus secreted by abnormal intestinal glands, abnormal concentrating processes in the proximal small intestine, and pancreatic enzyme insufficiency.

The histology is characterized by the presence of distended goblet cells in the intestinal mucosa.

#### **2.2 Pathophysiology**

The simple form of meconium ileus is characterized by thickened sticky meconium obstructing the ileum with consequent proximal dilatation, bowel wall thickening, and congestion. Immediately beyond the level of the obstructing inspissated meconium in the terminal ileum, there may be a few separate gray-white globular meconium pellets. Further distally, the colon is narrow and empty—the microcolon.

The complicated form may result in volvulus, atresia, necrosis, perforation, meconium peritonitis, and pseudocyst formation. These complications may manifest as incidental findings on abdominal radiographs or with clinical features suggestive of bowel obstruction caused by reactive fibro-adhesive bands due to the meconium in the peritoneal cavity or as clinical features of peritonitis. If a neonate at birth manifests features of peritonitis, it is likely due to meconium peritonitis

**73**

*Meconium Ileus*

rim calcification [26].

**2.3 Clinical features**

ness, and ascites.

**2.4 Investigations**

perforation [4].

*DOI: http://dx.doi.org/10.5772/intechopen.85548*

that results in stenosis or atresia [4].

should be monitored weekly in such infants.

secondary to meconium ileus bowel perforation. This may also result in intestinal atresia, intraperitoneal calcifications, or ascites [25]. Meconium pseudocyst is formed when the extruded meconium becomes walled off; it is a cystic mass with

In utero, about 50% of meconium ileus cases may be complicated by intestinal perforation, meconium peritonitis, volvulus, and ischemic necrosis of the bowel

Meconium ileus patients are at risk for developing cholestasis, especially if they

At birth, the neonate may be apparently normal. However, with progression of time and feeding, the infant develops abdominal distention, bilious vomiting, and failure to pass meconium. Sometimes thickened distended bowel loops are observed through the abdominal wall filled with rubbery meconium which when palpated feel characteristically doughy [3]. Bowel sounds tend to be hypoactive, and digital rectal examination may be followed by passage of pale mucosal plugs. Meconium pellets might be palpated in the scrotum of some infants who had in utero bowel perforation. In cases complicated by peritonitis or when postnatal perforation has occurred, the infant presents with respiratory distress, marked abdominal distention with abdominal erythema, significant abdominal tender-

Cases of meconium ileus are usually evaluated with abdominal radiograph in

A contrast enema examination is useful in confirming the diagnosis of meconium ileus in which microcolon is seen; this differentiates it from meconium plug syndrome in which a normal or dilated colon is seen [25]. The microcolon, which represents the underused colon, could also be seen in other congenital conditions causing complete intrauterine obstruction of the distal small bowel such as ileal atresia; however for cases of meconium ileus, the presence of meconium pellets distending the distal ileum is usually identified when the contrast refluxes into the

Water-soluble agents are typically used in contrast evaluation of meconium ileus, and several of such contrast agents have been used. The hyperosmolar meglumine (GastrografinRx) diluted at ratio 1:3 to water used to be the mainstay, but some radiologists have stopped using it because of the occurrence of deaths

Plain abdominal radiographs are routinely the first imaging done for cases of meconium ileus. They show numerous air-filled loops of bowel on the supine view with characteristic absence of air-fluid levels on the upright view due to the tenacious meconium and the abnormal mucous-gland secretion [5]. Although the absence of air-fluid levels strongly suggests meconium ileus, the presence of airfluid levels does not exclude it as it may occasionally be demonstrated in some cases. In some cases of meconium ileus, the admixture of meconium and bowel gas gives a soap-bubble appearance usually in the right lower quadrant (Neuhauser sign). The presence of calcification, free air, or multiple air-fluid levels suggests intestinal

which meconium might have a mottled appearance or be invisible [27].

small bowel, and the diagnosis is confirmed (**Figure 1**).

are on total parenteral nutrition. As such, alkaline phosphatase (ALP), alanine aminotransferase (ALT), aspartate aminotransferase (AST), and bilirubin levels

#### *Meconium Ileus DOI: http://dx.doi.org/10.5772/intechopen.85548*

secondary to meconium ileus bowel perforation. This may also result in intestinal atresia, intraperitoneal calcifications, or ascites [25]. Meconium pseudocyst is formed when the extruded meconium becomes walled off; it is a cystic mass with rim calcification [26].

In utero, about 50% of meconium ileus cases may be complicated by intestinal perforation, meconium peritonitis, volvulus, and ischemic necrosis of the bowel that results in stenosis or atresia [4].

Meconium ileus patients are at risk for developing cholestasis, especially if they are on total parenteral nutrition. As such, alkaline phosphatase (ALP), alanine aminotransferase (ALT), aspartate aminotransferase (AST), and bilirubin levels should be monitored weekly in such infants.
