ileus in the newborn discussed later. Prevention of DIOS relies on conscientious pancreatic enzyme

replacement. Finally, children with CF are at risk to cholestasis secondary to obstruction of small

intrahepatic bile ducts. Chronic hepatic inflammation can occur with subsequent fibrosis and cirrhosis,

causing hepatic failure and portal hypertension in approximately 5% of CF patients.

Diagnostic Evaluation

In nearly all newborns with CF, the diagnosis is clinically apparent by the presence of meconium ileus, a

family history of CF in a sibling, or a positive newborn screening test. Laboratory confirmation of CFTR

gene dysfunction is performed in several ways. The historical standard for the detection of CF has been

analysis of the sodium chloride content of the sweat. The most commonly used and reliable technique

uses pilocarpine iontophoresis, with positive sweat test results showing sodium and chloride

concentrations exceeding 60 mEq/L.96 This test is less useful during the first 4 to 6 weeks of age

because normal neonates do not reliably conserve sodium chloride in sweat. Generally, abnormal CFTR

gene is documented by two elevated sweat chloride tests obtained on separate days. With the

emergence of genetic technology capable of providing accurate assessment of CFTR gene mutations, the

sweat test is now largely used to provide clinical confirmation of CFTR gene dysfunction along with

molecular diagnosis of CF.

Figure 103-23. A: Plain film radiograph of calcified pseudocyst in complicated meconium ileus. B: In utero ultrasound

demonstrating calcified pseudocyst.

Clinical Presentation

With routine prenatal ultrasound practices along with selected fetal DNA screening, the prenatal

diagnosis of CF or meconium ileus is feasible, potentially allowing for improved management of

anticipated clinical problems following delivery.97 Initial signs of meconium ileus include neonatal

bowel obstruction with abdominal distention, bilious emesis, and failure to pass meconium. On

examination, the neonate may have palpable loops of meconium-filled intestine with a texture on

palpation described as “doughy.” Similar to other causes of proximal neonatal intestinal obstruction,

rectal examination and evaluation of the meconium typically reveals clear white mucus or thick gray

meconium. In utero intestinal perforation with pseudocyst formation in complicated meconium ileus

may cause a palpable abdominal mass that is not particularly tender. On plain films or ultrasound,

calcification is visible in the pseudocyst wall. In contrast, volvulus or intestinal perforation secondary to

meconium ileus following birth generally results in diffuse peritonitis and sepsis. Intestinal atresia may

also be seen as a consequence of complicated meconium ileus.

Diagnosis

Abdominal plain films may be diagnostic in meconium ileus, demonstrating multiple, distended loops of

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bowel (Fig. 103-24A). Fluid- or meconium-filled loops of bowel mixed with gas give a characteristic

“soap bubble” or “ground glass” appearance. Classic air-fluid levels seen in other causes of intestinal

obstruction are not expected because of the tenacious, sticky intraluminal meconium. The presence of

intraperitoneal calcifications or a calcified cyst is consistent with prenatal intestinal perforation of

sterile meconium.

A contrast enema is useful in the evaluation and treatment of simple meconium ileus. This study

usually demonstrates an unused but functionally normal microcolon (Fig. 103-24B). Reflux of contrast

into the terminal ileum may confirm the presence of inspissated meconium pellets. In conjunction with a

family history and plain films, this finding is sufficient evidence to confirm the diagnosis of neonatal

meconium ileus. Upper gastrointestinal contrast studies are generally unnecessary and may complicate

further therapeutic efforts.

Treatment

Nonoperative. Nonoperative management of simple meconium ileus is achieved in about 60% to 70%

of newborns. Once the diagnosis of meconium ileus is confirmed, the initial treatment of choice is to

perform retrograde irrigation of the terminal ileum with one of several solutions designed to dissipate

the obstructing meconium. In the United States, several different enema techniques and a variety of

contrast media have been described, including normal saline, hyperosmolar contrast agents, and dilute

N-acetylcysteine. Initially, it was believed that using hyperosmolar contrast material was necessary to

create an osmolar gradient. The resultant influx of fluid into the intestinal lumen was thought to

solubilize the inspissated meconium. Recent data suggest that successful meconium clearance is not

necessarily related to the osmolality of the contrast agent; however, a significantly higher overall

success rate is reported with the use of Gastrografin (sodium and meglumine amidotrizoate) and the use

of other solubilizing agents such as Tween-80 and N-acetylcysteine.98 As long as clinical progress is

being made, sequential enemas may be required to disimpact the inspissated meconium from the

terminal ileum. In similar fashion, children and older patients presenting with DIOS are treated with

retrograde enemas until the obstruction resolves. The distinct advantage of this treatment approach is

the avoidance of general anesthesia and exploratory laparotomy. Reported complications with this

approach include rare intestinal perforation, intestinal mucosal injury, and persistent obstruction

resulting from meconium concretions.

Figure 103-24. A: Plain radiograph of neonate with meconium ileus. B: Contrast enema in an infant with meconium ileus

demonstrating an unused but intrinsically normal microcolon.

Operative. The major indications for operative intervention are either failure to clear the obstruction

by retrograde enema or complicated meconium ileus with cyst formation, volvulus, atresia, or

perforation. For simple meconium ileus with persistent obstruction despite contrast enemas, the

operative goals are meconium disimpaction from the ileum and evacuation of the remaining stool from

the small intestine. These steps can be accomplished by either milking the meconium downstream into

the colon or solubilizing the meconium by transmural needle instillation of irrigant. However,

enterotomy or enterostomy and direct irrigation of the bowel lumen are usually required to completely

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clear the inspissated meconium. Simple closure of the enterotomy is preferred, but segmental resection

may be required if marginal or compromised intestine is found. End-to-end anastomosis is the

appropriate reconstruction technique following segmental bowel resection. A temporary enterostomy

may be required, and several historical techniques have been described. Another surgical option is the

placement of a T-tube into the ileum for continued irrigation with dilute N-acetylcysteine. Following

clearance of meconium from the intestine and the return of bowel function, the T-tube can be safely and

simply removed.99

Complicated meconium ileus occurs in about one-third of patients. The surgical management of this

entity is individualized. Intestinal atresia is not uncommon in meconium ileus, and the entire length of

the intestine must be inspected for patency. When possible, resection of nonviable, stenotic, or

perforated intestine is performed with immediate reconstruction via primary anastomosis. Patency of

the downstream bowel must be confirmed to prevent anastomotic leak resulting from distal obstruction.

If the infant is critically ill or has diffuse peritonitis, a safe primary anastomosis may not be possible and

a diverting enterostomy is required. Stoma closure may be performed promptly after resolution of

peritonitis and inflammation.

Postoperative Care and Results. If the meconium has been successfully cleared without opening the

intestine, dilute N-acetylcysteine may be given through the nasogastric tube or by enema. Alternatively,

if a T-tube has been placed, dilute N-acetylcysteine or other irrigant can be used directly into the ileum.

These efforts are aimed at keeping the meconium soluble and preventing recurrent ileal obstruction.

Following return of bowel function, enteral feeding using breast milk or an elemental formula is started

along with oral pancreatic enzyme replacement. Vigilant pulmonary therapy is routine and includes

mucolytics and antibiotics when indicated. Nutritional assessment and support are essential in long-term

management.

Successful nonoperative management of simple meconium ileus historically was associated with a

more favorable outcome; however, the operative mortality rates of infants with meconium ileus have

improved dramatically over the past several decades, and current short-term operative survival rates of

70% to 100% are reported.100,101 Long-term survival following meconium ileus is generally determined

by the course of the underlying pulmonary disease. Contemporary management of CF has produced a

mean survival age that approaches 30 years in most centers. With the exception of the development of

portal hypertension in about 5% of patients, intestinal manifestations of the CF are treatable. Future

medical and surgical efforts to improve the long-term outcome in these patients include direct

replacement of the diseased pulmonary system by lung transplantation, manipulation of the epithelial

chloride transport defect with pharmacologic agents, and gene therapy directed at CFTR gene transfer

into respiratory epithelial cells.

Meconium Plug Syndrome

Meconium plug syndrome is characterized by functional obstruction of the colon or the rectum by a

meconium plug. It affects both normal and premature infants with immature gastrointestinal motility

and must be differentiated from other causes of neonatal intestinal obstruction. Unlike meconium ileus,

in meconium plug syndrome the colon is of normal caliber and the meconium is not inspissated. The

infant’s symptoms within the first few days of life are abdominal distention and bilious emesis.

Spontaneous passage of meconium is often absent. On examination, the infant is normal with a patent

anus and a distended abdomen. Digital rectal examination may deliver the meconium plug. Plain films

of the abdomen demonstrate dilated loops of bowel consistent with distal bowel obstruction. The

diagnosis is confirmed by contrast enema, which is also therapeutic in helping the meconium plug pass.

The meconium plug is followed by bile-stained meconium of normal consistency. Importantly, although

the vast majority of these infants are normal, a few have Hirschsprung disease or CF. Therefore, infants

presenting with meconium plug syndrome should undergo routine rectal suction biopsy and have CF

screening tests performed.

Malrotation

Embryology

Normal midgut fixation requires sequential growth, elongation, and rotation of the intestine beginning

as early as week 5 of gestation as illustrated in Figure 103-25. Three distinct events occur during normal

midgut fixation. The first stage involves herniation of the primary midgut loop into the base of the

umbilical cord, where it remains until week 10 of gestation. The axis of the midgut loop is the superior

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mesenteric artery (SMA), with the omphalomesenteric duct at the apex of the midgut loop. The midgut

loop rotates 180° counterclockwise so that the proximal half passes posterior to the SMA. The proximal

portion gives rise to the proximal duodenum, which lies to the right of midline. A portion of this

segment becomes the third and fourth portions of the duodenum. The distal duodenum is normally fixed

to the left of the aorta at the ligament of Treitz, having rotated 270 degrees counterclockwise from its

original position. The jejunoileal segment undergoes dramatic elongation, forming about six primary

intestinal loops. The distal midgut loop gives rise to the cecum and the right colon, which also

undergoes growth and elongation with concomitant rotation 270 degrees counterclockwise. Therefore,

the cecum is initially positioned to the left, then anterior, and finally to the right of the SMA before

reaching its final location.102

Reduction of the extracoelomic gut is the second stage of midgut development and fixation, occurring

between weeks 10 and 12 of gestation. By this time, the duodenojejunal junction has passed posterior to

the SMA and the midgut has rotated 180 degrees counterclockwise; however, the small intestine

initially remains to the right side of midline, and the cecum and ascending colon are anterior to the SMA

after return of the gut into the abdomen. Many common abnormalities of intestinal fixation occur as a

result of arrested development during this 2-week period.

Figure 103-25. Normal midgut rotation is shown with appropriate positioning of the stomach, duodenum, small intestine, and

cecum from the fifth gestational week (A) through completion by the 12th week (E).

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Figure 103-26. Normal oblique fixation of the midgut mesentery at the ligament of Treitz and in the right lower quadrant. The

blue portions of the colon are extraperitoneal.

The final stage of midgut development is fixation of the intestine to the posterior body wall,

occurring after week 12 of gestation. Cecal descent occurs at this time. Normal points of fixation include

the cecum in the right iliac fossa and the duodenojejunal junction at the ligament of Treitz just to the

left of the aorta and anterior to the left renal vein (Fig. 103-26). Therefore, the normal intestinal

mesentery is fixed with a broad base extending from the ligament of Treitz to the cecum. This broadbased mesenteric attachment prevents volvulus from occurring. In contrast, in disorders of intestinal

rotation, the base of the mesentery is neither fixed nor broad, placing the entire midgut at risk for

volvulus.

Anatomy

The normal sequence required for intestinal positioning and fixation can be interrupted at any

developmental stage, producing a diverse spectrum of rotational abnormalities. Some neonatal surgical

conditions are nearly always associated with abnormal intestinal rotation or fixation resulting from

displacement of the midgut from the abdominal cavity during embryologic development. These

anomalies include omphalocele, gastroschisis, and congenital diaphragmatic hernia. The term

malrotation has been applied generically to describe disorders of intestinal rotation and fixation,

although specific definitions of the more commonly encountered lesions are provided in the following

sections.

Nonrotation. This common anomaly is characterized by inadequate counterclockwise rotation of the

midgut around the SMA. Instead of the normal 270-degree arc, rotation is either absent or arrested

before exceeding 90 degrees (Fig. 103-27). The small intestine resides on the right side of midline, the

colon resides on the left, and the cecum is anterior and near the midline. The duodenojejunal junction is

to the right of midline and more caudal and anterior in position. Nonrotation carries a significant

clinical risk of midgut volvulus because the mesenteric vascular pedicle is narrow. Duodenal obstruction

also may occur as a result of peritoneal attachments known as Ladd bands. These peritoneal bands fix

the cecum to the posterior body wall by passing anterior and lateral to the distal duodenum.

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Figure 103-27. Nonrotation. The proximal segment of the small intestine resides on the right side of the abdomen, and the distal

segment (colon) is on the left. Neither has rotated normally.

Mixed or Incomplete Rotation. This rotational abnormality is characterized by arrest of the normal

rotation at or near 180 degrees rather than the normal 270 degrees (Fig. 103-28). Instead of rotating

posterior and to the left of the SMA, incomplete or arrested rotation of the prearterial segment leaves

the duodenojejunal junction to the right of midline. The cecum also does not complete its

counterclockwise passage anterior to the SMA; it usually resides in the upper abdomen just to the left of

the SMA. Similar to nonrotation, fixation of the cecum to the posterior body wall by Ladd bands places

the duodenum at risk for compression or obstruction. In addition, the SMA pedicle is narrow and places

the midgut at risk for volvulus.

Figure 103-28. Incomplete rotation. The proximal segment has failed to rotate and is on the right. The distal segment has rotated

to reside anterior to the duodenum so that cecal bands to the posterior abdominal wall may compress and obstruct the duodenum.

Mesocolic Hernias. Mesocolic hernias are rare but important anomalies characterized by failure of

fixation of either the right or left mesocolon to the posterior body wall. Small bowel can become

entrapped in the resulting potential cavities on either side of the abdomen. A right-sided mesocolic

defect (paraduodenal hernia) is associated with nonrotation of the proximal midgut segment. Small

bowel entrapment posterior to the right colon and cecum may occur. Similar entrapment of small bowel

may occur from an incompletely fixed left mesocolon but is associated with normal colonic and cecal

position. Entrapped small bowel in a left mesocolic hernia usually is contained within a hernia sac with

the neck composed of the inferior mesenteric vein and peritoneal bands extending to the posterior body

wall. Both left and right mesocolic hernias carry the potential risks of obstruction, incarceration, and

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strangulation of bowel.

Clinical Presentation

Abnormalities of intestinal rotation are estimated to be present in about 1% of the population. Most

persons with intestinal rotational anomalies are clinically asymptomatic; therefore, some children are

found to have malrotation incidentally by upper gastrointestinal contrast studies conducted for other

reasons. Symptomatic malrotation is usually encountered clinically in the setting of duodenal

obstruction or midgut volvulus. Duodenal obstruction may occur as a result of Ladd bands fixing the

abnormally positioned cecum to the posterior body wall. These peritoneal bands cause duodenal

obstruction by extrinsic compression. Children with symptomatic duodenal obstruction typically present

with bilious emesis and distention of the stomach and the proximal duodenum. Similar to proximal

neonatal intestinal obstruction, newborn infants may present with bilious emesis without abdominal

distention secondary to partial duodenal obstruction. A paucity of small bowel gas may be seen on plain

abdominal films.

A potential consequence of intestinal malrotation is midgut volvulus. Midgut volvulus should be

considered in any infant or child presenting with bilious emesis. The clinical outcome of midgut

volvulus is time dependent, which is the fundamental reason that signs and symptoms of acute intestinal

obstruction in an infant or a child must be pursued aggressively until a clear diagnosis is made. The

devastating, life-threatening consequence of midgut volvulus is vascular insufficiency, gut ischemia,

and, if untreated, infarction of the entire bowel supplied by the SMA. The initial symptoms may be

subtle and limited to feeding intolerance, abdominal pain, and irritability, followed by bilious emesis.

Guaiac-positive stool from mucosal injury is a common early finding. Late findings include progressive

abdominal distention, hematemesis, and hypotension. Metabolic acidosis, coagulopathy, and shock may

become prominent clinical features. If unrecognized or left untreated, transmural necrosis of the entire

midgut will occur.

At least 50% to 75% of intestinal rotational abnormalities are discovered within the first week to

month of life, and about 90% occur in children younger than 1 year.103,104 Symptomatic infants and

children require emergent surgical exploration and correction. Older children and adults initially may

present with acute volvulus but also may have a history of vague symptoms of episodic intestinal

obstruction and chronic abdominal pain. It is essential to recognize that, regardless of age or chronicity

of symptoms, midgut volvulus from malrotation occurs in a completely unpredictable manner.105

Therefore, it is generally recommended that patients with incidentally discovered, asymptomatic

malrotation undergo operative management to reduce the risk of volvulus.

Diagnosis

As with other forms of neonatal intestinal obstruction, the diagnostic evaluation begins with a plain

abdominal radiograph. Classic findings with malrotation include gastric and proximal duodenal

distention with a paucity or absence of distal small bowel gas (Fig. 103-29A). The plain film alone may

not differentiate malrotation from duodenal atresia or stenosis. In most cases of suspected duodenal

obstruction with concern of malrotation, an upper gastrointestinal series is a conclusive imaging study

(Fig. 103-29B). Malrotation with volvulus typically produces incomplete duodenal obstruction with a

corkscrew or coiled appearance in the distal duodenum. Extrinsic compression of the duodenum by Ladd

bands may be visible on contrast study. Duodenal atresia and stenosis may occur anywhere within the

duodenum but tends to be more proximal. Complete absence of small bowel gas is typical of duodenal

atresia, whereas diminished but discernible distal gas is characteristic of duodenal stenosis or

malrotation with volvulus.

Other radiographic findings in malrotation include incorrect position of the duodenojejunal junction,

particularly to the right of midline. Failure to achieve normal cephalad and posterior fixation is typical

in malrotation and may be best appreciated on lateral views. The small bowel resides in the right side of

the abdomen, the colon, and cecum on the left (Fig. 103-29C). In a symptomatic infant or child,

radiographic evidence of malrotation alone is enough to warrant emergent exploration. A contrast

enema is helpful in the evaluation of neonatal intestinal obstruction, although it may not be the initial

study of choice if malrotation is suspected. The classic finding on contrast enema for malrotation is cecal

malposition, usually in the left abdomen or near the midline. Finally, the relative position of the SMA to

the superior mesenteric vein may be assessed by ultrasound. Normally, the superior mesenteric vein is

to the right of the SMA on transverse sonograms. Abnormal position of the superior mesenteric vein

either ventral or to the left of the SMA is associated with malrotation.106

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