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Case Based Pediatrics For Medical Students and ResidentsDepartment of Pediatrics, University of Hawaii John A. Burns School of Medicine

Chapter X.9. Intestinal Atresias, Duplications and

MicrocolonTimur M. Roytman

February 2003

This is a newborn infant male born to a 25 year old G1P1A0 mother at 36 weeks

gestation via vaginal delivery. Mother received appropriate antenatal care throughout herpregnancy. The pregnancy was remarkable for polyhydramnios. The baby looked normal

at birth, however, at 1 day of age (day 2 of life), the infant begins to vomit bilious

material and appears jaundiced. Physical exam of the infant is remarkable only for

jaundice. A pertinent negative finding is the absence of a distended abdomen.A plain abdominal radiograph reveals a "double-bubble sign." His symptoms along with

the radiographic findings are suggestive of duodenal atresia. Initial treatment consists of

insertion of a nasogastric tube along with IV fluid replacement. An echocardiogram and

radiographic studies of the spine are performed to evaluate for other congenitalabnormalities. No other abnormalities are found and the patient is referred to surgery for

surgical evaluation and treatment.

Atresia, by definition, is the absence of an opening of a hollow visceral organ, resulting

in a complete obstruction (1). There are several types of atresias: esophageal atresia with

and without tracheoesophageal fistula, duodenal atresia, jejunal atresia and ileal atresia.Esophageal Atresia

Esophageal atresia (EA) occurs in 1/3,000-4,500 live births. Approximately one third of

infants with esophageal atresia are born prematurely (2). EA occurs as a result of the

failure of the primitive foregut to recanalize (3). An overwhelming majority of EAs are

accompanied by a fistula between the trachea and the distal esophagus. Thesetracheoesophageal fistulas (TEF) occur due to the failure of the lung bud to separate from

the foregut (3). An EA with a TEF can be distinguished from an EA without a TEF by thepresence of a gas in bowel. EA without TEF does not permit any passage of gas into the

bowel, but a TEF permits a pathway from the trachea to the distal esophagus and the

stomach.In rare instances, infants have a tracheoesophageal fistula without an esophageal atresia.

This is known as an H-type TEF (the connection between the esophagus and trachea

looks like an H). It usually presents with recurrent coughing along with aspiration

pneumonia. H-type TEF is commonly diagnosed in childhood or sometimes adulthood byesophageal instillation of methylene blue followed by bronchoscopy to look for dye

entering the trachea. Once identified, H-type TEFs require surgical correction.Esophageal atresias should be suspected if any one of the following is present: maternal

polyhydramnios (from inability of the fetus to swallow and absorb amniotic fluid);excessive oral secretions in the newborn; cyanosis, choking, regurgitation or coughing

occurring with the first feeding. If suspected, the diagnosis of an esophageal atresia can

be confirmed by inability to pass the nasogastric tube into the stomach and by a chestradiograph, which shows the coiling of the tube in the proximal esophageal pouch.

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derangements. Prior to surgical correction of duodenal atresia, an evaluation for

associated life-threatening congenital abnormalities should be performed. Duodenal

atresia is usually repaired by duodenoduodenostomy which bypasses the obstruction.Long term prognosis is determined by the patient's associated congenital abnormalities

(5).

Unlike esophageal and duodenal atresias, jejunal and ileal atresias are not caused byfailure to recanalize the intestinal lumen. Instead it is thought that their etiology is anintrauterine ischemic event of the bowel such as intussusception, volvulus, malrotation,

arterial occlusion, internal hernia or strangulation due to an abdominal wall defect such as

an omphalocele or in gastroschisis (5). This may result in a focal infarction resulting in anatretic portion of bowel. These atresias are also associated with meconium ileus which

occurs in newborns with cystic fibrosis. Similarly to other atresias, a quarter of patients

with jejunoileal atresia have a history of polyhydramnios (4).

Jejunal atresias are more common than ileal atresias (5). Isolated jejunal atresia has ahigher prevalence in twins and infants with low birth weight. Also, patients with isolated

jejunal atresia are more likely to have other unrelated congenital abnormalities (3). There

are four different types of jejunal and ileal atresias. Type I is mucosal obstruction that iscaused by an epithelial intraluminal membrane, but the proximal and distal ends of the

bowel are intact. In type I, which accounts for 20% of jejunal and ileal atresias, the bowel

wall and the mesentery of the intraluminal membrane are both intact. Type II is

characterized by the connection of the blind ends of the bowel by a fibrous cord andconstitutes 35% of intestinal atresias. Type III is subdivided into Type IIIa and IIIb. In

type IIIa, the blind ends of the bowel are completely separated by a mesenteric defect that

is V-shaped. It accounts for 35% of all atresias. Type IIIb, also known as "apple peel" or"Christmas tree" deformity, describes a loss of the normal blood supply to the distal

bowel and is associated with a significant mesenteric defect. It appears that there is a

genetic predisposition to Type IIIb (3,5). Type IV comprises 5% of all bowel atresias and

is characterized by multiple bowel atresias which resemble a string of sausages (4,5).Jejunoileal atresia can be diagnosed by prenatal ultrasound. The majority of newborns

with jejunoileal atresia exhibit clinical symptoms during the first day of life. Symptoms

are characterized by abdominal distention, bilious emesis or bilious gastric aspirate.Other symptoms include jaundice and failure to pass meconium. However, the passage of

meconium does not rule out intestinal atresia because a third of infants with jejunoileal

atresia will pass meconium prior to development of obstructive symptoms (3). Air-fluidlevels or peritoneal calcifications may be seen on plain abdominal radiographs. In the

differential of jejunoileal atresia are: Hirschsprung's disease, meconium ileus and

meconium plug. These diseases can be distinguished from jejunoileal atresia by contrast

studies of the upper and lower bowel which will pinpoint the level of obstruction (4).Definitive treatment requires resection of the atretic portion of the bowel with an end-to-

end anastomosis. Postoperatively, nutritional support is provided by parenteral

hyperalimentation until bowel function is restored (5). Prognosis is determined by the

length and function of the remaining bowel. Long-term complications includemalabsorption, feeding intolerance and bacterial overgrowth (3). Multiple atretic

segments may result in a short gut syndrome with insufficient or marginal total bowel

nutrition absorptive capacity.Intestinal Duplications

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Intestinal duplications are rare congenital abnormalities that consist of tubular or

spherical structures with gastrointestinal epithelium. These structures are attached to the

intestine and are located on the mesenteric border. The lumen of the normal intestineusually is not continuous with that of the duplication. Usually the duplication and the

normal intestine share vascular supply and a fraction of the muscular layer. There are

three categories of intestinal duplications. The first category is localized duplications.These duplications are most common in the jejunum and the ileum, although they mayoccur in other areas of the GI tract. Localized duplications are usually tubular or cystic.

Their exact etiology is unknown, although it is thought that defects in the recanalization

of the intestinal lumen after the solid stage of embryologic development, may contributeto the development of these duplications. The second category is duplications that are

associated with spinal cord or vertebral abnormalities such as hemivertebra or anterior

spina bifida. A possible cause of these duplications may be the separation of the

notochord during embryologic development. The last category is duplication of the colon.This duplication is commonly associated with abnormalities of the genitals or the urinary

tract. In general, duplications tend to be symptomatic and present during the first year of

life as a palpable mass or they may cause intestinal obstruction, volvulus orintussusception. Other symptoms include vomiting, abdominal pain, constipation,

diarrhea and acute GI hemorrhage. Duplications may be diagnosed with ultrasound, MRI

or CT of the abdomen. Undiagnosed intestinal duplications may undergo malignant

transformation. Definitive treatment includes complete resection of the duplication withan end-to-end anastomosis (3,7).

Microcolon

Microcolon is a rare congenital cause of intestinal obstruction. The microcolon generallyresults from intrauterine underutilization of the colon, which would include conditions in

which intestinal contents are not passed into the colon during gestation. This would

include ileal atresia, but this would not include duodenal atresia, because duodenal atresia

is in the proximal small bowel, such that the middle and distal small bowel continue toshed epithelial tissue (meconium precursors) distally into the colon during gestation.

Microcolon is also part of a megacystis-microcolon-intestinal hypoperistalsis syndrome

(MMIHS). MMIHS is a genetic disorder with an autosomal recessive pattern ofinheritance. This syndrome affects primarily female infants. Infants with MMIHS present

with bilious vomiting, delayed passage of meconium and abdominal distention. Dilation

of the bladder and the small bowel causes abdominal distention. Physical exam revealsthin musculature of the anterior abdominal wall. Diagnosis is confirmed by ultrasound,

upper GI contrast study and an enema which shows a nonobstructed microcolon (7,8).

This syndrome is usually lethal within the first year of life (9).

Questions

1. The double-bubble sign on plain abdominal radiograph is diagnostic of what kind of

atresia?Duodenal atresia.

2. How could you distinguish between an esophageal atresia with tracheoesophagealfistula (TE) from an esophageal atresia without TE fistula?Esophageal atresia with tracheoesophageal fistula results in a gas within the bowel,

esophageal atresia without tracheoesophageal fistula does not.

3. What other abnormalities are associated with an esophageal atresia?

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VACTER association; includes vertebral defects, anal atresia, congenital cardiac anomalies,

tracheoesophageal fistula with esophageal atresia, radial upper limb hypoplasia and renal

defects.

4. How does an esophageal or duodenal atresia differ etiologically from a jejunal or anileal atresia?Esophageal or duodenal atresias result from failure of the lumen to recanalize. A jejunal or

ileal atresia results from an intrauterine ischemic event.

5. What makes undiagnosed intestinal duplication potentially life threatening?Undiagnosed intestinal duplications may cause a bowel obstruction or may undergo malignant

transformations in adults.