Neonatal Intestinal Obstruction

36. Neonatal Intestinal Obstruction 645

each disease, particularly since more than one may be present. Because several of these diseases can be life-threatening or lead to lifelong disability if not treated promptly, the diagnostic evaluation should be rapid and follows a series of logical steps (see Algorithm 36.1).

Presentation

The initial presenting signs and symptoms of neonatal intestinal obstruction are varied and include frothy oral secretions, poor feeding, bilious or nonbilious vomiting, abdominal distention, and absent or delayed passage of meconium. The timing and nature of each presenting finding can provide very useful information about the etiology of the intestinal obstruction. Proximal intestinal obstructions, such as esophageal atresia or congenital causes of gastroduodenal obstruction, usually present within the first 24 to 48 hours of life. Distal obstructions, such as ileal or colorectal atresias, may present a few days after birth, while functional obstructions, such as Hirschsprung’s disease, may present as late as a few weeks to years after birth. Esophageal atresia presents with prominent oral and upper airway findings, including excessive frothy oropharyngeal secretions and repeated episodes of coughing, choking, or cyanosis that become apparent with attempts at feeding. Although poor feeding eventually is a feature of all causes of newborn intestinal obstruction, this finding may be delayed in patients with distal gastrointestinal tract or functional obstructions. The absence of bile in the emesis suggests that the level of obstruction is proximal to the ampulla of Vater. Bilious vomiting suggests a more distal obstruction and is an important finding, since about 25% of neonates with this finding eventually require abdominal surgery. In the case presented above, bilious emesis suggests an obstruction that is distal to the ampulla of Vater.

The presence and timing of onset of abdominal distention also can provide useful diagnostic information. Abdominal distention that is present at birth can result from antenatal intestinal obstruction and perforation usually due to volvulus, intestinal atresia, meconium ileus (meconium peritonitis), an intraperitoneal mass (choledochal cyst, mesenteric cyst, duplication cyst, hydrometrocolpos, or ovarian cyst), a retroperitoneal mass (hydronephrosis or renal mass), or ascites.

Although epigastric fullness may be observed, generalized abdominal distention usually does not occur in neonates with gastroduodenal obstruction. Abdominal distention, however, can develop in the first hours after birth in neonates with esophageal atresia due to air passing through a concomitant tracheoesophageal fistula, particularly if the infant is ventilated mechanically. Neonates with malrotation and midgut volvulus also may develop abdominal distention due to dilatation of a closed segment of bowel distal to the usual site of duodenal obstruction. Abdominal distention usually is delayed in those infants with more distal or functional obstructions and may appear 24 hours or later after birth.

A mechanical or functional intestinal obstruction should be considered when passage of the first meconium stool is delayed or absent or

646 R.S. Burd

Table 36.1. Presentation of potential cause of neonatal intestinal obstruction.

648 R.S. Burd

Table 36.1. Continued

CHD, congenital heart disease; TEF, tracheoesophageal fistula; UGI, upper gastrointestinal tract; VACTERL, vertebral, anal, cardiac, tracheoesophageal fistula, renal and limb anomalies.

* Contrast enema not usually needed for diagnosis or treatment.

only scant amounts of meconium are passed. The initial passage of meconium usually occurs within the first 24 hours of life, but it may be delayed in normal premature infants without intestinal obstruction. Delayed passage of meconium is a frequent finding in patients with distal intestinal obstruction and is observed in 90% of infants with Hirschsprung’s disease. The passage of meconium does not indicate that a complete intestinal obstruction is not present, since meconium formed in utero distal to an obstruction may be evacuated.

The maternal ultrasound can provide important clues about the possible etiology of intestinal obstruction and should be reviewed when a neonate presents with signs or symptoms suggesting an intestinal obstruction. Amniotic fluid is normally swallowed by the fetus and absorbed from the gastrointestinal tract. Obstruction will impair intestinal absorption, leading to accumulation of amniotic fluid or polyhydramnios. As the length of intestine available for absorption decreases, the degree of polyhydramnios increases. Polyhydramnios more likely is observed in the fetus with a proximal obstruction, such as esophageal atresia without tracheoesophageal fistula or duodenal atresia, and not those with a distal obstruction, such as distal ileal or colonic atresia (Fig. 36.1).

Maternal ultrasound examination can provide other useful information. The sonographic findings of a dilated proximal esophageal pouch and lack of fluid in the stomach suggests esophageal atresia. Prominent upper abdomen fluid collections representing the fluid-filled stomach and duodenum suggest obstruction at the level of the duodenum, as in the case presented. Dilated loops of bowel with increased peristalsis may be observed in a fetus with distal intestinal obstructions, while

36. Neonatal Intestinal Obstruction 649

Table 36.1. Continued

Algorithm 36.1. Algorithm to determine the etiology of neonatal intestinal obstruction. USG, ultrasonogram.

650 R.S. Burd

Figure 36.1. Polyhydramnios/microcolon.

dilated bowel associated with echogenic meconium has been observed in fetuses who later present with meconium ileus. Calcifications can form when the peritoneal cavity is exposed to meconium, and their presence suggests an antenatal intestinal perforation. Morphologic abnormalities suggesting a chromosomal defect also may have been observed, prompting amniocentesis and chromosomal testing. Chromosomal defects are found in about 5% of infants with esophageal atresia (most frequently trisomy 18 and 21) and about 30% of infants with duodenal atresia (most commonly trisomy 21).

Family and maternal history may provide additional insight into the cause of neonatal intestinal obstruction. Because a familial association has been reported for most causes, a family history of newborn or childhood surgery for intestinal obstruction should be sought, and the cause should be determined, if possible. Family members with disorders and anomalies outside of the gastrointestinal tract also may suggest an etiology of neonatal intestinal obstruction. For example, siblings of children with esophageal atresia may exhibit features of the VACTERL association (vertebral, anal, cardiac, tracheoesophageal fistula, renal and limb anomalies), or a family history of epidermolysis bullosa may be observed in neonates with pyloric atresia. Almost half of neonates with small left colon syndrome are infants of diabetic mothers.

Physical Examination

A complete examination is mandatory for all neonates with suspected intestinal obstruction. Particular attention should be focused on the abdominal examination, on the perineal inspection, and on identifying other anomalies, including features suggesting a chromosomal disorder. In the case presented at the beginning of the chapter, the presence of trisomy 21 provides indirect evidence supporting the diagnosis of duodenal atresia. The abdomen should be inspected for distention. Although difficult to observe in most cases, gastroduodenal or high jejunal obstruction may result in epigastric distention with a scaphoid lower abdomen, as described in the case presented. As discussed previously, mechanically ventilated neonates with esophageal atresia and

36. Neonatal Intestinal Obstruction 651

a tracheoesophageal fistula also may exhibit abdominal distention. More distal obstructions produce progressive generalized abdominal distention. The abdomen should be examined for tenderness and masses, and the inguinal region should be inspected for hernia.

Examination of the perineum is important to rule out an imperforate anus. The main features to evaluate are the general perineal appearance and anal position and patency. The anal canal normally is positioned about halfway between the coccyx and base of the scrotum in males or the vestibule in females, and it is within a perineal depression surrounded by slightly pigmented skin. Variations from this standard suggest that a variant of imperforate anus may be present. Neonates with a short distance from the distal colon to the perineum (low imperforate anus) may have a perineal depression with pigmentation without a patent anal canal. With observation during the first 24 hours of life, meconium eventually may pass through a rectoperineal fistula and be seen exiting on the perineum anterior to the normal anal position or at midline raphe of the scrotum or penis in males or vestibule in females. Because meconium may be seen exiting on the perineum in patients with low imperforate anus, the examination should be performed carefully, since a normal anal canal may be confused by inexperienced observers with a low imperforate anus with a rectoperineal fistula. Neonates with a long distance from the distal colon to the perineum (high imperforate anus) have more remarkable perineal findings, including the absence of an anal opening, absence of a perineal depression (“flat bottom”), and lack of pigmented skin.

Additional screening maneuvers may be used to supplement the physical examination. To screen for esophageal atresia, a tube gently is passed through the mouth into the esophagus. In term infants with esophageal atresia, passage of the tube usually stops at about 10 cm (Fig. 36.2). If the tube successfully passes into the stomach, the gastric

Pass 10-Fr tube through

mouth Tube 10 cm

Dilated esophageal pouch

Fistula

Trachea

Figure 36.2. Passage of an oral tube to determine esophageal patency. (Adapted from Hutson JM, Beasley SW. The Surgical Examination of Children: An Illustrated Guide. Oxford: Heinemann Medical Books, 1988. Copyright © 1998 Elsevier Ltd. With permission from Elsevier.)

652 R.S. Burd

contents are aspirated and measured. Aspiration of more than 10 to 15 cc of bilious material suggests an intestinal obstruction and provides further support for pursuing additional workup for the cause.

Diagnostic Studies

At this point in the workup, the range of possible diagnoses may have been narrowed substantially, and minimal additional diagnostic studies may be required. When the clinical history, presentation, and examination suggest esophageal atresia, posteroanterior and lateral chest radiographs should be obtained while gently pushing an orogastric tube against the blind ending esophagus. The presence of a prominent esophageal air pouch containing a curled tube is observed in most cases of esophageal atresia. The chest radiograph also should be examined for an abnormal cardiac silhouette that may suggest concomitant congenital cardiac disease and for infiltrates attributable to aspiration of oropharyngeal secretions.

Posteroanterior and lateral decubitus abdominal radiographs should be obtained in all neonates with suspected intestinal obstruction. In the case presented at the beginning of the chapter, the next step is to obtain plain abdominal radiographs. In patients with esophageal atresia, the presence of air in the stomach confirms the presence of a tracheoesophageal fistula. Thoracic, lumbar, or sacral vertebral anomalies, including hemivertebrae and absent vertebrae, can be observed in patients with the VACTERL association and may provide further corroboration of the diagnosis of esophageal atresia. Neonates with pyloric atresia have a prominent dilated stomach. A “double bubble” corresponding to a dilated stomach and duodenum is characteristic of a duodenal obstruction and likely would be observed in the case presented. When duodenal obstruction is suspected but insufficient air has been swallowed to reveal this finding, it is useful to place 50 cc of air via a nasogastric tube and immediately obtain a prone abdominal radiograph. When few dilated loops of bowel are observed beyond the duodenum, jejunal atresia is most likely. When multiple loops of dilated bowel are observed, particularly at more than 24 hours of life, a more distal obstruction is likely (Fig. 36.3). Abdominal films demonstrating dilated loops of intestine without air-fluid levels and a groundglass appearance, particularly in the right lower quadrant, produced by a mixture of air with thick meconium, is characteristic of meconium ileus. Scattered intraabdominal calcifications suggest antenatal perforation and possible obstruction related to meconium peritonitis. Among infants with imperforate anus, the frequency of vertebral anomalies, including lumbar hemivertebrae or absent vertebra and a deficient sacrum, increases as the distance from the perineum to the distal end of the rectum increases.

Plain radiographs together with the history and examination are sufficient to establish the likely diagnosis in most cases of proximal intestinal obstruction. Upper gastrointestinal contrast studies usually are not required before laparotomy. The main role of this type of study is to

36. Neonatal Intestinal Obstruction 653

A B C

Figure 36.3. Characteristic abdominal film findings with high intestinal obstruction at the level of the duodenum (A), high obstruction at the level of the jejunum (B), and low obstruction at and distal to the ileum (C). (Adapted from Hutson JM, Beasley SW. The Surgical Examination of Children: An Illustrated Guide. Oxford: Heinemann Medical Books, 1988. Copyright © 1998 Elsevier Ltd. With permission from Elsevier.)

establish the diagnosis when it remains in doubt. An important use of this study is to distinguish duodenal atresia from malrotation and midgut volvulus when surgery is delayed because of the need to evaluate and manage suspected cardiac or other anomalies. In all cases of midgut volvulus, exploratory laparotomy should proceed expeditiously. Repair of duodenal atresia, however, may be delayed when it is likely that additional medical management will improve the postoperative course. An upper gastrointestinal contrast study performed to rule out malrotation is mandatory before discharge in all neonates with unexplained bilious vomiting and abdominal distention, since the failure to recognize malrotation before volvulus ensues can lead to midgut necrosis. Neonates with abdominal distention at birth usually should undergo abdominal sonography in addition to plain abdominal radiographs to evaluate for the previously mentioned intraperitoneal and retroperitoneal lesions.

A contrast enema is the most useful test to distinguish the varied causes of intestinal obstruction distal to the jejunum. The passage of intraluminal contents produced by antenatal mucosal shedding determines the degree of intestinal dilatation at birth. For this reason, a normal-caliber colon is observed in patients with proximal intestinal obstructions, and a microcolon is observed with complete obstruction at a point more distal to the jejunum. When meconium ileus is suspected, the contrast study should be performed with Gastrografin, which serves to draw fluid into the intestinal lumen and dislodge thick meconium because of its hyperosmolarity. The contrast study typically demonstrates an empty microcolon with meconium plugs within a narrow-caliber terminal ileum. Meconium plug syndrome is suggested by an obstructing intraluminal mass (usually inspissated meconium) with proximal intestinal dilatation. In small left colon syndrome, a narrow-caliber left colon and dilated proximal colon are observed.

654 R.S. Burd

Colorectal atresia may be demonstrated by failure to reflux contrast proximally past a point of obstruction.

The diagnosis of Hirschsprung’s disease warrants special consideration. The barium enema in a typical case of Hirschsprung’s disease shows an undilated rectum or distal colon with flow into a dilated proximal colon. The transition from ganglionic to aganglionic intestine is observed in the rectosigmoid colon in 85% of patients. When performed in the infant’s first month of life, a barium enema may fail to demonstrate a clear transition zone. An abdominal film obtained 24 hours after the initial studies may show retention of barium in infants with Hirschsprung’s disease even in the absence of an apparent transition zone. Although radiographic studies may suggest Hirschsprung’s disease, a biopsy confirming aganglionic distal colon is needed before surgery. Sampling of the distal rectal mucosa and submucosa usually can be accomplished using a suction rectal device. Biopsy of the rectum probably is indicated in cases of meconium plug syndrome or small left colon syndrome before discharge, since these disorders can be confused with Hirschsprung’s disease by clinical presentation and radiographic studies.

Differential Diagnosis

A range of medical conditions may present with symptoms and signs similar to the principal causes of neonatal intestinal obstruction. Adynamic ileus due to sepsis is the most common mimicker of the surgical causes of intestinal obstruction and can be associated with poor feeding, bilious vomiting, and abdominal distention. Intracranial lesions, including hydrocephalus, subdural hemorrhage, and tumors, and renal diseases, such as genitourinary tract obstruction or renal agenesis, also may result in poor feeding and vomiting. Evaluation for these nonsurgical disorders should be pursued promptly, and treatment should be begun when a surgical cause of obstruction is not identified.

Principles of Treatment

The surgical treatment of neonatal intestinal obstruction varies depending on the site of obstruction. In general, atresias are resected and gastrointestinal continuity is restored by anastomosis. In some cases, definitive treatment may need to be delayed for weeks or months to allow for further growth, such as in cases with infants with long-gap esophageal atresia or high imperforate anus. Malrotation with midgut volvulus is treated by immediate laparotomy and performing the Ladd procedure: derotation of the volvulus, division of aberrant peritoneal bands crossing the duodenum (Ladd’s bands), straightening of the duodenum by mobilizing its retroperitoneal attachments, appendectomy, and placement of the cecum in the left lower quadrant. For meconium ileus and meconium plug syndrome, the contrast enema may be both diagnostic and therapeutic. When the obstruction fails to resolve

36. Neonatal Intestinal Obstruction 655

with therapeutic enemas, surgical evacuation of the intraluminal obstruction may be needed with these two diagnoses. Small left colon syndrome most often improves with nonoperative management and requires surgical intervention only when obstructive symptoms persist or complications such as perforation are observed. The main indication for operation in meconium peritonitis is obstruction or perforation. Surgical repair varies depending on the etiology of the antenatal perforation and on the findings at laparotomy. The principal treatment for Hirschsprung’s disease is resection of the aganglionic distal intestine and anorectal anastomosis using ganglionic intestine. Although a neonate with imperforate anus always undergoes repair, the method and timing of repair depend on the type of defect and presence of associated defects. The reader is referred to the selected readings for additional details of treatment of these disorders.

Summary

While the causes of newborn intestinal obstruction are diverse, a systematic approach can be used to differentiate the most common causes. The antenatal history, initial presentation, physical examination, and plain radiographs frequently can establish the diagnosis. The choice of additional diagnostic imaging, such as an upper or lower gastrointestinal series or ultrasound, should be based on the results of the initial workup. The basic principle of treating neonatal intestinal obstruction is to relieve the mechanical obstruction, whether the cause is due to luminal or extraluminal obstruction.

Selected Reading

Albanese CT. Pediatric surgery. In: Norton JA, Bollinger RR, Chang AE, et al., eds. Surgery: Basic Science and Clinical Evidence. New York: SpringerVerlag, 2001.

Oldham KT. Introduction to neonatal intestinal obstruction. In: Oldham KT, Colombani PM, Foglia RP, eds. Surgery of Infants and Children: Scientific Principles and Practice. Philadelphia: Lippincott-Raven, 1997.

Pena A. Atlas of Surgical Management of Anorectal Malformations. New York: Springer-Verlag, 1992.