Pradeep Nazarey and Thomas T. Sato
Gastrointestinal obstructions are categorized according to etiology as either congenital or acquired. These broad categories are not mutually exclusive. For example, congenital lesions of the intestine such as an enteric duplication or Meckel diverticulum may not cause obstruction until later in life. Congenital anatomic defects and acquired disorders of the intestine presenting in the first 30 days of life are characterized as neonatal intestinal obstruction.
CLINICAL FEATURES AND DIFFERENTIAL DIAGNOSIS
Neonatal Intestinal Obstruction
The anatomic conditions that present with neonatal intestinal obstruction and their diagnostic features are summarized in Table 389-1. Accurate diagnosis of neonatal intestinal obstruction relies on a thorough history, careful examination, and directed radiological studies.1 In a newborn infant, postprandial nonbilious emesis, or spitting up, is quite common and does not require urgent evaluation (see Chapter 394). In contrast, neonatal intestinal obstruction is usually characterized by feeding intolerance, abdominal distention, bilious emesis, and failure to pass meconium. Bilious emesis is most frequently a consequence of mechanical intestinal obstruction, and prompt evaluation is necessary to exclude life-threatening conditions such as necrotizing enterocolitis or volvulus. The history provides clues to the potential etiology of intestinal obstruction, but history and physical examination alone are generally not reliable for establishment of a diagnosis. For example, a 3-week-old infant with bilious emesis who has passed meconium and previously tolerated feeding is unlikely to have intestinal atresia as a cause of emesis and more likely to have intestinal malrotation with midgut volvulus. Infants with trisomy 21 are more likely to have congenital duodenal obstruction2 and Hirschsprung disease. Neonates with anomalies of vertebral, anorectal, cardiac, esophageal, renal, and limbs are more likely to have esophageal atresia and anorectal malformations as possible causes of intestinal obstruction (VACTERL association). Extremely low birthweight, premature infants are much more likely than term infants to develop necrotizing enterocolitis.
Given the widespread practice of prenatal ultrasound, several conditions such as proximal jejunal atresia and congenital duodenal obstruction may be diagnosed prior to delivery. The presence of polyhydramnios on prenatal ultrasound requires careful review for anatomic lesions causing obstruction of the developing foregut. The prenatal identification of anatomic intestinal obstruction allows for prospective education and counseling of parents. Presently, the prenatal ultrasound diagnosis for more distal intestinal conditions, and in particular, imperforate anus and Hirschsprung disease, is not reproducibly accurate and of limited clinical value.3
Nonanatomic conditions may also lead to clinically significant feeding intolerance and abdominal distention that may be difficult to distinguish from anatomic obstruction. In particular, neonatal sepsis is a common cause of feeding intolerance, emesis, and abdominal distention. A variety of disorders cause gastrointestinal pseudoobstruction that mimics mechanical obstruction, but these should be considered only after careful evaluation for causes of mechanical obstruction (see Chapter 407).
Table 389-1. Diagnostic Features of Anatomic Conditions Presenting as Neonatal Intestinal Obstruction
Table 389-2. Features of Selected Anatomic Conditions Presenting as Acquired Intestinal Obstruction
Intestinal Obstruction in the Older Infant or Child
Table 389-2 lists selected, more commonly encountered causes of intestinal obstruction occurring in older infants and children. Consideration of the age of the infant or child is useful because the more common causes present at characteristic ages. Additionally, there are symptoms and signs characteristic of childhood diseases causing anatomic intestinal obstruction. The constellation of a history, examination, and clinical knowledge allow a pediatrician to form a rational approach to the use of appropriate diagnostic tools and development of a therapeutic plan for intestinal obstruction.
Volvulus from intestinal malrotation is more common in the first week to year of life but may occur at any age. Prompt diagnosis of volvulus mandates a high degree of clinical suspicion in any infant or child with bilious emesis. Emergent diagnosis of volvulus by upper gastrointestinal contrast study in a hemo-dynamically stable child without peritonitis is critical for successful outcome. However, it is important to recognize that intestinal obstruction from volvulus may occur in the absence of bilious emesis as well.
Progressive, postprandial, and nonbilious “projectile” emesis in a 1- to 2-month-old male infant previously tolerant of feeding suggests a diagnosis of hypertrophic pyloric stenosis (see Chapter 398). Lethargy, feeding intolerance, emesis, and hematochezia (“currant-jelly” stools) in a 6-month to 3-year-old child is characteristic of intussusception. A previous history of neonatal necrotizing enterocolitis, inflammatory bowel disease, or abdominal operations in an older child with suspected gastrointestinal obstruction increases the probability of obstruction from either intestinal stricture or intra-abdominal adhesions.
Perforated appendicitis and Hirschsprung disease both may present with obstructive symptoms. Many children with perforated appendicitis present with a several-day history of unremitting abdominal pain associated with anorexia, occasional emesis, and reproducible tenderness in the right iliac fossa. While CT scan has become a popular diagnostic adjunct in the workup of appendicitis, it has probably not reduced the negative appendectomy rate in children, and there is significant exposure to ionizing radiation.4-6 Most children with Hirschsprung disease are diagnosed during infancy. Occasionally, a child presents with a long history of constipation, failure to thrive, explosive stool on digital rectal examination, and obstructive plain films (see Chapter 407). Additional diagnostic examination, including retrograde contrast enema, rectal biopsy, and anorectal manometry, may be useful in the diagnosis of Hirschsprung disease in older children.
DIAGNOSTIC EVALUATION
Neonatal Intestinal Obstruction
Diagnosis of neonatal intestinal obstruction may be made with careful physical examination and directed diagnostic imaging studies. Figure 389-1 outlines a diagnostic approach to suspected neonatal intestinal obstruction. Examination of oropharynx, abdomen, perineum, and anus may help guide the diagnostic evaluation. The presence, position, and patency of the anus should be confirmed. Incarceration of an indirect inguinal hernia is a common cause of neonatal intestinal obstruction and can be easily diagnosed by physical examination alone. Abdominal distention is commonly observed in distal bowel obstruction, whereas the abdomen may be scaphoid in proximal obstruction. For example, infants with ileal atresia or meconium ileus will present with abdominal distension; in contrast, infants with clinically evident trisomy 21, feeding intolerance, and a nondistended or scaphoid abdomen should be evaluated for more proximal intestinal obstruction, such as duodenal atresia.
FIGURE 389-1. Initial approach to neonatal intestinal obstruction.
The mainstay of diagnostic imaging for neonatal intestinal obstruction is a plain abdominal radiograph. Swallowed gas acts as an excellent contrast media for most neonates, and the degree of abdominal distention found on examination generally correlates with the amount of intestinal distention observed on abdominal films. For example, an infant with duodenal atresia would be expected to have a relatively scaphoid abdomen; a plain abdominal radiograph will typically demonstrate a gas-filled stomach and duodenum, creating a “double-bubble” sign, while the remainder of the unused intestine remains gasless (see Fig. 399-1). More distal intestinal obstruction will be characterized by greater abdominal distention and gas-filled loops of intestine proximal to the obstruction. The presence of pneumatosis intestinalis on plain film in a premature infant with abdominal distention, feeding intolerance, and hematochezia is diagnostic for necrotizing enterocolitis.
Many causes of neonatal intestinal obstruction that may be diagnosed by history, examination, and plain films alone. Contrast studies are particularly useful in suspected distal intestinal obstruction or for suspected intestinal malrotation. Retrograde contrast enema studies are helpful for determining the anatomic site of distal obstruction. Occasionally, contrast enemas are also therapeutic, for example, in the resolution of meconium plug syndrome or simple meconium ileus. The finding of a small, unused microcolon on contrast enema may be observed with more proximal intestinal atresia or complete obstruction. An upper gastrointestinal series is the diagnostic procedure of choice in suspected intestinal malrotation to determine the anatomic location of the duodenojejunal junction (ligament of Treitz) and to assess whether there is associated volvulus or mesenteric twisting of the small intestine.4
Intestinal Obstruction in the Older Infant or Child
Many of the principles outlined for neonates apply to intestinal obstruction in the older infant or child. The urgency of the evaluation and specific diagnostic approach usually depend on findings on physical examination, laboratory results, and plain films of the abdomen. Ultrasound examination of the pylorus is the diagnostic test of choice if the history suggests pyloric stenosis and the pylorus is not readily palpable; however, if the diagnosis is uncertain, a radiographic upper gastrointestinal contrast study is preferred. In a child with suspected intussusception and the absence of peritonitis, a fluoroscopic retrograde enema using either contrast or air is diagnostic and may be therapeutic in reducing the intussusception in approximately 60% to 80% of children (see Chapter 404).5 Additional diagnostic examination, including retrograde contrast enema, rectal biopsy, and anorectal manometry, may be useful in the diagnosis of Hirschsprung disease.
INITIAL MANAGEMENT OF INTESTINAL OBSTRUCTION
Initial management of any infant or child with suspected intestinal obstruction includes discontinuation of feeding, proximal decompression of the gastrointestinal tract with orogastric or nasogastric tube, intravenous fluid resuscitation to euvolemia, and addressing any coexisting medical or electrolyte issues. Diagnostic imaging may be accomplished either at the bedside or, if stable, in the radiology suite. Most causes of neonatal intestinal obstruction are readily diagnosed by history, examination, and plain abdominal films, with the remainder diagnosed by retrograde contrast enema. Diagnosis of intestinal obstruction in the older infant or child requires individualized adjunctive tests directed by the child’s age, symptoms, signs, and clinical suspicion.
Anatomic lesions causing intestinal obstruction require operative treatment with variable urgency. While malrotation with midgut volvulus requires emergent intervention to prevent bowel loss and death, obstruction due to intestinal atresia is generally repaired electively within the first few days of life. Prompt evaluation and early surgical consultation is warranted for any suspected anatomic intestinal obstruction. If expert pediatric subspecialty surgeons are readily available, their consultation is preferred. However, if such consultation is not readily available, emergent evaluation and consultation by a general surgeon is recommended because a delay in diagnosis of volvulus can have profound long-term outcomes.