Eunice Y. Huang
• Intussusception is the commonest cause of intestinal obstruction in children less than 3 years of age.
• Pneumatic or hydrostatic contrast medium enema is the diagnostic imaging procedure of choice for its reduction.
• Although the diagnosis is typically made with ultrasound, the emergency physician can proceed directly to the enema in clinically obvious cases.
• The child can be discharged home from the emergency department following the reduction of the intussusception after a short period of observation.
ETIOLOGY AND PATHOGENESIS
Intussusception is the invagination of a segment of intestine into the adjacent distal bowel. The invaginating segment is referred to as the intussusceptum and the distal bowel is the intussuscipiens. It is the most common cause of intestinal obstruction in infants and young children 6 to 36 months of age and the most common abdominal emergency in early childhood. More than 50% of affected children present before 1 year of age, and 80% of cases occur before 2 years. Intussusception is rare before 9 weeks of age, but the incidence increases until about 6 to 7 months of age, where it occurs in about 60 per 100,000 infants. By 1 year of age, the rate is about half of this. Rates are higher among African American and Hispanic infants than among Caucasians. There is a 3:2 male predominance.
Ninety percent of cases are idiopathic, and the remaining 10% are associated with an underlying cause that produces a lead point.1 Cases associated with pathologic causes producing a lead point include Meckel’s diverticulum, intestinal polyps, intestinal lymphoma, duplication cysts, Henoch–Schänlein purpura, cystic fibrosis, and benign hamartomas and are much more common in children older than 5 years of age. Intussusception in children younger than 3 months is uncommon but is also highly associated with a pathologic lead point.2 After the age of 3 years, the incidence of a pathologic lead point increases with Meckel’s diverticulum, lymphoma, and polyps as the three most commonly found.1 Patients with Burkett’s lymphoma as a lead point usually present at an older age (median 10 years) and are almost always ileocolic in location.3 Patients with intussusception caused by pathologic lead points generally fail radiographic reduction and require surgical reduction with resection of the underlying pathology.
In idiopathic cases, the presumed pathogenesis is a preceding viral infection that produces lymphoid hyperplasia in Peyer’s patches in the terminal ileum. A strong association with preceding adenovirus infection has been reported.4–6 The lymphoid hyperplasia is thought to act as the lead point. Ileocolic intussusception is most common, but ileoileocolic, jejunoileal, or colocolic intussusception may also occur.
When the intussusceptum enters the intussuscipiens, its attached mesentery, blood supply, and lymphatic drainage are compromised. The invaginated portion of the intestine develops edema and venous congestion resulting in tissue ischemia. Luminal obstruction also occurs as a result of the intestinal invagination, which increases wall tension and worsens tissue compromise. If not recognized and treated, it may proceed on to ischemia, bowel necrosis, perforation, and peritonitis.1
HISTORY AND PHYSICAL EXAMINATION
Children classically present with sudden onset of intermittent, severe, crampy abdominal pain, inconsolable crying, and vomiting which may become bilious. Initially, the child may appear comfortable and act well between episodes, but if the intussusception is not reduced, dehydration and lethargy develops. Irritability interspersed with periods of quiet resting should prompt one to consider intussusception. In infants younger than 1 year of age, lethargy may predominate early in the symptom course and may be associated with miosis and pallor.7,8 This altered sensorium with intussusception may be seen after prolonged symptoms or during the early stages. Mental status changes may be accompanied by pronounced pallor, mimicking shock. A transient response to naloxone was documented in one case.8 In children younger than 12 months, the strongest clinical predictors are emesis, irritability, and blood in the stool.9
On inspection, the abdomen may appear normally soft or may be mildly distended, and the right lower quadrant may seem empty (Dance’s sign). Guarding is uncommon and should raise concern for the presence of bowel compromise. Bowel sounds may be normal, decreased, or absent. A sausage-shaped mass may be found. The advancing mass, typically ill-defined and variably tender, is most commonly palpable in the right upper quadrant or mid-abdomen, but may be palpated in any quadrant or on rectal examination. Many children have gross or occult blood in the stool on rectal examination, although grossly bloody bowel movements and “currant jelly stools” are late findings. “Currant jelly” stools, which are bloody, maroon-colored, and mucous-laden, are a result of mucous production and mucosal sloughing from vascular compromise. The classic triad of pain, a palpable sausage-shaped abdominal mass, and currant jelly stool is seen in fewer than 15% of cases.
DIAGNOSIS AND MANAGEMENT
Intussusception is reliably and rapidly diagnosed with ultrasonography. Prior to ultrasonography, abdominal radiographs, in two views, should be obtained to see if intussusception is a likely diagnosis and to identify contraindications for reduction by enema. A normal plain abdominal radiograph generally cannot exclude the diagnosis of intussusception.10 However, the presence of air in the cecum in at least two of three views (supine, lateral, and prone) has a negative predictive value of 98%.11 Enemas should not be performed in patients with radiographic evidence of intestinal perforation, such as intraperitoneal air or ascites, or pneumatosis intestinalis. In addition, evidence of complete bowel obstruction may be considered a relative contraindication for enema reduction, as the clinical status of these patients may place them at higher risk of aspiration, bacterial translocation, and perforation.
Ultrasonography tends to be of greater utility in patients with a nonspecific history, normal physical examination, or atypical clinical pattern. Ultrasound findings of intussusception include a large sonographic target, bull’s eye, or doughnut sign on the transverse or cross section (Fig. 48-1), and a sleeve or pseudo-kidney sign on the longitudinal section of the intussusception. The sensitivity and specificity of this imaging modality approaches 100% when performed by an experienced ultrasonographer.12 A diagnostic strategy based on initial ultrasonography followed by contrast enema was more cost-effective when compared with diagnostic contrast enema alone.13 However, in clinically obvious cases, proceeding directly to a reduction enema can be considered. Spiral computed tomography (CT) scan can also be employed to diagnose equivocal cases, but this test is not commonly used for this diagnosis in children and requires exposure to radiation.
FIGURE 48-1. Ultrasonography showing “target” sign of intussusception on a transverse view.
Once intussusception is diagnosed, treatment should be instituted rapidly. Nontoxic, hydrated children with a provisional diagnosis of intussusception should be kept nil per os. Those who appear dehydrated should receive a bolus of intravenous crystalloid, followed by balanced isotonic fluids pending measurement of serum electrolyte levels. A nasogastric tube may be inserted for decompression based on presence and severity of bowel obstruction. For patients without contraindications, the emergency physician in consultation with the pediatric surgeon and radiologist can determine whether pneumatic or hydrostatic enema reduction should be employed.
Pneumatic (air) or hydrostatic (contrast media) enemas are the first line of therapy and are successful in more than 85% of cases.14 Reduction of an intussusception is most commonly monitored with fluoroscopy (Fig. 48-2) but can also be monitored by ultrasonography. If pneumatic or hydrostatic pressure techniques fail to reduce the intussusception, a repeat effort at nonoperative reduction is one option. Should reduction techniques fail, operative therapy is necessary.
FIGURE 48-2. Reduction of intussusception by air contrast enema. Arrow shows location of intussusception.
If the patient has had prolonged symptoms (more than 1 to 2 days) or signs of peritonitis or the clinician has a high suspicion that there is a pathologic lead point (e.g., patients older than age 5 years or lead point seen on ultrasonography), laparotomy should be considered. This procedure allows for manual reduction, inspection of the bowel, and resection of necrotic segments or the pathologic lead point. Laparotomy is also indicated if successful reduction cannot be achieved with pneumatic or hydrostatic enema.
Once reduced, intussusception may recur in up to 10% of cases; this is usually in the first 72 hours, but occasionally it can occur later in time.2 Traditionally, patients have been admitted to the hospital for observation, but some authors have suggested that only a brief period of emergency department observation may be needed.15–17 Recurrent symptoms should prompt repeat investigations to rule out the presence of an intussusception. Multiple recurrences should prompt an investigation into whether a pathologic lead point is present.
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