Related narrative: Pediatric Iliocolic Intussusception
Epidemiology and Risk Factors
Intussusception occurs when a segment of the alimentary tract is telescoped into another, which results in decreased blood supply of the involved segment. It is the most common cause of intestinal obstruction between 3 months and 6 years of age. Sixty percent of patients are younger than 1 year, and 80% of the cases occur before 24 months; it is rare in neonates. The male:female ratio is 4:1. Siblings of affected children have a relative risk 15 to 20 times higher than the general population. The cause of most intussusceptions is unknown. In about 2-10% of patients, recognizable lead points for the intussusception are found, such as inverted appendiceal stump, Meckel's diverticulum, an intestinal polyp, duplication, or lymphosarcoma. Lead points are more common in very young and older patients. Correlation with viral infections has been noted, and the condition may complicate otitis media, gastroenteritis, or upper respiratory infections. Intussusceptions may occur at any point along the GI tract.
Almost a year after the rotavirus vaccine was introduced in 1998, investigators found that recently vaccinated infants were at increased risk of intussusception. Vaccinated infants had an overall 60% to 80% increased risk of intussusception as compared with unvaccinated infants. Little is known about the mechanism by which this live, attenuated rotavirus vaccine induced intussusception, but the vaccine was pulled from the market.
Principles of Disease
Intussusceptions are most often ileocolic and ileoileocolic, less commonly cecocolic, and rarely exclusively ileal. Very rarely, the appendix forms the apex of an intussusception. The exact etiology of intussusception remains unclear, but the most prevalent theory relates to a lead point that causes telescoping of one segment of intestine into another. As the process continues and intensifies, edema develops and obstructs venous return, resulting in ischemia of the bowel wall. As ischemia of the bowel wall continues, peritoneal irritation ensues, and perforation may occur. Most intussusceptions do not strangulate the bowel within the first 24 hours, but may later result in intestinal gangrene and shock.
The classic triad of intermittent colicky abdominal pain, vomiting, and bloody stools full of mucus is seen infrequently (about 20%). More infants present with only two symptoms. It is common for these infants to have a history of severe intermittent abdominal pain every 20 to 30 minutes, accompanied by straining efforts with legs and knees flexed and loud cries, with periods of relief lasting 10 to 20 minutes, during which they can appear calm and healthy. Other patients become extremely lethargic and pale. In infants without bloody stools, occult blood is present in up to 75%. Children occasionally present without a history of pain, and instead present with profound lethargy with vomiting or diarrhea.
At times, the lethargy is out of proportion to the abdominal signs. Eventually a shocklike state may develop, the pulse becomes weak and thready, the respirations become shallow and grunting, and the pain may be manifested only by moaning sounds. Vomiting occurs in most cases and is usually more frequent, early. In the later phase, the vomitus becomes bile stained. Stools of normal appearance may be evacuated during the first few hours of symptoms. After this time, fecal excretions are small or more often do not occur, and little or no flatus is passed. Blood generally is passed in the first 12 hours, but at times not for 1-2 days and infrequently not at all; 60% of infants pass a stool containing red blood and mucus, the currant jelly stool.
Palpation of the abdomen may reveal a sausage-like mass in the right upper quadrant representing the actual intussusception, and an empty space in the right lower quadrant representing the movement of the cecum out of its normal position. This is known as Dance's sign and is considered pathognomonic for intussusception. Its finding, though, is present in only 70%-85% of cases and might not be palpated in crying infants, who can have tense abdominal muscles. The physician should try to examine the abdomen with the infant asleep (not uncommon after paroxysmal attacks), which gives a softer and more revealing abdominal examination. The presence of bloody mucus on the finger as it is withdrawn after rectal examination supports the diagnosis of intussusception.
Diagnosis and Differential Considerations
Plain abdominal radiographs are the initial studies in children with possible intussusception. These films can be normal, particularly in infants who present early in their disease, and therefore normal plain films of the abdomen should not be used to exclude the diagnosis. Radiographic findings suggestive of intussusception include a paucity of intestinal gas, little or no stool in the colon, and small bowel obstruction. Initial screening films should be examined for evidence of a soft tissue mass or mass effect, obstruction, and free air.
Ultrasound is the least invasive and most commonly used modality for visualizing intussusceptions. Ileocolic intussusceptions are most common and easily detected by ultrasound, even in inexperienced hands. Barium enemas have historically been the gold standard and can be both diagnostic and therapeutic. The use of air enemas in the diagnosis and treatment of intussusception is supplanting hydrostatic reduction.
It may be particularly difficult to diagnose intussusception in a child who already has gastroenteritis; a change in the pattern of illness, character of pain, nature of vomiting, or the onset of rectal bleeding should alert the physician. Disorders that cause intestinal obstruction, abdominal pain, and blood in the stool should be considered, such as malrotation with midgut volvulus, Meckel's diverticulum (although this classically causes painless bleeding), and incarcerated inguinal hernia (although the inguinal mass should help differentiate from intussusception). Slow, progressive onset of pain is more likely associated with appendicitis, constipation, or pancreatitis.
Treatment and Prognosis
Once intussusception is suspected, a surgical consultation should be obtained, oral intake withheld, and intravenous fluid resuscitation provided prior to attempts at barium or air-contrast reduction. Air enemas are equally efficacious as barium enemas and have a success rate averaging 50% to 60%. Reflux of air into the terminal ileum and the disappearance of the mass at the ileocecal valve document successful reduction. Air reduction is associated with fewer complications and lower radiation exposure than traditional hydrostatic techniques. In patients with prolonged intussusception with signs of shock, peritoneal irritation, intestinal perforation, or pneumatosis intestinalis, hydrostatic reduction should not be attempted. Surgical intervention is required if the reduction is unsuccessful or if perforation occurs. (Bowel perforations occur in 0.5-2.5% of attempted barium reductions. The perforation rate with air reduction ranges from 0.1-0.2%).
The success rate of hydrostatic reduction under fluoroscopic or ultrasonic guidance is approximately 50% if symptoms are present longer than 48 hours and 75-80% if reduction is done within the first 48 hours. With adequate surgical management, operative reduction carries a very low mortality rate in early cases. Spontaneous reduction during preparation for operation is not uncommon. Untreated intussusception in infants is usually fatal; the chances of recovery are directly related to the duration of intussusception before reduction. Most infants recover if the intussusception is reduced within the first 24 hours, but the mortality rate rises rapidly after this time, especially after the 2nd day.
Intussusception may recur in 7% to 10% of radiologic and 2% to 5% of surgical reductions, usually within 24 hours, and admission for observation is therefore usually recommended for all patients after reduction.
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