Etiology and Epidemiology

Approximately 90% of cases of intussusception in children are idiopathic. The seasonal incidence has peaks in spring and autumn. Correlation with prior or concurrent respiratory adenovirus (type C) infection has been noted, and the condition can complicate otitis media, gastroenteritis, Henoch-Schönlein purpura, or upper respiratory tract infections. The risk of intussusception was increased in infants ≤1 yr of age after receiving a tetravalent rhesus-human reassortant rotavirus vaccine within 2 wk of immunization. The Advisory Committee on Immunization Practices no longer recommends this vaccine, and it is no longer available. Although rotavirus produces an enterotoxin, there is no association between wild-type human rotavirus and intussusception. The currently approved rotavirus vaccines have not been associated with an increased risk of intussusception.

It is postulated that gastrointestinal infection or the introduction of new food proteins results in swollen Peyer patches in the terminal ileum. Lymphoid nodular hyperplasia is another related risk factor. Prominent mounds of lymph tissue lead to mucosal prolapse of the ileum into the colon, thus causing an intussusception. In 2-8% of patients, recognizable lead points for the intussusception are found, such as a Meckel diverticulum, intestinal polyp, neurofibroma, intestinal duplication cysts, hemangioma, or malignant conditions such as lymphoma. Lead points are more common in children >2 yr of age; the older the child, the higher the risk of a lead point. Intussusception can complicate mucosal hemorrhage, as in Henoch-Schönlein purpura or hemophilia. Cystic fibrosis is another risk factor. Postoperative intussusception is ileoileal and usually occurs within several days of an abdominal operation. Intrauterine intussusception may be associated with the development of intestinal atresia. Intussusception in premature infants is rare.

Pathology

Intussusceptions are most often ileocolic, less commonly cecocolic, and rarely exclusively ileal. Very rarely, the appendix forms the apex of an intussusception. The upper portion of bowel, the intussusceptum, invaginates into the lower, the intussuscipiens, pulling its mesentery along with it into the enveloping loop. Constriction of the mesentery obstructs venous return; engorgement of the intussusceptum follows, with edema, and bleeding from the mucosa leads to a bloody stool, sometimes containing mucus. The apex of the intussusception can extend into the transverse, descending, or sigmoid colon, even to and through the anus in neglected cases. This presentation must be distinguished from rectal prolapse. Most intussusceptions do not strangulate the bowel within the 1st 24 hr but can eventuate in intestinal gangrene and shock.

Clinical Manifestations

In typical cases, there is sudden onset, in a previously well child, of severe paroxysmal colicky pain that recurs at frequent intervals and is accompanied by straining efforts with legs and knees flexed and loud cries. The infant may initially be comfortable and play normally between the paroxysms of pain; but if the intussusception is not reduced, the infant becomes progressively weaker and lethargic. At times, the lethargy is out of proportion to the abdominal signs. Eventually, a shocklike state, with fever, can 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 in the early phase. In the later phase, the vomitus becomes bile stained. Stools of normal appearance may be evacuated in the 1st 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 is generally passed in the 1st 12 hr, 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. Some patients have only irritability and alternating or progressive lethargy. The classic triad of pain, a palpable sausage-shaped abdominal mass, and bloody or currant jelly stool is seen in <15% of patients with intussuscpetion.

Palpation of the abdomen usually reveals a slightly tender sausage-shaped mass, sometimes ill defined, which might increase in size and firmness during a paroxysm of pain and is most often in the right upper abdomen, with its long axis cephalocaudal. If it is felt in the epigastrium, the long axis is transverse. About 30% of patients do not have a palpable mass. The presence of bloody mucus on rectal examination supports the diagnosis of intussusception. Abdominal distention and tenderness develop as intestinal obstruction becomes more acute. On rare occasions, the advancing intestine prolapses through the anus. This prolapse can be distinguished from prolapse of the rectum by the separation between the protruding intestine and the rectal wall, which does not exist in prolapse of the rectum.

Ileoileal intussusception can have a less-typical clinical picture, the symptoms and signs being chiefly those of small intestinal obstruction. Recurrent intussusception is noted in 5-8% and is more common after hydrostatic than surgical reduction. Chronic intussusception, in which the symptoms exist in milder form at recurrent intervals, is more likely to occur with or after acute enteritis and can arise in older children as well as in infants.

Diagnosis

When the clinical history and physical findings suggest intussusception, an ultrasound is typically performed. A plain abdominal radiograph might show a density in the area of the intussusception. Screening ultrasounds for suspected intussusception increases the yield of diagnostic or therapeutic enemas and reduces unnecessary radiation exposure in children with negative ultrasound examinations. The diagnostic findings of intussusception on ultrasound include a tubular mass in longitudinal views and a doughnut or target appearance in transverse images (Fig. 325-1). Ultrasound has a sensitivity of approximately 98-100% and a sensitivity of about 88% in diagnosing intussusception. Air, hydrostatic (saline), and, less often, water-soluble contrast enemas have replaced barium examinations. Contrast enemas demonstrate a filling defect or cupping in the head of the contrast media where its advance is obstructed by the intussusceptum (Fig. 325-2). A central linear column of contrast media may be visible in the compressed lumen of the intussusceptum, and a thin rim of contrast may be seen trapped around the invaginating intestine in the folds of mucosa within the intussuscipiens (coiled-spring sign), especially after evacuation. Retrogression of the intussusceptum under pressure and visualized on x-ray or ultrasound documents successful reduction. Air reduction is associated with fewer complications and lower radiation exposure than traditional contrast hydrostatic techniques.

Figure 325-1 Transverse image of an ileocolic intussusception. Note the loops within the loops of bowel.

Figure 325-2 Intussusception in an infant. The obstruction is evident in the proximal transverse colon. Contrast material between the intussusceptum and the intussuscipiens is responsible for the coiled-spring appearance.

Differential Diagnosis

It may be particularly difficult to diagnose intussusception in a child who already has gastroenteritis; a change in the pattern of illness, in the character of pain, or in the nature of vomiting or the onset of rectal bleeding should alert the physician. The bloody stools and abdominal cramps that accompany enterocolitis can usually be differentiated from intussusception because in enterocolitis the pain is less severe and less regular, there is diarrhea, and the infant is recognizably ill between pains. Bleeding from a Meckel diverticulum is usually painless. Joint symptoms, purpura, or hematuria usually but not invariably accompany the intestinal hemorrhage of Henoch-Schönlein purpura. Because intussusception can be a complication of this disorder, ultrasonography may be needed to distinguish the conditions.

Treatment

Reduction of an acute intussusception is an emergency procedure and should be performed immediately after diagnosis in preparation for possible surgery. In patients with prolonged intussusception and signs of shock, peritoneal irritation, intestinal perforation, or pneumatosis intestinalis, hydrostatic reduction should not be attempted.

The success rate of radiologic hydrostatic reduction under fluoroscopic or ultrasonic guidance is approximately 80-95% in patients with ileocolic intussusception. Spontaneous reduction of intussusception occurs in about 4-10% of patients. Bowel perforations occur in 0.5-2.5% of attempted barium and hydrostatic (saline) reductions. The perforation rate with air reduction is 0.1-0.2%.

An ileoileal intussusception is best demonstrated by abdominal ultrasonography. Reduction by instillation of contrast agents, saline, or air might not be possible. Such intussusceptions can develop insidiously after bowel surgery and require reoperation if they do not spontaneously reduce. If manual operative reduction is impossible or the bowel is not viable, resection of the intussusception is necessary, with end-to-end anastomosis.

Prognosis

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 in the 1st 24 hr, but the mortality rate rises rapidly after this time, especially after the 2nd day. Spontaneous reduction during preparation for operation is not uncommon.

The recurrence rate after reduction of intussusceptions is about 10%, and after surgical reduction it is 2-5%; none has recurred after surgical resection. Corticosteroids can reduce the frequency of recurrent intussusception. Recurrent intussusception can usually be reduced radiologically. It is unlikely that an intussusception caused by a lesion such as lymphosarcoma, polyp, or Meckel diverticulum will be successfully reduced by radiologic intervention. With adequate surgical management, operative reduction carries a very low mortality rate in early cases.