This condition involves the invagination of a proximal
segment of bowel (the intussusceptum) into a more distal
segment (the intussuscipiens) (A). It occurs most
frequently in infants between the ages of 5 and 12
months and is a leading cause of intestinal obstruction
in children aged 2 months to 5 years. Intrauterine intussusception
is associated with the development of intestinal
atresia. The male to female ratio is approximately
3:2. Intussusception is slightly more common in white
than in black children and is often seen in children
with cystic fibrosis.
In most patients with intussusception, the cause is
unknown, although some experts believe that hypertrophy
of Peyer patches from an antecedent viral infection
may be responsible. Recognizable pathologic lead points
for intussusception are found in about 2% to 10% of patients.
The most common is a Meckel diverticulum, followed
by intestinal polyp, duplication, appendix, ectopic
pancreas, enterogenous cyst, hemangioma, intramural
hematoma, foreign body, and neoplastic lesion. Inspissated
secretions and thick fecal matter in the bowel lumen
may act as a lead point.
More than 80% of cases of intussusception are ileocolic.
The ileoileal, jejunoileal, cecocolic, colocolic, and jejunojejunal
varieties occur less frequently.
Typical presenting features include colicky abdominal
pain, irritability, lethargy, vomiting, and passage of
"currant-jelly" stool. The characteristic stool suggests that
venous congestion--with ischemia in the affected area of
the bowel--has already occurred.
Children with intussusception sometimes also have
fever and diarrhea, which may create diagnostic confusion
and delay. The pathognomonic sign is an elongated mass
in the right upper quadrant or epigastrium with a feeling
of emptiness in the right lower quadrant (Dance sign). If
the intussusception has traveled far enough, its apex may
be felt, especially on bimanual rectal examination.
Plain abdominal radiographs may show dilated loops
of intestine, air-fluid levels, paucity of air in the right lower
quadrant, minimal fecal content, and a soft tissue mass in
the right or mid abdomen. Abdominal ultrasonography is
a sensitive noninvasive diagnostic tool and is very reliable
in experienced hands. The diagnostic findings include a
tubular mass ("sandwich" or "pseudokidney" sign) in longitudinal
views and a target appearance ("doughnut" sign)
in transverse views.
If doubt remains, the diagnosis can be confirmed by
radiography with barium or air insufflation; both procedures
are diagnostic as well as therapeutic. A barium enema
shows a filling defect or cupping in the head of barium,
where its advance is obstructed by the intussusceptum
(B). An air enema (C), however, is the procedure of
choice: it is safer, less expensive, and easier to perform
than a barium enema and involves less radiation exposure.
The reduction rate with an air enema is approximately
80%; the bowel perforation rate ranges from 0.1% to
0.2%. For barium enema, the reduction rate is 75% to 85%;
the bowel perforation rate is 0.5% to 2.5%. Air pressure
must be monitored during air reduction; the maximum is
110 mm Hg in children and 80 mm Hg in infants. Both
types of reduction should be attempted only under controlled
conditions. Evidence of peritonitis, intestinal perforation,
shock, advancing sepsis, and possible gangrenous
bowel precludes pneumatic or hydrostatic reduction.
Unsuccessful pneumatic or hydrostatic reduction,
shock, peritonitis, intestinal perforation, and demonstration
of a pathologic lead point are indications for laparotomy.
Preoperative measures include nasogastric decompression
and administration of intravenous fluids and broad-spectrum
antibiotics. Reduction can usually be accomplished
by gentle distal pressure, which milks the intestine out of
the intussuscipiens. Pulling out the intussusceptum should
never be attempted. An appendectomy is performed after
reduction, because the blood supply to the appendix is
often compromised. Bowel resection is indicated if the
bowel is nonviable, a pathologic lead point is found, or the
reduction is unsuccessful. A primary end-to-end anastomosis
can usually be performed after the resection.
The likelihood of recovery is directly related to the duration
of intussusception before reduction; most infants recover
if reduction occurs within the first 24 hours. The recurrence
rate of intussusception is between 8% and 12%
after an air or barium reduction and about 2% to 5% after
surgical reduction. There are no recurrences after surgical
resection. Infants with untreated intussusception usually die
of hypovolemia and the associated intestinal obstruction.