Imaging description

Intussusception is the telescoping or prolapse of one portion of the bowel into the adjacent downstream segment. Small bowel intussusception appears at CT as a targetlike or sausage-shaped intraluminal soft-tissue mass with fat attenuation due to invaginated mesentery; the so-called bowel-within-bowel appearance (Figures 62.1–62.4) [1–4]. Intussusception is the commonest cause of acute intestinal obstruction in young children, and pediatric intussusception can usually be successfully managed by pressure reduction using barium, air, or saline enema [5]. Conversely, small bowel intussusception in adults is sometimes detected unexpectedly at CT and may result in considerable uncertainty as to appropriate management.

Importance

Adult small bowel intussusception has traditionally been regarded as a surgical condition, because up to 90% of cases are said to be associated with a lead point tumor or other abnormality [6–12]. These older reports related to the frequency of lead point pathology are generally based on surgical series where patients presented with obstructive symptoms and the diagnosis of intussusception was made intra-operatively. These results are not applicable to adult intussusception identified on CT, since CT detects many subclinical cases. More recent studies confirm many CT-detected small bowel intussusceptions are transient. The reported rates of small bowel intussusception that is self-limiting in the CT era range from 79% (23 of 29) to 84% (31 of 37) to 96% (143 of 149) [13–15].

Typical clinical scenario

Adult small bowel intussusception is occasionally seen unexpectedly at CT, with a reported frequency in large unselected series of patients undergoing abdominal CT ranging from 1 in 1865 to 1 in 2557 [14, 15].