Intussusception / Radiology

When one segment of bowel is pulled into itself (or a neighbouring loop of bowel) by peristalsis.

Classic triad of intermittent abdominal pain, vomiting and right upper quadrant mass, plus occult or gross blood on rectal examination has great positive predictive value in children – these are seen in less than 20% of cases. ~ 15% (range 13-22%) of patients with intussusception do not even present with abdominal pain.

95% occur in children, usually after the first three months of life. Before 3 months is rare. Also occurs adults, in them we need to identify the LEAD POINT.

90% children, no lead point can usually be identified , this most frequently thought to relate to enlarged lymphoid tissue following an infection.

Up to 90% of the time identified, usually malignant in the large bowel and benign in the small bowel.

An enlarged lymphoid tissue following an infection becomes the lead point in children, and for it to happen active immunity (antibodies) is needed and that doesn’t happen in < 3 months infant. They only have passive immunity.

1. GI malignancy – most common in adults, 65%, colorectal ca (most common), metastases.
2. Benign – GIST, intestinal lipoma.
3. Congenital – meckel diverticulum, ectopic pancreas.
4. Inflammation.
5. Trauma – mural hematoma.

Focal lesion

Intussusceptum – proximal part of the bowel that is pulled in the distal lumen.
Intussusceptiens – distal part of the bowel that receives the intussusceptum.
Bowel necrosis since mesentary is also pulled in the intussusception.

Essentially anywhere, strong predilection for ileocolic region, 75-95%.
Ileoileocolic: second most common.
Ileoileal and colocolic: uncommon.

Presumably due to the abundance of lymphoid tissue related to the terminal ileum and the anatomy of the ileocaecal region.

Possible but rare.

Small bowel obstruction, intussusception, bowel perforation.

Absent “cecal bowel gas”, soft tissue mass in RUQ, sensitivity 45% (high false negatives i.e, increased differentials)

1. Target sign (AKA the doughnut sign). 2. Pseudokidney sign. 3. Crescent in a doughnut sign.

USG transverse appearance of intussusception – concentric alternating echogenic and hypoechogenic bands. The echogenic bands are mucosa and muscularis. submucosa is the hypoechoic bands.

USG longitudinal/ long looking intussuscepted segment of bowel. Renal hilum – formed by fat containing mesentary dragged into the intussusception. Kidney (renal parenchyma) – by oedematous bowel.

USG transverse appearance of intestinal intussusception, and is a variation of the target sign (which is also known as the doughnut sign).
The crescent is the mesentary dragged into the intussusception. It is naturally located only on one side of the bowel and therefore forms a crescent which is echogenic.

Crescent in a doughnut sign of intussusception.

Reliable screening tool in children with low risk for intussusception, high sensitivity i.e less false negatives.

1. The gold standard.
2. The “coiled spring” appearance – occluding mass prolapsing into the lumen. Barium in lumen of the intussusceptum and in the intraluminal space.

Perforation

Soft tissue mass surrounded by a crescent of gas, Evidence of distal small bowel obstruction, Absence of or decreased gas in the colon, Pneumoperitoneum (perforation), May be normal.

“Coiled spring” appearance.
Barium in lumen of the intussusceptum and in the intraluminal space.

1. Transverse: Target or doughnut sign, with hypoechoic rim (edematous bowel wall) surrounding hyperechoic central area (intussusceptum and associated mesenteric fat).
2. Longitudinal: Sandwich, trident or hayfork sign, with layering of hypoechoic bowel wall and hyperechoic mesentery.
3. Oblique: pseudokidney sign, with hypoechoic bowel wall mimicking the renal cortex and hyperechoic mesentery mimicking the renal fat.
4. Doppler may help determine viability of the tissue.
5. Adults: may be less useful, as often cannot identify the pathologic lead point and is most useful when an abdominal mass is palpated

1. Transverse – a.Target sign, with layers of fat and bowel wall visible. b. If enhanced may see mesenteric vessels in the layers and oral contrast in the intraluminal spaces.
2. Longitudinal – a. Elongated, sausage-shaped mass with visible layers.
3. May be helpful in judging the degree of vascular compromise if fluid or gas collections seen in between the walls of the intussusceptum.
4. May or may not see any pathologic lead point.

NPO, IV fluids, NG tube if gastric distention

1. Surgical consultation.
2. Then either reduction with barium, hydrostatic (lactated Ringer’s) or air enema, or surgery.

1. Colonic: surgical resection without reduction because of risk of venous embolization of tumor or seeding from a malignant tumor.
2. Enteroenteric: depends on cause and symptoms; may require resection or manual reduction during surgery, may be treated with enema reduction, or may require no intervention.