Intussusception
Submitted by Megan Werner, MSIV

Definition

·    Telescoping of a segment of bowel (the intussusceptum) into another, usually more distal, segment of bowel (the intussuscipiens)

Etiology/Pathophysiology

·    Intussusceptum is pulled further into the distal segment by peristalsis, pulling the mesentery along with it and trapping the vessels

·    If not reduced, edema, ischemia and bowel obstruction (usually partial) ensue with necrosis of bowel

·    Three etiologies

o    Intraluminal

·    Intraluminal mass (e.g., pedunculated tumor) is pulled forward by peristalsis and brings attached bowel wall with it

o    Intramural

·    Abnormality of bowel wall (e.g., sessile malignancy) causes it not to contract properly, allowing a kink which serves as a lead point

o    Extraluminal

·    Extraluminal factor (e.g., inflamed appendix) causes area of abnormal peristalsis, allowing a kink which serves as a lead point

·  In children

o       Over 90% have no pathologic lead point

·         Most thought due to lymphoid hypertrophy following viral infection

o       Less than 10% due to Meckel’s diverticulum, polyp, lymphoma, etc.

· In adults

o       Over 90% have a demonstrable cause

·    60% due to neoplasm (60% malignant, 40% benign)

·    30% due to non-neoplastic abnormalities, such as inflammation, trauma or suture lines

·    10% are idiopathic

Epidemiology

·         In developed nations

• Majority are in children

  • Peak incidence 5-9 months of age

• Approximately 10% occur in adults

  • Seen in all age groups

  • Approximately equal in males and females

·         In developing nations

• Incidence is higher in adults than it is in developed nations

• Fewer are associated with malignancy, and fewer have pathologic lead points

Clinical Findings

·         Children

o    Cyclical, colicky abdominal pain

o    Vomiting

o    “Currant jelly” stools (diarrhea with mucus and blood) or other blood in stool

§    Classic triad occurs in about 1/3 of patients; most have 2 of the 3

o    Palpable abdominal mass, often in right upper quadrant

o    Dance’s sign: RUQ mass (intussusception) with RLQ empty space (movement of cecum out of normal position)

·         Adults

o    Usually indolent, with intermittent crampy abdominal pain over days to months

o    Can be acute obstruction with hours to days of abdominal distention, pain, and constipation

o    Nausea and vomiting

o    Tenderness to palpation

o    Less than 20% have associated blood in stool

o    Rarely have a palpable abdominal mass

o    Can be incidental findings if intussusception is transient and asymptomatic

 Imaging Findings

·         Plain radiographs are not sensitive or specific

o       Children

• Soft tissue mass surrounded by a crescent of gas

• Evidence of distal small bowel obstruction

• Absence of or decreased gas in the colon

• Pneumoperitoneum

• May be normal

o       Adults usually normal bowel gas pattern

·         Barium enema (diagnostic and therapeutic)

-          “Coiled spring” appearance

o    Barium in lumen of the intussusceptum and in the intraluminal space

·         Ultrasound (not pathognomonic)

o   Transverse: Target or doughnut sign, with hypoechoic rim (edematous bowel wall) surrounding hyperechoic central area (intussusceptum and associated mesenteric fat)

o   Longitudinal: Sandwich, trident or hayfork sign, with layering of hypoechoic bowel wall and hyperechoic mesentery

o   Oblique: pseudokidney sign, with hypoechoic bowel wall mimicking the renal cortex and hyperechoic mesentery mimicking the renal fat

o   Doppler may help determine viability of the tissue

o    Adults: may be less useful, as often cannot identify the pathologic lead point and is most useful when an abdominal mass is palpated

·    CT (virtually pathognomonic, most commonly done in adults)

o   Transverse

§    Target sign, with layers of fat and bowel wall visible

§    If enhanced may see mesenteric vessels in the layers and oral contrast in the intraluminal spaces

o       Longitudinal

§    Elongated, sausage-shaped mass with visible layers

o    May be helpful in judging the degree of vascular compromise if fluid or gas collections seen in between the walls of the intussusceptum

o    May or may not see any pathologic lead point

Treatment

·         NPO, IV fluids, NG tube if gastric distention

·         Children

o    Surgical consultation

o    Then either reduction with barium, hydrostatic (lactated Ringer’s) or air enema, or surgery

·         Adults (best approach debated)

o    Colonic: surgical resection without reduction because of risk of venous embolization of tumor or seeding from a malignant tumor

o    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

Two images from a CT of the abdomen and pelvis show a lipoma of the ileum (red arrow)
which serves as the lead point for the intussusception shown by the target sign (blue arrow)
and a longitudinal view of the intussusception showing the sausage shaped mass (green arrow)