Peds Radiology Case - Intusussception Flashcards
What is intusussception?
Invagination of the bowel into itself; the bowel that is infolded (proximal bowel loop or intussusceptum) pulls the mesentery and possibly lymph nodes with it while stretching the receiving loop of bowel (the distal bowel loop or intussuscipiens), causing bowel wall edema and venous congestion. If not treated emergently, the arterial blood supply will be compromised causing bowel infarction.
How does intussusception present?
Classically presents in children between 6 months and 2 years with acute colicky abdominal pain (80%), frankly blood stools (currant jelly stools), palpable abdominal mass, and vomiting.
What are possible complications of intussusception?
Bowel infarction, perforation, peritonitis, and bowel obstruction
What are the imaging findings in intussusception (U/S)?
- Ileocolic intussusception - usually visualized as a large mass in the abdomen within the right subhepatic region. In the transverse plane, alternating echogenic and hypoechoic concentric layers of bowel wall are visualized (“target” or “donut” sign)
- Thickened bowel walls due to venous congestion and edema
- Hyperechoic mesenteric fat, mesenteric vessels, and lymph nodes may be identified within the receiving bowel lumen.
- Peritoneal fluid may be present as anechoic areas between the serosal layers of the intussusception
- Longitudinal view will show elongated hyperechoic mesenteric fat centrally that is surrounded by hyper and hypoechoic edematous bowel wall layers, looks like a kidney on U/S, “pseudokidney sign”
- If a lead point exists, it may be seen on U/S examination
Most cases of intussusception are idiopathic and thought to be due to ___. 5% of patients do have an underlying abnormality that acts as a lead point - list 4 examples.
Hypertrophied lymphoid tissue; Meckel’s diverticulum, cyst, polyp, tumor
What patient population are lead points more common in ?
Neonates and children over 5 years old (aka patients outside the usual range for intussusception)
What are the imaging findings of intussusception on fluoroscopic-guided contrast enema studies?
Subhepatic intraluminal mass or filling defect will be visualized
What are the imaging findings of intussusception on CT/MRI?
Both CT and MRI can show bowel within bowel positioning of intussusception - presence of this configuration with mesenteric fat and/or vessels within receiving loop lumen is pathognomonic for intussusception. Lead point abnormalities may be identified.
What are the imaging findings of intussusception on abdominal XR?
Rounded mass often in the RUQ of the abdomen
What is the imaging method of choice in suspected cases of intussusception? What is the sensitivity and specificity?
Transabdominal U/S; sensitivity - 97%, specificity - 95%, can exclude with a high negative predictive value of 99.7%
What are the pros and cons of U/S for diagnosing intussusception?
Pros - bedside, low cost, lacks radiation, sedation not needed, allows for simultaneous exclusion of DDx, such as apendicitis
Cons - operator dependent
How are fluoroscopic-guided contrast enema studies used to diagnose intussusception?
Used to treat by reduction, not a primary diagnostic tool; the reduction is performed with air (pneumatic reduction) or water soluble contrast or barium (hydrostatic reduction). COnfirmed when the mass has resolved and contrast is visualized entering the small bowel (for patients with symptoms <24 hours, fluoroscopic contrast studies have 90% success rate for reduction)
When is surgical reduction of intussusception considered?
If there is failure to reduce the intussusception on three separate attempts of three minutes each
Why are CT and MRI rarely used in the workup of intussusception? When are they appropriate?
Disadvantage of requiring sedation, more costly, exposure to ionizing radiation
May be appropriate if suspected to be associated with an oncologic disease process
When is XR useful in diagnosing intussusception?
Excluding complications, such as perforation, which allows free air to enter the peritoneal cavity (pneumoperitoneum), recognized as an area of lucency between the diaphragm and the liver on upright abdominal XR. Perforation is a contraindication for performing a pneumatic or hydrostatic reduction and requires surgical treatment. (Low sensitivity - 45% - for dx intussusception)
