Intussusception: Ultrasound

A longitudinal US image shows a "pseudokidney" sign of intussusception (arrows). Arrowheads point to enlarged mesenteric lymph nodes within the intussusceptum.

A transverse US image shows a "target" sign with a hypoechoic ring of the intussuscepiens surrouning the central echogenic area of intussusceptum. Arrowheads point to enlarged nodes.

Facts

• A segment of bowel (intussusceptum) prolapses into a more distal bowel segment (intussuscepiens)
• Most frequently seen in the first two years of life but can be seen up to 4 years. If older child has intussusception, looks for a lead point such as polyp, Meckel diverticulum, lymphoma, duplication cyst.
• Classic triad: colicky pain, vomiting and bloody (red currant jelly) stools (seen in less than 25% of cases)
• X-ray is positive in only 50% of cases, and is not reliable in diagnosing this condition

Ultrasound Findings

• Modality of choice to diagnose intussusception
• "Target" sign = hypoechoic ring with an echogenic center on transverse US image
• "Pseudokidney" sign = hypoechoic bowell wall extending along a hyperechoic mucosa
• Helpful in searching for a lead point. US can provide a specific diagnosis in one-third of these cases.

Reference:

1. Daldrup-Link HE, Gooding CA. Essentials of Pediatric Radiology: A Multimodality Approach, 2010.

2. Hodler J, Von Schulthess GK, Zollikofer CL. Diseases of the Abdomen and Pelvis 2010-2013: Diagnostic Imaging and Interventional Techniques, 2010.