Intussusception: Ultrasound for diagnosis and real-time monitoring

Intussusception is the most common cause of intestinal obstruction in very young children. Ultrasound imaging is the diagnostic imaging examination of choice due to its high sensitivity, specificity, pathologic characterization, and lack of ionizing radiation. Pediatric radiologists at Benioff Children’s Hospital at the University of California San Francisco also recommend its use to monitor intussusception reduction.

This recommendation is made in an article describing past and present diagnostic and treatment practices of intussusception published in Pediatric Radiology.  The authors explain that children under the age of one year represent about half of the intussusceptions that are diagnosed and that boys develop these twice as much as girls. They also caution that symptoms overlap multiple other abdominal disease processes. An accurate diagnosis is essential as failure to treat results in ischemia.

When a child is suspected of having an intussusception, the first-line modality for diagnosis is ultrasound imaging. Abdominal radiography is not recommended. With its high negative predictive value of 99.7%, an ultrasound exam can rule out intussusception in approximately 86% of patients but can identify the conditions that mimic it. The presence of mesenteric lymph nodes within the lumen of the intusscipiens is a highly specific ultrasound finding.

A typical ileocolic intussusception, which occurs in more than 80% of patients, has the appearance of a peripheral hypoechoic ring (the target sign) with central echogenicity (the pseudokidney sign). These correspond to the bowel wall surrounding hyperecohoic mesenteric fat contained within the intussusception. It is most commonly found in the right abdomen with a diameter of 2-4 centimeters (cm). Doppler ultrasound can improve diagnosis in a variety of ways.

Reduction, by introducing pressurized air or liquid into the colon to push the intussusceptum back through the ileocecal valve with real-time imaging observation, is the standard treatment. Lead author Emily A. Edwards, MD, of the department of radiology and biomedical imaging, and colleagues reference a meta-analysis of more than 32,000 children which advised that air enema reduction has similar performance and provides higher success rates than hydrostatic reduction.¹ Additionally, because shorter fluoroscopic times are used, there is lower radiation exposure to the pediatric patients. It also is a cleaner and less expensive procedure to perform.

Real-time imaging monitoring is predominantly performed using fluoroscopy. However, the authors advocate the use of ultrasound imaging. Unfortunately very few pediatric radiologists use ultrasound. The authors cited a 2015 survey which reported only a 4% adoption rate. The authors attribute this to lack of knowledge, experience, and comfort about using ultrasound for real-time monitoring of the procedure and lack of experienced sonographers after hours at many hospitals. At Benioff Children’s Hospital, the radiologists use a combination of ultrasound imaging and fluoroscopy in the diagnosis and treatment of routine intussusception.

The authors strongly recommend that a large population be recruited for a randomized study to evaluate whether the benefits of pneumatic reduction could be combined with radiation-free sonographic monitoring. Standards need to be established and clinically validated. They point out that if pediatric radiologists are not using ultrasound for procedure monitoring, radiology residents and fellows will not have the opportunity to become familiar with it in lieu of fluoroscopy. Ultrasound is safer and just as effective. The authors hope that for the safety of children, pediatric radiologists will take the initiative to utilize ultrasound imaging for both diagnosis and treatment.

REFERENCES

1. Sadigh G, Zou KH, Razavi SA, et al. Meta-analysis of air versus liquid enema for intussusception reduction in children. AJR Am J Rontengenol. 2015 205; 5: 542-549.
2. Edwards EA, Pigg N, Courtier J, et al. Intussusception: past, present and future. Pediatr Radiol. 2017 47; 9: 1101-1108.