Ultrasonography Offers Safe, Radiation-Free Alternative to CT Scan for Diagnosis of Pediatric Appendicitis

Nancy A. Melville

October 03, 2010

October 4, 2010 (Las Vegas, Nevada) — Choosing ultrasonography over computed tomography (CT) scans for the diagnosis of appendicitis can reduce radiation exposure in children without compromising the rate of false-positive or -negative evaluations, according to research presented here at the American College of Emergency Physicians 2010 Scientific Assembly.

Researchers at Mount Sinai School of Medicine in New York City reviewed the charts of children who underwent evaluation for appendicitis in an emergency department before and after the implementation of a protocol requiring that ultrasonography be used as the initial imaging modality whenever possible.

After a significant reduction in CT scanning and an increase in ultrasonography, researchers found no significant difference in the false-negative rate, and there were no false positives with either ultrasonography or CT.

In the ultrasonography group, 2 patients who received nondiagnostic ultrasounds returned to the hospital within several days. Both had positive CT scans for appendicitis. There were no bad outcomes in either group.

The researchers found that children were exposed to significantly less radiation after the protocol was implemented than before.

"Children in the [preprotocol] group were exposed to an equivalent of 3 CT scans to diagnose just a single positive appendicitis; this decreased to just 1.2 CT scans in the [postprotocol] group," said Suzanne Bentley, MD, chief resident at Mount Sinai and lead author of the study.

The levels of radiation that children are exposed to during CT scans of the abdomen are higher than many realize, Dr. Bentley said.

"Many may ask if we really need to care about radiation risk at this level, but we know that there is in fact a significant risk of cancer at this level of exposure."

"To put it into perspective, the annual dose of background radiation from simply being alive over a year is 3.6 millisieverts ," she said. "A single CT scan of the abdomen, in comparison, is 7.6 millisieverts — that's more than 2 years of background radiation. An ultrasound, meanwhile, exposes patients to zero radiation."

Children are more vulnerable to the exposure than adults, Dr. Bentley noted. They are "more at risk. Their tissues are more radiosensitive, they receive a larger dose of radiation, and they have a longer time to develop cancer from radiation exposure."

The study showed that 52 patients underwent radiographic evaluation for appendicitis after the ultrasonography protocol went into effect, compared with 62 patients before the protocol. There were 15 cases of appendicitis before (24.2%) and 19 cases after (36.5%; P = .016).

In the ultrasonography group, the false-negative rate was 0.05 before (95% confidence interval [CI] 0.002 - 0.260) and 0.07 after (95% CI, 0.01 - 0.24) the implementation of the protocol.

The study also showed that the overall length of stay was shorter for patients evaluated with ultrasonography alone than with CT scan.

"We found a decreased length of stay in the [postprotocol] group, with an average stay of 2 hours less than the [preprotocol] group, which not only makes patients happy, but it makes me happy because, in a busy emergency department, getting people out 2 hours early is pretty significant."

One big obstacle to greater ultrasound use in emergency departments is the need to have trained staff on hand, said Jill M. Baren, MD, director of pediatric emergency medicine education in the Department of Emergency Medicine at the Hospital of the University of Pennsylvania in Philadelphia, and moderator of the session.

"With ultrasound, you need to have a truly skilled technician, and it's much more operator-dependent. What ends up happening many times is that the services aren't available on a 24/7 basis, and people tend to use the easiest thing available to them, which is CT," said Dr. Baren.

"CT scans can use a lower level technician, and they are also readily available in most emergency departments or radiology suites adjacent to the department."

Levels of radiation exposure, particularly among children, are nevertheless a significant concern, Dr. Baren added.

"We're trying very hard in any way we can to develop new diagnostic imaging algorithms because of the better appreciated risk of radiation," she said. "The abdominal tests are associated with exposure that we don't want to [incur]. If you have to have more than one of them, you're getting much more exposure over your lifetime, which can increase the rate of getting cancer."

Dr. Bentley and Dr. Baren have disclosed no relevant financial relationships.

American College of Emergency Physicians (ACEP) 2010 Scientific Assembly: Abstract 1. Presented September 28, 2010.

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