Ultrasound Alternative: When Is it the Better Choice for Appendicitis?

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 - Ultrasound
Ultrasound imaging shows submucosal echogenic layer in inflamed appendix.
Source: Am J Roentgenol. 2013;200: 957-962.

When a child has appendicitis, it no longer is a hair-raising emergency bellyache. Instead it is just the beginning of a diagnostic puzzle that imaging helps to sort out. But which type of imaging to use is the question. Ultrasound offers a radiation-free alternative to CT, but it is not without its own drawbacks. The choice is crucial, but often determined by availability and influenced by a hospital’s size and patient base.

Appendicitis, which usually features stomach pain, a fever and vomiting, can be difficult to diagnose because its symptoms resemble those of other maladies. Delayed or incorrect diagnosis can lead to a ruptured appendix.

Usually, with few exceptions, instead of rushing a child straight to the operating room, doctors first make a critical choice to use either ultrasound, CT, or both to find the child’s tiny, worm-shaped appendix, no longer than four inches.

“It’s no longer automatically a middle-of-the-night kind of case,” says Brent A. Townsend, MD, of Wake Radiology in Raleigh, N.C. “A child comes in to the ER with belly pain. A physical exam, white blood cell count and other lab work are done. Serial exams can be done every six to 12 hours, or a full range of imaging, to confirm the diagnosis.”

“It’s rare if children go straight to the OR,” he adds. Often, a child who has appendicitis is given antibiotics and surgery is scheduled for the following day.

Advances in diagnostic imaging—and reliance on it—have steadily increased. Ultrasound produces diagnostic quality images and is free of ionizing radiation. CT scans produce more detailed images than ultrasound, but carry a radiation risk.

Imaging has become so pervasive that some physicians say the diagnosis of appendicitis has shifted from clinical diagnosis to diagnostic imaging for all patients.

Physicians almost inevitably turn to imaging each time a child with a suspected appendicitis turns up at the ED. About 280,000 appendectomies are done yearly in the U.S., making it one of the more frequently performed pediatric abdominal surgeries.

Deciding on which kind of imaging is the best one to use for diagnosing a suspected appendicitis is not cut and dried. “It’s a confusing issue. A multitude of people are advocating many different imaging modalities,” says Robert. C. Orth, MD, PhD, of Texas Children’s Hospital (TCH) in Houston.

Advocates for ultrasound see it as the go-to modality because it doesn’t carry the radiation risk of CT scans.

Ultrasound also is the least expensive modality by any measure. NewChoiceHealth.com, a company that compares medical costs using hospitals’ list prices, pegged the cost for an abdominal ultrasound at about $400, while a recent study using data from Medicare and Medicaid found costs for a limited ultrasound in appendicitis evaluation could be as low as just $88 (Am J Roentgenol. 2014 Jan;202(1):124-35). The same study also found that using ultrasound first then CT for appendicitis saved as estimated $24.9 million per year across the U.S. population despite extra surgeries being conducted.

Many children’s hospitals, including TCH, the nation’s largest, use ultrasound first followed by CT if needed. About 5 to 10 percent of ultrasound exams are followed by CT scans to confirm diagnosis at TCH. Out of the 3,000 cases per year of suspected appendicitis seen at TCH, approximately one third require appendectomies, Orth says. The rest turn out to be stomach bugs, constipation, or other conditions.

Among other advantages, ultrasound doesn’t require IV contrast, unlike CT. Ultrasound is seen as ideal to use on small children because their lack of fat, which is a barrier for sound waves, allows a better image than it might in adults.

Learning curve

One potential drawback of ultrasound is that image quality is heavily operator dependent. “The bottom line is that it depends on whether the ultrasound technologist and radiologist have the skill and experience to perform the exam,” Orth explains. “The sonographer may see the whole appendix, part of it, or none of it. Sound waves don’t travel well through gas. If there is a lot of gas or stool, the appendix can be hard to see.”

This learning curve of ultrasound training is something that Einat Blumfield, MD, of the Jacobi Medical Center of the Albert Einstein College of Medicine, in the Bronx, N.Y., is very familiar with. She trains the ultrasound operators at the adult and pediatric trauma center, which uses ultrasound first followed by CT, if needed. 

“It takes about a year