Color Doppler ultrasound best initially for appendicitis
Sensitivity, specificity rates up, but radiation a concern
While ultrasound is generally accepted as the preferred imaging modality for the diagnosis of appendicitis in pediatric patients, investigators from the Rambam Health Care Campus in Haifa, Israel, suggest that it should also be the initial imaging examination for most adult patients with suspected acute appendicitis.
The findings are based on a review of the medical records of 420 adult patients who were referred to the emergency department for sonography for suspected appendicitis between January 2003 and June 2006.1
Investigators, lead by Diana Gaitini, MD, director of the ultrasound unit at Rambam Health Care Campus, found that color Doppler ultrasound correctly ruled out acute appendicitis in 303 of 312 patients, which showed that it is highly reliable with respect to negative findings. However, Gaitini points out that the sensitivity rate of the ultrasound exams was just 74%, which resulted in the missed diagnosis of appendicitis in 23 of 89 patients. Additionally, the ultrasound exams were inconclusive in 17 patients.
A total of 132 patients were referred for CT examination, either because the ultrasound examinations were inconclusive or their signs and symptoms strongly suggested acute appendicitis despite negative ultrasound exams. Based on results from surgery and/or clinical follow-up, in these cases CT correctly diagnosed acute appendicitis in 38 of 39 cases for a sensitive rate of 99%, according to Gaitini. CT was inconclusive in one case.
Ultrasound is safe and effective
Despite the fact that CT has a higher specificity rate and a higher sensitivity rate than ultrasound, ultrasound can assist the radiologist in making a definitive diagnosis in most cases, stresses Gaitini.
"Our clinicians have already internalized the need of performing a non-invasive and radiation-void study in the first term whenever possible," she says. "After this study, showing the advantages of ultrasound as the first diagnostic and triage examination, patients always undergo ultrasound as a first-line study."
Gaitini points out that sonographers are available or on-call 24 hours a day at her center in Israel. However, that is not always the case at medical centers in the United States. In fact, clinicians here are inclined to feel more comfortable with CT for the diagnosis of appendicitis, and there are economic incentives for using CT as well, says Philip Ralls, MD, vice chair of radiology at the Keck School of Medicine, University of Southern California in Los Angeles. It is, for example, more widely available and generally can be performed more quickly than sonography in most centers. Nonetheless, he agrees that ultrasound should be the initial imaging test used in most, but not all cases.
"Computed tomography should be used first in obese patients, but ultrasound should be used first in slender patients, and women and children," he says.
More studies planned
Ralls explains that while an inflamed appendix is easily diagnosed via sonography in a thin person, CT does a better job in patients with a significant amount of fat because periappendiceal inflammatory changes are easier to visualize. Consequently, he suggests that CT can be used as a primary imaging modality in obese patients; patients who have a rigid, non compressible abdomen; and patients in which advanced complicated appendicitis with periappendiceal abscess is suspected.2
However, Ralls agrees with Gaitini that graded compression sonography should definitely be used as a screening test in children, young women, and women who are pregnant.2 These groups are at greater risk from the radiation exposure associated with CT.
More data on the use of ultrasound in pregnant women should be forthcoming. Gaitini says she plans to study the accuracy of ultrasound in this group and the yield of upper-abdomen CT for alternative diagnosis when an abdominal-pelvic ultrasound has already been performed.
References
- Gaitini D, Beck-Razi N, More-Yosef D, et al. Diagnosing acute appendicitis in adults: accuracy of color Doppler sonography and MDCT compared with surgery and clinical follow-up. Amer J Rotentgen 2008; 190:1,300-1,306.
- Ralls P. Imaging in appendicitis: CT and sonography. Diagnostic Imaging: Continuing Medical Education, CMPMedica, March 2007; 1-6. TH.
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