MRI Proves Cost-Effective for Diagnosing Appendicitis

James Brice

November 04, 2011

November 4, 2011 — The ability of magnetic resonance imaging (MRI) to help avoid unnecessary appendectomies outweighs the cost of using the sophisticated technology to assess equivocal cases of suspected appendicitis, according to a study published online October 27 in the Journal of Magnetic Resonance Imaging.

Johannes T. Heverhagen, MD, PhD, from Philipps University, Marburg, Germany, and colleagues tested the diagnostic value of MRI in 109 consecutive patients who presented at the university’s medical center emergency department with right lower abdominal pain. Physicians sent 12 patients for immediate appendectomy based on a standard clinical evaluation, laboratory tests, and diagnostic ultrasound and discharged another 45 who did not require further evaluation. The 52 remaining patients (31 men/21 women) had equivocal clinical findings and were sent for an abdominal MRI.

Dr. Heverhagen and colleagues report that MRI evaluation helped 3 of the 52 patients avoid surgery. The cost of the 3 surgeries and 18 days of postoperative observation would have been €16,011. By contrast, the cost of MRI for all 52 patients was €13,676, or €263 per procedure. Therefore, using MRI to evaluate equivocal cases resulted in a net cost savings of €2335, or €45 per patient.

The clinical and cost results suggest that abdominal MRI is a legitimate alternative to computed tomography (CT) for diagnosing acute appendicitis, especially for infants, children, adolescents, and pregnant women, according to the authors.

Currently, physicians use CT and ultrasound to help diagnose appendicitis, but the techniques have drawbacks. Clinical experience and previous trials have demonstrated that abdominal CT is extremely fast and accurate, but it exposes patients to 10- to 20-mSv doses of ionizing radiation, according to the authors. Published assessments estimate that the procedure carries the risk for 1 to 2 radiation-induced cancer cancers per 2000 exams.

Diagnostic ultrasound, on the other hand, is inexpensive and easily accessible and does not involve radiation. However, its operator dependence can affect accuracy, especially when it is applied to obese or pregnant patients.

The current study shows that MRI is feasible and relatively accurate, despite previous concerns about possible lack of around-the-clock accessibility, relative slow speed compared with CT, and high cost.

Dr. Heverhagen and colleagues found that MRI sensitivity and specificity for appendicitis were 85% and 97%, respectively. One false-positive and 2 false-negative results arose when MRI could not distinguish the appendix or signs of periappendiceal inflammation. Its positive and negative predictive values were 92% (11/12 patients) and 95% (38/40 patients), respectively.

Previous studies have also reported good accuracy and cost savings with MRI. Lodewijk Cobben, MD, PhD, a radiologist at the Central Hospital of Haaglanden, the Netherlands, for example, reported in 2009 that MRI would save money as an instrument for diagnosing appendicitis, despite the high perceived costs. Patient selection in that trial, which included patients at low to high probability of appendicitis, probably exaggerated cost savings.

"Our more clinically relevant scenario of including just patients with an equivocal clinical presentation also demonstrates minor savings per patient but mainly no increase in the use of hospital resources," Dr. Heverhagen and colleagues write.

The findings are limited by the single-center nature of the trial, a lack of histopathologic verification, and the authors' use of dated CT clinical data to compare with recent MRI findings. MRI also is generally less expensive in Europe than in the United States, which may confound comparisons.

The investigators have disclosed no relevant financial relationships.

J Magn Reson Imaging. Published online October 27, 2011. Abstract

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