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Invited Commentary

Department of Radiology, Boston Medical Center Boston, Massachusetts

The article by Kim et al (1) regarding the added diagnostic value of MPR with eight- and 16-channel CT in patients with suspected appendicitis is both an excellent review of the subject and well illustrated. The added value of MPR arises from both improved visualization of the normal and abnormal appendix and improved diagnostic certainty for the radiologist and clinician (2–4). The goal of a radiologist supervising and interpreting a CT examination for suspected appendicitis must be to perform the best study possible for the individual patient.

"Best" can be defined in a number of different ways. It can be defined relative to diagnosis in terms of (a) the percentage of equivocal examinations performed with a given technique; or (b) the sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of the technique. It can also be defined relative to patient outcome in terms of measures such as nontherapeutic appendectomy rate, unnecessary or unnecessarily long admissions, incorrect discharge of a patient with appendicitis from the emergency department, and adverse effects of scanning. In addition, "best" can be defined relative to economic impact in terms of the costs to either the hospital or the payer (reimbursement required) for the care of all patients with suspected appendicitis.

In the past, performing the best diagnostic study meant using intravenous and oral or colonic contrast material. As Kim et al (1) point out, investigations have also shown a fortuitous relationship between best diagnosis, best patient outcome, and best use of resources, given the careful selection of patients for CT. Investigations conducted without contrast material have shown accuracies of 90%–95%, whereas those conducted with intravenous and enteric contrast material have shown accuracies of 95%–100%.

The improvement in diagnosis resulting from the use of coronal and sagittal MPR images in addition to axial scans raises the possibility of discontinuing the use of enteric contrast material, at least if a second enteric contrast material–enhanced scan can be justified in equivocal examinations. The challenge will be to show that diagnostic accuracy (especially in terms of false-negative diagnoses) and the rate of equivocal examinations are as good with MPR and enteric contrast material as with MPR and intravenous contrast material alone. Such investigations will require a large number of patients, assuming the hypothesis that there will be no more than a 3%–5% difference in diagnostic accuracy between the two types of studies.

So, while we wait for subsequent investigations, the take-home message of the preceding article is to always perform MPR regardless of what contrast material you currently use for evaluating suspected appendicitis, assuming that the resolution of the MPR images is essentially the same as that of the axial scans (1). With 64-channel CT, at least the sagittal and coronal images can be automatically generated by the scanner, making their creation less labor intensive than with a satellite workstation as used by Kim et al (1). Current picture archiving and communication systems also make it relatively easy to create curved reformatted images as needed to follow the course of the appendix to its tip.

	References

Top References

 

1. Kim HC, Yang DM, Jin W, Park SJ. Added diagnostic value of multiplanar reformation of multidetector CT data in patients with suspected appendicitis. RadioGraphics 2008;28(2):393–406.[Abstract/Free Full Text]
2. Yaghmai V, Brandwein WM, Hammond N, Nikolaidis P. MDCT diagnosis of appendicitis using only coronal reformations. Emerg Radiol 2007; 14(3):167–172.[CrossRef][Medline]
3. Zangos S, Steenburg SD, Phillips KD, et al. Acute abdomen: added diagnostic value of coronal reformations with 64-slice multidetector row computed tomography. Acad Radiol 2007;14(1):19–27.[CrossRef][Medline]
4. Paulson EK, Harris JP, Jaffe TA, et al. Acute appendicitis: added diagnostic value of coronal reformations from isotropic voxels at multi–detector row CT. Radiology 2005;235(3):879–885.[Abstract/Free Full Text]

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