90th Annual Meeting Abstracts

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Computed Tomography Reliably Excludes Necrotizing Soft Tissue Infections
George C Velmahos, MD, PHD, *Nikos Zacharias, MD, *Ahmed Salama, MD, *Hasan Alam, MD, *Marc de Moya, MD, *David King, MD, *Robert Novelline, MD
Massachusetts General Hospital, Boston, MA

Objective: To evaluate the diagnostic accuracy of computed tomography (CT) for necrotizing soft tissue infection (NSTI).
Design: Retrospective and prospective case series.
Setting: Academic medical center.
Interventions: CT
Main Outcome Measure: Sensitivity and specificity of CT.
Patients: 58 patients with clinical suspicion of NSTI (01/01/2003 to 4/30/09) who were imaged by a 64-slice helical CT scanner. The test was considered negative in the absence of ischemic tissue, gas, or involvement of the fascia or muscle and positive, if any of these findings existed. The disease was considered present, if an operation showed necrosis of the subcutaneous tissue, fascia, and/or muscle with confirmation by pathology. It was considered negative, if an operation failed to identify any of these findings or the patient was successfully treated without an operation.
Results: Fifty patients were surgically explored, and NSTI was confirmed in 24 (48%). The remaining 26 were found to have cellulitis without necrosis and did not require debridement. Eight more were managed non-operatively with successful resolution of the symptoms.

	NSTI	No NSTI	Total
CT positive	24	6	30
CT negative	0	28	28
Total	24	34	58

The sensitivity of CT was 100%, specificity 82%, positive predictive value 80%, and negative predictive value 100%. There were no differences in demographics, white blood cell count on admission, symptoms, or site of infection between those with a false or true positive CT.
Conclusion: A negative CT reliably excludes NSTI. A positive CT identifies correctly the disease in 80% of the cases.

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