External compression computed tomography may increase diagnostic accuracy in appendicitis

1. In a prospective trial of 168 patients with suspected acute appendicitis (AA), patients that underwent external compression (EC) computed tomography (CT) demonstrated higher specificity for the diagnosis of acute appendicitis compared to standard CT scan.

Evidence Rating Level: 2 (Good)           

Study Rundown: In patients with suspected AA, imaging with ultrasound (US) or CT is crucial in confirming the diagnosis. The diagnosis of AA can be made via ultrasound (US) by visualizing the appendix with a mean outer diameter (MOD) >6mm. Although this 6mm cut-off value is used for diagnosis with both US and CT, previous studies have demonstrated that such a cut-off may not be reliable for CT. The objective of this study was to determine whether incorporating a technique used in US examinations, external compression of the right lower quadrant (RLQ), into CT could improve the diagnosis of AA.

This study prospectively compared EC-CT and standard CT in patients with suspected AA. At the conclusion of the study, the MOD was significantly lower in the EC-CT group compared to the standard CT group in patients without AA. Additionally, there was no difference in the MOD between the two scanning modalities in patients with pathology-confirmed AA. The findings of this study demonstrate that EC-CT may help to reduce the false positive rate of diagnosing AA in CT. This study is strengthened by the use of controls matched for age and sex and the use of pathology-proven cases of AA. However, the study is limited by the use of a control group for comparison rather than conducting non-compression and compression CTs in the same patient. Larger, prospective multicenter trials where both standard CT and EC-CT are performed on the same patient may improve the external generalizability of this result.

Click to read the study in European Radiology

Relevant Reading: CT following US for possible appendicitis: Anatomic coverage

In-Depth [prospective cohort]: This study prospectively compared radiological findings of EC-CT and standard contrast-enhanced CT in patients with a suspected diagnosis of AA. Overall this study recruited 71 patients for EC-CT and identified 97 controls matched for age and sex who had undergone standard CT. EC was accomplished by strapping a 1-L normal saline bag to the RLQ with Velcro strips. Two radiologists interpreted the images and agreed to the final diagnosis via consensus. The final diagnosis was confirmed via pathological examination. Kruskal-Wallis test was conducted to assess differences in MOD. Receiver operating characteristic (ROC) analysis was performed to assess diagnostic performance. In patients with pathology-confirmed AA, there was no significant difference between MOD in EC-CT and standard CT groups (p=1.0). In patients without AA, MOD was significantly decreased in the EC-CT group compared to the standard CT group (p<0.01). The specificity of EC-CT in the diagnosis of AA was significantly greater than standard CT (94.9% vs. 67.7%).

Image: PD

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