Acute appendicitis: relationships between CT-determined severities and serum white blood cell counts and C-reactive protein levels

Abstract

Objectives: The aim of this study was to evaluate the relationships between the severity of appendicitis as depicted on CT and blood inflammatory markers of serum white blood cell (WBC) count and C-reactive protein (CRP).

Methods: CT images in 128 patients (109 surgically proven and 19 with clinically excluded appendicitis) were retrospectively reviewed. Two radiologists by consensus evaluated and scored (using a 0, 1 or 2 point scale) severities based on CT-determined appendiceal diameters, appendiceal wall changes, caecal changes, periappendiceal inflammatory stranding and phlegmon or abscess formation. We investigated whether CT findings were significantly related to elevated WBC counts or CRP levels and performed the correlations of WBC counts and CRP levels with CT severity scores. Patients were also subjectively classified using four grades from normal (Grade I) to perforated appendicitis (Grade IV) on the basis of CT findings to evaluate differences in WBC counts and CRP levels between grades.

Results: Only appendiceal wall changes and the phlegmon or abscess formation were related to elevated WBC counts and CRP levels, respectively (p<0.05). CT severity scores were found to be more strongly correlated with CRP levels (r = 0.669) than with WBC counts (r = 0.222). On the basis of CT grades, the WBC counts in Grade I were significantly lower than in other grades (p<0.001), whereas CRP levels in Grade IV were significantly higher than in other grades (p<0.001).

Conclusion: CRP levels were found to correlate with CT-determined acute appendicitis severity and could be a useful predictor for perforated appendicitis, whereas WBC counts might be useful to detect early acute appendicitis.

Figure 1

The four-point grade CT scale. (a) Example of Grade I showing a 28-year-old woman with a normal appendix. The coronal reformation image shows the entire length of the normal appendix (arrows). (b) Example of Grade II showing a 20-year-old woman with appendicitis. This coronal reformation image shows a fluid-filled appendix (arrows) of diameter 8 mm. The appendiceal wall shows enhancement without periappendiceal stranding. (c) Example of Grade III showing a 47-year-old man with appendicitis. This axial image shows a fluid-filled appendix (arrows) of diameter 12 mm with moderate periappendiceal stranding (open arrowhead). (d) Example of Grade IV showing a 69-year-old woman with a perforated appendix with periappendiceal abscesses. This axial image shows the abscess (open arrows) and an inner tubular area of increased enhancement (arrows), which represents an inflamed appendix.

Figure 2

Scatter plots of correlations between the CT severity score and (a) white blood cell (WBC) count and (b) C-reactive protein (CRP) levels. CT severity scores were found to be more strongly correlated with CRP levels (r = 0.669, p<0.01) than with WBC count (r = 0.222, p = 0.012).