Serum bilirubin concentration as a marker of severity of acute appendicitis

Acute appendicitis (AA) is one of the most common causes of urgent admission to the hospital. Clinically applicable classification distinguishes simple and complex inflammation. Among commonly used inflammation markers of AA, bilirubin concentration is not well studied and thus is rarely applied.

To examine the association between increased serum total bilirubin concentration and the severity of AA.

This retrospective study included 169 patients with a presumptive diagnosis of AA who were operated upon between 2015 and 2017. The determined study endpoints were simple complex inflammation and a different diagnosis after surgery. The Mann-Whitney U, Kruskal-Wallis, Fisher's exact, Spearman correlation coefficient and logistic regression tests and receiver-operating characteristics (ROC) were used in analyses. The area under the curve (AUC) was presented with 95% confidence intervals (95% CIs). Statistical significance was set at 0.05.

In total, 84 (49.7%) patients underwent laparotomy and 85 (50.3%) laparoscopy. After surgery, 45 (26.6%) patients had a diagnosis other than AA. Furthermore, 83 (49.1%) and 41 (24.3%) patients had simple and complex AA, respectively. The median bilirubin concentration was 0.56, 0.69, and 1.08 mg/dl in patients without AA, with simple, and complex AA, respectively (p < 0.01). The optimal cut-off for serum bilirubin concentration to predict AA severity was ≥ 0.94 mg/dl (AUC = 0.652; 95% CI: 0.543-0.761) with a 44.9% positive and 83.9% negative predictive value (p = 0.006).

The serum bilirubin concentration should be considered as one of the possible markers of AA. Moreover, it can be used to predict the severity of AA.