Hyperbilirubinaemia in appendicitis: the diagnostic value for prediction of appendicitis and appendiceal perforation

The aim of this study is to evaluate the diagnostic value of pre-operative bilirubin levels in the diagnosis of acute appendicitis and appendiceal perforation.

A retrospective analysis of 557 patients undergoing emergency appendicectomy over a 24-month period at a large teaching hospital. Hyperbilirubinaemia was defined as >25 µmol/L. Data were analysed using descriptive statistics.

484 of the 557 (86.9 %) operated cases were found histologically to be appendicitis. 116 cases of the 484 were perforated (24 %). Bilirubin levels were significantly higher in the group with appendicitis versus the group found to have a normal appendix at histology, [median (IQR) 12.0 µmol/L (9.00) vs. 8.0 µmol/L (7.00) respectively, p < 0.001], despite being within normal serum bilirubin range. Sensitivity of hyperbilirubinaemia for acute appendicitis was only 8 %, however specificity was 94 %. PPV was 85 % and NPV was 26 %. Whilst bilirubin was higher in patients with a perforated appendix versus acute appendicitis [median (IQR) 13.0 µmol/L (9.00) vs. 11.0 µmol/L (9.00), respectively], statistically, there was no significant difference in pre-operative bilirubin levels between the perforated appendicitis cases and the non-perforated appendicitis cases (p = 0.326). However, the specificity of hyperbilirubinaemia for perforated appendicitis was 93 %, sensitivity 9.4 %, PPV 24 % and NPV 82 %.

Bilirubin levels may be high, but remain within normal range, in cases of appendicitis. Therefore, bilirubin levels may be a useful measurement when investigating a patient with suspected appendicitis. Hyperbilirubinaemia is highly specific with regards to perforation, a finding supported by other studies. However, possibly because of the few perforated cases in this study, we cannot recommend that hyperbilirubinaemia be used to predict perforation.