Background: Acute appendicitis is a common emergency surgical problem. Pre-operative complete blood count and urinalysis are used for supporting diagnosis. Blood chemistry is also requested for patient’s status evaluation despite limited evidence of its cost-effectiveness.
Objective: The primary objective was to determine the incidence of abnormal pre-operative blood chemistry result. The
secondary objectives were the relationship between preoperative abnormal blood chemistry and postoperative complication and to find the risk factors of abnormal blood chemistry.
Material and Method: 450 patients underwent emergency appendectomy at Siriraj Hospital from January 1st, 2012 to March 31st, 2014 were included in this retrospective descriptive study. Demographic data, blood chemistry test result and postoperative complication were recorded. The incidence of abnormal blood chemistry results was reported. Relationship between abnormal laboratory results, postoperative complications and predisposing factors were analyzed.
Results: The incidence of abnormal pre-operative serum BUN, creatinine, sodium, potassium, bicarbonate and chloride were
19.1%, 35.4%, 26%, 24%, 32.9% and 24.3%, respectively. Abnormal blood chemistry results were not associated with
postoperative complications. However, ASA physical status equal or more than 3 and duration of symptoms >48 hours are
significantly associated with postoperative complications (adjusted OR 2.91, 95% CI 1.04-8.13, p-value = 0.041 and
adjusted OR 2.78, 95% CI 1.24-6.25, p-value = 0.013, respectively). The predisposing factors of abnormal blood chemistry are ASA physical status equal or more than 3 (adjusted odd ratio 4.27, 95% CI 1.25-14.65, p-value = 0.021) and duration of symptoms >48 hours (adjusted odd ratio 1.79, 95% CI 1.01-3.20, p-value = 0.047).
Conclusion: There was no association between abnormal blood chemistry result and postoperative complication. Preoperative
blood chemistry should be tested only if indicated.

Keywords: Preoperative tests, Postoperative complication, Appendectomy, Risk factors