Is urinary 5-hydroxyindoleacetic acid helpful for early diagnosis of acute appendicitis?

OBJECTIVE Acute appendicitis is the most common abdominal emergency in children and young adults. There are a lot of serotonin-containing cells in the appendix, which release serotonin into the bloodstream in response to inflammation. Consequently, serotonin is converted to 5-hydroxyindoleacetic acid (5-HIAA) and secreted into the urine. On this basis, urinary 5-HIAA could be a marker for acute appendicitis. In this study, we investigated the value of 5-HIAA levels in spot urine in the diagnosis of acute appendicitis. METHODS The urinary 5-HIAA was measured by an enzyme-linked immunosorbent assay in the spot urine of 70 patients who presented to the emergency department with a clinical picture of acute appendicitis. Urine concentration results were correlated to final histopathologic reports, and the diagnostic value of this factor was measured. RESULTS Diagnosis of appendicitis was confirmed by histopathologic reports in 59 of 70 patients with presumptive diagnosis of appendicitis. Considering 5.25 mg/L as the cutoff point for urinary 5-HIAA, 28 patients had high urinary 5-HIAA levels, whereas 42 patients had values within reference range. The sensitivity and specificity of this test was 44% and 81%, respectively. CONCLUSIONS The measurement of urinary 5-HIAA levels is not an ideal diagnostic tool for ruling out or determination of acute appendicitis.