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.