The purpose of this study is to assess the usefulness of Tc-HMPAO (technetium-99m hexamethylpropyleneamineoxide) labeled white blood cells abdomen scan to differentiate acute appendicitis from periappendiceal abscess. Methodology: Forty-five patients with atypical symptoms and signs of appendicitis were included in this preliminary study. At 4 hours after an intravenous injection of Tc-HMPAO labeled white blood cells, static images over the anterior abdomen were obtained using a gamma camera. Two regions of interest were selected, one was over the lumbar spine and the other was over the appendiceal area. The mean count ratio of the appendiceal area over the mean pixel count of the lumbar spine was calculated. Sixteen patients were diagnosed with acute appendicitis and 19 patients with periappendiceal abscess by final operative findings. Meanwhile, the other 10 patients with acute abdomen but with no appendicitis served as controls. Results: The mean count ratio of controls, acute appendicitis and periappendiceal abscess was 0.65±0.05, 0.82±0.07, and 1.25±0.11, respectively. If the mean count ratio ≥1.00 was defined as the cutoff value to diagnose periappendiceal abscess, the specificity and the positive predictive value was 100%. Conclusions: We concluded that Tc-HMPAO white blood cells abdomen scan should be a potential tool to differentiate periappendiceal abscess from acute appendicitis.
