Comparison between technetium 99m hexamethylpropyleneamine oxide labeled white blood cell abdominal scan and abdominal sonography to detect appendicitis in adult patients with atypical clinical presentation

Background: Acute appendicitis is much more serious in the elderly, and early diagnosis is very important. However, the diagnosis of acute appendicitis in older patients is often difficult because these patients may present with atypical clinical manifestations. Methods: We conducted a prospective study to evaluate and compare the value of technetium 99m hexamethylpropyleneamine oxide (Tc 99m HMPAO) labeled white blood cell (WBC) abdominal scan and abdominal sonography in the diagnosis of acute appendicitis in older patients with an atypical clinical presentation. Forty-nine patients (age > 50 years) with acute abdominal pain and suspected appendicitis, but with atypical findings, were included in this study. Results: Twenty-seven patients received laparotomy for final surgical and pathologic diagnoses. The remaining 22 patients did not receive surgery and showed no evidence of appendicitis after at least 1 month of follow-up. Two patients had false-positive WBC scan findings and two patients had false-negative WBC scan findings. The overall sensitivity, specificity, and accuracy for WBC scans in diagnosing appendicitis were 92.0%, 91.7%, and 91.8%, respectively. The overall sensitivity, specificity, and accuracy for abdominal sonography in diagnosing appendicitis were 84.0%, 95.8%, and 89.8%, respectively. Conclusion: The Tc 99m HMPAO WBC scan provides a more sensitive and accurate method for diagnosing appendicitis in older patients with equivocal clinical examinations when compared with abdominal sonography.