The value of 99mTc-HMPAO labelled white blood cell scintigraphy in acute appendicitis patients with an equivocal clinical presentation

Various imaging studies can be performed in the evaluation of patients with a clinical presentation equivocal for acute appendicitis. One of these studies is technetium-99m hexamethylpropylene amine oxime (HMPAO) labelled white blood cell (WBC) scintigraphy. The aim of this study was to evaluate the accuracy and clinical value of 99mTc-HMPAO WBC scintigraphy in the aforementioned group of patients. Forty-one patients who had acute right lower quadrant abdominal pain with a clinical presentation equivocal for acute appendicitis were included in the study. The anterior abdomen and pelvis were imaged up to 4 h after the injection of 125-300 MBq 99mTc-HMPAO WBCs and the results were immediately reported to the surgeon before a decision was taken on whether to perform laparotomy. Diagnostic accuracy was established by the intra-operative findings and the histopathology in operated patients. In non-operated patients, absence of abdominal symptoms 1 month after scintigraphy and/or identification of another cause of abdominal pain was used to rule out acute appendicitis. There were 16 patients with positive scintigraphy and 81% of these patients were positive within 2 h post injection. There were no false-positive or false-negative results. We operated on 17 (41.4%) patients, and only one patient (5.9%) underwent unnecessary laparotomy. We conclude that 99mTc-HMPAO WBC scintigraphy is a rapid, highly accurate method for the exclusion of acute appendicitis and that its use can lower the unnecessarily high laparotomy rate in patients with an equivocal clinical presentation.