The value of Tc-99m-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 stu dies is technetium-99m hexamethylpropylene amine oxime (HMPAO) labelled whi te blood cell (WBC) scintigraphy. The aim of this study was to evaluate the accuracy and clinical value of Tc-99m-HMPAO WBC scintigraphy in the aforem entioned group of patients. Forty-one patients who had acute right lower qu adrant abdominal pain with a clinical presentation equivocal for acute appe ndicitis were included in the study. The anterior abdomen and pelvis were i maged up to 4 h after the injection of 125-300 MBq Tc-99m-HMPAO WBCs and th e results were immediately reported to the surgeon before a decision was ta ken on whether to perform laparotomy. Diagnostic accuracy was established b y the intra-operative findings and the histopathology in operated patients. In non-operated patients, absence of abdominal symptoms 1 month after scin tigraphy and/or identification of another cause of abdominal pain was used to rule out acute appendicitis. There were 16 patients with positive scinti graphy and 81% of these patients were positive within 2 h post injection. T here were no false-positive or false-negative results. We operated on 17 (4 1.4%) patients, and only one patient (5.9%) underwent unnecessary laparotom y. We conclude that Tc-99m-HMPAO WBC scintigraphy is a rapid, highly accura te method for the exclusion of acute appendicitis and that its use can lowe r the unnecessarily high laparotomy rate in patients with an equivocal clin ical presentation.