Tc-99m labeled leukocytes in imaging of patients with suspected acute abdominal inflammation

One hundred patients with suspected acute abdominal inflammation were imaged at 0.5, 2-3, 4-6, and 24 hours after the administration of Tc-99m HMPAO labeled autologous leukocytes. Scan findings were retrospectively compared with final diagnosis, serum C-reactive protein (CRP), and antibiotic treatment. Clinical findings were confirmed with surgery, barium enema, or sigmoidoscopy in 61 patients, and diagnosis was based only on clinical findings in 13 patients. In 26 patients, symptoms subsided before a final diagnosis was made. Tc-99m leukocyte images were positive in 45 of the 61 patients with a confirmed diagnosis, including all patients with acute cholecystitis (N = 4) and inflammatory bowel disease (N = 8). They were also positive in nineteen out of 25 patients who had acute colonic diverticulitis and in 6 out of 7 who had intra-abdominal abscesses. Abnormal activity was found in patients with colonic carcinoma, small bowel infarction, and acute appendicitis. Abnormal activity was visualized in 0.5-hour images in all but one of the positive cases. With the exception of two postoperative cases, malignant lymphoma, and a liver abscess, a CRP level of greater than 75 mg/L was associated with positive image findings. Antibiotic treatment did not affect imaging findings. Imaging with Tc-99m labeled leukocytes appears to be valuable for detecting and localizing abdominal inflammation, and three-phase imaging during the first 4-6 hours is recommended. In some cases, 24-hour images may be useful for distinguishing small bowel from large bowel inflammation.