Comparison of the sensitivity of early versus delayed imaging with Tc- 99m HMPAO WBC in children with inflammatory bowel disease

The difference in sensitivity of early imaging at 30 minutes after injection of Tc-99m HMPAO WBC versus delayed imaging at 2 or 3 hours for depiction of active inflammation in children with inflammatory bowel disease was established. The charts of 220 children who had early (30-minute) and delayed (2 or 3 hours) imaging performed for evaluation of inflammatory bowel disease were reviewed. There were 107 boys and 113 girls (average age, 12 years; median, 13 years). The bowel was divided into eight segments (with the total for all patients being 3,520) graded on a scale of 0 to 6 (with reference points in the iliac crest and liver). Any grade I was abnormal. The uptake in each segment was summed. One hundred and twenty-two studies were abnormal (55%). The average uptake in the early images was 5.1 ± 0.41 and that in the late images was 9.3 ± 0.64. The Friedman nonparametric test of comparison of rank was significant at the 0.001 level. One hundred and five patients had abnormal studies at 30 minutes (88%). An additional 12% of patients had abnormal studies only on the late images. There were 245 abnormal segments at 30 minutes and 413 abnormal segments at 2 or 3 hours. When the uptake was analyzed segment by segment, 62 patients (52%) had abnormal segments at 30 minutes but also had additional abnormal segments at 3 hours. Sensitivity of Tc-99m HMPAO WBC imaging was significantly improved when late imaging was performed.