The application of technetium-99m hexamethylpropyleneamine oxime (Tc-99m-HMPAO) labeled white blood cells for the diagnosis of right dorsal ulcerative colitis in two horses

The application of Tc-99m-HMPAO labeled white blood cells to support the di agnosis of right dorsal ulcerative colitis was studied in two horses with a history and clinical signs consistent with phenylbutazone toxicity. These images were compared to a reference horse unaffected by right dorsal ulcera tive colitis. Blood was collected aseptically in heparinized syringes from the patients for ill vitro white blood cell (WBC) radiolabeling. The buffy coat was separated out and radiolabeled with Tc-99m-HMPAO. The radiolabeled blood was re-injected IV and four images of the right and left side of the patient's abdomen were acquired at 4 hours and 20 hours post-injection. Re sults of the nuclear study revealed no abnormal findings in the abdomen at the four-hour post-injection images in any horse. Images obtained 20 hours post-injection revealed a linear uptake of radiolabeled WBCs in the right c ranioventral abdomen in the region of the right dorsal colon in both horses with right dorsal ulcerative colitis. The reference horse had no radiophar maceutical uptake in this region. This nuclear imaging study was a rapid, n on-invasive method to identify right dorsal colon inflammation, These findi ngs not only supported the diagnosis of right dorsal ulcerative colitis, bu t also facilitated appropriate medical management of each horse.