THE APPLICATION OF TECHNETIUM‐99m HEXAMETHYLPROPYLENEAMINE OXIME (^99mTc‐HMPAO) LABELED WHITE BLOOD CELLS FOR THE DIAGNOSIS OF RIGHT DORSAL ULCERATIVE COLITIS IN TWO HORSES

Abstract

The application of 99mTc-HMPAO labeled white blood cells to support the diagnosis 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 ulcerative colitis. Blood was collected aseptically in heparinized syringes from the patients for in vitro white blood cell (WBC) radiolabeling. The buffy coat was separated out and radiolabeled with 99mTc-HMPAO. The radiolabeled blood was re-injected i.v. and four images of the right and left side of the patient's abdomen were acquired at 4 hours and 20 hours post-injection. Results 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 cranioventral abdomen in the region of the right dorsal colon in both horses with right dorsal ulcerative colitis. The reference horse had no radiopharmaceutical uptake in this region. This nuclear imaging study was a rapid, non-invasive method to identify right dorsal colon inflammation. These findings not only supported the diagnosis of right dorsal ulcerative colitis, but also facilitated appropriate medical management of each horse.

Ultrasonographic findings in horses with right dorsal colitis: five cases (2000–2001)

“…4 However, both of these methods are costly and require specialized facilities and equipment. A definitive diagnosis cannot be made solely on the basis of clinical signs, because they are not specific for RDC.…”

Use of 99mtechnetium hexamethylpropyleneamine oxime labelled leucocyte scintigraphy in equine medical investigations: 8 cases

“…111 Indium-oxine ( 111 In-oxine) and 99m Tc-hexamethylpropyleneamine oxime ( 99m Tc-HMPAO) are the two most commonly used radiopharmaceuticals. 99m Tc-HMPAO appears to have some advantages over 111 In-oxine with regard to overall image characteristics, half-life and expense (Reynolds et al 1990;Daniel et al 1992;East et al 2000) and is the most frequently used radiopharmaceutical for the labelling of equine leucocytes.…”

“…The accuracy of labelled leucocyte scanning in veterinary medicine has not been evaluated fully (Hoskinson and Tucker 1996). While the technique has been applied to a variety of conditions in horses, the total number is small and evidence of usefulness in nonskeletal investigations is limited (Koblik et al 1985;Butson et al 1995;East et al 2000;Long et al 2000;Weller and Marr 2000). Here we report on our experience in 8 medical cases in which labelled leucocyte scans were undertaken and our assessment of the perceived benefit of use in a practice setting.…”

Clinical Approach to Commonly Encountered Problems

“…Although isotope-labeled white blood cell scintigraphic scans also may help identify colonic ulcerations, the availability and sensitivity of the procedure are limited. 618 In cases of L. intracellularis, ultrasonography may reveal thickened small intestinal loops and possibly excess free abdominal fluid. 335,563 Endoscopy.…”