Findings: There is persistent, increased activity within the descending colon which appears unchanged 24 hours and 48 hours post injection, despite the administration of a bowel prep between the two scans.

Diagnosis: Infectious and/or inflammatory process involving the descending colon.

Discussion: One third of infections responsible for fevers of an unknown origin are found in the abdomen. In patients with fever of unknown origin and leukocytosis in whom an abdominal infectious process is suspected, radiolabeled leukocytes are chosen as the initial radionuclide imaging study, especially if symptoms have been present for less than two weeks. A negative indium leukocyte exam essentially excludes an acute infection as the cause of fever of unknown origin.

Because of the lack of normal bowel activity with In WBC's, this is the preferred pharmaceutical for investigating abdominal infection. Indium labeled leukocytes accumulate nonspecifically in sites of inflammation and/or infection. The study has a sensitivity of 90% in detecting an acute inflammatory process. The differential diagnosis for accumulation of indium labeled leukocytes involving the abdomen, most commonly includes Crohn's disease, ulcerative colitis, diverticulitis, ischemic or infarcted bowel, phlegmon, and wound infection. False positive results can be secondary to swallowed leukocytes, enteric tubes, or a gastrointestinal bleed.

References:
Mettler FA, Jr. Essentials of Nuclear Medicine Imaging. 1998:392-402.

Vijayakumr V, Bekerman C. Clin Nucl Med 1991 Feb; 16(2):98-102.

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