Why are radionuclide scans performed before angiography in the workup of lower gastrointestinal (GI) bleeding (LGIB)?

Updated: Jul 26, 2019
  • Author: Burt Cagir, MD, FACS; Chief Editor: BS Anand, MD  more...
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Answer

Radionuclide scans frequently are performed before angiography, because the scans detect bleeding at a slower rate than what can be detected with angiography, thereby potentially eliminating the need for an invasive procedure. [46] Negative findings on radionuclide scan make subsequent angiography less likely to be of benefit. In patients who are hemodynamically unstable and in patients with brisk ongoing LGIB, an angiography with or without a preceding radionuclide scan can be performed.

Ng and colleagues retrospectively reviewed the records of 86 patients with positive TRBC scintigraphy findings and found that those with an immediate blush (within 2 min of the study) revealed a positive predictive value of 75% for angiography. [47] However, patients with a delayed blush (after 2 min of the study) had a negative predictive value of 93% for angiography. Thus, patients with delayed blush should proceed with colonoscopic evaluation instead of mesenteric angiography. Use TRBC scintigraphy as a prescreening test for selective mesenteric angiography. TRBC or arteriography may be used in patients with continued bleeding when endoscopy has not aided in making a diagnosis. [27]


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