Grady Morning Report: How can you radiologically manage lower gastrointestinal bleeding?

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The Bottom Line:

Computed tomography angiography and Tc-99m-labeled red blood cells (‘tagged RBC scan’) can be used to evaluate and treat lower gastrointestinal bleeding in adults.

Tc-99 labeling of erythrocytes followed by serial scintigraphy may help localize general area of bleeding and guide endoscopy, angiography, or surgery.

If the source of bleeding cannot be identified, angiography is typically deferred. However, in cases of hemodynamic instability, preprocedural diagnostic imaging may be obviated in favor of direct angiographic evaluation. In these circumstances, angiography is the most pragmatic option because it allows for concomitant diagnosis and therapy in patients who are critically ill.

  Computed tomography angiography (CTA) Tagged RBC scan/RBC nuclear scan
  Can detect lesions that are not bleeding at the time of the study

Provides up to a 90-second window of time to evaluate for bleeding

Minimally invasive and is associated with lower mortality

Accuracy 97.6% in localizing GI bleeding
  • Sensitivity 90.9%
  • Specificity 99%

Intravenous iodinated contrast may elicit a hypersensitivity reaction or cause renal injury

Consider use to assist localization of bleeding in patients with recent significant hemorrhage


Consider in high-risk patients with ongoing bleeding, negative upper endoscopy, inadequate response to hemodynamic resuscitation who are unlikely to tolerate bowel preparation for urgent colonoscopy

May be most appropriate for patients with intermittent, obscure-overt GI bleeding since repeated scans are possible after injection of tagged cells

Rate of positive scan approximately 50% with 66% accuracy in locating bleeding site but up to 25% false-positive localization of bleeding site

Major limitation is inability to determine source of bleeding. Angiography should be performed as soon as possible after positive scintigraphy to determine the precise location of bleeding.

See also: American College of Radiology Appropriateness Criteria Radiologic Management of Lower Gastrointestinal Tract Bleeding

DynaMed [Internet]. Ipswich (MA): EBSCO Information Services. 1995 – . Record No. T114280, Acute Lower Gastrointestinal Bleeding in Adults; [updated 2018 Nov 30, cited 2021 March 01]. Registration and login required.

Funaki B, & Lorenz J.M., & Navuluri R, & Van Ha T.G., & Zangan S.M. (2014). Interventional radiology. Hall J.B., & Schmidt G.A., & Kress J.P.(Eds.), Principles of Critical Care, 4e. McGraw-Hill.