These images are from a Tc99m-labeled RBC study. In the final 30 minutes (last 30 images) of the 90 minutes study, abnormal radiotracer activity appears and is seen to move in a superior-inferior direction.
The patient went to angiography…
The superior mesenteric artery angiogram show active contrast extravasation from a right colic artery branch. This was subsequently treated with coil embolization.
This patient has an active gastrointestinal bleedfrom the right colic artery.
Labeled RBC imaging has traditionally been cited as the most sensitive test for lower GI bleeding, detecting bleeding rates as low as 0.1 mL/min, compared with 0.5-1.0 mL/min for angiography.
More recently CT angiography has been proven as a useful tool in this setting, detecting bleeding rates as low as 0.25-0.35 mL/min. However labeled RBC imaging remains a superior evaluation of intermittent bleeding, given the ability to image for longer periods of time (90 minutes or more, compared to a fraction of a second in CTA).
Ziessman HA, O’Malley JP, Thrall JH, eds. Nuclear Medicine, the Requisites, 4th ed. Philadelphia: Elsevier, 2014. Geoffroy Y, et al. Multidetector CT angiography in acute gastrointestinal bleeding: Why, when, and how. Radiographics 2011;31:E35-46. Wortman JR, et al. CT angiography for acute gastrintestinal bleeding: what the radiologist needs to know. Br J Radiol 2017;90:20170076.
