Gastrointestinal Bleeding Scintigraphy

Michael A. McDonald, MD, PhD; Harvey A. Ziessman, MD

Disclosures

Appl Radiol. 2016;45(5):19-22. 

In This Article

Comparisons

In the emergency setting, RBC scintigraphy plays a complementary role to endoscopy and angiography and should be the initial imaging study in the evaluation of lower GIBs. Colonoscopy, often the initial step in attempting to identify the source of lower GIBs after upper GIB sources have been ruled out, suffers from the potential 4–6 hour delay needed for colon preparation, the need for sedation, the invasive nature of the procedure, the difficulty in identifying bleeding sites during active bleeding, the delay it causes, preventing prompt GIB scintigraphy, and rare but serious complications such as perforation and hemorrhage.[4] If colonoscopy is unable to accurately localize the source of bleeding while confirming its presence in the colon, localization with RBC scintigraphy in combination with angiography is often utilized prior to surgical intervention.

Angiographic evaluation of patients with acute GIB ideally involves selective catheterization of the most likely arterial bleeding source as suggested by prior imaging studies such as RBC scintigraphy.[15] RBC scintigraphy often plays a significant role in determining both the site of initial catheter placement at angiography and in directing the surgical approach, sometimes in an emergent setting.[2] RBC scintigraphy is often performed with the aim of determining a sufficient rate of bleeding to facilitate successful angiography and possible angiographic intervention.[10] A positive RBC scintigraphy study increases the likelihood of a positive angiogram from 22% to 53%.

While angiography has the advantage of allowing therapeutic intervention, it has a 9.3% visceral angiography complication rate including acute renal failure, contrast reactions, arterial thrombosis or dissection and bowel infarction.[16] Although the specificity of angiography approaches 100% the sensitivity for acute bleeds is 46% and 30% for recurrent, intermittent bleeds. Among the advantages of RBC scintigraphy vs. angiography are the 10-fold greater sensitivity for detection of slow bleeding rates or chronic bleeding, the ability to examine the entire lower GI tract simultaneously and continuously over an extended period of time (60 to 90 minutes), and the ability for repeat imaging out to 24 hours. Many angiographers prefer to have RBC scintigraphy prior to the contrast study to ensure that bleeding is active, i.e., the contrast study is more likely to identify the bleeding site if scintigraphy is positive.

RBC scintigraphy also plays an important role in the diagnosis of small intestinal bleeding, when conventional endoscopy (EGD, push enteroscopy and colonoscopy) has limited value, and costly innovative methods such as capsule endoscopy and double-balloon enteroscopy are not readily available.[17] Of note, unlike RBC scintigraphy, capsule endoscopy is contraindicated in patients with known or suspected gastrointestinal obstruction, strictures or fistulae, which can necessitate surgical removal, as well as prior pelvic or abdominal surgery, pregnancy, implanted electronic devices such as pacemakers and extensive Crohn and diverticular disease.[16]

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