Diagnosing gastrointestinal bleeding (GIB) can be especially difficult when endoscopic evaluation do not reveal a clear source. In this report, we describe 20 patients with suspected GIB in whom initial evaluations were inconclusive. All underwent dynamic planar 99mTc-RBC scintigraphy followed by SPECT/CT imaging. This combination proved valuable in either identifying active bleeding sites or clarifying non-bleeding causes of tracer accumulation. The added anatomical detail from SPECT/CT helped distinguish true bleeding from normal physiological activity, vascular landmarks, or postoperative alterations—areas where planar imaging is not enough. In some patients, imperfect red blood cell labeling introduced challenges in image interpretation, occasionally mimicking bleeding. Even so, the fusion of functional and anatomical data improved diagnostic clarity in most cases. This series emphasizes how hybrid nuclear imaging can provide critical insight when other diagnostic methods fail, enabling more accurate localization and better-informed clinical decisions. Our experience supports the broader use of SPECT/CT in evaluating complex or obscure GIB, offering clinicians a noninvasive yet highly informative diagnostic option.
Lau JHY-h, Ng KK, Wong WC, Kung BT. Case series review illustrating the utility of SPECT/CT in enhancing reader confidence and avoiding pitfalls in interpreting 99mTc-labeled red blood cell scans. Radiology Case Reports. 2025; 20(4):2080-6.
Kang SY, Moon BS, Kim HO, Yoon H-J, Kim BS. 99mTc-RBC SPECT/CT for duodenal bleeding point detection. Clinical Nuclear Medicine. 2020; 45(9):e411-e2.
Wang L, Jing H, Chen L, Wang Z, Li F. Gallbladder activity on 99mTc-labeled red cell scintigraphy confirmed by SPECT/CT imaging. Clinical Nuclear Medicine. 2016; 41(9):734-6.
Wang G, Lu X, Wang W, Yang J. Menstruation confounding the correct interpretation of 99mTc-RBC bleeding scan. Clinical Nuclear Medicine. 2022:10.1097.
Yaxley KL, Mulhem A, Godfrey S, Oke JL. The accuracy of computed tomography angiography compared with technetium-99m labelled red blood cell scintigraphy for the diagnosis and localization of acute gastrointestinal bleeding: a systematic review and meta-analysis. Current Problems in Diagnostic Radiology. 2023; 52(6):546-59.
Samadi MH, Elahifard H, Barashki S, Ghahraman M, Sadeghi R. Premensturation hyperemia of the uterus and endometrial shedding on delayed RBC scan: Potential cause of the false-positive RBC scintigraphy. Clinical Nuclear Medicine. 2022:10.1097.
Wang G, Zhang S, Kan Y, Liu J, Yang J, Wang W. Comparison of diagnostic value of technetium 99m-labeled red blood cell computed single photon emission computed tomography/computed tomography (99mTc-RBC SPECT/CT) and contrast-enhanced multi detector computed tomography (MDCT) for small bowel bleeding: a retrospective study. Quantitative Imaging in Medicine and Surgery. 2024; 14(8):6087.
Chen PN-C, Brown RK. False positive GI bleed on Tc-99m RBC scintigraphy due to ileal varices. Journal of Radiology Case Reports. 2012; 6(2):23.
Hsieh H-J, Lue K-H, Kao C-HK, Hsu Y-H, Liu M-C, Kao P-F. Portosystemic collateral circulation: Demonstrated by Tc-99m–RBC SPECT/CT. Clinical Nuclear Medicine. 2009; 34(12): 958-9.
Karamian F, Sahafi P, Tanha AS, Sadeghi R. Omental hernia as a potential cause of false-positive GI bleeding on 99mTc-RBC scintigraphy. Clinical Nuclear Medicine. 2022: 10.1097.
Lu X, Feng L, Wang W, Yang J. Incidental detection of ectopic ovary varices by 99mTc–red blood cell bleeding scintigraphy in a patient with cirrhosis. Clinical Nuclear Medicine. 2023; 48(8): 746-9.
Soyluoğlu S, Korkmaz Ü, Özdemir B, Altun The diagnostic contribution of SPECT/CT imaging in the assessment of gastrointestinal bleeding: Especially for previously operated patients. Molecular Imaging and Radionuclide Therapy. 2021; 30(1): 8.
Wu C, Menshikova E, Sethi I. Incidental bleeding gastrointestinal stromal tumor identified on 99mTc-RBC scintigraphy. Clinical Nuclear Medicine. 2022; 10: 1097.
Samadi, M. Hadi , Sahafi, P. and Sadeghi, R. (2026). Atlas of 99mTc-RBC scan for gastrointestinal bleeding with emphasis on SPECT/CT imaging: A case series. Asia Oceania Journal of Nuclear Medicine and Biology, 14(1), 98-106. doi: 10.22038/aojnmb.2025.88577.1637
MLA
Samadi, M. Hadi, , Sahafi, P. , and Sadeghi, R. . "Atlas of 99mTc-RBC scan for gastrointestinal bleeding with emphasis on SPECT/CT imaging: A case series", Asia Oceania Journal of Nuclear Medicine and Biology, 14, 1, 2026, 98-106. doi: 10.22038/aojnmb.2025.88577.1637
HARVARD
Samadi, M. Hadi, Sahafi, P., Sadeghi, R. (2026). 'Atlas of 99mTc-RBC scan for gastrointestinal bleeding with emphasis on SPECT/CT imaging: A case series', Asia Oceania Journal of Nuclear Medicine and Biology, 14(1), pp. 98-106. doi: 10.22038/aojnmb.2025.88577.1637
CHICAGO
M. Hadi Samadi , P. Sahafi and R. Sadeghi, "Atlas of 99mTc-RBC scan for gastrointestinal bleeding with emphasis on SPECT/CT imaging: A case series," Asia Oceania Journal of Nuclear Medicine and Biology, 14 1 (2026): 98-106, doi: 10.22038/aojnmb.2025.88577.1637
VANCOUVER
Samadi, M. Hadi, Sahafi, P., Sadeghi, R. Atlas of 99mTc-RBC scan for gastrointestinal bleeding with emphasis on SPECT/CT imaging: A case series. Asia Oceania Journal of Nuclear Medicine and Biology, 2026; 14(1): 98-106. doi: 10.22038/aojnmb.2025.88577.1637
)