CTA-positive, angiography-negative lower GI bleeding: an institutional imaging-guided management algorithm

Gastrointestinal bleeding is a common acute presentation in the emergency department (ED) that may require immediate, life-saving intervention. Lower gastrointestinal bleeding (LGIB) represents a frequent source of high-acuity ED presentations, requiring time-sensitive decisions regarding imaging selection, level of care, transfusion strategy, and subspecialty consultation. In such cases, rapid diagnosis and hemodynamic assessment are crucial and facilitated by a multimodal diagnostic approach. Colonoscopy, nuclear medicine studies, and cross-sectional imaging are well-established modalities for evaluating LGIB, with computed tomography angiography (CTA) rapidly emerging as a first-line diagnostic tool, particularly in hemodynamically unstable patients. When active extravasation is identified on CTA, patients are often referred for transcatheter angiography (TA) to enable localization and potential endovascular intervention. However, ambiguity remains regarding the appropriate management of cases in which active hemorrhage is identified on CTA but not reproduced on TA. This discordance may reflect the intermittent nature of hemorrhage, temporal delays between imaging and intervention, or differing detection thresholds across modalities, creating a significant diagnostic and therapeutic dilemma for emergency, gastroenterology, and interventional radiology teams involved in the acute management of LGIB. We propose an institutional, imaging-guided management strategy for patients with CTA-positive but angiography-negative LGIB, emphasizing a tiered approach that prioritizes conservative management with arterial sheath retention, followed by provocative angiography, and selective use of colonoscopy. These strategies are not applied in a rigid or sequential manner but rather represent complementary options that are selectively employed based on hemodynamic status, clinical trajectory, transfusion requirements, and evidence of ongoing or recurrent bleeding.