2.1 Patient population
This single-center retrospective study evaluated the outcomes of TAE using IPM/CS as an embolic agent for acute LGIB. A total of 47 patients underwent angiography to evaluate acute LGIB, including 12 patients (nine males and three females; age range, 37–93 years; mean age, 67 years) treated with TAE using IPM/CS as an embolic agent. All patients were treated at the National Hospital Organization Disaster Medical Center in Tokyo, Japan, and provided written informed consent for the procedure, which included information regarding the potential risks and benefits.
2.2 TAE methods and techniques
TAE is typically performed when there is active extravasation in the lower gastrointestinal tract on a dynamic contrast-enhanced computed tomography (CT) scan and when catheter access is possible. Angiography was performed by a team of radiologists, including at least one diagnostic specialist who is a member of the Radiological Society and a specialist who is a member of the Japan Society of Interventional Radiology. These specialists have extensive training and experience in performing and interpreting angiography examinations and are authorized to be involved in planning and performing interventional procedures, including TAE.
All procedures were performed using an angiographic system (Allura Xper FD 20/10 or Azurion 7 M20, Philips Healthcare, Best, The Netherlands) under local anesthesia administered through the femoral artery using a 4- or 5-French (Fr) sheath (Medikit Super Sheath, Medikit, Tokyo, Japan; Radiforcus Introducer IIH, Terumo, Tokyo, Japan). A 4-Fr angiographic catheter shepherd hook-type catheter (SHK or SHA, Medikit, Tokyo, Japan) or 5-Fr guiding catheter Cobra (C1, Medikit, Tokyo, Japan) was injected into the superior mesenteric artery (SMA) or inferior mesenteric artery (IMA), and diagnostic angiography was performed to identify the bleeding site. Even if the bleeding site could not be identified using SMA or IMA arteriography, arteriography using the SMA or IMA branches (right colic, middle colic, ileocolic, and sigmoid arteries) or selective angiography using the vasa recta or marginal artery was performed using 1.9- to 2.9-Fr microcatheters (BISHOP HF, PIOLAX, Kanagawa, Japan; LEONIS Mova HF, Sumitomo Bakelite, Tokyo, Japan; Carnelian® MARVEL Non-Taper or Carnelian® MARVEL S, Tokai Medical Products, Aichi, Japan).
Our team had a standard approach for managing cases of acute LGIB using TAE. Our priority was to identify the bleeding vessel using contrast-enhanced CT and selective angiography, using the vasa recta or marginal artery; and, if possible, stopping the bleeding using superselective embolization with microcoils. If this was impossible or unfeasible, the team would use IPM/CS as an alternative embolic material. Based on this management technique, the final decision regarding which embolization agent to use and whether to perform the embolization procedure was at the operators’ discretion, based on their clinical judgment.
After the embolization procedure was completed, angiography was performed to confirm the technical success of the procedure and check for any other possible sources of bleeding.
2.3 Using IPM/CS as an embolic agent
The use of IPM/CS as an embolic agent is not typically covered by insurance in Japan; therefore, we obtained approval from the institutional review board before using this treatment.
We prepared an intravenous injection of a mixture of IPM/CS (0.5 g) and nonionic contrast medium (5 mL). The mixture was drawn into a syringe and gently pumped approximately 10 times to ensure it was mixed properly. The mixture was mainly injected through a high-flow microcatheter or a microcatheter placed in a marginal artery near the bleeding site until the blood flow in the bleeding site and the surrounding marginal artery became stagnant. However, in some cases, it was necessary to inject the mixture tightly to achieve this effect.
2.4 Assessment
Technical success was defined as the success of the angiographic procedure based on the disappearance of extravasation or blood flow in the target artery. Clinical success was defined as the cessation of bleeding without needing additional hemostatic treatment within 7 days. Early recurrent bleeding was defined as bleeding from the treated area within 3 days after TAE. Complications from embolization procedures can be divided into two categories: "non-specific" and "specific". Non-specific complications are those that are due to the angiographic procedure itself, such as bleeding, infection, or allergic reactions to the materials used. Specific complications refer to those that are specific to the area being embolized, such as intestinal ischemia in the case of intestinal embolization.