Mesenteric Embolization: Solid Organ, Pelvic Trauma, and GI Bleeding

Procedure Recommendations: The Dos and Don’ts

Ideally, it is best to prepare a separate embolization table distinct from the standard procedural set-up for catheters, guidewires, etc., with two distinct bowls of saline and contrast. Use small syringes (<5 mL) for embolization and specifically mark them as “embolization” or “particles”. After selective catheterization, always ensure optimal catheter positioning prior to embolization by performing a test injection of contrast to assess the potential for reflux of embolic material into nontarget areas.

Magnify the field of view to focus on the target region, collimate the borders, and under constant fluoroscopic guidance begin to slowly inject particles in a series of small puff-like injections, using the same pressure for each. Commonly, particles and Gelfoam have a tendency to aggregate and to form a clump at the junction of the tip of the syringe and the hub of the catheter. This may form a plug and result in catheter occlusion. Plug formation can be prevented by flushing the catheter after each syringe of particles injected to ensure a purged or clean catheter that is free from any residual embolization material. The key to this technique is to continue flushing normal saline until the operator no longer visualizes the opacified agent and there is free flow of saline with minimal injection force.

Occasionally, operators may encounter sudden and/or increased resistance during embolization. In this situation, a common mistake is to forcefully flush large volumes of saline with increasingly higher pressure in a vigorous attempt to clear the blocked catheter. This forceful maneuver may lead to an explosive and uncontrolled dislodgement of embolization agent into nontarget area(s) as the obstruction is relieved. Encountering such resistance is common, and it can be better addressed by injecting small aliquots of saline using a 1-mL syringe.

It is important to remember that as embolization with particles or Gelfoam progresses, the speed and dynamics of vascular flow change. Peripheral flow in distal small vessels becomes progressively stagnant, and further embolization can lead to reflux into nontarget vessels, proximal to the catheter tip. Approaching the end of the embolization process, it is critical to recognize that the catheter system is still full of the embolization agent and large puffs of contrast or saline, even during catheter withdrawal, can cause accidental nontarget embolization of other organs.

Special care should be taken while performing postembolization arteriography to avoid any inadvertent use of embolization syringes, because residual particles can transiently adhere to the wall and/or hubs of syringes. Similarly, it is a good precautionary practice following embolization to aspirate and to discard one syringe of blood before performing a completion arteriogram.

Temporary Agent—Gelfoam—Properties and Uses

Gelfoam is a water-soluble, readily available, temporary embolic agent supplied as a powder or pad that can be easily prepared for transcatheter use. Postembolization, it is completely absorbed by the body with an arterial vascular recanalization time of 2–3 weeks. Gelfoam is available in powder form with a particle size of 40 to 60 μm, which is preferable for distal capillary-level embolization. Alternatively, a slurry of Gelfoam is prepared by scrapping the sponge in a bowl of contrast or chopping out 1- to 2-mm cubes with scissors from a larger pad and then mixing them with contrast to attain a size variation of 500 and 2000 μm. A microcatheter with a relatively large lumen of 0.027–0.028″ is generally recommended for delivery of the agent is this form.

A single large piece or “torpedo” of Gelfoam can be used for proximal embolization, but difficult catheter loading and catheter occlusion are potential disadvantages, especially when using catheters with an internal diameter of less than 0.035″. The most distinctive characteristic of Gelfoam is its rapid absorbability by macrophages, thus restoring vascular patency in a relatively short timeframe of a few days to weeks.