HydroFill®: Hydrogel Filling Coil Combining Volume Expansion with Ultra-Soft Platinum Construction

HydroFill® is a hydrogel-coated filling coil from MicroVention Terumo that brings together two complementary technologies: the ultra-soft platinum coil formulation of the HyperSoft family and the volume-expanding hydrogel coating of the HydroSoft/HydroFrame family. When HydroFill is deployed into the aneurysm sac and contacts blood, the hydrogel layer absorbs water and swells, expanding the effective volume of the coil to fill residual gaps left between adjacent coil loops while the ultra-soft platinum wire adapts to the available space geometry.

The combination of softness and hydrogel expansion gives HydroFill a dual filling advantage over its component technologies used separately: compared to HyperSoft (no hydrogel expansion), HydroFill fills more total volume per coil mass; compared to HydroSoft 3D (stiffer wire baseline before hydrogel expansion), HydroFill has a lower wire modulus and is gentler on the established coil basket during deployment.

HydroFill is available in a range of diameters and lengths appropriate for the filling phase of aneurysm embolization. It is delivered via Headway 17 microcatheter. The hydrogel coating follows the same formulation as HydroSoft, swelling to approximately 2–4 times initial volume within 5–10 minutes of blood contact. The platinum wire base is softer than HydroSoft 3D wire, providing a lower packing modulus before swelling.

Because the hydrogel swells after deployment, the final packed volume of HydroFill is substantially greater than its initial deployment volume. This means that fewer HydroFill coils are needed to fill a given residual void compared to non-swelling bare-platinum filling coils, potentially reducing procedure time and total coil count.

HydroFill occupies the same protocol position as HyperSoft — the final filling phase after framing is complete — but with the added benefit of hydrogel volume expansion reducing the number of coils required to achieve target packing density. It is most advantageous in large aneurysms where the residual void after framing is substantial, as the hydrogel expansion contribution per coil is more meaningful with larger void volumes.

In aneurysms where recanalization after a previous bare-platinum coiling procedure has created a residual cavity, HydroFill is a natural choice for retreatment: its volume expansion fills the recanalized space without requiring the operator to pack an equal volume with non-expanding platinum coils, which would be harder to introduce into the already-occupied sac.

Allow adequate dwell time after HydroFill deployment before assessing for further coil addition — at least 5 minutes to allow partial swelling. If additional coils are planned, introduce them during the swelling phase and account for the increasing void restriction as the HydroFill expands.

Do not use HydroFill for framing: its ultra-soft modulus makes it unsuitable for forming a stable basket. Always establish the frame with Cosmos 18 or HydroFrame 18 before introducing HydroFill in the filling phase.

Modern Medical Solutions is the authorised MicroVention Terumo distributor for Tajikistan and Afghanistan. HydroFill is available for neurointerventional programmes in Tajikistan and Afghanistan.

Contact Modern Medical Solutions to discuss HydroFill alongside HydroSoft, HyperSoft, and the full MicroVention Terumo coil range for optimal filling-phase coil selection tailored to aneurysm size and patient population.