Last revised by Calum Worsley on 13 Feb 2024

Hydrodissection is an organ displacement technique consisting of percutaneous fluid injection in the fatty interface between the target lesion and non-target organs in order to prevent thermal injury during microwave, radiofrequency, or cryoablation by:

  • establishing a safe distance between the lesion requiring treatment and the organ at risk

  • facilitating the dissipation of heat/cold by maintaining a continuous injection flow during the ablation process; this is particularly important when the safety gap is limited to just a few millimeters (such as in the epidural space) or, at most, not exceeding 10 mm.

  • fluids 1:

    • 5% dextrose in water

      • 0.9% saline should not be used during radiofrequency ablation to avoid electrical conductivity by ions

    • contrast agent - to allow better visualization of the hydrodissection

      • should be diluted to 5% for most procedures

      • for spinal epidural hydrodissection, a dilution of 50% should be performed, to allow good visualization of the injected fluid

    • the fluid temperature should be

      • at ambient room temperature (20°C) for microwave/radiofrequency ablation

      • around 37°C for cryoablation

  • 5F sheath catheter or hydroguard coaxial needle

  • IV extension tubing

  • 60 mL Luer lock syringe

  • before dissection, a scan is conducted to ensure the quality of dilution within the syringe. to avoid injecting excessively high density contrast

  • inject low volume of dissection fluid (5-10 mL) to confirm the good positioning of the needle

  • after confirmation of the good positioning, larger volume of fluid can be injected (10 ml to 2 L), until the non-target organ is displaced

  • high volume injections (1-2 L) can be safely performed in peritoneal and retroperitoneal spaces, in the mediastinum, epidural space and subcutaneous tissues

  • sometimes more than one needle/catheter are needed to properly displace a non-target organ

  • combined with hydrodissection in high-risk lesions, a thermocouple can be placed at the interface between the non-target organ and the target lesion, allowing for the adjustment of injection rates during the ablation phase

Two types of hydrodissection are described:

  • normal pressure hydrodissection

  • pressurised hydrodissection 2

As a general rule, hydrodissection is indicated when there is non-target structure proximity ≤10 mm 8.

Requires inexpensive and available equipment.

It is not time consuming especially for pressurized hydrodissection 2.

Hydrodissection is usually ineffective when there are postoperative adhesions or after radiotherapy.

Dissection with very high volumes (>3 L) should be avoided since it can induce

  • hemodilution and hypervolemia

  • fluid overload

  • electrolyte imbalance

  • cervical hydrodissection

    • there is no significant increase in complications such as airway compression, between small and large volume-hydrodissection (<450 mL) 3

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