Hydrodissection

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.

Procedure

Equipment

• 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

Technique

• 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

Indications

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

• cervical hydrodissection - prevents nerve damage during:

  • radiofrequency ablation of thyroid nodules ³

  • deep nerve hydrodissection ⁴ - in neuropathic pain or complex regional pain syndrome

• thoracic hydrodissection - prevents vascular or cardiac injury during:

  • percutaneous mediastinal biopsy

• breast hydrodissection - prevents pneumothorax during:

  • ultrasound guided breast biopsy ⁵

  • ultrasound-guided breast cancer cryoablation ⁶

• retroperitoneal hydrodissection - prevents complications of:

  • percutaneous renal tumor ablation

  • percutaneous renal biopsy

  • nephrostomy

    • percutaneous nephrostomy

    • percutaneous nephrolithotomy (PCNL)

    • percutaneous nephrostomy salvage and tube exchange

  • pyelostomy

• peritoneal hydrodissection or artificial ascites

  • all peritoneal mass biopsies and percutaneous procedures

• epidural hydrodissection

  • spinal thermoablation

Advantages

Requires inexpensive and available equipment.

It is not time consuming especially for pressurized hydrodissection ².

Disadvantages

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

Precautions

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

• hemodilution and hypervolemia

• fluid overload

• electrolyte imbalance

Complications

• cervical hydrodissection

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