What is the technique for percutaneous ethanol injection of a cystic thyroid nodule and the appropriate ethanol volume to inject?

Percutaneous Ethanol Injection Technique for Cystic Thyroid Nodules

Percutaneous ethanol injection should be performed as an outpatient procedure under ultrasound guidance, injecting 95-99% ethanol at a volume corresponding to approximately 20-50% of the aspirated cyst fluid, with the needle preferably inserted through the thyroid isthmus to prevent leakage. 1

Procedural Steps

Pre-Procedure Preparation

• Perform strict antisepsis of the puncture site
• Optional: Apply local anesthesia with 2% lidocaine along the planned puncture route (operator discretion) 1
• Position the needle through the isthmus when possible to minimize ethanol leakage during injection 1

Aspiration Phase

• Drain the cyst as completely as possible before ethanol injection 1
• For thick colloid fluid that resists aspiration:
  • Inject isotonic saline to reduce viscosity, OR
  • Use a larger gauge needle (18-21G instead of standard 23-27G), OR
  • Plan multiple treatment sessions 2, 1

Ethanol Injection Phase

Volume of ethanol to inject:

• Standard approach: 50-70% of the aspirated fluid volume 3
• Alternative evidence-based approach: Approximately 20% of initial cyst volume (based on successful outcomes in 200 cysts) 4
• Use 95-99% sterile ethanol 1, 5

The evidence shows variability in recommended volumes, but recent large-scale data 4 demonstrates excellent results (95% volume reduction) using only 20% of initial cyst volume, suggesting less may be more effective and safer.

Injection Technique

• Inject the ethanol slowly under continuous ultrasound guidance 1
• Monitor in real-time to ensure:
  • Correct needle positioning within the cyst
  • No extra-nodular leakage of ethanol 1

Post-Injection Management

Critical caveat: There is no clear consensus on whether to re-aspirate the ethanol or leave it in place 1. The literature reports:

• If re-aspirating: Leave ethanol in place for 2-10 minutes before aspiration 1
• Many operators do not re-aspirate at all

After needle removal, apply careful compression to the puncture site 1

Expected Outcomes by Nodule Type

Purely Cystic Nodules

• 85-95% volume reduction 1
• Best candidates for ethanol injection 1

Mixed Cystic-Solid Nodules (predominantly cystic >50%)

• 60-90% volume reduction 1
• May require combination with thermal ablation for solid components 1

Treatment Sessions Required

• Single session often sufficient for simple cysts
• Multiple sessions may be needed for:
  • Complex cystic nodules 6
  • Nodules with thick colloid 1
  • Volumes >20 mL 7

Important Clinical Pitfalls

Refractory cases: 5-25% of cystic nodules do not respond adequately to ethanol treatment 1. In non-responding mixed nodules that eventually undergo surgery, approximately 15% harbor differentiated thyroid carcinoma 1—emphasizing the critical importance of confirming benign cytology before treatment.

Complications are rare but include:

• Transient pain/burning (most common, preventable with local anesthesia and saline needle flushing) 1
• Transient dysphonia: 1-3% 1
• Hematoma: <1% 1

Contraindication: Never perform on nodules without two benign fine-needle aspiration biopsies confirming benign cytology 1

Follow-Up Protocol

• First ultrasound at 3-6 months post-procedure 1
• Then at 1 year
• If complete remission achieved, further ultrasound monitoring is unnecessary 1
• For hyperfunctioning nodules: Long-term thyroid hormone monitoring required due to high recurrence risk 1