What is the role of percutaneous ethanol injection (PEI) in treating a patient with a thyroid cyst?

Percutaneous Ethanol Injection for Thyroid Cysts

Percutaneous ethanol injection (PEI) is a safe, effective, and well-established first-line treatment for symptomatic thyroid cysts that recur after simple aspiration, achieving volume reduction rates exceeding 90% in most patients. 1, 2

Treatment Efficacy and Outcomes

PEI achieves excellent volume reduction with minimal ethanol requirements:

• Volume reduction rates of 95% can be achieved at 12 months after treatment completion 1
• Success rates exceed 85-100% across multiple studies, with most patients experiencing greater than 90% volume reduction 1, 3, 4
• The total amount of ethanol needed corresponds to only approximately 20% of the initial cyst volume 1, 5
• Treatment effects are durable, with sustained results at 9-10 year follow-up showing only 6.5% relapse rates among responders 4

Treatment Protocol and Technical Considerations

The procedure requires relatively few sessions with small ethanol volumes:

• Small cysts (<10 mL) typically require 1.1 sessions on average 5
• Medium-sized cysts (10-20 mL) require approximately 2.0 sessions 5
• Large cysts (>40 mL) can be successfully treated with a mean of 2.7 sessions 4
• Single-session treatment is sufficient in 45% of patients, with 31% requiring two sessions and only 13% requiring three 2

Volume of ethanol instilled should be limited:

• Use less than 2 mL of ethanol per procedure 2
• The mean ethanol volume used is typically 2.4 mL of 96% ethanol 5

Patient Selection and Indications

PEI is indicated for:

• Symptomatic thyroid cysts that have recurred after at least two complete aspirations 3
• Patients with compressive symptoms (tracheal displacement, cosmetic concerns) 3, 2
• Cysts of all sizes, though particularly effective for cysts >10 mL where surgery would otherwise be considered 3, 4
• Patients refusing surgery or at high surgical risk 5

Cytological examination must be performed before treatment to exclude malignancy 3

Important Caveats and Predictors of Success

Complex cysts respond less favorably than simple cysts:

• The presence of complex cyst architecture is an independent negative predictor of treatment efficacy 1
• Complex cysts may require more time to achieve final volume reduction 5
• Initial cyst volume positively correlates with volume reduction rate—larger cysts actually respond better 1

Viscous cysts require modified technique:

• When cystic fluid is too thick for aspiration, perform an initial PEI session to reduce fluid density before attempting complete evacuation 3
• Subsequent PEI sessions can then be performed using the standard technique 3

Safety Profile and Patient Tolerance

PEI demonstrates excellent safety with minimal complications:

• No serious complications were observed in large cohorts 1, 5, 2
• Pain perception during the procedure is minimal: 39% experience virtually no pain, 43% mild pain, and only 17% moderate pain 2
• The procedure is well-tolerated with high patient compliance 4

Symptom relief is substantial:

• Significant reduction in compression symptoms and cosmetic complaints occurs post-treatment 2
• Health-related quality of life scores at 6 months post-PEI do not differ significantly from the healthy population 2

Comparison to Alternative Treatments

PEI offers advantages over surgery:

• Avoids surgical risks and general anesthesia 5, 2
• Significantly less invasive with faster recovery 2
• More cost-effective than surgical intervention 4
• Can be performed as an outpatient procedure 2

PEI is superior to simple aspiration alone:

• Simple aspiration has high recurrence rates, making PEI the appropriate next step after failed drainage 3, 2