Ultrasound-guided microwave ablation combined with polidocanol versus anhydrous ethanol for benign cystic-solid thyroid nodules: a retrospective comparative study

Thyroid nodules are small lumps that form on the butterfly-shaped gland sitting at the base of the neck. While the vast majority of these growths are harmless and cause no trouble, some people find them bothersome. A large nodule can press on the windpipe or esophagus, causing a feeling of tightness, or it might simply be unsightly, leading to self-consciousness about one's appearance. For decades, the standard solution for a bothersome lump was surgery, which involves cutting into the neck to remove the tissue. However, surgery carries risks like scarring, infection, and the need for lifelong medication if the gland is damaged. In recent years, doctors have turned to a less invasive approach called microwave ablation. This technique uses a thin needle guided by ultrasound to deliver heat directly into the nodule, cooking the solid tissue until it shrinks and is eventually reabsorbed by the body. For nodules that contain both solid parts and fluid-filled cysts, doctors often add a second step: injecting a liquid sclerosing agent. This chemical irritates the lining of the fluid pocket, causing it to collapse and stick together so the fluid does not return. The question facing clinicians is which chemical works best to pair with the heat treatment.

A team of researchers at hospitals in Huai'an, China, set out to compare two common options for this liquid injection. One option is anhydrous ethanol, a highly concentrated form of alcohol that has been used for years to treat cysts. The other is polidocanol, a detergent-like substance often used to treat varicose veins and other cystic conditions. The researchers wanted to know if swapping the alcohol for the detergent would change how well the nodules shrank or how safe the procedure felt for the patient. They looked back at the medical records of 152 patients who had undergone this combined treatment between 2023 and 2025. Roughly half of the patients received the alcohol mixture, while the other half received the polidocanol mixture. All patients had benign nodules that were at least two centimeters wide and were large enough to cause cosmetic concerns or physical discomfort.

The procedure itself is a careful, step-by-step process. Under local anesthesia, a doctor uses ultrasound to locate the nodule and guide a needle into it. First, they drain the fluid out of the cyst. Then, they wash the empty space with a liquid. In one group of patients, this liquid was the anhydrous ethanol; in the other, it was the polidocanol. The liquid is left inside for ten minutes to work its magic on the cyst wall before being sucked out. Immediately after, the doctor uses the microwave antenna to heat the remaining solid part of the nodule, destroying the cells so the lump will shrink over time. The team checked on these patients at one, three, six, and twelve months to see how much the nodules had disappeared. They also measured how the patients' necks looked, checked their thyroid hormone levels to ensure the gland was still working normally, and recorded any side effects like pain, fever, or hoarseness.

The results showed that both methods were highly effective at shrinking the lumps. After one year, the nodules in the alcohol group had shrunk by an average of 86.85 percent, while those in the polidocanol group had shrunk by 88.03 percent. Statistically, this tiny difference meant the two treatments performed equally well. The researchers also looked at specific types of nodules, such as those with more fluid versus more solid tissue, or those with different levels of blood flow, and found that neither chemical worked better than the other in any of these subgroups. The cosmetic results were equally matched; patients in both groups saw their necks become smoother and less noticeable, with no significant difference in how visible the lumps remained after a year. Furthermore, the thyroid function of the patients remained stable in both groups, confirming that the heat and the chemicals did not harm the healthy parts of the gland.

The most notable difference between the two groups emerged when the researchers looked at how patients felt during and after the procedure. The group that received the polidocanol injection reported far fewer side effects. Only about 10 percent of the patients in the polidocanol group experienced any adverse event, such as pain, nausea, or a fever. In contrast, nearly 31 percent of the patients who received the alcohol injection reported similar issues. The alcohol group saw more instances of pain, nausea, vomiting, and a specific reaction that felt like being drunk, likely because the alcohol can irritate nearby tissues or be absorbed into the bloodstream. While serious complications were rare in both groups, the lower rate of discomfort with polidocanol suggests it might be the gentler choice for patients. The study concludes that while both chemicals achieve the same goal of shrinking the nodule, polidocanol offers a smoother recovery with fewer unpleasant side effects, making it a strong candidate for future treatments, though larger studies are needed to confirm these findings over the long term.