Continuous, Large-Volume Hydrodissection to Protect Delicate Structures around the Thyroid throughout the Radiofrequency Ablation Procedure

Abstract

<b><i>Introduction:</i></b> Small-volume hydrodissection liquid dissipates rapidly and confers only short-term protection during radiofrequency ablation (RFA) of benign thyroid nodules. The aim of this study was to establish a safe method for continuous, large-volume hydrodissection. <b><i>Methods:</i></b> A long needle was inserted and positioned outside the thyroid capsule; 5% glucose was injected to maintain a 3- to 5-mm continuous safety buffer. From October 2015 to July 2020, 166 patients underwent hydrodissection with different volumes, and ablation efficacy and complications associated with different liquid volumes (≤40 mL vs. >40 mL) were compared at 1-month postprocedure. Moreover, 20 mL liquid (equivalent to 250 mL in the human body) was injected around the thyroid of a rhesus monkey, after which CT scans were used to visualize the liquid’s fate and verify its safety. <b><i>Results:</i></b> The 51 patients with 10–40 mL injections and 116 patients with larger injections (45–450 mL) showed similar complete ablation rates (88.46% vs. 90.44%, <i>p</i> = 0.582), comparable 6-month VRR (82.79% vs. 76.62%, <i>p</i> = 0.079), and complication incidences, although the latter group had larger nodules (9.11 mL vs. 13.79 mL, <i>p</i> = 0.003), more energy delivered (3.44 kcal vs. 6.04 kcal, <i>p</i> < 0.001), and longer operation times (51.37 min vs. 69.2 min, <i>p</i> < 0.001). In the animal experiment, the 20 mL of liquid diffused quickly (within 10 min) from the vicinity of the thyroid to the mediastinum and retropharyngeal space. It was observed in the kidneys at 10 min and disappeared from the neck and chest space by 24 h. <b><i>Conclusions:</i></b> Continuous, large-volume hydrodissection can protect the delicate structures around the thyroid throughout the RFA procedure and might be beneficial in large thyroid nodule ablation.

Perithyroidal hemorrhage caused by hydrodissection during radiofrequency ablation for benign thyroid nodules: Two case reports

“…It is widely regarded as safe, and few studies have shown reports of its related complications or side effects. Regarding RFA for BTNs, only one study showed that large-volume hydrodissection might cause more patients to suffer pain and chest tightness[ 9 ], but whether hydrodissection causes perithyroidal hemorrhage has not been reported. We supposed that the possible causes of perithyroidal hemorrhage secondary to hydrodissection during RFA were as follows: (1) Most BTNs that need treatment are large and hypervascular.…”

“…This technique could effectively avoid thermal injury to the surrounding critical structures and achieve complete treatment. The injection needle should remain in place[ 8 ] so that the fluids can be injected continuously to achieve a sufficient safety margin during the procedure because the injected fluid may spread to other cervical spaces[ 9 ]. In that case, the remaining needle has a possibility of causing perithyroidal hemorrhage if the nodule has a rich blood supply.…”

Novel and Advanced Ultrasound Techniques for Thyroid Thermal Ablation

“…This technique aims to minimize pain during ablation and to protect adjacent structures, especially those located laterally to the thyroid, such as the middle cervical sympathetic ganglion and the vagus nerve [ 15 , 18 , 19 ]. The injected lidocaine serves as a temporary barrier between the thyroid capsule, strap muscles, and carotid sheath, but it eventually disperses into the mediastinum [ 20 ]. Care should be taken to avoid complications such as voice change if lidocaine leaks into the peri-tracheal area.…”

“…4 ), where the solution is injected from the posterior surface of the isthmus (pre-tracheal) and directed toward the space around the “danger triangle.” Skilled practitioners may choose to keep the injection needle in place ( Fig. 5 ) [ 17 , 20 ] to continuously administer the solution and maintain the dissection gap. The posterior approach, involving HD between the thyroid and retropharyngeal space, can be applied using either trans-isthmic or lateral cervical approaches ( Fig.…”

“…The posterior approach is strongly recommended for ablating deep nodules in the right lobe, considering the slightly lateral path of the RLN compared to the left side [ 10 ]. Using a large volume of HD fluid, typically greater than 40 mL, has yielded satisfactory outcomes [ 20 ]. In our experience, transient hoarseness or voice changes can sometimes occur due to compression and the cooling effect on the superior laryngeal nerve or RLN, but these symptoms usually resolve before the ablation procedure is completed.…”