Iatrogenic thyroid pseudoaneurysm following thyroid nodule radiofrequency ablation

Abstract

A 54-year-old Chinese woman presented for radiofrequency ablation (RFA) of benign thyroid nodules. A few hours after the procedure, the patient developed neck swelling and tenderness. Doppler ultrasound (US) images of the neck revealed haematoma with a vascular hypoechoic mass at the RFA site, suspicious for pseudoaneurysm. These findings were confirmed on subsequent on-table fluoroscopy following direct US-guided needle puncture and injection of contrast, demonstrating opacification of the mass and extravasation. Successful occlusion of the pseudoaneurysm was performed using US-guided thrombin injection. The patient made a good recovery with follow-up US 1 month later showing no recurrence of haematoma or pseudoaneurysm.

Background

Radiofrequency ablation (RFA) is a minimally invasive treatment for thyroid nodules that is increasingly being used as established practice, with significant reduction in nodule volume at follow-up.¹ Compared with surgical treatment, RFA has been shown to result in fewer complications, shorter hospital length of stay and preservation of thyroid function.²

We report a case of iatrogenic thyroid pseudoaneurysm (ITPA) formation following thyroid nodule RFA, which to our knowledge has not been previously reported thus far in the literature. Given the increasing trend of RFA usage in this clinical setting, it is prudent to be aware of the features of this rare but life-threatening complication. This case highlights the clinical presentation, salient imaging findings and treatment undertaken.

Case presentation

A 54-year-old Chinese woman was referred for RFA due to a visible right neck mass of 3-year history secondary to thyroid nodules. These were previously sampled and found to be benign (nodular goitre with cystic degeneration). She had no other comorbidities. Examination was significant for palpable right thyroid nodules. The patient was otherwise clinically and biochemically euthyroid.

Investigations

Preprocedure thyroid ultrasound (US) was obtained (figure 1). Following core biopsy of the dominant right thyroid lobe nodule under real-time US guidance using an 18G biopsy needle (Supercore, Argon Medical Devices, Texas, USA), RFA was performed. A peristaltic pump RF generator (Viva RF System, Starmed, Gyeonggi-si, South Korea) and an internally cooled 18G active tip electrode (Star RF Electrode, Starmed, Gyeonggi-si, South Korea) were used.

Figure 1.

Preprocedural axial ultrasound view demonstrates thyroid nodules in right upper pole and right mid pole.

Using the transisthmic approach, the RF probe (7 cm×7 mm exposed tip) was advanced into the nodules in right upper pole and right upper-mid pole. The position of the probe was confirmed with real-time US and ablation of 5 min total duration was performed using the moving shot technique. Energy applied during the RFA process was standardised at 60 W. At the end of the procedure, the RF probe was slowly withdrawn with tract ablation. Haemostasis was secured.

At postprocedure review a few hours later, the patient reported increasing neck swelling and tenderness. No focal neurological deficit, hoarse voice or pupil asymmetry was present. Repeat thyroid US was performed at the bedside, revealing sizeable haematoma at the ablation site with a vascular hypoechoic mass at its base, in keeping with a pseudoaneurysm (figure 2).

Figure 2.

Axial ultrasound view with real-time colour Doppler demonstrating haematoma at ablation site (*) surrounding a tubular hypoechoic mass with flow (black arrow), in keeping with pseudoaneurysm.

Treatment

Manual compression was attempted for approximately 30 min, which was unsuccessful. This was expected due to the size and depth of the iatrogenic thyroid pseudoaneurysm (ITPA). Following which, an attempt to inject the ITPA with thrombin was made. US findings of pseudoaneurysm were confirmed with on-table fluoroscopy following direct US-guided puncture of the pseudoaneurysm sac with a 21G needle and injection of contrast, demonstrating opacification of the mass and subsequent extravasation. Only small thyroidal branches were opacified (figure 3).

Figure 3.

Selected fluoroscopy image following direct puncture of the mass detected on ultrasound and injection of contrast, confirming findings of pseudoaneurysm (black arrow) with opacification of small thyroid branches (white arrow) and contrast extravasation (#).

Thereafter, 0.1 mL (1000 IU) of thrombin (thrombin-JMI bovine, Gentrac, Wisconsin, USA) was injected into the sac. Postprocedure US revealed complete thrombosis of the pseudoaneurysm sac with no residual flow (figure 4A).

Figure 4.

Axial ultrasound view with real-time colour Doppler demonstrating complete thrombosis of pseudoaneurysm sac immediately following thrombin injection (A) and after 1 month (B), showing no colour flow and resolution of haematoma.

Outcome and follow-up

The patient was reviewed the next day and had decreased neck swelling clinically, with bedside US (not shown) again demonstrating that the ITPA remained thrombosed. Follow-up US 1 month later revealed postablation changes with no haematoma or recurrence of the pseudoaneurysm (figure 4B).

Discussion

Thyroid nodule RFA is a safe procedure, particularly if the transisthmic approach and moving shot technique are used to avoid damage to critical structures in the ‘danger triangle’ within the neck, such as the recurrent laryngeal nerve.^1–3 Complications following thyroid RFA previously reported in the literature include laryngeal nerve palsy, sympathetic ganglion injury, brachial plexus injury, cutaneous burns and haematoma formation. Haematoma formation rate in particular has been quoted as up to 12.5%.^{2 4 5}

ITPAs are rare, with only a few cases reported in the literature. These predominantly arise following fine needle aspiration and core needle biopsy of thyroid nodules, with a minority following parathyroid gland intervention, hypopharyngeal radiotherapy and transoesophageal echocardiography.^6–9 To our knowledge, there are no prior cases specifically documenting ITPA formation following thyroid nodule RFA.

Due to its rarity, there are no established treatment guidelines for ITPA. Management options in order of invasiveness include conservative management, US-guided compression, percutaneous US-guided thrombin injections, endovascular embolisation and surgical repair.^6–10

Percutaneous thrombin injection is an effective treatment modality for treatment of pseudoaneurysms with success rate between 90% and 100%. This method has been shown to be successful in treatment of pseudoaneurysms with narrow neck (<10 mm) and sac too large for compression.^{8 10 11} Percutaneous thrombin injection was used in our case as the pseudoaneurysm neck demonstrated favourable anatomy and was easily accessible by US. Other advantages of percutaneous thrombin injection include rapid onset of effect, minimal invasiveness without need for direct arterial puncture (as compared with endovascular embolisation), shorter recovery time, low cost and low complication rate between 1% and 4%.^10–12

One concern would be non-target embolisation which may be catastrophic in the head and neck if there were intracranial communications; hence, the need to perform angiography in our case via the needle to ensure there was no aberrant communication with the central nervous system.

In summary, we present a case of ITPA following RFA of thyroid nodule. Given increasing RFA usage in this clinical setting, proceduralists should be mindful of this potentially severe complication. Our experience supports the findings in the literature that pseudoaneurysms may be effectively and safely treated using percutaneous thrombin injection.

Learning points.

• This case highlights the importance of periprocedural imaging in recognising the characteristic imaging features of thyroid pseudoaneurysms, an uncommon but potentially life-threatening complication.

• Familiarity with various embolisation procedures to apply the most appropriate and effective minimally invasive treatment.

• Strict postprocedure imaging protocols should form part of established practice guidelines to minimise adverse patient outcomes.