Ultrasound-Guided Sialendoscopy with Holmium: Yttrium Aluminum Garnet (YAG) Laser Treatment of Parotid Sialolithiasis.

BACKGROUND At present, promptly diagnosing sialolithiasis is easy with the assistance of various noninvasive diagnostic procedures. However, the treatment of parotid sialolithiasis remains inadequate. An immense challenge for oral maxillofacial practitioners is the treatment of large radiolucent stones, especially of those that are located in a hard-to-approach positions in the salivary ducts. This case report aims to propose the protocol of a new technique to improve the management of parotid salivary stones. In 2017, our hospital was the first medical center in Vietnam to implement this technique in the treatment of parotid sialolithiasis. CASE REPORT A 38-year-old man was diagnosed with parotid sialolithiasis based on ultrasound and computed tomography (CT) scanning results. He underwent ultrasound-guided sialendoscopy with holmium: yttrium aluminum garnet (YAG) laser lithotripsy. The stone was large (22×12 mm) and in an unfavorable position. A narrow strip of fibrous tissue in front of the stone was also noted. However, 1 week after surgery the patient had local swelling of the parotid gland and no manifestation of inflammation, facial paralysis, or obstructed saliva through the drainage ducts. The patient was examined for clinical symptoms and glandular ultrasound at 3 months and 6 months after the procedure. The follow-up examination results showed normal parotid gland function, no complications or recurrence of stones, and no narrowing of the gland duct. CONCLUSIONS Ultrasound-guided sialendoscopy with holmium: YAG laser is safe and effective for treating parotid salivary gland stones.

Background

Sialolithiasis is the presence of calcified stones in the salivary gland or ducts. Submandibular gland sialolithiasis is most common (80–85%), followed by parotid gland sialolithiasis (5–10%), and sublingual and minor salivary gland sialolithiasis, which constitute the remaining 5% of cases [1-3]. The most common management is complete excision of the malfunctioning gland with the stones [4-6]. In certain patients, an intraoral sialolithotomy is indicated when a stone is palpable and solitary without a difficult location in the oral cavity [7].

At present, prompt diagnosis of sialolithiasis is not difficult owing to the availability and assistance of various noninvasive diagnostic procedures; however, the treatment of parotid sialolithiasis remains inadequate [8,9]. An immense clinical challenge for oral maxillofacial practitioners is the treatment of large radiolucent stones, especially those that are located in a hard-to-approach positions in the salivary ducts. In recent decades, the implementation of medical lasers in lithotripsy has been a groundbreaking management technique in urological operations, and laser lithotripsy has also been used in dentistry, plastic surgery, dermatology, otolaryngology, and oral and maxillofacial surgery [10]. Some recent reports indicate that the success rate of laser applications, especially holmium: yttrium aluminum garnet (YAG) lasers, is >80%, and this type of laser has been positively rated with regard to its fragmentation properties [11]. Whether the composition of a salivary stone affects outcomes is unknown; however, some experimental studies using in vitro models have shown that a holmium: YAG laser may be effective in disintegrating stones, regardless of their physical and radiological characteristics [12]. Based on the results of recent studies on the clinical use of this type of laser, and considering the cost-effectiveness of the method, the holmium: YAG laser is a popular option if laser lithotripsy is intended.

This report describes the case of a patient who was diagnosed with large parotid salivary gland stones in a remote and complex anatomical site of the parotid salivary gland duct that were successfully treated using ultrasound-guided sialendos-copy with holmium: YAG laser lithotripsy.

Case Report

On June 5, 2020, a 38-year-old man was admitted to the hospital complaining of a painful left ear infection, which had been ongoing for approximately 1 week. The patient also reported having painful swelling of the left parotid area several times in the past 5 years. Approximately 1 week after the hospital visit, the patient experienced pain in the left parotid area. He underwent medical examination and treatment at other specialized teeth and maxillofacial hospitals, but without improvements. Therefore, he requested a transfer to our institution, the Hue Central Hospital (Hue City, Vietnam), for further treatment.

On examination, the patient’s face was unbalanced through the middle line and the left parotid region was swollen. He had moderate palpable pain and normal skin appearance (). Upon clinical examination of the mouth, we found a Stenon tube hole on the left was red. On pressing the left ear canal and stroking along the left Stenon tube, white pus flowed through this opening.

To clarify the diagnosis, the patient underwent an ultrasound of the cheek and left ear parity and a computed tomography (CT) scan of the head and face (). The ultrasound revealed that the left parotid salivary gland was approximately 10×4 mm, with a dilated duct of approximately 4 mm. Its position was just below the left cheekbone arc, and the hole diameter was approximately 2.4 mm. The patient was informed of the left parotid salivary gland stones, which were identified on the CT scan. In particular, the parotid salivary gland on the left had a higher density than did the right gland, and it had infiltrated the surrounding adipose tissue. After injecting contrast material, a strong and inhomogeneous absorption of contrast by the salivary gland was noted. The damage inside was limited and was 22×12 mm in size. Thus, based on clinical history, clinical examination, and subclinical results, the patient was diagnosed with left parotid salivary gland stones.

Based on the diagnosis, we advised the patient regarding treatment. The patient and family agreed on our performing holmium: YAG laser therapy under ultrasound guidance. Preoperative tests to ensure eligibility for surgery and participation in clinical research were done. Two hours before surgery, the patient underwent a second ultrasound to determine the location of the stones.

The surgical procedure was conducted as follows: (1) the Stenon duct opening in the mouth and face was located; (2) the catheter and endoscopic guidewire were placed through the catheter hole under ultrasound guidance and the stone was approached; (3) the endoscopic guidewire was fixed and the catheter was removed; (4) 4 Fr, 6 Fr, 8 Fr, or 10 Fr catheters via the guidewire were used under ultrasound guidance to approach the stones; (5) the lithotripsy machine parameters were checked and the scanner was placed close to the gravel under ultrasound support; (6) holmium: YAG laser lithotripsy was used with the power installed at 6 W, frequency at 10 Hz, and power at 0.6 J; (7) the plastic tube (6–8 Fr) was passed through the guidewire under ultrasound guidance; and (8) the guidewire was unplugged and the plastic tube was fixed into the lining close to the Stenon tube and the lip edge (). The patient was treated with antibiotics and anti-inflammatory analgesia for 7 days after surgery.

The stone was large and in an unfavorable position. A narrow strip of fibrous tissue in front of the stone was also noted.

However, 1 week after surgery the patient had only local swelling of the parotid gland, with no manifestation of inflammation, facial paralysis, or obstructed saliva through the drainage ducts. Four weeks after surgery, further drainage was performed and he underwent an on-site ultrasound before tube removal. No stones were detected. After withdrawing the tube, local stimulation revealed saliva secretion through the Stenon tube. The patient was scheduled for follow-up visits at 3 months and 6 months after surgery (). Ultrasound examination revealed that the left parotid duct was slightly dilated but had no stones, and the parenchymal salivary tissue was non-edematous.

Discussion

The first application of endoscopic laser lithotripsy of the salivary gland may have been recorded in 1990 by Gundlach et al [13], who used a laser beam to fragment salivary stones. Since then, many systems of medical laser have been tested for this application, with different results [7]. In 2017, our hospital was the first medical center in Vietnam to implement this technique in the treatment of parotid sialolithiasis.

Few studies have been conducted to compare the different laser systems in the application of sialendoscopic laser lithotripsy [11]. Whether the holmium: YAG laser is more effective than other treatments remains unknown. In an in vitro study in 2008, Siedek et al [14] compared 2 different clinically approved laser systems. These authors found that the holmium: YAG laser could fragment all stones to a powder in a somewhat slow but effective soft milling process. The holmium: YAG laser also revealed minimal direct risks to the nearby tissue. The high success rate of holmium: YAG laser-assisted lithotripsy was further established by a recent study by Sionis et al [15], who found that total extraction after disintegrating stones was achieved without complications in 14 of 15 patients. They reported removing large stones successfully.

Our initial results show the effectiveness and safety of laparoscopic salivary gland surgery using a holmium: YAG laser under ultrasound support. This success was based on the good coordination between doctors, facilities, and equipment from 3 specialties of maxillofacial surgery, urology, and functional exploration at the Hue Central Hospital.

The use of holmium: YAG laser under ultrasound guidance requires further study. Particularly, the coordination of doctors and equipment from different departments and the procedure for using the surgical laser machine, including its frequency, energy level, and pulse duration, need to be studied further. Surgeons should be trained to use optic endoscopes, in addition to other methods of surgery. Difficulty in accessing and dispersing stones in abnormal cases is owing to glandular anatomy (narrow, zigzag, and small branching anatomy) or the location of stones in hard-to-approach places (deep in glandular tanks).

In recent years, endoscopically controlled laser lithotripsy has become a regular procedure to fragment urinary stones and it has also been applied in treating sialolithiasis, with favorable preliminary results [15-17]. This approach has more advantages than do conventional methods using baskets or forceps. By using the highly focused laser beam, surgeons can manage several difficult types of clinical cases, which are contraindicated with the previous approaches, such as abnormally shaped and fixed stones. Moreover, the ability to crush large stones (>4 mm) into smaller pieces and to lyse the stenosis or web formation of the duct are important advantages of the endoscopically controlled laser lithotripsy technique [15].

The previous studies did not mention the application of ultra-sound in the laser sialendoscopy management of parotid gland stones [7]. Based on our clinical experience, ultrasound has proven to be a very effective and supportive diagnostic technique, having many benefits that contribute significantly to the success of all 3 stages of the treatment protocol. Ultrasound is low-cost and easy to use for exploring parotid gland stones. Preoperatively, ultrasound helps to evaluate the size and position of stones and the dilation of the duct. Ultrasound also contributes to evaluation and guidance during surgery, including accessing stones in complex anatomical sites, and in early detection of complications. Furthermore, ultrasound can aid in monitoring and evaluating postoperative results before withdrawal of the drainage duct.

Conclusions

By clinically applying a holmium: YAG laser to treat parotid salivary gland stones under ultrasound support, we found that this method has the following outstanding advantages: it is less invasive than open surgery; it leaves no scars, unlike open surgery; it has a reduced risk of complications, including bleeding, nerve damage, and facial paralysis; and the time of postoperative care is shorter for patients, compared with that of open surgery. Ultrasound helps in surveying stone position and fibrotic sites and the location of tube narrowing, and accurately identifies the location of laser heads in contact with stones, increasing the efficiency of lithotripsy. Finally, it aids in evaluating the results of postoperative monitoring. This study also promotes the effectiveness of multispecialty coordination.