To Evaluate the Success of Sialendoscopy Assisted Intraoral Approach for Removal of Submandibular Hilar Stones

Abstract

To assess the success of sialendoscopy assisted intraoral approach for removal of hilar stone of submandibular gland. To evaluate the ductal system for any concomitant pathology. Conventionally the treatment for submandibular hilar stones has been gland excision. Being an open procedure, sialadenectomy has its own range of complications. After the advent of sialendoscopy there has been a paradigm shift in the management of hilar stones. The current study was done to evaluate the success of sialendoscopy assisted intraoral approach for removal of submandibular hilar stones. The sample size was 30. A diagnostic sialendoscopy was performed followed by intraoral dissection using “the surgical triangle approach” defined by Park et al. The light of sialendoscope was used as a marker of intraoral incision which was given lateral to sublingual gland in the floor of mouth corresponding to the last three teeth. The surgical triangle was exposed which was bounded by the lingual nerve, medial border of mandible and posterior border of mylohyoid muscle. The hilum lies within this triangle and hence incision was given on the duct and stone retrieval was done. 88.8% of palpable submandibular hilar stones and 66.7% of the non palpable stones could be removed. 87.5% of hilar stones and 83.3% of hiloparenchymal stones could be removed. 86.7% of the glands can be preserved by this approach for management of large submandibular hilar and hiloparenchymal stones. Using this approach non palpable stones can also be removed.

Introduction

Sialolithiasis is the most common cause of sialadenitis worldwide. Its incidence as reported on autopsy is 1.2% [1]. About 80–90% of these stones affect the submandibular gland of which 40% are found in the distal part of the duct and the remaining 60% in the hilum or the parenchyma of the gland [2].

Before the advent of sialendoscopy most of the submandibular stones were removed by gland excision except the distal ductal stones in which intaoral approach was tried [2]. Sialadenectomy being a more radical procedure has its own set of complications ranging from intraoperative haemorrhage, injury to the lingual, marginal mandibular and hypoglossal nerve, wound infection, hematoma and neck scar [1, 3].

In the era of minimally invasive surgeries, various conservative techniques have been developed such as extracorporeal lithotripsy, sialendoscopy with basket retrieval and intracorporeal lithotripsy [4–8]. Sialendoscopy was introduced in the year 1994 by Nahlieli who used rigid miniendoscopes. In 2000 Marshal used similar approach for removal of these stones because of its minimally invasive nature and avoidance of complications. The advantage of this new technique is that the surgeons can visualize the duct lumen as well as the pathologic features, making the diagnosis according to the endoscopic findings [9, 10]. Also, interventional approaches can then be performed, aiming to eliminate the obstruction or dilate the duct [10].

But for the large, hilar and hiloparenchymal stones in which sialendoscopy has failed or cannot be employed, intraoral approach for stone removal can be employed. In the conventional intraoral approach, under general anaesthesia after exposing the floor of mouth the sublingual gland is identified and an incision is made along its medial border. The submandibular duct and the lingual nerve are identified and preserved. The sublingual gland is retracted laterally and the submandibular duct is traced proximally till the location of the stone. The assistant then raises the floor of the mouth with pressure in the submandibular triangle. A longitudinal incision is given on the stone protuberance which is followed by stone retrieval. The duct is then irrigated using saline and closed using 6–0 polyglactin sutures and the floor of mouth with 4–0 polyglactin sutures [2].

Another technique of intraoral approach as described by Zenk et al. involves dissection of the submandibular duct from the ostium until the stone becomes visible. The duct is exposed intact along with the lingual nerve followed by a limited incision of the duct over the stone. In this technique suturing open duct to the floor of the mouth creates a neo-ostium proximally while the limited ductotomy allows the duct anatomy to be maintained [2].

These intraoral approaches have certain disadvantages such as injury to lingual nerve as well as ranula formation which occurred when the sublingual gland was transgressed through an incision that was placed too laterally in the floor of mouth. To overcome the above mentioned complications alterations have been used in the surgical technique in one of which the incision was made medially and the sublingual gland retracted laterally therefore allowing the dissection to proceed below the deep surface of the sublingual gland [2].

In our study we will used intraoral approach as described by Park et al. which is based on ‘the surgical triangle’ as the landmark. This triangle is delineated by the lingual nerve, medial border of the mandible and posterior border of mylohyoid muscle. In contrast to the conventional approach, this approach does not require exposure of the submandibular duct in its entire length. Also, the sublingual gland will not be dissected or removed thereby preventing ranula formation which is not an uncommon complication of the conventional approach [4].

Materials and Methods

This study was conducted in the Department of Otorhinolaryngology, Guru Teg Bahadur Hospital, Delhi. Thirty patients with submandibular hilar stone were included in the study. The study was carried out in accordance with the ethical guidelines of the ‘Declaration of Helsinki’ and Institutional Review Board approval was obtained.

Patients presenting with submandibular gland pain and swelling were included in whom non contrast computed tomography was suggestive of submandibular hilar stone.

Exclusion Criteria

• History of any prior surgical intervention of oral cavity

• Any limitation in mouth opening

• All patients in whom the stone could be removed using sialendoscopy were excluded from the study.

Workup of Patient

Patients presenting with submandibular gland swelling or pain were subjected to a detailed history and clinical examination (general and local) followed by preoperative anaesthesia checkup clearance. A pre operative non contrast computed tomography of the submandibular gland was performed in all cases for stone localization and assessment of its size. Informed consent was taken for sialendoscopy assisted intraoral stone removal from all patients. An informed consent for participation in the study and publication was taken from all the patients.

Technique

Under general anaesthesia with nasotracheal intubation, patient was placed in supine position with the surgeon positioned at the head end of the patient. After opening the mouth, the tongue was retracted to the opposite side. One assistant was there in the surgery who pushed the submandibular area in the upward direction for better elevation of the Wharton’s duct and the submandibular gland within the oral cavity.

In our study, a diagnostic submandibular sialendoscopy was performed in all cases to rule out any ductal pathology and for exact localization of the stone (Fig. 1). All patients were then given a trial of stone removal using sialendoscopy. Only in cases where stone removal was not possible by sialendoscopy were included in this study and thereby subjected to intraoral technique.

Fig. 1.

Stone behind mucosal fold in the hilum

The light of endoscope delineated the duct location in the proximal region and was used as a marker for incision. The posterior tongue was retracted to the opposite side and incision corresponding to the last three teeth was made in the floor of the mouth approximately 1 cm away from the mandible. Blunt dissection was done to expose the hilar area of submandibular gland using “the surgical triangle” (Fig. 2) as the surgical landmark without dissecting or removing the sublingual gland [3]. The boundary of the surgical triangle was delineated by the lingual nerve, medial border of the mandible and posterior border of mylohyoid muscle.

Fig. 2.

The surgical triangle

We then considered an imaginary line along the Wharton’s duct. After performing the mucosal incision along the lateral border of the sublingual gland located in the floor of the mouth up to the third molar tooth we visualized the sublingual gland and lingual nerve. Next, we retracted the lingual nerve to the medial side and identified the medial border of the mandible and the posterior border of mylohyoid. Due care is taken to prevent injury to lingual nerve.

In the surgical triangle delineated by these three structures, we tried to visualize the hilar area of the submandibular gland (Fig. 3) by again putting the endoscope for stone localization. Following this, incision was made over the duct and the stone was retrieved. Stenting was done using nasogastric tube no. 5. Mucosal incision was closed. In some cases mylohyoid muscle had to be partially incised to expose the hilar area. The duration of surgery ranged between 70–120 min.

Fig. 3.

Hilum with stone in the surgical triangle

Postoperative course of antibiotic and analgesic was given to all patients for a period of one week. Patients were discharged after 3 days in which they received intravenous steroids for reducing post operative oedema. Stent was kept for at least one week. Patients recovered within 10 days post surgery.

Observations and Results

In this study, the mean age of presentation was 31.80 ± 12.01 years and the range of age varied between 12–60 years.

30% (9) patients had symptoms for less than 1 year while 26.7% (8) patients had symptoms for more than 5 years.

In 27 patients the stone was palpable.

88.8% (24) of the palpable stones could be removed by intra oral approach.

66.7% (2) of the non-palpable stones could also be removed by intra oral approach.

The success rate of stone removal for hilar stones was 87.5% whereas for the hiloparenchymal stones the success rate was 83.3%.

In 90% (27) of the patients stone could be seen on diagnostic sialendoscopy.

88.8% (24) of the patients in whom stone could be seen on sialendoscopy had successful removal of the stone.

Successful stone removal by intra oral approach was achieved in 86.7% (26) patients.

However, in 4 cases stone could not be visualized on dissection and hence not removed. Two of these patients were subjected to submandibular gland excision by external approach. In other two cases the consent for gland excision was not given.

Out of 26 successful cases stenting was done in 24 patients.

After a follow up period of 2 weeks 20 patients (66.7%) complained of tongue numbness, restricted tongue movement was seen in 2 (6.7%) patients while only 1 patient complained of decreased taste perception.

After a follow up period of 4 weeks 4 patients (13.3%) complained of tongue numbness, restricted tongue movement was seen in 2 (6.7%) patients while only 1 patient complained of decreased taste perception.

Initial transient tongue numbness was due to stretching of the lingual nerve during dissection. All patients with numbness of tongue were relieved within 3 months after the surgery.

The restricted tongue mobility and decreased taste perception was also relieved within a follow up period of 3 months. The restriction in tongue movement was experienced due to suturing in the floor of the mouth.

Follow up of 1 year was done in all cases. One patient developed a recurrent stone 9 months after the surgery.

The demographic profile of all patients with their clinical and radiological features has been summarized in Table 1.

Table 1.

Patient demography with clinical and radiological findings

Age
< 25 yr	9
25–45 yr	17
> 45 yr	4
Gender
Male	21
Female	9
SIDE
Right	17
Left	13
Intra oral discharge
Present	25
Absent	5
Stone palpability
Yes	27
No	3
Stone site on NCCT
Hilum	24
Hiloparenchymal	6
Size (mm) on NCCT
< 5	2
10	21
> 10	7
Number of stones on NCCT
Single	26
Multiple	4

Discussion

Sialolithiasis is the most common cause of salivary gland obstruction, mainly in submandibular gland [11]. It is widely held view that hilar stones cause permanent structural damage to the gland thereby predisposing to recurrent infection of the salivary gland [12].

Transcervical excision of the submandibular gland has been regarded as the standard treatment for the intraglandular stones and large hilar stones. However, this approach has several disadvantages such as cosmetic problem and scarring [13], marginal mandibular nerve injury causing facial weakness and altered sensation over the lateral border of the tongue due to streching of lingual nerve [14–16]. Rarely hypoglossal nerve can also be injured. Also, histopathological study of submandibular gland after excision for sialolithiasis demonstrated that a significant percentage of gland exhibit normal histologic findings [17]. Recent advancement in research and literature suggest that salivary gland can regain useful function after removal of hilar calculi [18–23].

Therefore, nowadays treatment of salivary stones is changing from gland extirpation to gland preserving surgery by minimally invasive techniques, including lithotripsy and sialendoscopy [7, 19, 24]. Despite their desirable results, these minimally invasive techniques have their limitations. The success rate of extracorporeal lithotripsy ranges from 40% in submandibular gland to 75% in parotid gland, with poorer results in cases of large stones. Intraductal laser fragmentation and basket extraction of stones are possible in only 80% of cases. The remaining 20% fail because of large stones and stenotic ducts, which prevent retrieval even if these stones can be captured [9].

Sialendoscopy is a minimally invasive surgical technique. The miniaturisation of the instrumentation has made it possible to eliminate pathologic features located in the deep ductal system with a high cure rate and a low morbidity rate of postoperative complications. However large hilar stones are still one of the most technically challenging issues in sialendoscopic surgery. Such stones are usually attached to the ductal wall rendering them incapable of being removed by the minimally invasive techniques. Even if these stones can be captured it is not possible for them to pass through the relatively narrow duct. Therefore, we used the surgical technique of sialendoscopy assisted open sialolithectomy to remove large submnadibular hilar stones [10].

The following study was undertaken for removal of hilar stones diagnosed on Non contrast computed tomography scan. Thirty cases were included in the study who underwent surgery under general anaesthesia with nasotracheal intubation which was essential for providing the necessary exposure of the surgical field required for inta oral dissection.

In our study the size of stone ranged from 4–32 mm while in a study by Liu D G et al. on 70 patients, the stone size ranged from 4 to 15 mm.

The mean (SD) size of stone in our study was 8.53 mm (5.31). The mean size of successfully removed stone was 8.95 mm (5.6) and that of unsuccessful cases was 5.8 mm (0.54).

Eun Y G et al. reported the mean stone size as 9.0 mm (4.5) in intraoral stone removal cases while the mean size of stone in submandibular gland resection cases was 5.2 mm (2.7).

The median diameter of stone removed by Su Y et al. using sialendoscopically assisted open sialolithectomy was 1.5 cm (range 0.8–2.5 cm) [10].

Capaccio et al. studied 84 patients with a mean stone size of 11 mm and range 7–25 mm by transoral approach [1]. In their study 46 patients had hilar stone, 34 had hiloparenchymal stone and 4 had parenchymal stone. Successful removal was possible in all but one patient with parenchymal stone [1].

They reported recurrent stone in 16 out of 84 patients within 12 months post surgery i.e. 19% recurrence. Persistent tingling of the tip of tongue was seen in 3 patients (5.9%), hilar stenosis in 1 patient and ranula formation in 1 patient [1].

Capaccio et al. in a recent study on 479 patients with hilar stone had reported a success rate of 98.5% and all of the 7 patients with failure had intraparenchymal stones. 54 patients with successful removal developed a recurrent stone one year after the procedure [25].

In our study the successful stone removal by “the surgical triangle” technique was achieved in 26 out of 30 cases (86.7%) while in the rest four cases where intra oral stone removal was not possible two underwent gland excision. The remaining two patients did not give consent for gland excision. Marginal mandibular paresis was seen in both cases where gland excision was performed. One of them had complete recovery at 4 weeks while other patient had residual palsy at 3 months.

Woo et al. studied 29 cases and reported five of them to be having multiple stones [26]. All the patients with multiple stones had successful removal of stones via intraoral approach. They reported the mean stone size of 9 mm (5) for hilar stone removal by transoral approach [26]. They reported that the duct returns to normal anatomy without sialodochoplasty suggesting that the hilar duct has adequate plasticity to regain its normal anatomy when the obstruction has been resolved. However, saccular dilatations usually developed after the removal of large stones (> 10 mm). Since the severely dilated duct had little plasticity, the duct did not recover and saccular pooling developed [26].

In the study by Park et al. on 172 cases, 75% patients had a stone size of less than 9 mm similar to our study whereas 76.7% patient had a stone size less than 10 mm [5]. They had 8.1% cases with multiple stones [5]. They found mild paraesthesia on the same side of tongue in all patients which got relieved within 3 months in all but one patient in whom it lasted for more than 3 months [4].

They had recurrent stone in 13 patients. 12 of them again underwent intra-oral stone removal and one had gland excision. Temporary lingual nerve paraesthesia was seen in only 1 patient [5].

In the approach described by McGurk et al. the duct is exposed, opened over the stone, and then resutured [19]. They stated that the small stones which cannot be palpated are contraindication for intra oral removal [19] as oppose to our study where non palpable stones were also removed.

They reported repeated infection of gland in 3 out of 54 patients (5%) due to stricture, ranula in 1 patient (1.8%), meal related syndrome in 2 patients (4%) and temporary tongue numbness in all patients [3].

Zenk et al. in his technique described the incision of the submandibular duct together with the oral mucosa from the ostium until the calculus becomes visible, identifying the lingual nerve in the process, thus creating a neo-ostium [11].

Nahlieli et al. reported a ductal stretching technique for removal of hilar stone under endoscopic guidance in which the duct was isolated over the first molar and then stretched forward. Ductal incision was given over the stone and the distal 5 mm of the duct was excised and sutured over the orifice region followed by drain insertion. Advantages of the endoscopy like exact localisation of stone, occurrence of multiple stones, ductal strictures and any other ductal pathology as described by Nahlieli is shared by our study as well [27].

In the technique described by Marshal et al. the oral floor incision was guided by the location of the illuminated area and was usually approximately 2 cm in length. He emphasised that the minimal posterior incision decreases the risk of further ductal stenosis and provided a more rapid recovery for the patient [28].

Combes et al. in their study on 105 patients documented ranula formation in two patients and persistent tingling sensation on lateral border of tongue in 6 patients (6%) [2].

In a study by Liu et al. one out of 65 patients complained of temporary lingual nerve paresis, 2 developed ranula, 11 had a meal related syndrome and 2 developed recurrent stone [9].

Roh et al. in their study on 59 patients reported recurrent stone in 4 patients out of 54 successful cases (7.4%), temporary lingual nerve hypoesthesia was seen in 3 patients while none developed ranula [29].

4 of our patients had multiple stones with 100% successful removal. Two patients out of these four had 2 stones each, one had three stones and one of them had four stones.

In our study a diagnostic sialendoscopy was done in all cases to know the exact location of stone and any concomitant ductal pathology. In two patients a mucosal band was seen just distal to the stone in hilum. In one of the patient the mucosal band was seen in the hilar area with non visualisation of the stone as the scope could not be negotiated beyond it. In another patient during sialendoscopy ductal perforation occurred due to which the procedure was abandoned and stone could not be visualised. In two cases stone was seen perforating the floor of the mouth in the area of proximal duct. In two cases with multiple stones two stones were seen separately in two primary branches at the hilum. In all the above mentioned cases stone was successfully removed.

In previous studies the criteria for surgery have been that the stone should be either sonographically localised above the mylohyoid or palpable [3, 11, 19].

Our study corroborate with the findings of Park et al. where 97% patients with palpable calculi had successful removal while the success rate in stones which were uncertain or non palpable was 66.7% [5]. Similar results were obtained in our study where 27 (90%) patients had palpable stones out of which 24(88%) patients had successful removal. While in the 3 non palpable cases, successful removal was possible in 2 (66.7%) patients.

Unlike most of the studies the surgical procedure adopted in our study is different as the submandibular duct was not fully exposed for detecting the hilar or intraparenchymal stones. We only exposed the hilar area using “the surgical triangle” as the landmark without dissecting or removing the sublingual gland which is otherwise required to trace the submandibular duct from the distal to the proximal end. The incision in our study was made lateral to the sublingual gland in the floor of mouth which is mobilised medially thereby preventing injury to the sublingual gland and postoperative ranula formation [4]. We did not create a neo-ostium or repair the incision site of the duct similar to that by Eun Y G et al. [18].

In our study, patients were followed up at 2 weeks and 4 weeks for tongue numbness, any restriction of tongue movement and altered taste sensation.

Numbness in the anterior part of the tongue was noticed in 20 (66.7%) patients at 2 weeks which got reduced to 13.3% at the end of 4 weeks. Complete recovery was seen in 100% patients at the end of 3 months signifying that none had permanent lingual nerve injury. During the course of surgery, in each case the lingual nerve was identified, dissected and retracted off the submandibular duct in its entire course. In none of the cases was the nerve injured thereby attributing the postoperative temporary numbness due to intra-operative streching of the nerve.

None of our patients had an altered perception of taste. Restricted tongue mobility was seen in two (6.7%) patients at 2 weeks in one of which it was relieved at 4 weeks and in another within 3 months.

Four weeks after the surgery, 3 patients (10%) complained of meal related syndrome in which the gland swells on food intake. Resolution of symptoms was seen in two cases within 3 months. One of them who had persistent symptoms underwent an NCCT Scan with no evidence of any calculus.

Recurrent stone was only seen in 1 out of 30 patients after a period of 9 months post-surgery which was diagnosed on an NCCT scan.

Hypoglossal nerve is not in the surgical field by using this intraoral approach, so was never injured. None of the patient developed post-operative ranula, hematoma formation, wound dehiscence etc.

The limitation of our study was a small follow up period. A longer follow up is required to evaluate any post operative strictures and also for assessment of gland function.

We conclude that sialendoscopy assisted intraoral approach for submandibular hilar stone removal is a safe, feasible technique with high success rate and minimal complications. Using this approach majority of the glands can be preserved as well as non palpable stones can also be removed.

Funding

None for any of the authors.

Declarations

Conflict of interest

None for any of the authors.