Large tonsillolith associated with the accessory duct of the ipsilateral submandibular gland: support for saliva stasis hypothesis

Introduction

Tonsilloliths or tonsil stones are singular or multiple calculi found in tonsillar crypts that are located unilaterally or bilaterally. A review report determined the exact location of the tonsillolith, showing that in 69.7% of cases they are located in the tonsillar tissue, 21.2% in the tonsillar fossa and 9% in the soft palate.¹ Tonsillolith prevalence in population ranging from 10 to 77 years is up to 16%.² Stones are composed of calcium salts such as hydroxyapatite or calcium carbonate apatite, oxalates and other magnesium salts.³ They can vary in size, measuring from microscopic to a few centimetres in diameter.⁴ A histological study of excised tonsils found microscopic size in 8% of specimens, while intermediate size (up to 7 mm) was found in 2%.⁴ Small tonsilloliths are usually asymptomatic and have small clinical importance. Large tonsilloliths are extremely rare, measuring several centimetres in diameter.^3,5,6 They result in clinical symptoms such as dysphagia, otalgia, chronic halitosis and foreign body sensations.^7,8 Differential diagnosis of the large tonsillolith includes phleboliths, lymph node calcifications, tuberculosis and other chronic granulomatous diseases, elongated styloid process, prominent hamular process, foreign bodies, displaced tooth, peritonsillar abscess and neoplasm.¹ Today, a detailed clinical ear, nose and throat (ENT) examination and a CT scan are sufficient for a proper diagnosis. Treatment is linked to the size and clinical symptoms and usually involves removal of the stone by curettage or tonsillectomy under general anaesthesia.⁷ A large majority of published articles regarding tonsilloliths are focused on size of the particular stone, but only a few discuss the pathogenesis of stone formation. Most authors believe that chronic tonsillitis is a sufficient factor for localized salt precipitation and formation of a tonsillolith.^3,5,7 However, some authors alternatively suggest that the tonsilloliths form as a result of saliva stasis in the efferent ducts of the small accessory salivary glands located in the oral cavity.⁹

Up to now, we have found only a few reports referencing an accessory duct of the submandibular gland.^10–13 This anomaly is defined as a duplication of the main Wharton's duct and usually running parallel to it. Its opening can be at the orifice of the gland together with the main duct or separate in the floor of the oral cavity.¹³

Case report

A 32-year-old male patient was referred to our ENT department by his general practitioner under suspicion of left peritonsillar abscess. His main symptoms were slight dysphagia and foreign body sensation, which lasted for 1 year. He had no medical history of chronic tonsillitis, peritonsillar abscess or any other diseases. ENT examination revealed an intraoral, submucosal, hard and well-delineated mass protruding from the soft palate and tonsillar fossa of the left side, measuring 30 × 20 mm. Overlying mucosa was slightly erythematous but with neither oedema nor displacement of the uvula. There was no sign of trismus. The rest of the head and neck examination findings were within normal limits with no palpable neck lymphadenopathy. Laboratory blood test parameters were normal. CT of the head and neck showed a large hyperdense oval mass in the left tonsillar fossa between the palatoglossus and palatopharyngeus muscles, measuring approximately 30 × 20 mm (Figure 1). In order to exclude a possible lithiasis in other regions of the body, we performed ultrasounds of salivary glands, kidney and gallbladder, and results were within normal values. The diagnosis of a large left tonsillolith was made and, owing to the size of the stone, we decided to perform a left tonsillectomy under general anaesthesia. During surgery, upon manipulating to release the upper pole, we noticed a flow of blocked saliva around the stone. Progressing from the upper to the lower pole of the tonsillar bed, at the level of lower pole, we opened a fistulous tract filled with saliva. It was approximately 5 mm in width and 30 mm long (Figure 2), running from the lower pole of the left tonsil, medial to the mandibular bone and towards the left submandibular gland. The lumen of the fistula was wide enough to accommodate the endoscope (Supplementary Video 1). We suspected that this fistula tract is an accessory duct of the submandibular gland and therefore inspected the sublingual region and probed the left orifice of Wharton's duct. As they appeared normal, we placed a suture around the duct at the lower pole of the tonsil bed. We found no abnormal adhesions between the tonsillar capsule and the superior constrictor muscle. The rest of the surgery and post-operative period were uneventful, and the patient recovered well. There was no post-operative swelling in the left submandibular region. The stone was hard, yellowish-white, measuring 3.1 × 2.6 cm, the weight was 6.99 g (Figure 3).

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Additionally, a detailed analysis of the pre-operative CT scan showed a well-defined, hypodense fistulous tract measuring 6 mm in width and 36 mm in length, extending from the lower tonsillar pole towards the left submandibular gland (Figure 4). It was then diagnosed as an accessory duct of the submandibular gland extending to the tonsil associated with a large tonsillolith.

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Discussion

Up to now, case reports with large giant tonsilloliths were mainly focused on the particular size of the stones, localization and clinical presentation.^3,5,6 However, aetiopathogenesis of tonsilloliths is still unknown. Most authors believe tonsilloliths are formed in cases of chronic tonsillitis; as a result of organic debris, epithelial tissue and dead bacteria collections in tonsillar crypts which are a nidus for salt precipitation from the saliva secreted in the mouth by major and minor salivary glands.^1,4,6 The second theory similarly explains the mechanism by which these stones are formed by calcification of peritonsillar abscess.^3,5 However, a different theory was presented by Mishenkin and Shtil⁹ hypothesizing that tonsilloliths are a part of the pathology of salivary glands. They performed a histological examination of the adjacent tissue of a tonsillolith and found small salivary gland lobuli with efferent ducts surrounded by lymphoid tissue. Their conclusion was that stone formation results from stasis of saliva in the efferent ducts of the small accessory salivary glands in the oral cavity, owing to their mechanical obstruction caused by post-tonsillectomy scar or chronic inflammation. In our case, a tonsillolith was formed only by the saliva from the accessory duct of the large salivary gland. Inflammation was excluded as an aetiological factor as the patient was without any inflammation of the tonsils. This finding put emphasis on saliva stasis and accessory ducts of salivary glands as a possible cause of tonsillolith as hypothesized by Mishenkin and Shtil.⁹ It is important to note that probably, in most cases, the minor salivary glands are the aetiological cause of a tonsillolith and not the major glands, which can be diagnosed with a comprehensive radiological assessment (CT, MRI).

The accessory duct of the submandibular gland was reported in only a few cases up to now.^10–13 This anomaly was described in most cases as a duplication of the main Wharton's duct, with the uniform opening at the orifice or as a separate opening in the oral cavity.¹³ Gaur et al¹¹ even reported three ducts with each opening separately at the floor of the mouth. Our patient had no medical history of chronic tonsillitis, peritonsillar abscess or tonsillectomy. Laboratory findings were all in normal range. Lithogenic diathesis was excluded based on normal ultrasound findings of the salivary gland, kidneys and gallbladder. During the standard tonsillectomy surgery and removal of the stone, we found a flow of blocked saliva and, more surprisingly, a large accessory salivary duct (Figure 2). Although we performed the routine pre-operative CT scans, no accessory duct or fistula formation was reported by the radiologist. However, after the surgery and intraoperative visualization of the duct, we collaborated with radiologists and analysed the pre-operative CT scan in detail. We found a well-defined, hypodense fistulous tract measuring 6 mm in width and 36 mm in length, extending from the lower tonsillar pole towards the left submandibular gland. This was defined as a large accessory duct of the left submandibular gland with a direct opening at the lower level of the tonsillar pole (Figure 4). The inability to diagnose this pre-operatively can be attributed to the fact that a similar case did not present itself before, and therefore its possibility was not taken into account. Furthermore, there was a possibility that the duct observed intraoperatively was not the accessory but rather the main duct of the submandibular gland, in which case a submandibulectomy would have to be performed. Intraoperative probing of the left orifice of the submandibular gland was normal, so we decided to leave the submandibular gland intact and closely monitor the patient in the post-operative period for signs of possible submandibular swelling and/or inflammation. Our patient had an uneventful post-operative period and recovered fully.

We found only a few reports presenting patients with a combination of pathology of salivary glands and tonsilloliths.^14,15 However, a direct link between those two conditions, as in our case, was never documented. Giudice et al¹⁴ reported the case of a patient who was diagnosed with a left tonsillolith and 2 years prior with lithiasis of the left Wharton's duct. They found no anatomical connection between the left tonsil and the left submandibular gland. However, the reason for that could be that, similar to our case, the radiologist did not actively look for the possibility of an accessory salivary duct and, furthermore, the duct remained unobserved during surgery.

To our knowledge, this is the first report of a large tonsillolith associated with the accessory duct of the ipsilateral major salivary gland. It is important to diagnose this condition prior to the surgery to be able to adequately deal with the accessory duct. Furthermore, from the aetiopathological point of view, this finding supports the saliva stasis hypothesis for formation of the tonsilloliths and brings them closer to the pathology of salivary glands. However, larger studies including a detailed radiological analysis, as in our case, are needed to further investigate this possible aetiology of tonsilloliths. Additionally, future studies should consider using MRI, specifically MR sialography, in clarifying the nature and course of the accessory salivary duct between the tonsillar calcification and the salivary gland.