Sialolithiasis: An Unusually Large Salivary Stone

Abstract

Sialolithiasis is characterized by obstruction of a salivary gland or its duct due to the formation of calcareous concretions, leading to recurrent painful swelling of the involved gland. It is aggravated while eating. Submandibular gland is the most commonly affected gland. The size of the sialolith may range from 1 to 10 mm. Sometimes, the formation of sialo-oral or sialo-cutaneous fistula may promote the growth of the sialolith to a giant size of 15 to 20 mm. Giant sialolith of size greater than 20 mm is sparse in the literature. The purpose of this presentation is to report a case of an unusually large sialolith measuring 28 mm located in the left submandibular salivary gland of a 29-year-old male patient.

Sialolithiasis is the second most common disease of the salivary glands. It is characterized by the obstruction of salivary gland or its excretory duct by calculus or sialolith resulting in swelling, pain and infection of affected gland. Males are affected twice as much as females. Children are rarely affected. Sialolithiasis predominantly involves the submandibular gland (80% to 95%) followed by parotid (5% to 20%), sublingual gland and rarely the minor salivary glands in 1% to 2% [1]. The sialolith is the result of the deposition of tricalcium phosphate salts around an initial nidus that consists of altered salivary mucin, desquamated epithelial cells and bacteria [2]. Clinically sialoliths are round or ovoid, rough or smooth and yellowish in colour. The size of the sialolith may vary from less than 1 mm to few cm in largest diameter. However, majority (88%) are less than 10 mm. Calculi of size more than 15 mm are termed giant sialoliths that are considered rare [3]. As 20% of submandibular stones are not radiopaque, additional radiographic techniques such as ultrasonography, sialography, scintigraphy, computerized tomography (CT) may be required to locate them [1]. The mode of treatment depends on the stone’s location and its size, with giant intraglandular sialolith requiring surgical removal of the involved gland.

Case Report

A 29-year-old male patient was referred to our hospital for the evaluation of a firm mass below the left angle of the mandible. The patient gave a history of episodic pain localized in the left submandibular region since 4 years which aggravated during meal time. Extra oral examination showed asymmetry towards the left side below the angle of mandible (Fig. 1). Bimanual palpation of the left submandibular salivary gland revealed a large swelling that was firm, non-tender and non-adherent to any deeper structures. Roentgenographic examination (Fig. 2) revealed a radiopaque mass on the left floor of the mouth in the submandibular salivary gland region extending posteriorly beyond the lower-left second molar. CT images (Fig. 3) revealed the dimension (28 mm) and the precise location of the sialolith. Findings on blood and serum biochemistry were within normal limits. The gland and the calculus were excised via an incision in the skin crease, 2 cm below the lower border of mandible and directly over the palpable submandibular gland (Fig. 4). The wound was closed in layers with insertion of a vacuum drain. The salivary gland measured 6 cm in its largest dimension, and the enclosed calculus was creamy yellow and round with rough and irregular surface measuring 28 mm (Fig. 5). It weighed 6 g. Microscopic evaluation of the gland revealed chronic inflammation, destruction of the acini, fibrosis and destruction of the main duct.

Fig. 1.

Extra oral appearance

Fig. 2.

Lateral oblique view demonstrating sialolith (3 years before surgery)

Fig. 3.

Computed tomography image

Fig. 4.

Surgical site

Fig. 5.

Excised gland and sialolith

Discussion

On the basis of a review of the literature, most of the sialoliths are usually of 5 mm size in maximum diameter and all stones over 10 mm should be reported as a sialolith of unusual size. Although large sialoliths have been reported both in salivary glands and in salivary ducts, stones larger than 20 mm are rare [4].

The greater susceptibility of submandibular gland for the development of salivary calculi is due to the following factors: (1) the longer and tortuous course of its Wharton’s duct, (2) flow of saliva against the gravity, (3) more alkaline pH of its saliva and (4) greater amount of salivary mucin, proteins, calcium and phosphates [5].

Regarding the clinical diagnosis of sialolithiasis, careful history and meticulous clinical examination becomes crucial. Symptoms such as pain and swelling of the concerned gland at meal times and the response to other salivary stimuli give a clue to its diagnosis. The aggravation of these symptoms during meal time is due to the higher stimulation of the salivary secretion that is prevented from its smooth flow due to obstruction of the duct. Complete obstruction may cause constant pain and swelling, and a secondary infection in the gland may cause pus drainage from the duct. Bimanual palpation of the floor of mouth often reveals a palpable stone in a large number of cases of submandibular sialolith. It was observed in the present case also.

Imaging studies are very useful for diagnosing sialolithiasis. Intraoral radiographs (occlusal) are useful in showing submandibular sialoliths in majority of cases. As 20% of submandibular stones are reported to be radiolucent, ultrasonography is widely reported as being very helpful in detecting salivary stones. As many as 90% of all stones larger than 2 mm can be detected as echo dense spots on ultrasonography. Computed tomography is also highly diagnostic, albeit more expensive. Some authors have recommended that preoperative technetium-99m pertechnetate scintigraphy be obtained to determine how functional the gland is and thus to determine its treatment [6].

Regarding the management, the most appropriate mode of treatment depends primarily on the stone’s location. In this case, the recurrent infection and fibrosis of the affected gland, the intraglandular position of the calculi and the massive size of the sialolith left us with no other option except the excision of the involved gland. Submandibular stones are treated surgically via either an intraoral or an extraoral approach. The resection of the submandibular gland is a very demanding act and requires maximum precision due to the presence of the marginal mandibular nerve. Literature reveals that the excision of the submandibular gland carries a 0% to 8% risk of permanent or temporary marginal mandibular nerve palsy. However, Smith et al. [7] reported that when a low approach was used, no permanent marginal mandibular nerve palsy occurred, although 36% of nerves were temporarily dysfunctional. The likely reason for this is that the nerve is stretched during the lower surgical approach to the gland. Moreover, care should also be taken in preservation of lingual and hypoglossal nerves during the excision of the gland. In this case report, no permanent or temporary nerve palsy occurred subsequently during the post-operative follow-up.

Conclusion

Sialolithiasis is a condition caused by the obstruction of salivary gland or its duct by calculus. The clinical symptoms are clear and allow an easy diagnosis. Giant sialolith of size 28 mm is rare in the literature. Once the diagnosis of an intraglandular salivary stone with destruction of the gland is established, removal of the entire gland via an extraoral approach is recommended with careful preservation of the marginal mandibular nerve, lingual nerve and hypoglossal nerve.

Compliance with Ethical Standards

Conflict of interest

The authors declare that they have no conflict of interest.

Informed Consent

The authors declare that they have obtained the appropriate consent form from the patient, in the language that he understood. The patient has given his consent for his images and other clinical information to be used in the journal, but without revealing his identity.