Submandibular sialolithiasis: The roles of radiology in its diagnosis and treatment.

E. N was a 48-year-old man referred from a peripheral hospital to the Maxillofacial unit of Ahmadu Bello University Teaching Hospital, Zaria, on account of 1-year history of left-sided jaw pain and swelling, particularly after meal. The conventional plain radiograph of the jaws appeared normal as there was no opacity of soft tissue or calcific density visualized. Sialography revealed an oval-shaped filling defect in the dilated left Wharton's duct, which could suggest radiolucent calculus. Ultrasound scan showed the lesion as a brightly echogenic mass surrounded by anechoic clear fluid (saliva), casting posterior acoustic shadow. A diagnosis of left submandibular sialolithiasis was made. The maxillofacial surgeons decided to remove the calculus surgically, but the patient refused surgery and then defaulted from subsequent follow-up visits.

INTRODUCTION

The salivary glands are exocrine glands that produce saliva to moisten the mouth, aid digestion, and help protect the teeth from decay. Sialolithiasis is the formation of stones within the salivary gland or ducts that drain the salivary gland, and it is the most common disease of the salivary glands,[1] affecting 12 in 1000 of the adult population.[2] Males are much more affected than females,[3] and children are rarely affected.[4] The most common localization is the submandibular gland where 92% of calculi are found, the ducts being more frequently affected than the parenchyma. The parotid gland is affected in 6% of cases, while the sublingual gland is affected in 2% of cases and minor salivary glands in another 2%.[35] Submandibular sialolithiasis is more common as its saliva is more alkaline, has an increased concentration of calcium and phosphate and has a higher mucous content than saliva of the parotid and sublingual glands. In addition, the submandibular duct is longer and the gland has an antigravity flow.[2] It should be noted that stone formation in the salivary glands is not associated with systemic abnormalities of calcium metabolism.[6] Electrolytes and parathyroid hormone studies in patients with sialolithiasis have also not shown abnormalities. Gout is the only systemic disorder known to predispose to salivary gland stone formation although in gout the stones are made predominantly of uric acid.[6]

In this report, we present a case of left submandibular sialolithiasis, illustrating the radiological revolution in its diagnosis.

CASE REPORT

E. N. was a 48-year-old man referred from a peripheral hospital to the Maxillofacial unit of Ahmadu Bello University Teaching Hospital on account of 1-year history of left-sided jaw pain and swelling, particularly after meal. He also noticed that the pain and swelling were more pronounced when he ate sour food or took drinks such as lime. Several minutes, close to an hour after meal, the pain and the swelling usually subsided. He was treated in a peripheral hospital with several courses of antibiotics but all to no avail.

When examined, he was found to be calm, afebrile with no obvious jaw swelling noted. There was no submental, axillary, or cervical lymphadenopathy seen. The major salivary glands were not palpable and no obvious mass lesion was palpable along the Wharton's or Stenson's ducts.

The conventional plain radiograph of the jaws appeared normal as no opacity of calcific density was visualized. A conventional sialography revealed an oval-shaped filling defect in the left Wharton's duct, almost occupying the entire caliber of the lumen [Figure 1], which could suggest a radiolucent calculus. The duct was also dilated proximal to the filling defect.

Figure 1

Conventional sialogram showing an oval-shaped filling defect (due to calculus) obstructing almost the entire lumen of the left Wharton's duct. The Wharton's duct is dilated proximal to the obstruction (original image)

Ultrasound scan revealed the lesion as a brightly echogenic mass surrounded by anechoic clear fluid (saliva) in the left Wharton's duct, casting posterior acoustic shadow [Figure 2]. It measured 0.52 cm × 0.22 cm in dimension. The right submandibular gland and the remaining salivary glands were preserved.

Figure 2

Left submandibular ultrasound scan showing an oval-shaped brightly echogenic mass (m) casting posterior acoustic shadow (s) in the left Whanton's duct surrounded by anechoic fluid (saliva). (original image)

A diagnosis of left submandibular sialolithiasis was made in view of the aforementioned radiological findings. The maxillofacial surgeons decided to remove the stone surgically, and if difficult, an option of total removal of the submandibular gland was made known to the patient. He refused the surgery and then defaulted from subsequent follow-up for fear of complications such as trauma to the lingual nerve which lies deep to the duct, and the fact that there were no other treatment options available for him in our health facility such as endoscopically-controlled intracorporal lithotripsy and extracorporeal shock wave lithotripsy (ESWL).

DISCUSSION

The salivary glands produce saliva to moisten the mouth to help protect the teeth from decay and to also aid food digestion. The three major salivary glands are the parotid, submandibular, and sublingual glands. The parotid glands make 25% of saliva and drains into the mouth near the upper teeth, while the submandibular glands produce 70% of saliva and drains into the mouth from the frenulum of the tongue, and the sublingual glands account for 5% of saliva production and drains into the floor of the mouth. In addition, 600–1000 tiny glands (the minor salivary glands) are located in the lips, inner cheek, and in the lining of the mouth and throat.[3]

Sialolithiasis accounts for the most common disease of the salivary gland,[1] and the most common localization is the submandibular gland where 92% of the calculi are found, the duct being more frequently affected than the parenchyma.[5] Sialolithiasis is composed of varying ratios of organic acid and inorganic substances. The organic substances are glycoproteins, mucopolysaccharides, and cellular debris.[7] The inorganic substances are mainly calcium carbonates and calcium phosphates. The sialoliths are usually laminated, and often, the organic substances predominate in the center of the stone while the periphery is essentially inorganic.

The etiologic agents responsible for sialolithiasis remain elusive. Sherman and McGurk[8] attempted to correlate the geographic distribution of water hardness and salivary calculi, but no link was established, suggesting that high calcium intake might not necessarily lead to sialolithiasis. A recent interest in the effects of tobacco on saliva has been documented. Tobacco smoking has been shown to result in increased cytotoxic activity of saliva, decreased polymorphonuclear phagocytic ability, reduction of salivary amylase, and peroxidase which then results in stone formation.[9] Furthermore, salivary stagnation, increased alkalinity of saliva, infection or inflammation of the salivary duct or gland, and physical trauma to salivary duct or gland may predispose to calculus formation.[2] This patient, however, had no history of trauma, inflammatory, or infective processes that could warrant his ailment, and he has never smoked so, the pathogenesis of sialolithiasis in him is still elusive.

Sialolithiasis affects 12 in 1000 of the adult population with higher male preponderance.[23] Children are rarely affected. This index case was a 48-year-old male, which concurred with earlier reports.[2]

Submandibular sialolithiasis is the most common of all sialolithiases,[2] and it is consistent with the observation made in the index case. Furthermore, pain and swelling of the involved salivary gland by obstructing the food-related surge of salivary secretion are the most classical symptoms, and these were the presenting symptoms in the index patient. Long-term obstruction in the absence of infection can lead to atrophy of the gland with resultant lack of secretory function and ultimately fibrosis. But in the index case, the left submandibular gland was still found preserved on sonographic assessment. Its size and parenchymal echopattern were found similar to the contralateral gland. This may be explained by the fact that the obstruction caused by the calculus was not total. Imaging studies are very useful in the diagnosis of sialolithiasis as demonstrated in this patient. A plain radiograph of the jaws was done, and there was no radiopaque stone seen in the submandibular or parotid regions. Sialography was therefore found necessary, and it revealed a left Wharton's duct's radiolucent calculus. A thin rim of radio-opaque contrast medium was seen passing through both sides of the calculus, indicating that the mass was not attached to the walls of the duct and it was therefore not likely a polyp or a salivary duct neoplasm. Ultrasound is generally useful in evaluating patients with radiopaque or radiolucent sialolithiasis. This was brought to the fore in this patient as the submandibular stone was unequivocally visualized as a brightly echogenic mass casting posterior acoustic shadow in the left Wharton's duct.

The treatment options available for sialolithiasis include conservative management, surgical management, and noninvasive therapy using endoscopically-controlled intracorporal lithotripsy. Conservative management is usually prescribed for patients with small stones.[6] The patient must be well hydrated and the clinician applying moist warm heat with gland massage, while sialogogues are used to promote saliva production which may then flush the stone out of the duct. Antibiotics must be prescribed as infection is almost always certain.[6]

Surgical opening of the duct for stone removal is also advocated. This involves transoral approach where an incision is made directly on the stone. Care must be taken here to avert traumatizing the lingual nerve that lies deep in close association with the submandibular duct. If the gland has been damaged by recurrent infection and fibrosis, or calculi have formed within the gland, it may require removal. Interventional radiological management such as ESWL, and more recently, the use of endoscopic intracorporal shockwave lithotripsy (EISWL), in which shock waves are delivered directly to the surface of the stone lodged within the duct without damaging adjacent tissue (piezoelectric principle),[1011] have both emerged and are becoming increasingly popular. They are found to be safe, comfortable, and effective minimally invasive nonsurgical treatment for salivary stones. If these interventional procedures were available in our health institution and most hospitals in the country as an alternative to surgery, this patient may not have defaulted from follow-up and treatment. I consider this index case a missed opportunity.

CONCLUSION

A case of left submandibular sialolithiasis has been presented, illustrating the radiological revolution in its diagnosis and treatment. Training and retraining of health personnel coupled with provision of relevant equipment for interventional radiological procedures such as ESWL and EISWL as alternative to surgery, is recommended as that will enhance the quality of patients’ care and reduce to the barest minimum the rate of patients’ defaults.

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Conflicts of interest

There are no conflicts of interest.