Sialolithiasis of the right parotid duct

Clinical History

A 56-year-old man came to the emergency department with pain that had started one week before, on the right hemiface, exacerbated with meals, accompanied by oedema and local inflammatory signs.

Imaging Findings

Ultrasound showed a hyperechoic round formation in the Stenon´s duct extremity, causing acoustic shadow, associated with dilatation of the parotid duct upstream, swelling of the parotid gland and prominent lymph nodes in the glandular parenchyma and in the submandibular region.
CT evaluation confirmed the stone in the right parotid duct, measuring 5 mm, and a marked swollen gland, accompanied with stranding of the loco-regional tissues.
The final diagnosis was consistent with acute parotiditis caused by sialolithiasis.

Discussion

Sialolithiasis is an obstruction of the excretory duct of a salivary gland due to sialoliths, resulting in salivary duct dilatation and enlargement of the salivary gland [1].
Sialolithiasis most commonly involves the submandibular gland (about 80%). It is less common in the parotid and in the sublingual glands [1].
The exact pathogenesis of sialolithiasis remains unknown, but its higher frequency in the submandibular gland is thought to be due to a more alkaline and mucinous secretion, while the parotid gland has a more acid and serous secretion. Also, the uphill course of the submandibular duct might cause stasis of the salivary secretion, increasing the risk of stone formation [1].
Sialolithiasis accounts for 30% of salivary diseases, it is the most frequent salivary gland pathology beyond the second decade of life and it is the most frequent cause of recurrent sialadenitis. Most stones are solitary, but multiple stones may occur [2].
Parotid stones are usually seen in the distal part of Stenon´s duct. The typical symptoms of sialolithiasis are pain and swelling with eating. Superinfection may cause fever and cellulitis. Sometimes a painless mass, simulating tumour may be present. It may be asymptomatic and discovered accidentally [2].
The radiological evaluation includes plain radiography, conventional sialography, CT, ultrasound, and MRI sialography. The classic occlusal film shows large ductal stones, but intraglandular and small stones can be missed. Smaller or faintly calcified stones are more likely to be detected using thin slices CT, but we cannot visualize the ducts and their anomalies unless they are markedly enlarged. Ultrasound is a noninvasive appropriate method for detecting sialoliathiasis, including non-calcified concretions and shows the upstream ductal ectasia. Sialography gives a detailed visualisation of the ductal morphology, allowing the diagnosis of opaque and nonopaque stones and also evidence of ductal strictures. Magnetic resonance sialography consists of 3-mm T2-weighted fast spin–echo (FSE) slides, performed in the sagittal and axial planes, with volumetric reconstruction and MIP reconstruction. New 3D T2-weighted FSE techniques allow depiction of subcentimetric stones [3].
The classic treatment of sialolithiasis consists of antibiotics and anti-inflammatory agents, hoping for a spontaneous stone output through the papilla. In cases of submandibular stones located close to Wharton papilla, a marsupialisation (sialodochoplasty) is performed and the stone is removed [3].
In cases of posterior-located submandibular or parotid stones, a conservative approach is preferred, because parotidectomy is associated with a high incidence of facial nerve complications [3].

Differential Diagnosis List

Final Diagnosis

Sialolithiasis of the right parotid duct

URL:	https://eurorad.org/case/9518
DOI:	10.1594/EURORAD/CASE.9518
ISSN:	1563-4086