Volume 4, Issue 4 , Pages 147-149, December 2009
Unilateral congenital cystic dilatation of the submandibular gland duct: MDCT findings
Article Outline
Summary
A male infant presented with unilateral cystic swelling in the floor of his mouth as a result of congenital stenosis of the orifice of duct of Wharton. Early diagnosis and treatment is important to avoid feeding difficulties and to prevent later complications. Multidetector computed tomography can be used as a diagnostic tool in order to differentiate congenital cystic lesions of the floor of the mouth.
Keywords: Submandibular duct, Salivary glands, Multidetector computed tomography, Stenosis
1. Introduction
Congenital dilatation of the submandibular gland duct is an extremely rare condition. Only a limited number of patients have been reported since the first report of Scher in 1955 [1]. Imperforate submandibular duct should be distinguished from other cystic lesion in the floor of the mouth. A possible role for ultrasound and magnetic resonance imaging has been implicated; however, multidetector computed tomography (MDCT) findings of submandibular duct atresia have not been reported. We report multidetector computed tomography findings in a case of unilateral congenital dilatation of the submandibular gland duct.
2. Case presentation
An otherwise healthy 2-month-old newborn has been admitted to the department of pediatric surgery with a painless swelling in the floor of his mouth. He was born at 38 weeks of gestation following a normal pregnancy. The parents noticed the swelling under the tongue during the infant's early days of life, and there was no history of trauma at birth. The swelling was gradually enlarging. He had neither airway obstruction nor respiratory difficulty. Physical examination revealed a smooth, fluid-filled, noninflammed and linear cystic swelling in the left floor of the mouth. The swelling followed a course parallel to the submandibular ducts. There was no associated lymphadenopathy.
In order to clarify the origin and extent of the lesion, a contrast enhanced MDCT was performed using a low-dose technique. MDCT examination was performed using a 16-detector CT (Sensation, Siemens Medical System, Erlangen, Germany) and sagittal MPR views were then reformatted from axial slices. The patient was administered 2
mL/kg nonionic contrast material (Optiray 350/100ml, Covidien) intravenously. Anaesthesia or sedation was not necessary in the patient. MDCT examination was free of motion artefact. Scanning parameters were 16×0.75mm detector collimation, 1mm slice thickness, 0.5 sn gantry rotation, 100kVp, and 40mA. The scanning duration was 5–7s (mean 6.81s). The pitch was automatically adjusted to 1. Images were reconstructed in the axial plane at 1mm intervals with a standard reconstruction algorithm.
CT demonstrated that there was a tortuous tubular cystic structure in the submandibular region in axial sections (Fig. 1a). Sagittal MPR images revealed that the course of the lesion was continuous with the duct of Wharton (Fig. 2). Also dilatation of the intraglandular segments measuring 2.8mm in largest diameter was noted (Fig. 1b). Dilatation of both the intra and extraglandular segments of duct of Wharton was presumed to be due to the congenital stenosis of the orifice of duct of Wharton. No accompanying mass lesion was detected.
Fig. 1.
(a) Axial contrast enhanced computed tomography image is seen. Asterisk shows the cystic dilatation of duct of Wharton. Arrow indicates the left submandibular gland. (b) Axial contrast enhanced computed tomography image is seen. Asterisk shows dilatation of both the intra- and extra-glandular segments of duct of Wharton. Arrow indicates the normal appearing right submandibular gland.
Fig. 2.
Sagittal MPR image clearly demonstrates the course of the unilateral congenital cystic dilatation of left Wharton's duct. Arrow shows the left submandibular gland.
He subsequently underwent corrective surgery. Fluid in the cavity was aspirated and marsupialization of the duct was planned. When punctured, a clear serous rather than mucous material flowed from the lesion. Under general anesthesia, a simple stab incision was made and marsupialization was done. On histopathological examination there were normal appearing minor salivary glands beneath the oral cavity epithelium and the lesion had single stranded cuboidal epithelium with apical secretions. His follow up was uneventful. He was discharged on the second postoperative day without any complications.
3. Discussion
Submandibular gland duct starts to develop by the ingrowth of the ectodermal cells in the oral cavity [2]. Following the development of mucous acini until the age of 28 weeks, further differentiation into acinar complexes or ductal system takes place. Initially a solid cord is formed which is followed by hollowing out of the cord to form a patent duct [2], [3]. Failure of the latter hollowing process has been suggested to be the cause of the congenital dilation of the submandibular duct, which has also been referred to as imperforation [2]. Congenital abnormalities of the submandibular duct are rare and to our knowledge only 17 cases of duct ectasia have previously been reported [1], [2]
Any congenital cystic lesion in the floor of the mouth should be differentiated from congenital ranula formation. By definition, congenital ranula is a mucocele of the salivary glands, mainly the sublingual gland [4]. They occur secondary to the aggregation of saliva within the tissues usually after trauma [5]. Simple ranulas are confined to the sublingual space in CT images [6]. Diving or plunging ranulas herniate into the adjacent spaces. They extend slightly in to the sublingual space (giving a tail sign) [4]. In the present case, multidetector CT findings clearly demonstrated that the lesion was arising from the submandibular gland in the submandibular region and the lesion was not showing a tail sign. MPR images showed that it had a tubular configuration extending to the frenulum in the sublingual space which was consistent with a ductal structure rather than a mucocele.
We also observed that the intraglandular segments of the submandibular duct were dilated, which further supported the continuation of the lesion with the duct of Wharton. Thus our diagnosis was congenital dilatation of Wharton's duct rather than a ranula. Although, Aasen and Kolbenstvedt recommended using 3mm as a threshold level for intraglandular dilatation, in their study none of the normal intraglandular ducts exceeded 2.5mm [7]. But one should remember that our patient was only 2 months old. There may be bilateral involvement; however unilateral occurrence is more common as in our case [8]. In order to prevent complications such as infection, glandular atrophy, feeding difficulty or airway compromise early recognition and treatment of submandibular duct atresia had been advocated [5].
The differential diagnosis of congenital cystic lesions of the floor of the mouth also includes lymphatic malformation, teratoma, dermoid cyst, thyroglossal duct cyst, and heterotopic gastric cyst [5]. The lesion was away from the midline so that we excluded thyroglossal cyst. There was no solid component of lesion and we did not observe any fat density within the lesion, so that we did not take teratoma or dermoid cyst into consideration. Lastly, there was no sign of lymphatic involvement.
4. Conclusion
Congenital dilatation of the submandibular gland duct is an extremely rare condition and to our knowledge, MDCT findings of atresia of the submandibular duct orifice have not been reported. MDCT can be used as a diagnostic tool in order to differentiate congenital cystic lesions of the floor of the mouth. The major advantages of the MDCT technology allows for acquisition of different image thicknesses from the same acquisition data set. MDCT, as used in our cases, multiplanar reformatted images from the axial data set allows visualizing the extent of the lesion as well as its anatomical relationships. This investigation provides useful diagnostic information for the surgeon since the lesion may be related to vital organs.
References
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PII: S1871-4048(08)00073-7
doi:10.1016/j.pedex.2008.10.004
© 2008 Elsevier Ireland Ltd. All rights reserved.
Volume 4, Issue 4 , Pages 147-149, December 2009
