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Diagnosis of the salivary glands is an important part of the evaluation of patients, especially because of their involvement in most systemic diseases. Patients most often seek medical attention when large salivary glands such as the parotid, submandibular, or sublingual glands become enlarged or tender. The various imaging modalities used to examine the pathology of the salivary glands include plain radiography, sialography, ultrasound, computed tomography, radionuclide diagnostics, and magnetic resonance imaging. Sialography is one of the oldest research methods, first mentioned by Carpi in 1902 using mercury as a contrast agent. It is the most commonly practiced as it is simple and economical to use.
Sialography or radiosialography is an X-ray visualization of the salivary gland after the injection of a contrast agent into its ducts. In most cases, this procedure requires a minimum of specialized equipment and can be performed in a conventional X-ray room. Assessment of the salivary glands is most commonly performed using computed tomography or magnetic resonance imaging, however, sialography is the first diagnostic method in cases where it is necessary to diagnose sialadenitis (inflammation of the salivary glands) and manifestations of Sjögren’s syndrome (an autoimmune disease process that causes dry eyes and dry mouth ).
Diseases of these organs can be both inflammatory and immune in nature. Treatment primarily depends on the diagnosis, which the doctor can make only after high-quality studies. Sialography also remains a useful technique for the study of patients with obstructive symptoms of the parotid and submandibular glands, with congenital and acquired anomalies of the ductal system. It can be used as a therapeutic aid in obstructive diseases of the salivary glands, as it helps in the displacement of small stones and mucous plugs in the channels of the salivary glands, which cannot be identified on plain radiographs. In addition, this type of study can be used in cases of recurrent infections, as it helps in flushing the salivary glands.
Anatomical features of the salivary glands
The salivary glands secrete slightly alkaline saliva in the mouth. Saliva is a liquid that is approximately 99% water. These organs secrete between 1000 and 2000 ml of saliva daily. It contains mainly two types of substances that are secreted by the salivary glands. The first substance is mucus, a combination of mucin and water, which is a highly viscous substance used to lubricate food particles and maintain oral hygiene. The second is a serous fluid containing the enzymes amylase, ptyalin, maltase, peptidase, proteinase. For example, amylase is a substance that starts the process of digestion by breaking down starch into oligosaccharides.
There are three pairs of major salivary glands – parotid, submandibular and sublingual. Three ducts, respectively, depart from them, which open into the oral cavity. Also on the oral mucosa are the buccal, lingual, palatine, labial, molar minor salivary glands.
parotid gland
This is the largest pair, each of which consists of a superficial and deep part. It produces saliva containing a large amount of protein. The parotid glands lie in front and are somewhat inferior to the ear. The deep part of the parotid gland extends into the neck below the angle of the mandible. A dense connective tissue capsule covers this organ, the parenchyma of which has a lobed alveolar structure. These alveoli are made up of secretory cells. The excretory duct of the parotid gland, also called Stensen’s duct, is 5 to 7 cm long. It runs across and to the anterior edge of the muscle, where it pivots medially to open into the mouth opposite the second upper molar.
submandibular gland
The submandibular glands lie medial to the mandible, with each gland also consisting of a superficial and a deep portion. The superficial part is lower and is located in front of the angle of the lower jaw, and its back part lies next to the top of the parotid gland. A small deep part of the gland flows around the posterior border of the maxillohyoid muscle. From this deep part, the submandibular canal, also called the “Warton’s duct”, departs. It averages about 5 cm in length, running anteriorly and medially to the mandible and opening laterally near the frenulum of the tongue. The organ has a complex mixed alveolar-tubular structure, the second largest.
sublingual gland
It is the smallest of the three pairs of salivary glands. It is also alveolar-tubular, but the difference is that it is a mucous type. The organ is located under the oral mucosa and forms a longitudinal ridge on both sides of the base of the tongue, the sublingual fold. Large sublingual ducts depart from each of them, which can open into the submandibular canal. There are also approximately 12 small sublingual ducts, the ducts of Rivinus, running from the upper border of the gland to open in the hyoid fold.
Indications for sialography
Sialography is used to demonstrate the relationship of the salivary glands to their adjacent structures. It provides diagnostic, including preoperative information in cases of pathology of the salivary glands. This study is indicated for:
- persistent inflammatory diseases of the glands (mumps);
- the presence of stones (sialoliths) in the excretory ducts;
- siaekzatiyah – expansion of the ducts;
- fistulas and tumor neoplasms;
- determination of cysts of varying severity and obstruction of the ducts.
Patients will complain of weakness, swelling of the jaw in the parotid region, pain and discomfort in the face, in the mouth area.
Contraindications for this procedure
It is forbidden to carry out diagnostics if patients have acute infections and inflammations of the oral mucosa and excretory ducts of the salivary gland. Do not conduct a study in persons suffering from allergic reactions to iodine and in the presence of thyroid disease. It is not recommended to perform sialography during pregnancy, except in cases that threaten the health of the mother.
The choice of contrast agent for sialography
Contrast agents are divided into two groups: fat-soluble and water-soluble agents. Water-soluble contrast agents can fill the thinner elements of the flow system. Fat-soluble ones are viscous and can cause allergic reactions, which causes discomfort to patients.
They also fill not the thin elements of the channels, but the larger ones.
The contrast used for sialography was originally developed for other medical applications. Therefore, scientists came to the conclusion to investigate the properties of these substances for use in sialography. 11 radiopaque substances were selected, their properties for sialography were studied. An in vitro study was conducted to determine their contrast qualities and their degree of evacuation after sialography. In animal experiments, their possible harmful effects on the tissues of the salivary glands were studied. In addition, the effects of radiopaque material on extragranular tissues were investigated, which are important for determining the consequences after the introduction of contrast into these tissues. The results of this study were compared with data from the literature. Conray 80, Amipaque 440, Lipiodol UF, Myodil and Duroliopaque appear to be the media most suitable for sialography.
Sialography technique
This procedure does not require special preparation. The patient may continue to take their medications, drink and eat before the study. But if a person has dentures, the doctor will ask you to remove them before the procedure. They will also ask if the patient is allergic to the contrast agent or iodine, and if there is a possibility that the patient may be pregnant.
For sialography, a contrast agent is injected into the ducts of the salivary glands. First, the contrast is heated to 40 degrees Celsius in order not to cause convulsions. The substance is administered with a syringe. Depending on gender, age and type of gland, determine the required amount of contrast. For the diagnosis of the submandibular gland, approximately 1,5 ml of contrast agent is needed, for the parotid – 2,5 ml. Then the ducts are washed with an isotonic sodium chloride solution, a catheter already filled with contrast is taken and advanced inside the duct up to approximately three centimeters. It is fixed on the skin of the cheek.
Then a series of radiographs is taken to determine the distribution of fluid and the level of filling of the duct, to identify any obstructions and their location, the rate of fluid release from the gland. Pictures are taken in direct, profile, tangential and axial views. It is by them that the normal functional activity of the salivary organs is determined. To stimulate the secretion of saliva, citric acid is used. The excretory function of the glands is assessed every half hour for two to three hours. X-rays are taken in at least two projections. If a more detailed study is needed, a panoramic tomography is performed.
Influence and side effects
As with any medical research using ionizing radiation, there will be some degree of direct ionizing damage and indirect damage from free radicals created when water molecules within cells are ionized. The risk of malignant neoplasms is very low, since there is minimal ionizing radiation.
Types of sialography
This study should be carried out not during the period of exacerbation of the disease, but during the period of remission. Indeed, in acute processes, there may be a worsening of the course of inflammation of the salivary glands – sialadenitis.
There are several types of studies of the salivary glands – pantomosialography, digital sialography, sialadenolimphography, computed sialotomography, sialosonography, thermosialography. Sialotomography, electroroentgenosialography, pneumosubmandibulography, stereoroentgenography and many other types of examinations are used very rarely today, except for scientific research.
Pantomosialography
This examination includes simultaneous contrasting of one and the other parotid or submandibular glands, or all four glands are examined simultaneously. After that, a panoramic tomography is performed – an orthopantomogram – a picture of both jaws to identify pathologies of all teeth, bone tissue, paranasal sinuses. The study is carried out with the same indications as conventional sialography. The advantage is that with the simultaneous examination of paired glands, the chances of detecting inflammatory processes in paired organs under study increase without the presence of an obvious clinic. When diagnosing, the doctor will be able to identify uniform or uneven narrowing and expansion of the duct, their displacement or discontinuity, determine whether the contours are clear and whether there are various defects in the filling of the ducts.
Sialadenolymphography
The procedure for diagnosing pathologies of the salivary glands by determining the work of their lymphatic system. Scientists have proven that an unevenly depleted pattern of lymphatic vessels inside organs with preserved organ contours and regional lymphatic outflows indicates the possible presence of chronic sialadenitis in a patient. And filling defects are observed in tumor formations. The manipulation takes place in such a way that the medical worker subcutaneously injects two milliliters of a fat-soluble contrast or four milliliters of a water-soluble substance into the parotid gland with a syringe needle. After five and twenty minutes, and then after two hours and a day, a series of shots is taken.
Digital sialography
This is an examination of the salivary organs, which is carried out on an X-ray machine with digital material. The examination time is usually less than one minute. It allows you to study a more detailed contrast image at the time of filling and exit of the contrast agent, as well as the state of all tissue and bone formations.
Sialosonography
This is the name of the ultrasound examination of the salivary glands. Only it helps to establish the macrostructure of the organ under study. The echogram determines the size, shape, ratio of tissue layers at different densities, sclerotic changes, the presence of salivary stones and tumors.
Thermosialography
This method helps to monitor the dynamics of changes in the temperature of the organs under study. For this, a thermal imager is used, the kinescope of which creates a thermal cartogram of the temperature of the neck and face of a person. As you know, there are three types of temperature picture of the face: cold, intermediate and hot faces. Each type is purely individual and, as a rule, does not change throughout life.
Malignant neoplasms and inflammation in the salivary glands lead to an increase in the temperature of the skin of the face, especially in comparison with the healthy side. This diagnostic method allows you to simply, harmlessly and without contraindications to conduct, detect hidden inflammatory pathologies in the glands.
Computed sialotomography
Scanning is performed from the level of the hyoid bone and parotid glands. The resulting cross section is displayed on computed tomography. The computer makes fifteen sections, the thickness of which is about two to five millimeters. This method is used to diagnose tumors of the salivary glands and salivary stones.
Sialography remains the most popular diagnostic procedure for evaluating inflammatory and degenerative diseases of the salivary ducts, despite more sophisticated imaging modalities currently available. Sialography also provides therapeutic help in cases of obstructive sialadenitis and recurrent infections.