Sialolithiasis, is a condition where a calcified mass forms within a salivary gland, usually
in the duct of the submandibular gland.
Less commonly the parotid gland or rarely the sublingual gland or a minor salivary gland
may develop salivary stones.
The usual symptoms are pain and swelling of the affected salivary gland, both of which
get worse when salivary flow is stimulated, e.g. with the sight, thought, smell or taste
of food, or with hunger or chewing.
This is often termed "mealtime syndrome".
Inflammation or infection of the gland may develop as a result.
Sialolithiasis may also develop because of the presence of existing chronic infection
of the glands, dehydration, Sjögren's syndrome and/or increased local levels of calcium,
but in many instances the cause is idiopathic.
The condition is usually managed by removing the stone, and several different techniques
are available.
Rarely, removal of the submandibular gland may become necessary in cases of recurrent
stone formation.
Sialolithiasis is common, accounting for about 50% of all disease occurring in the major
salivary glands and causing symptoms in about 0.45% of the general population.
Persons aged 30–60 and males are more likely to develop sialolithiasis.
Classification The term is derived from the Greek words sialon
and lithos, and the Latin -iasis meaning "process" or "morbid condition".
A calculus is a hard, stone-like concretion that forms within an organ or duct inside
the body.
They are usually made from mineral salts, and other types of calculi include tonsiloliths
and renal calculi.
Sialolithiasis refers to the formation of calculi within a salivary gland.
If a calculus forms in the duct that drains the saliva from a salivary gland into the
mouth, then saliva will be trapped in the gland.
This may cause painful swelling and inflammation of the gland.
Inflammation of a salivary gland is termed sialadenitis.
Inflammation associated with blockage of the duct is sometimes termed "obstructive sialadenitis".
Because saliva is stimulated to flow more with the thought, sight or smell of food,
or with chewing, pain and swelling will often get suddenly worse just before and during
a meal, and then slowly decrease after eating, this is termed meal time syndrome.
However, calculi are not the only reasons that a salivary gland may become blocked and
give rise to the meal time syndrome.
Obstructive salivary gland disease, or obstructive sialadenitis, may also occur due to fibromucinous
plugs, duct stenosis, foreign bodies, anatomic variations, or malformations of the duct system
leading to a mechanical obstruction associated with stasis of saliva in the duct.
Salivary stones may be divided according to which gland they form in.
About 85% of stones occur in the submandibular gland, and between 5-10% occur in the parotid
gland.
In about 0-5% of cases, the sublingual gland or a minor salivary gland is affected.
When minor glands are rarely involved, caliculi are more likely in the minor glands of the
buccal mucosa and the maxillary labial mucosa.
Submandibular stones are further classified as anterior or posterior in relation to an
imaginary transverse line drawn between the mandibular first molar teeth.
Stones may be radiopaque, i.e. they will show up on conventional radiographs, or radiolucent,
where they not be visible on radiographs.
They may also symptomatic or asymptomatic, according to whether they cause any problems
or not.
Signs and symptoms Signs and symptoms are variable and depend
largely upon whether the obstruction of the duct is complete or partial, and how much
resultant pressure is created within the gland.
The development of infection in the gland also influences the signs and symptoms.
Pain, which is intermittent, and may suddenly get worse before mealtimes, and then slowly
get better.
Swelling of the gland, also usually intermittent, often suddenly appearing or increasing before
mealtimes, and then slowly going down.
Tenderness of the involved gland.
Palpable hard lump, if the stone is located near the end of the duct.
If the stone is near the submandibular duct orifice, the lump may be felt under the tongue.
Lack of saliva coming from the duct.
Erythema of the floor of the mouth.
Pus discharging from the duct.
Cervical lymphadenitis.
Rarely, when stones form in the minor salivary glands, there is usually only slight local
swelling in the form of a small nodule and tenderness.
Causes
There are thought to be a series of stages that lead to the formation of a calculi.
Initially, factors such as abnormalities in calcium metabolism, dehydration, reduced salivary
flow rate, altered acidity of saliva caused by oropharyngeal infections, and altered solubility
of crystalloids, leading to precipitation of mineral salts, are involved.
Other sources state that no systemic abnormality of calcium or phosphate metabolism is responsible.
The next stage involves the formation of a nidus which is successively layered with organic
and inorganic material, eventually forming a calcified mass.
In about 15-20% of cases the sialolith will not be sufficiently calcified to appear radiopaque
on a radiograph, and therefore be difficult to detect.
Other sources suggest a retrograde theory of lithogenesis, where food debris, bacteria
or foreign bodies from the mouth enter the ducts of a salivary gland and are trapped
by abnormalities in the sphincter mechanism of the duct opening, which are reported in
90% of cases.
Fragments of bacteria from salivary calculi were reported to be Streptococci species which
are part of the normal oral microbiota and are present in dental plaque.
Stone formation occurs most commonly in the submandibular gland for several reasons.
The concentration of calcium in saliva produced by the submandibular gland is twice that of
the saliva produced by the parotid gland.
The sumbandibular gland saliva is also relatively alkaline and mucous.
The submandibular duct is long, meaning that saliva secretions must travel further before
being discharged into the mouth.
The duct possesses two bends, the first at the posterior border of the mylohyoid muscle
and the second near the duct orifice.
The flow of saliva from the submandibular gland is often against gravity due to variations
in the location of the duct orifice.
The orifice itself is smaller than that of the parotid.
These factors all promote slowing and stasis of saliva in the submandibular duct, making
the formation of an obstruction with subsequent calcification more likely.
Salivary calculi sometimes are associated with other salivary diseases, e.g. sialoliths
occur in two thirds of cases of chronic sialadenitis, although obstructive sialadenitis is often
a consequence of sialolithiasis.
Gout may also cause salivary stones, although in this case they are composed of uric acid
crystals rather than the normal composition of salivary stones.
Diagnosis
Diagnosis is usually made by characteristic history and physical examination.
Diagnosis can be confirmed by x-ray, or by sialogram or ultrasound.
Treatment
Some current treatment options are: Non-invasive:
For small stones, hydration, moist heat therapy, NSAIDs occasionally, and having the patient
take any food or beverage that is bitter and/or sour.
Sucking on citrus fruits, such as a lemon or orange, may increase salivation and promote
spontaneous expulsion of the stone.
Some stones may be massaged out by a specialist.
Shock wave therapy.
Minimally invasive: Sialendoscopy
Surgical: An ENT or maxillofacial surgeon may cannulate
the duct to remove the stone.
A surgeon may make a small incision near the stone to remove it.
In some cases when stones continually reoccur the offending salivary duct is removed.
Supporting treatment: To prevent infection while the stone is lodged
in the duct, antibiotics are sometimes used.
Epidemiology The prevalence of salivary stones in the general
population is about 1.2% according to post mortem studies, but the prevalence of salivary
stones which cause symptoms is about 0.45% in the general population.
Sialolithiasis accounts for about 50% of all disease occurring in major salivary glands,
and for about 66% of all obstructive salivary gland diseases.
Salivary gland stones are twice as common in males as in females.
The most common age range in which they occur is between 30 and 60, and they are uncommon
in children.
References