Salivary mucocoele in dogs – symptoms and treatment

Overview

A sialocele is also called a salivary mucocoele or, informally, a salivary gland cyst. However, it is a pseudocyst: its wall consists of inflammatory and connective tissue, rather than true glandular epithelium.

It is the most common salivary gland disease in dogs. A salivary gland tumour is a different diagnosis, although treatment may also require gland removal.

The most common location is beneath the jaw or in the upper neck. A collection beneath the tongue is called a ranula.

A collection in the throat wall is less common. The form involving the salivary gland beneath the eye is very rare.

Symptom severity depends on the collection's location and size.

Causes

Saliva leakage and the surrounding capsule

Leaking saliva irritates surrounding tissues and triggers inflammation. A connective tissue capsule gradually develops around it, limiting spread.

The original cause of leakage often remains unknown. Possible triggers include a bite, neck injury or chewing foreign material.

A salivary stone, foreign body or tumour may also be associated with damage to a gland or duct. A salivary stone can block normal flow through a duct.

Which gland does the saliva come from?

A dog's four major salivary gland groups lie around the lower jaw, tongue, ear and eye. The most common source of leakage is the sublingual gland beneath the tongue or its duct.

The mandibular and sublingual ducts open into the mouth through small raised areas beneath the tongue. Neck and sublingual collections can occur together in the same dog.

The collection's lining does not itself produce fluid in the same way as a true cyst's epithelium.

Risk factors

A salivary mucocoele can develop in any breed. Increased susceptibility has been suspected in Poodles, German Shepherds, Dachshunds and Silky Terriers.

It can occur at any age. In a study of mandibular and sublingual forms published in 2006, the average age was five years.

That study found no breed or sex predisposition. In a study of 14 dogs with the pharyngeal form, 50% were Miniature or Toy Poodles.

Among 16 dogs with the cervical form in a 2016 study, the male-to-female ratio was 2.2:1. Breed or age therefore does not determine whether a neck swelling is a saliva collection; diagnosis is based on the findings.

Typical symptoms

A cervical collection may initially appear only as a soft lump without other signs.

• A soft swelling beneath the jaw or at the front of the neck slowly enlarges.

• A bulge beneath the tongue may push it to one side.

• Picking up food, chewing or swallowing becomes difficult.

• Your dog drools, gags or coughs.

• A bulge inside the mouth may break open and bleed during eating.

• Swelling appears around or beneath the eye.

• The eye bulges outwards or the third eyelid becomes visible.

Early inflammation may cause pain even if the lump noticed later is painless. A pharyngeal collection may remain externally unnoticed until the mouth and throat are examined under sedation.

An infected collection may also produce pus.

Complications and consequences

Breathing, eating and infection

A growing throat collection can narrow the airway to a life-threatening degree. Swelling beneath the tongue can interfere with eating and be injured by chewing.

Infection of a collection can cause pain and fever. In the 2012 study of pharyngeal cases, six of 14 dogs also had a cervical collection on the same side.

Repeated drainage alone can introduce bacteria and make later surgery more difficult. After adequate removal of the affected glands, the outlook for normal life is generally excellent.

Removal of the mandibular and sublingual glands does not usually cause dry mouth, even on both sides.

Diagnosis at the vet

The lump, mouth and correct side

The vet feels the swelling's location, extent and consistency. Similar lumps may be caused by an abscess, tumour or enlarged lymph node.

An abscess or tumour often feels firmer or more painful than an ordinary soft saliva collection. A longstanding sialocele may feel firmer than a recent fluid collection.

The mouth is examined even when the owner has only noticed external neck swelling. Diagnosing the pharyngeal form requires examination of the upper airway.

A large cervical collection can move into the midline and conceal which side the leak started on. When a dog is examined lying on their back, the swelling may fall towards the affected side and help localisation.

Samples and imaging

The vet may take a fine-needle sample under clean conditions. Fluid consistent with saliva is often stringy, clear, yellowish or blood-stained.

Cell examination helps distinguish a saliva collection from an abscess or other lesion. A special mucin stain may confirm that the sample contains saliva.

An ordinary saliva collection often has few cells in the fluid. A high white blood cell count may suggest gland inflammation or an abscess.

Ultrasound shows the fluid cavity and its relationship to nearby tissues. It may sometimes also identify a foreign body or salivary stone.

A recent collection may appear as a fluid cavity with a bright wall on ultrasound. A longstanding collection may have more granular, uneven contents.

Contrast-enhanced CT helps locate the leak's origin and plan surgery. The wall may enhance with contrast while the fluid contents do not.

A calcified structure within the collection may be a salivary stone. In contrast imaging of the salivary duct, contrast is placed directly into the duct to examine its structure and integrity.

If sampling and imaging do not resolve the diagnosis, a tissue biopsy is sometimes needed. When a tumour is suspected, chest X-rays can look for metastases before treatment decisions.

Routine blood tests do not usually confirm a sialocele. Nevertheless, a general examination and blood tests help plan anaesthesia.

Treatment

Removing the leaking gland and duct

The vet prescribes treatment and any medication according to the collection's location and the dog's condition. The usual treatment intended to achieve lasting resolution is removal of the leaking salivary gland and its duct.

Surgery takes place under general anaesthesia. For neck and sublingual collections, the mandibular and sublingual glands on the same side are usually removed together.

The glands are closely associated and partly share a capsule. Sublingual gland tissue continues as small clusters beside the duct, which must be considered for complete removal.

The collection's connective tissue wall may be removed or left in place after drainage. Important blood vessels and nerves in the area must be protected while tissues are separated.

A collection beneath the tongue may be opened into the mouth so that saliva drains there. This procedure, called marsupialisation, can be combined with gland removal.

The pharyngeal form needs prompt treatment because of the risk of airway obstruction. In the form around the eye, treatment targets the salivary gland beneath the eye.

Its deep position near the eye makes surgery more demanding. Removal of the parotid gland near the ear is also technically challenging.

Radiotherapy has been studied for the cervical form

A study published in 2018 used radiotherapy for cervical sialoceles in 11 dogs. Six dogs, about 54%, had a complete response.

Five, about 45%, had a partial response. The collection began progressing again in three dogs, at two, three or nine months.

These results concern a small group with the cervical form; the usual treatment remains surgical removal of the gland and duct.

Drainage and postoperative care

If surgery is not possible, the vet may use drainage as a temporary measure. Draining can reduce swelling for weeks or months, but most collections refill.

Treating pain or inflammation alone does not correct the cause of leakage. A drain may be left at the surgical site to carry fluid out during early healing.

The drain is often removed within 1–3 days of the procedure. Removable skin stitches are usually taken out at 10–14 days.

The area around a drain may discharge fluid for several days. A bandaged surgical wound needs dressing changes.

For an unbandaged wound, the surrounding area may be cleaned with a warm, damp towel as instructed by the treating vet. This helps remove discharge from the skin and encourages fluid drainage.

A seroma, a pocket of tissue fluid, may form after surgery. It may be drained if necessary or allowed to disappear on its own.

Other possible complications include wound infection, bleeding and damage to an adjacent nerve. Facial nerve injury can cause weakness of facial muscles, which may be temporary or permanent.

However, surgical site infections are uncommon after an appropriately performed procedure.

Prevention

Not all sialoceles can be prevented by removing an identified risk factor, because the original cause often remains unclear. Avoiding neck injuries is sensible, because bites and trauma from a tightening collar are possible triggers.

Reducing recurrence depends on adequately removing the affected gland and leaking duct. Avoid puncturing or opening the collection at home because of the risk of introducing bacteria.

Identifying the side of origin before surgery prevents removal of a gland on the wrong side.

Important for dog owners

Record which side the swelling began on, because a large collection's origin may become difficult to identify later.

A photograph may help show changes at the appointment. Also record whether your dog eats and swallows normally and whether breathing has become noisy.

Before discharge, confirm drain and wound care instructions and the follow-up date. Report new neck swelling, pus from the wound or inability to eat immediately. Breathing difficulties need emergency assessment.

Frequently asked questions

Is a sialocele the same as a salivary gland tumour?

No. A sialocele is saliva that has leaked into tissues, although its swelling can resemble a tumour. The vet distinguishes them through palpation, a fluid sample and imaging when needed, because a lump's appearance alone does not establish its nature.

Can a saliva collection simply be drained?

Drainage may temporarily shrink it but usually does not remove the original cause of leakage. Most collections refill. Repeated puncturing also increases the risk of introducing bacteria. Lasting treatment is usually removal of the leaking gland and duct.

Will my dog's mouth become dry after salivary gland removal?

Removing the mandibular and sublingual glands does not usually cause dry mouth, even when removed on both sides. After appropriate treatment, the outlook for normal life is excellent when leaking gland tissue has been adequately removed.

When does swelling need emergency care?

A collection in the throat can narrow the airway, and breathing difficulty needs prompt treatment. Difficulty swallowing may also occur with a pharyngeal sialocele even without a large visible neck lump, so tell the vet about changes in eating and breathing.

How long does recovery from surgery take?

If a drain has been left at the site, it is often removed after 1–3 days. Skin stitch removal is usually scheduled for 10–14 days after surgery. Drain requirements and wound condition affect follow-up visits, so your own discharge instructions determine monitoring and wound care.