Salivary Mucocele in Dogs

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Salivary mucocele is a condition in which saliva leaks from a damaged salivary gland or duct and collects in the surrounding tissues. The condition is also known as sialocele, cervical sialocele, cervical mucocele, ranula, and salivary cyst.

Although trauma is considered to be the usual cause for the damage to the duct or gland, it is rare that a specific traumatic event can be identified. Salivary mucoceles are more common in dogs than cats. Any age and any breed can be affected with this problem.

They cause a soft, usually non-painful, swelling located adjacent to the affected salivary gland. Cervical mucocele is the most common form of this condition and usually show no symptoms except for the swelling under the rear portion of the jaw.

A mucocele under the tongue, called a ranula, is also very common and can cause difficulty chewing or bloody saliva. Less common forms of salivary mucoceles are pharyngeal mucoceles that can cause difficulty swallowing or breathing, and zygomatic mucoceles that occur near the zygomatic cheek bone beneath the eye, which can cause swelling under the eye or problems with the eye itself.

Mucoceles can become infected if not treated, but the prognosis is excellent with treatment.

Diagnosis

Diagnostic tests may include:

  • Palpation of the swelling under the neck or on the face, or examination of the mouth if the swelling is under the tongue or in the back of the mouth.

  • Fine-needle aspiration of the swelling to determine if the swelling is filled with saliva.

  • Radiographs and blood tests are not necessary for this diagnosis.

    Treatment

    Treatment may include:

  • Periodic lancing or drainage of the mucocele. Unfortunately, this usually results in recurrence.

  • Definitive treatment is by surgical drainage of a ranula or pharyngeal mucocele or by excision of the affected salivary glands and ducts for cervical or zygomatic mucoceles.

  • Antibiotic therapy may be instituted to prevent infection or if infection is suspected.

    Home Care and Prevention

    Inform your veterinarian about any abnormal swelling, whether it appears to be bothering the animal or not. Any difficulty in chewing, swallowing, and especially breathing problems, should be brought to your veterinarian's attention immediately.

    After surgery, watch for potential complications:

  • Redness or drainage of the incision
  • Recurrence of swelling
  • Bloody saliva

    Even though trauma is suspected to be the cause for most mucoceles, it is unreasonable to try to avoid all situations that could lead to this problem. The use of choke collars should be limited and the animal should be prevented from chewing on sticks.

  • Several salivary glands supply saliva to the mouth to assist with lubrication of the food and begin the process of digestion. Salivary glands are located under the ears, in the back of the mouth, and under the tongue, and the saliva produced within each gland travels through a small duct to get to the oral cavity. Damage to the gland or the duct can lead to leakage of the saliva into the adjacent tissues and create a mucocele. The saliva is mildly irritating to the tissues, and these tissues respond to the irritation by creating a layer of granulation tissue around the pocket of saliva.

    Depending on which salivary gland and duct are actually affected and where the resulting swelling occurs, the problem may be given a different name and may cause different symptoms.

    The common forms of this condition are:

  • Cervical mucocele (or sialocele), if the mandibular salivary gland and its duct are the source for the leakage. The cervical mucocele causes a soft, non-painful swelling under the rear corner of the lower jaw under the neck.

  • Ranula, if the sublingual gland and its duct are the source. A ranula causes a soft swelling under the tongue that leads to difficulty in chewing or swallowing and can cause blood-tinged saliva if it breaks open in the mouth.

  • Pharyngeal mucocele, if the zygomatic salivary gland is involved, which leads to a swelling in the back of the mouth. A pharyngeal mucocele may cause the animal to have difficulty breathing as the collection of saliva in the wall of the back of the mouth gets large enough to occlude the airway. These mucoceles can also lead to difficulty swallowing and can cause blood-tinged saliva if they break open in the mouth.

  • Zygomatic mucocele, also originates from the zygomatic salivary gland behind and under the eye A zygomatic mucocele can cause swelling under the eye or bulging of the eye out of the socket.

    Blunt trauma is usually suspected as the cause for a mucocele, but rarely is an actual event identified as the cause of the problem. Animals that chew on hard toys or sticks can develop ranulas or pharyngeal mucoceles. Trauma to the neck, as might occur with the use of a choke collar, can result in development of a cervical mucocele.

    This problem can occur in any age or breed of dog. Dogs are more frequently affected than cats. Untreated, the salivary mucocele can become infected. With treatment, however, the prognosis is generally excellent for these patients.

  • Diagnosis In-depth

    Simple palpation of the swelling under the neck or under the tongue is often all that is necessary to make the presumptive diagnosis of salivary mucocele. These swellings are soft and feel like fluid within a pocket of tissue. This is unlike the feel of a tumor that might cause a similar swelling in these areas. Tumors usually have a firm, often irregular, feel to them and may be painful to touch.

    The definitive diagnosis is made by removal of a sample of the fluid from the swelling and examining it under the microscope. The fluid from a mucocele is usually clear or slightly yellow and thick like mucus. There are usually few cells seen in the sample. Special stains are used to determine if the fluid is saliva. It is important to make sure that the problem is not a pocket of infection (abscess) that might require different treatment.

    No other tests are usually necessary to make the diagnosis.

    Treatment In-depth

    Some veterinarians attempt to treat salivary mucocele with periodic drainage by lancing the swelling and placing a rubber drain within the pocket. This may work in the lucky patient, but for most, the newly created hole quickly seals over after the drain is removed and the swelling occurs again.

    The most reliable treatment for these conditions is by surgery.

  • Ranulas and pharyngeal mucoceles are treated by "marsupialization." This the conversion of a closed cavity into an open pouch, in this case forming a permanent large opening from the mucocele into the oral cavity. This is accomplished by suturing the walls of the mucocele to the surface of the under portion of the tongue or back of the mouth. It allows any further leakage of saliva to drain directly into the mouth without creating a swelling. In most cases, as the swelling reduces in size, so does the size of the permanent opening.

  • Cervical mucoceles are best treated by removal of the entire mandibular salivary gland and its duct. The duct travels from the gland under the base of the ear to an opening under the tongue along with the sublingual salivary gland, which is removed along with the mandibular gland and duct during this procedure. This is done through an incision behind the corner of the jaw. In animals with very large swellings under the neck, it can be difficult to determine which side is the source of the problem. If it cannot be determined which side is the cause, both sides can be removed without long-term problems for the animal.

  • Antibiotics are often given to these animals whether an infection is present or not, although they may not be necessary at all. The swelling under the skin or inside of the mouth can be a source for infection, but infection is not a frequent occurrence with these problems.

  • After surgery, some potential minor complications can occur. As with any incision, it can become infected or break open. The incision should be monitored daily for signs of swelling, redness, or discharge. Notify your veterinarian if these occur.

    Occasionally, the "permanent" opening into the mouth can completely seal over and a swelling recur. This is not a likely occurrence, but if it happens, the original symptoms can recur.

    Sometimes the space from which the mandibular salivary gland was removed fills with other body fluids. This causes another soft swelling called a seroma that usually resolves with time. Your veterinarian may have you applying hot compresses to the area to help the fluid reabsorb.

    Frequently, bloody saliva continues for several days after marsupialization of a ranula. You may notice blood in the dog's water bowl after he drinks. This will usually clear up within a few days, but if it persists or becomes more profuse, contact your veterinarian.

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