Dogs and cats have four salivary glands, and all can become affected by cysts. These salivary gland cysts are known as sialocele (or a salivary mucocele). It is the most common salivary disorder in dogs and is noticed by swelling under their neck or jaw. It is most frequently seen in dogs, but it sometimes can affect cats as well. Sialocele can impact all breeds, but a few breeds seem more prone to them, including poodles, German shepherds, dachshunds, and Australian silky terriers.
A sialocele is a cyst filled with a collection of mucoid saliva in the tissues surrounding a salivary gland. The most commonly affected salivary glands are the large ones under the jaw, called the mandibular salivary glands. The sublingual glands located under the tongue can also be affected. The cysts can become quite large and press against the animal's larynx or trachea, causing them to cough.
There are four types of salivary mucoceles that range from most common to very rare:
- Cervical Mucocele: This is the most common type of mucocele. This forms from a collection of saliva in the upper neck, under the dog's jaw, or in the area between the jaws (the intermandibular region).
- Sublingual Mucocele (also called a ranula): This is the formation of mucocele on the bottom floor of the mouth, near the tongue. It is also common.
- Pharyngeal Mucocele: This type of mucocele is much less common. It's a variation of the cervical mucocele, with fluid accumulation almost all in the throat.
- Zygomatic Mucocele: This is a very rare type of mucocele. In this type, the saliva originates from the small zygomatic salivary glands. These are located just below the eye.
The development of sialocele is a gradual process. In most cases, there is a gradually enlarging, soft, painless mass in the upper neck or jaw. While it may develop and not cause immediate problems, it can lead to a number of symptoms including:
- Difficulting eating
- Difficulting swallowing
- Bleeding from the mucocele
- Difficulting breathing and respiratory distress
While not usually painful, these cysts can become infected, which may cause pain and a generalized fever.
The exact cause of these cysts is often hard to determine. They may be induced by trauma to the gland or ducts or caused by an infection. It's possible that trauma or choke collars can also lead to them. Additionally, they could be the result of a growth that obstructs the ducts and causes a rupture. The saliva and mucus then escape into the surrounding tissues.
If you notice swelling below your pet's muzzle or neck, it is important to get them to a veterinarian for proper diagnosis and treatment. The cause may be sialocele or it may be something else, but in either case, they do need to be examined as soon as possible
When diagnosing sialocele, the vet will most likely use needle aspiration. During this procedure, a small needle is inserted into the lump and a sample of cells and liquids are removed. It is a very useful diagnostic tool for many veterinary situations, including salivary cysts. The characteristic aspirate for sialocele is a clear and sticky or stringy fluid (saliva) that may be tinged with a little blood. It is important to look at the sample microscopically, too. This will help your vet rule out other diseases, such as cancer or infection. It also helps differentiate between problems with a salivary gland and another tissue that is in the area such as a swollen lymph node.
Surgical removal of the damaged gland and duct is the treatment of choice. Some cases can be managed by installing drains and periodically emptying the cyst. The hazard with simply draining the cyst is that it is prone to infection, which can then complicate or eliminate surgery as an option. This will further complicate the animal's health, especially if symptoms worsen. Some cysts will resolve on their own, but infection, pain, and critical obstruction of the airways are potential risks if treatment is not utilized. Since there are four different salivary glands in different locations, discuss with your veterinarian the best individual treatment option for the dog.
If surgery is conducted, you can likely expect some healing time for your dog. Your surgeon may leave the drain to empty the site as it continues to heal. If there is a bandage at the surgery site, you'll need to change the bandage frequently. If it's not bandaged, it can be helpful to use a warm compress on the site. The goal is to keep the surgery area and skin surrounding it clean, to prevent infection, and to encourage the fluid in the area to drain. Post-operative complications are rare.
Poirier, V.J. et al. Efficacy Of Radiation Therapy For The Treatment Of Sialocele In Dogs. Journal Of Veterinary Internal Medicine, vol 32, no. 1, 2017, pp. 107-110. Wiley, doi:10.1111/jvim.14868
Salivary Mucocele. American College of Veterinary Surgeons, 2020.