Gallbladder Mucocele in Dogs

What is a gallbladder mucocele?

A gallbladder mucocele is a condition in which the gallbladder fills up with thick bile and mucus, making it difficult to function well.

The gallbladder normally stores bile, a digestive fluid produced by the liver. The gallbladder contracts in response to eating, releasing bile into the small intestine where it works to break down fats from the diet.

A mucocele makes it harder for the gallbladder to both store and release bile into the intestine. Over time, it can block bile from moving from the liver into the intestine. If the gallbladder gets too full and bursts, the bile can leak into the belly and cause a potentially life-threatening infection called peritonitis.

What causes a gallbladder mucocele and what dogs are more commonly affected?

The underlying condition that leads to a mucocele is believed to be cystic mucosal hyperplasia, which causes the inner lining of the gallbladder to secrete too much mucus. This mucus builds up into a gel that is too thick to be released and so fills the gallbladder.

The exact reason this happens isn’t fully known, but may be linked to certain hormonal disorders, such as hyperadrenocorticism (Cushing’s disease), hypothyroidism, or hyperlipidemia (high levels of fat in the blood). There may also be a genetic component, as it occurs more frequently in certain breeds, including:

• Cocker spaniels
• Shetland sheepdogs
• Border terriers
• Miniature schnauzers

What are the signs of a gallbladder mucocele?

Some dogs diagnosed with a gallbladder mucocele are asymptomatic, but most experience one or more of the following signs with different degrees of severity:

• Vomiting
• Not eating or reduced appetite
• Lethargy
• Diarrhea
• Pain when their belly is palpated (examined by touching it)
• Yellow gums and skin (icterus/jaundice)
• Fever if the gallbladder has ruptured

How is a gallbladder mucocele diagnosed?

The presence of a gallbladder mucocele may be suspected based on history, physical exam, and results of bloodwork and urinalysis. Affected dogs may have:

• Elevated white blood cell count
• Elevated liver enzymes, including alkaline phosphatase (ALP), alanine aminotransferase (ALT), and gamma glutamyltransferase (GGT)
• Elevated total bilirubin
• Elevated protein in the urine

Abdominal radiographs (X-rays) are usually unremarkable unless the gallbladder has ruptured. Ultrasound can show a characteristic image of the gallbladder known as the “kiwi sign.” A mature gallbladder mucocele on ultrasound looks similar to the cross section of a kiwi. Ultrasound may also detect a developing gallbladder mucocele, catching it earlier than when it looks like a kiwi.

How is a gallbladder mucocele treated?

Immediate treatment depends on how severe the condition is when it is diagnosed. Dogs that have signs of obstruction or gallbladder rupture need emergency surgery to remove the gallbladder (cholecystectomy). This surgery may be done through a routine surgical incision or with laparoscopic surgery (requiring a few small incisions).

Rarely, if a surgeon finds an obstruction of the bile duct that cannot be resolved, they will need to perform a cholecystoenterostomy: creating an opening from the gallbladder into the small intestine. More severely affected dogs will also need supportive care such as intravenous fluids, and certain medications described below.

In dogs that are asymptomatic or those with mild clinical signs for whom surgery is not an option, medical therapy may be discussed; however, there is still the risk of gallbladder rupture and death. Medical therapy may include:

• Ursodiol to improve bile flow and for its protective effects on liver cells that can be damaged from reduced bile flow
• S-adenosyl-methionine (SAMe) for its ability to support the liver
• Broad-spectrum antibiotics to prevent or treat bacterial infections that may occur in the liver or bile ducts secondary to reduced bile flow
• Pain medication to reduce the discomfort and pain caused by increased pressure in the gallbladder, gallbladder rupture, or post-surgical pain
• Low-fat diet to reduce any hyperlipidemia (high fat in the blood) because increased ingested fat may increase mucus in the bile and decrease gallbladder contractions, causing more mucus buildup

What is the prognosis for dogs with a gallbladder mucocele?

Prognosis depends on how sick the dog is before surgery. An asymptomatic dog will generally have a good outcome with surgery and recover quickly. The chance of a good outcome is lower in dogs who have a ruptured gallbladder and peritonitis. For this reason, surgery is recommended even if the dog has no or minimal signs.