It all starts with a sick, usually middle-aged or older dog. He is listless, not eating, and maybe has vomiting and/or diarrhea and fever. These are symptoms that could mean any number of things, but usually, when he reaches the veterinarian’s examination table, he has jaundice (yellow pigmentation visible in the whites of his eyes and possibly on his skin and gums). Hospitalization is recommended to rehydrate him and provide supportive care. Blood tests point to a liver problem. Medications are given to minimize the liver’s workload, but soon, an ultrasound is being discussed to image the liver, and costs may be rising quickly.

Why Do We

Need an Ultrasound if We Already Know the Problem Is Liver Disease?

While blood testing can point to the liver, the fact is that numerous diseases can affect the liver. The liver can have an infection, cancer, scarring (cirrhosis), or any number of conditions. The more specific our diagnosis gets, the more specific treatment can be.

One of the more important diseases to rule out promptly is the biliary mucocele because it is commonly a surgical emergency. As we will describe in more detail, a biliary mucocele is a wad of sludged mucus inside the gall bladder. If you wait a few days to see how the patient responds to general liver support, it may be too late for surgery. Furthermore, ultrasound can evaluate the gall bladder’s integrity; if the mucocele ruptures and spills bile into the belly, the surgeon will need to know that as additional treatment is needed. Ultrasound also evaluates concurrent abdominal conditions that might impact recovery, including pancreatitis, which can occur alone with similar symptoms or in addition to a biliary mucocele.

If the patient has a surgical disease, they will not get better until surgery is performed in the vast majority of cases. Furthermore, it may be a surgical emergency (not only will surgery be needed but it will be needed immediately). The sooner the need for surgery is identified, the better the chance of survival.

What Is the Gall Bladder and What Is the Biliary System?

During food digestion, hormones cause the gall bladder to contract and squirt bile through the large common bile duct and into the intestine. The bile assists with digestion and carries toxins out of the body so they may be eliminated in feces. The gall bladder and its ducts represent the biliary system.

If the biliary tract becomes obstructed, the patient becomes rapidly jaundiced, painful, and sick.

What Is a Biliary Mucocele?

When this is seen on ultrasound in a sick, jaundiced patient, surgery to remove the diseased gall bladder should be performed as soon as possible.

Why Does This Happen?

Several hormone imbalances have been associated with altered fat metabolism and reduced gall bladder contraction: diabetes mellitus, hypothyroidism, and Cushing’s disease. Cushing’s disease patients have an incidence of biliary mucocele development that is 29 times the incidence of patients without Cushing’s disease. Mucocele development has been linked to pancreatitis (inflammation of the pancreas) as well.

Having Cushing’s Syndrome increases a dog’s risk of developing a biliary mucocele by 29 times.

No one knows why this might be so but it does correspond to the mainstreaming of diagnostic ultrasound into general practice.

The Shetland sheepdog, cocker spaniel, miniature schnauzer, and dachshund seem predisposed to developing biliary mucoceles.

Removing the Gall Bladder (Cholecystectomy)

Removing a dog’s gallbladder is a serious surgery that not all veterinarians are comfortable performing. Discuss with your veterinarian whether a referral to a specialist would be best for you and your pet.

The goal is to remove the gall bladder before it ruptures. If it has already ruptured, tissue damaged by the rupture must be cleansed or removed. Whether or not the gallbladder that has a mucocele is removed before or after rupture does not affect the rate of survival.

Mucocele surgery survival rate is 75-80%. However, if the gallbladder ruptures before surgery occurs, survival rate decreases significantly to 25-40%, depending on the study.

The gall bladder’s function is mainly one of bile storage. Without the gall bladder, bile simply dribbles into the intestine constantly rather than in controlled squirts. You might think this would be a problem, but it turns out not to be. Some patients require long-term medication for liver support but generally speaking, if the dog recovers from surgery, the prognosis is excellent, and the patient can return to normal life.

What if Surgery is Not an Option, or What if the Dog Isn’t that Sick?

There is no question that surgery is the best treatment choice, but there is more to the story. Biliary mucoceles can be an incidental finding in dogs who are not sick or who are sick from something else and are having an ultrasound of the belly for some other reason. In a patient that is not experiencing problems with a mucocele, medication may be able to stave off illness in some cases.

As for skipping surgery on a dog that is sick from its mucocele, this is a very risky move.

It is possible to attempt treatment with general liver support medications, a low-fat diet, and choleretics (medications to help liquefy bile, such as ursodiol), but the problem is that the gall bladder is obstructed with a big wad of goop. This goop is unlikely to liquefy in a timely fashion, if at all, no matter what we do. If medical management is attempted, it is important to regularly recheck the gall bladder by ultrasound to watch for any sign of progression that would indicate that surgery should no longer be postponed.

The ultrasound can help discover where and why a problem is occurring so that appropriate treatment can be started. In some cases, the ultrasound findings may result in your pet needing additional testing. This does not mean that the ultrasound was unhelpful. It usually just means that the findings pointed the veterinarian in the right direction to correctly solve the pet’s problem.

Why Does my Pet Need an Ultrasound?

If your pet has been showing symptoms associated with a problem in one of those belly organs, an ultrasound may be needed. This can include diarrhea; throwing up; belly pain; abnormal urination; a mass that can be felt when pressing on the belly; or if internal injuries are suspected, such as after being hit by a car. Sometimes the veterinarian will find something specific during a pet’s physical exam, such as feeling fluid buildup in the belly, that could be seen by ultrasound. Other situations in which an ultrasound may be necessary are if lab work or x-rays show something unusual.

Abdominal ultrasounds can also be used to take samples of fluid or tissues in order to get a diagnosis of the problem. This can include guiding a needle to biopsy unusual masses or removing fluid for analysis. Veterinarians can either view these samples themselves or send them to a pathologist for testing.

As with people, ultrasounds can also be used to check for pregnancy. Pregnancy is best diagnosed after roughly 20 days from the last heat cycle. Intestinal contents and gas can occasionally cause inaccurate results. Ultrasound is not particularly useful for estimating litter or individual fetus size, so x-rays are more commonly performed. X-rays also tend to be less expensive.

The Procedure

Ultrasounds are typically done with the pet lying on a table. The veterinarian holds a transducer or probe against the belly skin. As the transducer is moved over the skin, it sends sound waves to the structures inside, which are then translated to black and white real-time images on a screen. Hair does not conduct sound waves well, so the pet’s belly is usually shaved beforehand. Alcohol or ultrasound gel may be used to provide better conduction.

Ultrasounds are usually painless and often performed in a quiet, dark room. Most pets are able to lie comfortably without stress and with minimal restraint during the brief procedure. Most pets do not need sedation. Almost all pets can safely undergo an ultrasound, regardless of medical concerns.