Gallbladder mucoceles are increasingly diagnosed, relatively common in some popular dog breeds, and survival after surgical treatment isn't great. What is a mucocele though, and can they be treated or prevented with dietary change?
What is a gallbladder mucocele?
The gallbladder is found between the lobes of the liver. It is essentially a sac, which stores and concentrates bile. Bile is a greenish liquid that is made by the liver – it helps with digestion of fat, and is released from the gallbladder into the intestine, in response to the presence of food.
A mucocele forms when the lining of the gallbladder secretes abnormally thick mucous. This mucous accumulates, becomes increasingly thick or sludge-like, and obstructs the normal flow of bile from the gallbladder into the small intestine. The gallbladder may even rupture secondary to overdistention by this sludge, requiring emergency surgery to save the dog’s life. Unfortunately, mortality following surgery is high, with only 22-50% of dogs surviving to be discharged from hospital.
A gallbladder mucocele visible on ultrasound. The gallbladder should appear full of bile (which looks black); here it is filled with mucous that has a "stellate" or striated appearance.
What cause/s a mucocele to develop?
The causes of mucocele development are not well-understood, and there are likely multiple factors involved, including genetic factors. Gallbladder mucocele is more common in Shetland Sheepdogs, Miniature Schnauzers, and Cocker Spaniels, but can also be seen in other breeds like Pomeranians and Chihuahuas, as well as mixed breeds.
Recent research has shown that affected dogs are likely to have concurrent hypothyroidism, Cushing’s disease (hyperadrenocorticism), proteinuria (protein loss in the urine), and/or hyperlipidemia.
Hyperlipidemia is defined as a persistent elevation in serum triglycerides and/or cholesterol and has been associated with decreased gallbladder motility in humans and rodents. In dogs, it leads to gallbladder distention, which may lead to bile retention. Obesity, very high fat diets, some medication, and some endocrine diseases like diabetes mellitus, have all been associated with hyperlipidemia in dogs.
We don’t know, however, how all these risk factors fit together, and if they are the primary cause/s of mucocele development. Some dogs will obviously tolerate high fat diets without developing hyperlipidemia, whereas others may not.
If you own an at-risk breed:
Talk with your vet about proactive screening for these diseases, and for gallbladder mucoceles themselves.
Keep your dog lean and active throughout his or her life. This may help to reduce the risk of hyperlipidaemia developing.
Avoid high fat diets. For healthy adults, we recommend diets with a moderate fat content (up to 35% calories from fat). You can use this free online calculator to check the percentage of calories from fat in commercial diets. A moderate fat diet may also help with maintenance of ideal body weight, because higher fat diets are more energy-dense, and therefore even slight overfeeding can significantly increase daily calories.
Open Farm Wild-caught salmon and ancient grains dry diet has 34% calories from fat, which could be considered moderate.
Other moderate to low fat options could include Royal Canin Lightweight Care dry diet, Lyka turkey or kangaroo bowls, Black Hawk Adult chicken and rice dry diet, Prime100 air-dried kangaroo and pumpkin diet, or Purina HA dry diet (a hydrolysed veterinary diet for dogs with allergies). There are many other options available.
Treatment and diet options
Researchers at North Carolina State University are currently investigating whether feeding a low-fat diet, in combination with additional supplements, results in resolution of gallbladder mucoceles. We don’t have the results from that study yet, though, unfortunately.
A case report on two dogs with mucoceles and hypothyroidism reported successful (nonsurgical) treatment, which included different medications and supplements - treatment of the underlying hypothyroidism was likely key in these cases.
For now, surgery to remove the entire gallbladder (cholecystectomy) remains the most widely recommended treatment. Early surgical intervention may reduce mortality rates, so this is definitely something to discuss with your dog’s veterinarian. If you can't or choose not to opt for surgery, definitely transition your dog to a fat-restricted prescription diet, as there is a high likelihood that this may be helpful.
What about ursodiol, silymarin and SAMe?
S-adenosyl-L-methionine (SAMe) and ursodeoxycholic acid (UDCA or ursodiol) are supplements that are often recommended for the medical management of gallbladder sludge or gallbladder mucoceles (where surgery is not an option). As mentioned previously, these nutraceuticals should be combined with a low fat diet.
Ursodiol is a naturally occurring bile acid (first identified in the bile of bears) that increases bile flow (a 'choleretic') from the gallbladder into the intestine. This may help to reduce accumulation of mucous in the gall bladder.
Silymarin (milk thistle) alters the composition of hepatocyte membranes and limits the entry of hepatotoxins into cells. S-adenosylmethionine (SAMe) is a precursor to glutathione and has antioxidant effects. While research indicates that milk thistle and SAMe may protect hepatocytes from damage, studies have not confirmed that either is useful in dogs with mucoceles.
What to feed post-cholecystectomy?
Research has demonstrated that, in cholecystectomy patients, a high-fat diet may cause bile acid malabsorption, resulting in diarrhoea due to increased passage of bile acids into the colon.
In addition, after cholecystectomy, some human patients report dyspepsia and intolerance to fatty foods, which may be due to delayed gastric emptying.
What we recommend:
Feed a low-fat diet. Prescription low-fat diets are a good choice; Royal Canin Gastrointestinal Low Fat wet or dry diets, or Hill’s Prescription Diet i/d Low Fat wet or dry diets are available in Australia and New Zealand. If you would prefer to feed a raw or cooked homemade therapeutic diet, make sure it is properly formulated by a Board Certified Veterinary Nutritionist.
Feed small, frequent meals – six to eight small meals per day is ideal.
Transition gradually to any new diet over at least 4-5 days.
Other considerations
As mentioned previously, we know that dogs diagnosed with a gall bladder mucocele may also have elevated triglycerides and/or cholesterol in their blood (hyperlipidemia) and/or protein loss in the urine (proteinuria).
For dogs diagnosed with hyperlipidaemia:
We recommend a low-fat prescription diet or a properly formulated low-fat homemade therapeutic diet (see below for more information on brands).
Supplementary omega-3 fatty acids from fish oil or marine algae oil may help to reduce serum triglycerides. Your vet or veterinary nutritionist can recommend products and appropriate doses.
For dogs diagnosed with proteinuria (protein loss in the urine):
Dietary change, supplements, and/or medication may be helpful. Please talk with your vet or specialist for their recommendations.
For dogs with multiple conditions including kidney disease:
A referral to a small animal internal medicine specialist may be helpful. There may be no commercial diet options that suit some combinations of diseases, therefore a referral to a veterinary nutritionist for a personalised homemade therapeutic diet may be necessary.
Could diet play a role in prevention of gall bladder mucoceles?
There is some evidence to suggest that high fat diets (especially high saturated fat and/or cholesterol) may increase the risk of gallbladder sludge and/or mucoceles. Unfortunately, we don't really have a lot of evidence on diet and gallbladder mucocele development in dogs, though.
In a small study, Kakimoto et al. looked at the effects of feeding diets with low vs. high saturated fat and cholesterol content on bile acid metabolism and gallbladder motility. They found that the high fat diet increased the risk of sludge formation and decreased gallbladder contraction, relative to the lower fat diet. The high fat diet contained 21% calories from protein, 46% calories from fat, and 33% calories from carbohydrate.
The low fat diet contained 28% calories from fat - reasonably comparable to many maintenance diets available for adult dogs. However, there are many commercial diets that contain more than 46% calories from fat. For example, Ziwi air-dried diets contain 53-63% calories from fat, and their canned diets contain 43-66% calories from fat.
For at-risk breeds, again, we recommend selecting a diet that is moderate to low in fat, maintain lean body condition, and proactively monitor fasted serum triglycerides, as per your vet's recommendations. Omega-3-rich diets (fish-based maintenance diets or prescription joint diets) may provide some added benefit, for breeds at increased risk of developing hyperlipidaemia.
Thanks for reading, and if you have any questions: info@vngpets.com
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