10 | The complete guide to gallbladder mucoceles in dogs

PodcastLiver
Written By Laura Jones

Ever seen a cholecystectomy before?

They’re great fun, but when they go wrong… well, they go really wrong. These patients are at a high risk of complications in recovery, and require intensive treatment and nursing care.

 

From careful monitoring to placing advanced vascular access, tubes and drains… from administering epidural anesthesia and calculating CRIs, nutritional planning and more, the opportunities for us to use our skills with these patients are endless.

In today’s episode of the medical nursing podcast, we’re diving into what a gallbladder mucocele is, how they occur, and how we can best treat and nurse these patients.

What is a mucocele?

To understand what a mucocele is, we first need to recap a little bit about how the biliary system works. Normally, the gallbladder functions to store bile between meals.

When the patient eats, the fatty acids and amino acids trigger the release of cholecystokinin, stimulating gallbladder contraction. As the gallbladder contracts, stored bile is emptied into the duodenum where it aids in the digestion and absorption of dietary fat.

The gallbladder is lined with epithelial cells that secrete a glycoprotein called mucin, and concentrate the bile within the GB by absorbing water.

When changes to the viscosity bile occur, for example due to excessive mucin production, or delayed gallbladder emptying (and therefore more time for water reabsorption), the flow of bile is reduced - and this can predispose patients to developing a mucocele.

A gallbladder mucocele is a non-inflammatory condition where the gallbladder becomes distended with abnormal, mucin-rich, thick, gelatinous bile.

What causes a mucocele?

The underlying cause of mucocele in dogs is still not known - in humans it is associated with stones in the biliary tract causing a bile outflow obstruction, but that doesn’t appear to be the case in dogs. Instead, it seems to be associated with dysfunction primarily with the mucous-secreting cells in the gallbladder mucosa, causing overproduction and thick, mucoid or jelly-like bile. Gallbladder stasis and dysmotility have also been identified as possible causes.

Mucoceles are seen most commonly in middle-aged to older dogs, dogs with endocrinopathies including cushings disease, hypothyroidism and diabetes mellitus, dogs with hyperlipidaemia or hypercholesterolaemia, and patients with gallbladder dysmotility.

In cats, they are very rare - because they have less mucin-secreting glands naturally in their gallbladder.

What happens when one is formed?

When a mucocele forms, it places increasing pressure on the gallbladder wall, causing necrosis, rupture, and bile peritonitis - as bile leaks into the abdominal cavity.

Extrahepatic bile duct obstruction can also occur, as the thick, jelly-like mucous and bile also obstruct the cystic duct and biliary tree.

What signs do we see?

Clinical signs are usually vague and nonspecific to begin with, including inappetence, vomiting, and lethargy. These signs are usually relatively acute in onset (between 5 days and 3 weeks).

Inappetence, vomiting, vague abdominal pain, jaundice, tachypnoea, tachycardia, PUPD, pyrexia and diarrhoea are all reported in dogs with a mucocele. If a patient progresses to gallbladder rupture, they will present acutely unwell with marked abdominal pain, jaundice, tachycardia and tachypnoea, along with pyrexia. In some cases, septic shock is seen, as opportunistic infection within the GB can occur - and if this ruptures, this infection then spreads to the abdomen.

That being said, it’s worth noting that up to 45% of dogs with a mucocele are asymptomatic, especially in the early stage of development - and often, we will find a mucocele incidentally on ultrasound when investigating other clinical signs.

How is it diagnosed?

Like our other liver conditions, mucoceles are diagnosed using a combination of bloodwork and abdominal imaging. They have a characteristic appearance on ultrasound and are being diagnosed with increasing frequency, after noticing signs of biliary disease on initial bloods.

Aside from bloodwork and imaging, sampling of the gallbladder and liver for histology is advised - this is performed at the time of surgery to treat the mucocele, by removing the gallbladder in its entirety - a procedure called a cholecystectomy.

What about treatment?

There are both surgical and medical approaches to mucoceles - and whether we go for surgery or not (as well as how quickly we go for surgery) depends on the patient, the extent of the mucocele formation, and whether gallbladder rupture is suspected.

In patients with a forming mucocele, delayed gallbladder emptying or changes in their mucin production, but who do not yet have a ‘proper’ mucocele, we can manage them medically.

Medical management includes administering choleretics (eg ursodiol), antioxidants (SAMe) +/- antimicrobials, alongside feeding a low-fat diet.

In patients with a mucocele, complete removal of the gallbladder is the treatment of choice.

Critically ill patients must be stabilised before anaesthesia and have surgery as an emergency. Crystalloid boluses +/- vasoactive medications are used to maintain normotension and restore circulating volume, analgesia is administered to manage their marked abdominal pain, and acid-base and electrolyte derrangements are corrected.

Patients who have a mucocele but are otherwise stable can have their surgery scheduled and performed routinely - but it’s worth noting that on histology, microruptures are also commonly noted in mucocele patients, so we still want to prioritise performing surgery as soon as practically possible in any mucocele patient.

Cholecystectomy has a high perioperative and postoperative mortality rate, especially where bile peritonitis is present. Non-elective cholecystectomies have mortality rates of 23% and complication rates of 52% reported, so careful monitoring and intensive treatment and nursing are required postoperatively.

And what about postoperatively - how will we nurse these patients?

There is a LOT to think about when nursing mucocele patients - they require ICU care after surgery, have a high complication rate, are often very painful, and with this, they’ll also be less likely to eat or drink, have fluid and electrolyte abnormalities, and are at risk of things like ileus. They’re also at risk of developing pancreatitis, adding to their pain and making them even less likely to eat.

Our goals when nursing these patients are:

  • To monitor their cardiovascular status closely and identify complications such as hypovolaemic or septic shock

  • To provide sufficient analgesia and perform regular pain assessment

  • To maintain fluid and acid-base balance

  • To provide nutritional support and maintain GI motility

  • To maintain vascular access and indwelling devices

  • And on top of all of this, there are all of our general nursing considerations too!

Did you enjoy this episode? If so, I’d love to hear what you thought - screenshot it and tag me on instagram (@vetinternalmedicinenursing) so I can give you a shout out, and share it with a colleague who’d find it helpful!

Thanks for learning with me this week, and I’ll see you next time!

References and Further Reading

Laura Jones
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09 | The complete guide to caring for cats with inflammatory liver disease