Updated: Jul 11, 2020
The term “gallbladder mucocele” (MC) commonly refers to an over-distended gallbladder filled with an immobile mixture of mucus and inspissated bile that can cause obstruction of the biliary tract.
Gallbladder mucoceles are commonly diagnosed and a reason for biliary tract surgery in dogs. Its etiology is unclear, however it is believed to be related to many other disorders of the biliary tract. Most dogs with MC are asymptomatic and they are diagnosed while performing an abdominal ultrasound for other reasons; however, these patients are at risk of further complications such as gallbladder rupture, peritonitis, sepsis and related coagulopathies, and should be considered for surgical intervention. Some MC produce severe clinical signs and they need to be treated promptly.
It has been found that MC usually occur in geriatric patients with a median age of 9 years. No sex predisposition has been noted. Smaller dogs (<20 kg) seem to be more commonly diagnosed.
Breeds that are over-represented include:
Cocker Spaniels, Shetland Sheepdogs, and Miniature Schnauzers. Other breeds affected include; Terriers (West Highland White, Scottish), Maltese, Shih Tzu, Pug and Bichons. Felines can also be affected although this is less common.
Gallbladder mucoceles have been found to occur with cholelithiasis, cholangitis, cholecystitis, extra- hepatic bile duct obstruction, neoplasia obstructing the biliary tract, pancreatitis, hyperadrenocorticism, diabetes mellitus and hypothyroidism. These last three conditions can affect bile acid production.
Dogs with MC should be tested for hyperadrenocorticism, hypothyroidism, and diabetes mellitus, as these conditions are commonly diagnosed together with MC.
Although not specific for MC, the most common abnormalities are:
· Stress leukogram (neutrophilic leukocytosis)
· Increase in; ALP (11-15x), ALT (4-6x), GGT (2-8x), Cholesterol.
· Bacteria have been reported in up to 30% of cases with E. coli, Streptococcus and Enterococcus often isolated.
Ultrasound is the gold standard diagnostic method for a definitive MC diagnosis. This is because ultrasound can clearly evaluate the gallbladder wall and its lumen, including evaluation of the cystic and common bile duct, and the hepatic parenchyma.
Ultrasound can also differentiate MC from other pathologies associated with the same clinical signs, such as pancreatitis with extrahepatic biliary obstruction, cholecystitis, cholelithiasis and acute hepatitis.
Ultrasound is also sensitive to detect abdominal free fluid when gallbladder rupture is suspected, and ultrasound-guided abdominocentesis can be used to evaluate the fluid IMPORTANT: Cholecystocentesis is not recommended in cases of gallbladder mucoceles.
So far no classifications of MC have been documented in the literature and it is usually described only as a characteristic “kiwi” or “stellated” appearance. However, clinical sonographers unofficially stage MC in the following way:
Emerging or early mucocele, when there is evidence of stationary sediment, and organized bile sludge that only encompasses a small portion of the gallbladder and some bile is still observed surrounding it.
Mucocele: when the gallbladder is almost completely or completely filled with a stellate appearing sludge that is non-gravity dependent with attachments to the wall. A dilated cystic duct might be present.
Inflamed mucocele: Usually pain is present while scanning, the gallbladder wall is thickened and the peritoneal fat surrounding it is echogenic. A double-layer appearance of the wall can be observed especially when free fluid is present and this could be a concern as rupture is possible.
Treatment: Cholecystectomy is usually the preferred treatment for gallbladder mucocele, because of the high risk of rupture and secondary peritonitis. Medical therapy is often ineffective once the mucocele has formed.
Duodenostomy and catheterization of the bile duct is sometimes performed at the same time to flush the bile duct retrograde. Culture of the gallbladder content should be performed to determine if an infection is present. Liver biopsy should be recommended for histopathological evaluation. And if the gallbladder has ruptured, abdominal lavage is warranted.
Post-operative care should include:
• Antibiotics if culture is positive (4-6 weeks)
• Ursodeoxycholic acid (Ursodiol) (10-15mg/kg SID) for long term treatment to ensure choleresis
• Low fat diet
• Monitor liver enzymes.
The most common post-operative complications include pancreatitis, necrosis of the common bile duct and bile peritonitis.
Medical therapy can be attempted, especially if the patient is asymptomatic, if surgery presents a risk to the patient, or if the owner has declined to follow surgical intervention. If medical therapy is attempted consider close monitoring of the gallbladder with ultrasound and follow up blood work.
Medical therapy usually consists of:
• Antibiotics like Amoxicillin and Clavulanic acid or Fluoroquinolone with Metronidazole.
• Ursodeoxycholic acid (not recommended if there is suspected perforation or inflammation)
• S-adenosyl methionine (SAMe) at 20-40 mg/kg per day
• Fat restricted diet
• Identify and treat endocrinopathies
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Dr. Veronica Damian MVZ, MVS, MANZCVSc (Radiology)
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