Have you heard of Gallbladder Mucoceles?
This condition is due to an overabundance of bile/mucus in the gallbladder. It is more commonly seen in dogs. Clinical signs may be vague such as lethargy, anorexia, abdominal pain or icterus (yellow tinge to skin/mucus membranes)

The defining characteristic is a “kiwi”-like appearance on ultrasound
If the gallbladder is ruptured or obstructed, this is an emergency that requires surgical intervention.
There can be underlying causes such as Cushing’s disease, hypothyroidism, lipid disorders, gallbladder motility issues or other endocrine disorders so it is important to screen for these as well
References:
1) Veterinary Partner. Veterinarypartner.com
2) Tilley, L. P., & Smith, F. W. (2005). The 5-minute veterinary consult: Canine and feline. Philadelphia: Lippincott Williams & Wilkins.
3) Yin, S. A. (2010). The small animal veterinary nerdbook. Davis, CA: CattleDog Pub.