The liver contains very small bile channels (tubes) called canaliculi that collect bile from the liver cells. These ducts join larger and larger ducts that ultimately terminate in three to five visible ducts that empty bile into the gallbladder. The common bile duct (technically called the “bile duct”) is the final stretch of tubing that delivers bile into the first part of the small intestine.
The gallbladder is nestled between two liver lobes on the right side of the liver. Bile, which is concentrated by the gallbladder, serves as a vehicle for fat absorption. Cholecystokinin, a hormone that is released from the pancreas when food is consumed, causes the gallbladder to contract and expel its contents into the intestine via the bile duct.
Cause of gallbladder mucoceles
Historically, gallbladder diseases were rarely diagnosed in dogs and cats. With the advent of advanced imaging tools such as ultrasound, the diagnosis of gallbladder disease is commonly recognized in dogs and cats. Unlike humans, dogs and cats rarely develop stones in the gallbladder. A mucocele is the most common condition that afflicts the gallbladder. By definition, a mucocele is an accumulation of thick mucus within the gallbladder; this thick mucus cannot be expelled from the gallbladder. This condition occurs as a result of excessive proliferation of the mucus-producing cells within the lining of the gallbladder, and infection is infrequently associated with it. As the gallbladder becomes distended, its blood supply is impaired, and it subsequently is prone to rupturing. Once ruptured, bile will leak into the abdomen from the gallbladder and cause the patient to become severely ill.
A gallbladder mucocele is more prevalent in middle-aged to older medium-sized breeds of dogs such as cocker spaniels, miniature schnauzers, and Shetland sheepdogs. Most dogs with a mucocele have nonspecific signs such as vomiting, loss of appetite and lethargy. Other signs that may be found on a physical examination include abdominal pain, jaundice, elevated respiratory rate, fever and elevated heart rate.
Blood work will frequently show elevation of liver enzymes with this condition. With rupture of the gallbladder, liver enzymes are usually very elevated and the white blood cell counts are mild to markedly elevated. Ultrasound is the “gold standard” to diagnose the problem and commonly reveals a “kiwi” appearance of the gallbladder (see photo).
Medical therapy may be recommended in select cases; however, surgery is typically needed in most cases. Surgical removal of the gallbladder is the treatment of choice. In some cases, a stent may be placed in the common bile duct, to ensure continued flow of bile. Following surgery, the patient will receive pain-relieving medication to ensure a comfortable recovery, and intravenous fluids will be administered to ensure that your companion remains hydrated. Blood testing will also be performed to monitor your companion’s recovery.
Perioperative mortality ranges from 22 to 32%; however, rupture of the gallbladder has been shown to worsen the prognosis when infection is present. Long-term survival of patients that have undergone gallbladder removal is excellent. Liver enzymes remain elevated in most patients, but these values usually are much lower after the healing process is completed.
For more information on this subject, speak to the veterinarian who is treating your pet.