Vet360 Vol 03 Issue 03 June 2016 | Page 27

CANINE MEDICINE Article reprinted with the permission of DVM360, April 2009, Veterinary Medicine is a copyrighted publication of Advanstar. Communications inc. All rights reserved. An Update on Gallbladder Mucocoeles in Dogs Apr 01, 2009 By Audrey K. Cook, BVM&S, MRCVS, DACVIM, DECVIM-CA, Rebecca Quinn, DVM, DACVIM VETERINARY MEDICINE Once thought to be rare in dogs, gallbladder mucocoeles are now frequently diagnosed. And although primarily thought to be best treated surgically, mucocoeles may be effectively managed medically in some patients when caught early. Before 2000, gallbladder mucocoeles were rarely reported in dogs. However, they are now considered one of the more common causes of extrahepatic biliary disease. While gallbladder mucocoeles were initially treated by cholecystectomy, case-based evidence indicates that some may resolve with medical therapy.1 In this article, we review gallbladder anatomy and physiology and discuss the pathophysiology of mucocele development. We also describe the clinical presentation, diagnosis, and management of dogs with gallbladder mucocoeles. Gallbladder Anatomy The gallbladder is an excretory organ found between the quadrate and right medial liver lobes. It is pearshaped and composed of a fundus, body, and neck. From the gallbladder's neck, the hepatic ducts join the cystic duct to form the common bile duct, which leads to the duodenum. The gallbladder wall has five layers: epithelium, mucousa, tunica muscularis externa, tunica serosa, and tunica adventitia.2 1. The epithelium is simple columnar and highly absorptive. It plays an important role in gallbladder function because it secretes mucin, immunoglobulins, and acid. 2. The mucousa is a combined layer consisting of the lamina propria and tunica submucousa.2 These layers of the mucousa are indistinguishable and contain a dense population of lymphocytes and plasma cells. 3. The tunica muscularis externa consists of scant, randomly organized smooth muscle fibers. 4. The tunica serosa is a membranous layer sur- rounding the gallbladder that faces away from the liver. 5. The tunica adventitia is the outermost gallbladder layer and faces the liver. Gallbladder Functions The gallbladder plays many important roles in digestive health and function, including storing and concentrating bile. Within the gallbladder, water, electrolytes, lipids, and proteins are absorbed from the bile. This absorption allows for a five- to 20-time increase in bile bilirubin and bile salt concentrations. The gallbladder also acidifies bile through epithelial acid secretions and adds mucin to bile by bile acid stimulation of the mucousa. Issue 03 | JUNE 2016 | 27 03:00:26 PM JUNE 2016 Vet360 working.indd 27 2016/05/24 12:04 AM