Ultrasonographic and clinical findings in dogs with gallbladder mucocele

Gallbladder contents are a common finding when imaging canine gallbladders, with up to two-thirds of dogs having gallbladder debris. The clinical significance of gallbladder sediment varies widely, with small amounts of sediment often being an incidental finding. Conversely, gallbladder mucoceles have been associated with gallbladder rupture, emergency, and high rates of morbidity/mortality [1]. The ultrasonographic classification of gallbladder mucocele in dogs has evolved since it was first described more than 20 years ago with 6 types of gallbladder mucocele based on unique ultrasonographic patterns. This classification scheme, combined with the widespread use of ultrasonography, allows for earlier recognition and intervention in dogs with gallbladder mucocele. In addition, the identification of gallbladder mucocele type could have clinical value. In the retrospective cohort study carried out by Jaffey JA et al., it was found that dogs with higher gallbladder mucocele type were more likely to exhibit signs of biliary tract disease. Increasing developmental stage of gallbladder mucocele could be associated with an increased likelihood of biliary tract related clinical signs, such as anorexia, abdominal pain or distention, diarrhea, vomiting, lethargy [2,3]. The main goal of this study was to detect the most commonly found gallbladder ultrasonographic changes as well as gallbladder mucocele types and to observe if there is any association between gallbladder mucocele type and clinical signs of biliary disease in dogs. 66 dogs (31 male and 35 female) that had clinical signs of biliary tract disease and were diagnosed with gallbladder mucocele after ultrasound examination were included in this retrospective study. Dogs were considered to have clinical signs of biliary tract disease if they exhibited one or more of these symptoms: anorexia, abdominal pain or distention, diarrhea, vomiting, lethargy, polydipsia. Documented gallbladder ultrasonographic abnormalities included gallbladder wall thicker than 1 mm and common bile duct diameter larger than 3 mm. Pathologic gallbladder lumen components were described as sediments or choleliths. Gallbladder mucoceles were divided into 6 groups based on their morphological appearance. Type I mucocele was defined as immobile echogenic bile occupying more than 30% of the lumen, type II as incomplete stellate pattern, type III as typical stellate pattern, type IV as kiwi fruit like pattern and stellate combination, type V as kiwi fruit pattern with (central) echogenic bile, and type VI as kiwi fruit pattern. There were 16 mixed breed dogs and 50 purebred dogs. The most common purebred breeds included Yorkshire Terrier (11, 16.7%), Miniature Schnauzer (5, 7.6%) and West Highland White Terrier Dog (4, 6.1%). The average weight was 9.6 ± 1.1 kg and the average age was 9.7 ± 0.4 years. Gallbladder wall thickening was identified in 36% of patients and common bile duct diameter enlargement in 56% of patients. All 66 dogs exhibited gallbladder lumen sediments and only 4 dogs were diagnosed with gallbladder choleliths. The most common gallbladder mucocele types were type I (53%), type II (36%) and type III (6%). All 66 dogs had at least one of clinical signs of biliary tract disease. Frequently reported clinical signs were vomiting (41%), abdominal 5 distention and pain (27%), lethargy (26%), and anorexia (24%). 34 dogs exhibited only 1 symptom, 10 dogs – 2 symptoms, 11 dogs – 3 symptoms, 8 dogs – 4 symptoms and 3 dogs – 5 symptoms. Based on findings of this retrospective study it is concluded that exact description of gallbladder mucocele ultrasonographic appearance can help to determine it’s type. The most common ultrasonographic changes of gallbladder included common bile duct diameter enlargement and gallbladder wall thickening. Furthermore, association found between patients’ clinical signs and their gallbladder mucocele type were not statistically significant. Identification of more clinical signs did not correlate with higher gallbladder mucocele type (p>0.05). Limitations of this study include relatively small patient cohort which could have caused inaccurate results. Furthermore, ultrasonographic gallbladder features were studied using stored images and videos, so exact description of gallbladder mucocele was limited.