Ultrasonographic Evaluation of Gallbladder Wall Thickness in Cats

Abstract

Ultrasonography of the gallbladder and biliary tract was performed on 42 cats: 22 clinically healthy cats (group A) and 20 cats with hepatobiliary disease and post mortem confirmation of gallbladder abnormalities (group B). The gallbladder wall was visible in 9 of 22 cats in group A and all 20 cats in group B. Additional gallbladder findings in group B included shape anomalies, biliary tract obstruction, wall thickening, polyps, neoplasia, and biliary sludge. Ultrasonographic evaluation of abdominal organs identified pancreatic disease as the predominant pathological cause of extrahepatic biliary obstruction. Hepatic parenchymal involvement was noted with inflammation and thickening of the gallbladder wall. Histologically, gallbladder walls were characterized by mucous gland hyperplasia, inflammation, infiltration, edema, epithelial detachment, and/or neoplasia. Ultrasonographic and histologic gallbladder wall measurements of 20 cats in group B agreed within 0.4 mm and all cats with a gallbladder wall thickness > or =1.0 mm had histopathologic abnormalities of the wall. Serum biochemical analysis revealed elevations of one or more parameters in all cats of group B, but was non-specific for a gallbladder lesion. The results of this study indicate that a visible, echogenic gallbladder wall can be considered a normal variant and is not always associated with hepatobiliary disease. Ultrasonography is accurate in measuring gallbladder wall thickness. Wall thickness greater than 1 mm is accurate in predicting gallbladder disease in cats, while a thickness less than 1 mm cannot rule out mild or chronic inflammation.

ULTRASONOGRAPHIC ABDOMINAL ANATOMY OF HEALTHY CAPTIVE CARACALS (CARACAL CARACAL)

“…13 In all five caracals, the wall of the gall bladder was clearly visualized, contrary to domestic cats and dogs in which it is poorly seen or not identified. 3,13 The mean gall bladder wall thickness in caracals (0.6 mm) measured within the reported range in domestic cats (0.4-0.9 mm) 7 but lower than the reported mean in cheetahs (1.1 mm). 4 Caracals had five characteristic ultrasonographic layers of the gastrointestinal tract similar to those of domestic cats 11 and dogs.…”

“…9 The normal ultrasonographic anatomy of abdominal viscera in domestic small animal species is well documented, 1,6,7,10,11,16 providing useful reference for diagnosis of diseases.…”

Liver

“…The thickness of the wall depends on angulation of the sound beam and degree of distention. 13 In our experience, most normal gallbladders in both dogs and cats are less than 1 mm. Normal thickness in dogs is reported in one study 12 as 2 to 3 mm; in another, it was found to be approximately 1 to 2 mm.…”

“…11 The gallbladder wall is poorly seen or appears as a thin (1 to 2 mm) echogenic line in dogs. 13 Distal acoustic enhancement is commonly seen deep to the gallbladder. 13 Distal acoustic enhancement is commonly seen deep to the gallbladder.…”

Liver and biliary tract

“…In one study an ultrasound measurement of the wall ≥1 mm was accurate in predicting gallbladder disease in cats. 14 Enlargement of the CBD can occur within 24-48 hours of acute bile duct obstruction, whereas intrahepatic biliary duct distension requires five to seven days of obstruction. Cholelithiasis can be diagnosed by ultrasonography because both radiodense and radiopaque stones can be imaged but stones within the cystic or CBD can be difficult to visualize as they are not surrounded by anechoic bile and there is the presence of interference by intestinal or gastric gas.…”