Hepatobiliary Imaging with Radiography & Ultrasonography: Biliary System

FIGURE 1A Lateral radiographs of a clinically normal cat (A) and a 14-year-old neutered male domestic shorthair cat (B) presented with icterus and elevated liver enzymes. A normal feline liver should have a sharp, pointed margin (A; arrows) and should not extend past the costal arch; the gastric axis should be parallel to the ribs (A; line). The liver in the icteric cat extends past the costal arch, and has rounded borders (B; arrows). The stomach is displaced caudally (B; line; gastric axis from the fundus to the antrum). An ovoid mineralization (B; arrowheads) is also superimposed with the cranioventral liver in the location of the gallbladder. This cat was diagnosed with cholangitis, lipidosis, and a cholelith.

FIGURE 1B Lateral radiographs of a clinically normal cat (A) and a 14-year-old neutered male domestic shorthair cat (B) presented with icterus and elevated liver enzymes. A normal feline liver should have a sharp, pointed margin (A; arrows) and should not extend past the costal arch; the gastric axis should be parallel to the ribs (A; line). The liver in the icteric cat extends past the costal arch, and has rounded borders (B; arrows). The stomach is displaced caudally (B; line; gastric axis from the fundus to the antrum). An ovoid mineralization (B; arrowheads) is also superimposed with the cranioventral liver in the location of the gallbladder. This cat was diagnosed with cholangitis, lipidosis, and a cholelith.

FIGURE 2A Ventrodorsal radiographs of the cats in Figure 1, including the clinically normal cat (A). The liver of the cat in B is enlarged mainly on the right side and rounded. The cholelith (B; arrowheads) is superimposed with the right cranial aspect of the liver in the location of the gallbladder. Although the right side of the liver enlargement is easy to see, there is generalized enlargement with caudal displacement of the stomach nearly outside the confines of the ribs. The spleen, colon, and kidneys are also displaced caudally as a result of generalized hepatomegaly.

FIGURE 2B Ventrodorsal radiographs of the cats in Figure 1, including the clinically normal cat (A). The liver of the cat in B is enlarged mainly on the right side and rounded. The cholelith (B; arrowheads) is superimposed with the right cranial aspect of the liver in the location of the gallbladder. Although the right side of the liver enlargement is easy to see, there is generalized enlargement with caudal displacement of the stomach nearly outside the confines of the ribs. The spleen, colon, and kidneys are also displaced caudally as a result of generalized hepatomegaly.

FIGURE 3A Lateral (A) and ventrodorsal (B) radiographs of the cranial abdomen of a 13-year-old spayed domestic shorthair cat with vomiting and icterus. A small, mineralized structure (arrowheads) is evident in the midcranial and right side of the abdomen. This is the location of the common bile duct. 

FIGURE 3B Lateral (A) and ventrodorsal (B) radiographs of the cranial abdomen of a 13-year-old spayed domestic shorthair cat with vomiting and icterus. A small, mineralized structure (arrowheads) is evident in the midcranial and right side of the abdomen. This is the location of the common bile duct. 

FIGURE 4 Ultrasound image of the cat in Figure 3 that confirms a hyperechoic, irregularly shaped structure (arrowheads) with acoustic shadowing (dashed arrows) in the lumen of the common bile duct determined to be a choledocholith. The bile duct is mildly distended (between the X’s). Shadowing structures in the biliary tract may be a result of choleliths or concrements of inspissated bile that can become dense and create acoustic shadowing. It is thus important to confirm with radiography whether a shadowing structure is actually mineralized.

FIGURE 5 Ultrasound of an 18-year-old domestic shorthair cat presented with chronic kidney injury. The liver contains irregularly shaped, hypoechoic, fluid-filled cavities (arrowheads). The common bile duct (CBD; arrow) is dilated. These findings did not cause the clinical signs and were considered incidental cystadenomas and bile duct dilation, which can be found in older cats. Differential diagnoses include cystadenocarcinoma and biliary carcinoma.

FIGURE 6A Normal gallbladder (GB) in a dog (A) and a cat (B). The gallbladder wall should be thin (1 mm) and uniform, and bile should be anechoic to hypoechoic. In dogs, the amount of hyperechoic sludge increases with age. Cats typically have no or only minimal amounts of sludge. Sludge should always be gravity dependent and often creates a solid–liquid bile interface. This dog is in right lateral recumbency (right is located on the left side of the image), and a sharp demarcation between the sludge and liquid bile is evident. A distinct interface is not always seen. It is important to note the occurrence of settling (versus suspension).

FIGURE 6B Normal gallbladder (GB) in a dog (A) and a cat (B). The gallbladder wall should be thin (1 mm) and uniform, and bile should be anechoic to hypoechoic. In dogs, the amount of hyperechoic sludge increases with age. Cats typically have no or only minimal amounts of sludge. Sludge should always be gravity dependent and often creates a solid–liquid bile interface. This dog is in right lateral recumbency (right is located on the left side of the image), and a sharp demarcation between the sludge and liquid bile is evident. A distinct interface is not always seen. It is important to note the occurrence of settling (versus suspension).

FIGURE 7 Example of cholelithiasis in a dog with cholecystitis. The gallbladder contains multiple hyperechoic structures with acoustic shadowing. The presence of choleliths can be incidental and should be correlated with patient history, physical examination, CBC, and serum chemistry profile to determine clinical significance.

FIGURE 8 Gallbladder images of a 5-year-old Doberman pinscher with elevated ALT, which prompted abdominal ultrasonography. A wall-associated, round, and mildly heterogeneous mass that showed diffuse vascularization on color Doppler was detected. Differential diagnosis based on ultrasonography findings included a polyp. Wall-associated lesions can be benign or malignant. Cytology of the mass revealed a neuroendocrine carcinoid neoplasm. Doppler confirmed vascularization of the mass that was suggestive of tissue versus a nonmineralized cholelith. Repositioning and wall-associated vascularity both confirmed the mass was attached to the wall and was not gravity dependent.

FIGURE 9 Gallbladder in a dog with regularly spaced, small, wall-associated villus-like structures projecting into the lumen. This is a typical appearance of mucosal hyperplasia and is considered an incidental finding in dogs. It is unclear whether this is a precursor to mucocele formation.

FIGURE 10 A 10-year-old spayed American shorthair cat was presented with vomiting and icterus. Ultrasound showed a gallbladder wall diffusely thickened and poorly marginated at the luminal interface. Thickening of the gallbladder wall is common with cholecystitis, and ultrasound-guided cholecystocentesis can safely be performed if clinical findings can be correlated. Cholecystitis was diagnosed after cholecystocentesis was performed.

FIGURE 11A Gallbladder mucoceles in dogs are accumulations of gelatinous mucus and inspissated bile, with variable appearances on ultrasound. They may appear as immobile suspended echogenic sludge (A), have a stellate internal architecture (B), or resemble a kiwi fruit (C).

FIGURE 11B Gallbladder mucoceles in dogs are accumulations of gelatinous mucus and inspissated bile, with variable appearances on ultrasound. They may appear as immobile suspended echogenic sludge (A), have a stellate internal architecture (B), or resemble a kiwi fruit (C).

FIGURE 11C Gallbladder mucoceles in dogs are accumulations of gelatinous mucus and inspissated bile, with variable appearances on ultrasound. They may appear as immobile suspended echogenic sludge (A), have a stellate internal architecture (B), or resemble a kiwi fruit (C).

FIGURE 12 Ultrasound of the gallbladder in a dog presented with an acute abdomen. The gallbladder (GB) has a complex luminal structure with multiple hyperechoic strands, a wall that cannot be traced as a continuous border (arrow; marks region of discontinuity), and a perivesicular mesentery with complex hypoechoic regions and free fluid. In addition, the mesentery is hyperechoic, indicating inflammation. The dog had a ruptured gallbladder mucocele.

FIGURE 13 Emphysematous cholecystitis in an 11-year-old male dachshund presented with vomiting and abdominal pain. Reverberation echoes (arrows) are radiating out of nondependent gallbladder (GB) lumen, representing gas in the wall and/or lumen of the gallbladder. Bactibilia and emphysematous cholecystitis can occur without recognizable gallbladder wall thickening.

FIGURE 14 The common bile duct in dogs and cats can be localized by identifying the portal vein (red on color Doppler) near the porta hepatis. The duct (between the X’s) is situated between the portal vein and the duodenum and will not have a Doppler signal.

FIGURE 15A A 5-year-old neutered male Scottish terrier with icterus and acute abdomen that has a hyperechoic nodule (arrows) at the location of the major duodenal papilla (A). The common bile duct (CBD) is dilated (B). Differential diagnoses for a nodule in this location include an inflammatory polyp, an inspissated bile sludge ball, and a bile duct carcinoma. Doppler evaluation can help differentiate between avascular sludge and a vascular mass. An inflammatory polyp was diagnosed after surgical resection.

FIGURE 15B A 5-year-old neutered male Scottish terrier with icterus and acute abdomen that has a hyperechoic nodule (arrows) at the location of the major duodenal papilla (A). The common bile duct (CBD) is dilated (B). Differential diagnoses for a nodule in this location include an inflammatory polyp, an inspissated bile sludge ball, and a bile duct carcinoma. Doppler evaluation can help differentiate between avascular sludge and a vascular mass. An inflammatory polyp was diagnosed after surgical resection.