Feline abdominal ultrasonography: what’s normal? what’s abnormal? The biliary tree

Abstract

Practical relevance: Abdominal ultrasound plays a vital role in the diagnostic work-up of many cats presenting to general and specialist practitioners. The biliary tree encompasses the liver, gall bladder and bile ducts, although only diseases affecting the latter two are discussed here. Diseases of the bile ducts and gall bladder are more common than those of the liver parenchyma and ultrasound plays an important role in their diagnosis. Clinical challenges: Despite ultrasonography being a commonly used modality, many practitioners are not comfortable performing an ultrasound examination or interpreting the resulting images. Even differentiating between normal variation and pathological changes can be challenging for all but the most experienced. In addition, a lack of pathological change does not necessarily rule out disease; for example, absence of gall bladder and/or extrahepatic biliary distension is not sufficient to exclude the possibility of biliary obstruction, and in many cases of cholangitis the liver and biliary tree are unremarkable on ultrasound examination. Equipment: Ultrasound facilities are readily available to most practitioners, although use of ultrasonography as a diagnostic tool is highly dependent on operator experience. Aim: This review, part of an occasional series on feline abdominal ultrasonography, discusses the appearance of the normal and diseased biliary system. It is aimed at general practitioners who wish to improve their knowledge and confidence in feline abdominal ultrasound and is accompanied by high-resolution images. Percutaneous ultrasound-guided cholecystocentesis is also covered. Ultrasound examination of the liver was discussed in an article published in January 2019 and an upcoming article will cover hepatic vascular anomalies. Evidence base: Information provided in this article is drawn from the published literature and the author’s own clinical experience.

Pancreatic enzyme activity in the bile of healthy cats and its association with biliary morphology

“…Several variations of biliary morphology are reported in cats, 19 , 22 but the clinical relevance of these variations is unknown. 21 , 25 Additionally, some reports 26 , 27 , 28 , 29 discuss the relationship between gallstones and cholecystitis, but the details of this relationship are unclear. Therefore, we performed detailed laparoscopic observations of the biliary system morphology in healthy cats that visited our clinic for laparoscopic ovariohysterectomy.…”

“…Several variations of biliary morphology are reported in cats, 19,22 but the clinical relevance of these variations is unknown 21,25 . Additionally, some reports 26‐29 discuss the relationship between gallstones and cholecystitis, but the details of this relationship are unclear.…”

“…Gallbladder malformations were classified based on previous reports in cats, as double, bilobed, or trilobed gallbladder. 19 , 21 , 22…”

“…19,21,22 Tortuosity of the CD or CBD is commonly observed in healthy cats, [21][22][23] and clearly identifying the transition between the CD and the CBD in cats has been difficult. [21][22][23] In both the medical and veterinary fields, the CD is defined as the conduit that connects the gallbladder to the CBD, and the CBD as the conduit from the junction of the left and right hepatic ducts to the duodenum. 23 We measured the diameter of the CD and CBD based on this definition.…”

Diagnosing and treating chronic vomiting in cats

“…The presence of a thick left limb of the pancreas, severely irregular pancreatic margins, and hyperechoic peripancreatic fat in cats with appropriate clinical signs and elevated serum fPLI are highly suggestive of pancreatitis (Williams and others 2013). Cholangitis/cholangiohepatitis may result in the thickening of the wall of the gall bladder and/or common bile duct (CBD), biliary sludge, cholelithiasis and CBD dilation (Griffin 2019b). The liver can have normal, increased, decreased or heterogeneous echogenicity and it may have a uniform or heterogeneous nodular echotexture and, although often normal in size, maybe enlarged in some cases (Griffin 2019a).…”