Conventional imaging methods have limitations in assessing the feline biliary tract. In human medicine, magnetic resonance cholangiography (MRC) is the noninvasive gold standard to evaluate biliary tract disorders. In veterinary medicine, first reports deemed MRC feasible in cats for qualitative assessment. However, MRC-based, quantitative measurement data of the feline biliary tract have been missing. With this postmortem MRC pilot study, we aimed at determining the reference diameters of gallbladder, cystic duct, and common bile duct (CBD) in adult cats by comparing cats without and with biliary tract disorders.

Bodies of 10 adult pet cats donated for research purposes underwent MRC and necropsy. For MRC, a human extremity coil was used in a 1.5 Tesla MRI system (Ingenia, Philips, The Netherlands). T1 and T2 weighted turbo spin echo (TSE) sequences were used to localize the region of interest followed by three-dimensional (3D) T2w-TSE-MRC to visualize biliary tract anatomy. 3D-TSE-MRC images were saved in 2D and measurements of the biliary tract conducted using the image analysis software ImageJ 1.45 (Bethesda, MD, USA). Gross pathology and histology after MRC revealed no evidence of biliary tract disorders in six cats (control group). Reported disorders in the remaining four cats were mild to moderate multifocal lymphocytic cholangitis (two cats), bilobed gallbladder and alimentary lymphoma (one cat each). None of the four cats had histopathological evidence of ductal stricture or dilation. Diameters were measured for gallbladder (fundus, body, and neck), cystic duct (where leaving the gallbladder) and CBD (at duodenal papilla and extrahepatic duct junction).

Median (range) diameters in the control group were for gallbladder at fundus 7.39 mm (5.70–11.73 mm), body 11.52 mm (8.72–18.98 mm) and neck 2.67 mm (1.96–5.38 mm), for cystic duct 1.55 mm (1.39–2.01 mm), and for CBD at extrahepatic duct junction 2.04 mm (1.39–3.49 mm) and at duodenal papilla level 1.85 mm (1.30–2.28 mm). Respective diameters of the cats with lymphocytic cholangitis and alimentary lymphoma were within the same ranges. The cat with bilobed gallbladder had a wider CBD diameter at the duodenal papilla (2.50 mm).

This postmortem pilot study provided normative MRC measurements for the gallbladder, cystic duct, and CBD for adult cats. Quantitative measurements in cats with biliary tract disorders did not reveal major differences, probably due to missing formation of ductal strictures or dilations. Future studies in larger numbers of cats are warranted to assess the diagnostic value of quantifiable data in 3D-TSE-MRC images of cats.

Disclosures

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