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Cystic Bile Duct Lesions in Cats Are Common and Often Benign, Study Shows
Veterinary Pathology 2025
Obi Veterinary Education
February 06, 2026
Megan E. Schreeg, John M. Cullen
Background:
Fibrocystic hepatobiliary lesions (FHLs) and extrahepatic biliary malformations (EBMs) in cats are thought to be relatively common and likely congenital, yet their prevalence and histologic characterization have been poorly documented. Most are presumed to represent ductal plate malformations (DPMs), which can lead to lesions such as von Meyenburg complexes (VMCs) or congenital hepatic fibrosis (CHF). This study aimed to document the prevalence, gross and histologic features, and associated comorbidities of these biliary anomalies in a feline autopsy cohort.
Methods:
A retrospective review of 140 feline necropsy cases from a single institution (2017–2020) was conducted. Gross and histologic findings from liver and biliary tissues were analyzed to classify lesions as FHLs or EBMs using a veterinary-adapted DPM classification. Comorbidities and causes of death were extracted from records. Statistical comparisons were made to assess age associations.
Results:
Twenty of 140 cats (14.3%) had FHLs and/or EBMs. FHLs were most common (15/20), primarily cystic biliary lesions (CBLs, 14/15), with one case of CHF. CBLs varied grossly from small subcapsular cysts to large multilocular masses but consistently showed histologic features of VMCs—well-demarcated, bile duct–lined cysts in hyalinized stroma. Gallbladder malformations were found in 5 cats (3 bilobed, 2 duplex), and 2 cats had blind-ended extrahepatic bile ducts extending into the pancreas. CHF was the only lesion directly causing morbidity; all other FHLs and EBMs were incidental. Cats with lesions were significantly older, and comorbidities included renal, cardiac, and neoplastic diseases. Renal or pancreatic cysts were infrequent.
Limitations:
The study was retrospective and relied on variable tissue quality. Some lesions were not histologically confirmed due to autolysis or absence of samples. The cohort skewed toward older cats, and no genetic testing (e.g., for PKD1) was performed, limiting conclusions about heritability or early lesion development.
Conclusions:
Cystic biliary lesions consistent with VMCs are common incidental findings in cats and likely represent congenital DPMs. While most are benign, CHF can cause significant hepatic dysfunction. Gallbladder and extrahepatic biliary malformations are also present but rarely clinically significant. These findings support routine consideration of congenital bile duct anomalies in feline hepatic pathology and highlight the need for further studies on genetic and developmental correlations.
Figure 1. Gross and histologic features of cystic biliary lesions (CBLs) in cats. (a) Multifocal CBLs, liver, 10-year-old, spayed female domestic shorthair (DSH) cat. Case 2. Several small, flat-to-depressed, green cysts (arrowheads) are scattered throughout the liver. Inset: higher magnification of cyst. (b) Focal CBL, liver, 14-year-old, spayed female DSH cat. Case 8. Within the right medial lobe is a focal, flat to depressed, clear, cyst (white arrowheads). Note multifocal telangiectasia present elsewhere in the liver (black arrowheads). (c) Multifocal CBLs, liver, 8-year-old, spayed female DSH cat. Case 5. Three small to medium-sized, flat to raised, clear to white, multilocular cysts (white arrowheads) are scattered throughout the liver. Inset: higher magnification of an additional CBL. Photo courtesy of Amy Flis. (d) Focal CBL, liver, 18-year-old, castrated male Himalayan cat. Case 1. Arising from the left medial lobe is a focal, raised, white to pale pink, well-demarcated, multiloculated nodule comprised a myriad of cysts (white arrowheads). Smaller CBLs (not pictured) and foci of telangiectasia (black arrowheads) were present throughout the liver. (e) Focal CBL, liver, 12-year-old, castrated male DSH cat. Case 10. Within the left lateral lobe is a focal, slightly raised, multiloculated cystic nodule that is mottled white to dark red (arrowhead). On cut surface (inset), dark red opaque fluid is present within the cyst. Because of this finding, telangiectasia was also considered as a differential diagnosis at the time of gross examination. Photo courtesy of Elizabeth Alloway. (f–i) Histologic features of CBLs. Hematoxylin and eosin. (f) Focal CBL, liver, 18-year-old, castrated male Himalayan cat. Case 1. The CBL comprised multiloculated cystic structures lined by an attenuated biliary epithelium (upper left inset) with intervening thin, hyalinized collagenous trabeculae that contain few, small caliber blood vessels and entrapped islands of unremarkable hepatocytes (arrowheads, lower right inset). (g) Focal CBL, liver, 17-year-old, castrated male domestic longhair cat. Case 11. The CBL comprised multiloculated cystic structures lined by a cuboidal biliary epithelium (upper left inset) supported by thicker hyalinized beams of edematous collagenous stroma (asterisks). Note the scant eosinophilic fluid present in cyst lumina. (h) Focal CBL with lymphoplasmacytic inflammation, liver, 14-year-old, castrated male DSH cat. Case 14. Hyalinized to fibrillary collagenous trabeculae are multifocally expanded by moderate numbers of lymphocytes and plasma cells. (i) Focal CBL with intracystic hemorrhage, liver, 12-year-old, castrated male DSH cat. Case 10. Cysts within the CBL are multifocally filled with free erythrocytes (hemorrhage) admixed with fibrin and pale eosinophilic fluid. Telangiectasia is ruled out for this lesion based on the cuboidal epithelium lining cystic structures (upper left inset), consistent with biliary epithelium.
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