Cystic liver mass in the cat: biliary cystadenoma

Question

7-year-old neutered male domestic shorthair cat with several weeks of vomiting, reduced appetite and abdominal distension. Biochemistry shows a cholestatic pattern (raised ALP and GGT). Lateral and ventrodorsal radiographs and ultrasound of the lesion:

Lateral and ventrodorsal radiographs of a cat with a large soft-tissue opacity in the cranial and mid abdomen, and ultrasound of an anechoic lesion next to the liver divided by thin septa — Image: Rostami et al., Vet Med Sci 2026 (recortada) · CC BY 4.0, Wikimedia Commons

The lesion is a multiloculated cyst with thin septa and no mural nodules or solid component. What is the most likely diagnosis and how is it confirmed?

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A. Biliary cystadenoma; confirmed by histopathology

Correct. In adult and older cats, a multiloculated cystic liver lesion is most often a biliary cystadenoma (adenoma), the most common benign liver tumour in the cat. Imaging is suggestive but cannot reliably separate it from a cystadenocarcinoma: confirmation is histological, and complete resection is usually curative.

B. Hepatorenal polycystic disease; PKD1 genetic test

Polycystic disease in Persian cats can involve the liver, but it causes multiple, usually small cysts and almost always renal cysts. A single giant septated cystic mass is not typical.

C. Liver abscess; percutaneous drainage and antibiotics

Abscesses have echogenic content and a thick, irregular wall, and usually come with fever and neutrophilia. An anechoic lesion with thin septa in a cat without systemic signs does not fit.

D. Hepatic lymphoma; ultrasound-guided aspirate cytology

Hepatic lymphoma causes diffuse hepatomegaly or solid hypoechoic nodules, not anechoic cystic lesions with septa.

lightbulb Key takeaway

In the cat, a multiloculated cystic liver lesion is usually a biliary cystadenoma, benign and resectable. Look for mural nodules or a solid component, which would raise suspicion of malignancy, and confirm with histology.

The lesion is a multiloculated cyst with thin septa and no mural nodules or solid component. What is the most likely diagnosis and how is it confirmed?

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