Introduction
Biliary cystadenoma is a rare, slow-growing, benign cystic tumor of the liver, arising from the biliary epithelium. It predominantly affects middle-aged women and has the potential for malignant transformation into biliary cystadenocarcinoma.
Radiology plays a crucial role in early detection, differentiation from simple hepatic cysts, and surgical planning.
Ultrasound (USG) Findings
- Multiloculated cystic lesion with thin or thick internal septations.
- May contain papillary projections or mural nodules.
- Variable internal echogenicity depending on fluid content (clear, mucinous, or hemorrhagic).
- Doppler: vascularity within septa or nodules may suggest malignancy.
CT Imaging Features
- Well-circumscribed, multiloculated cystic hepatic lesion.
- Enhancing septations after IV contrast.
- Calcification may be seen in the wall or septa.
- No solid enhancing component (helps differentiate from cystadenocarcinoma).
MRI Imaging Features (Modality of Choice)
- T1-weighted: Hypointense (unless hemorrhage or proteinaceous content).
- T2-weighted: Hyperintense cystic lesion with internal septations.
- Post-contrast: Enhancing septa and capsule; mural nodules (if present) should raise suspicion for malignancy.
- MRCP: Shows non-communication with biliary ducts (helps differentiate from biliary cystic dilation).
Differential Diagnosis
- Simple hepatic cyst (unilocular, no septations, no enhancement).
- Hydatid cyst (daughter cysts, calcified wall, hydatid membranes).
- Intraductal papillary neoplasm of bile duct (IPNB) (communicates with biliary system).
- Cystadenocarcinoma (presence of mural nodules, irregular thickened wall, solid component).
📊 Differentiating Cystic Liver Lesions on Imaging
| Feature | Biliary Cystadenoma | Biliary Cystadenocarcinoma | Simple Hepatic Cyst | Hydatid Cyst |
|---|---|---|---|---|
| Number | Usually single | Usually single | Single or multiple | Single or multiple |
| Wall | Smooth, well-defined | Irregular, thickened | Thin, imperceptible | Thick, calcified possible |
| Septations | Present, thin or thick, enhance on contrast | Thick, irregular septa, may enhance markedly | Absent | Present, daughter cysts form “cyst within cyst” appearance |
| Mural Nodules | Absent (if present, suspect malignancy) | Present (hallmark of malignancy) | Absent | Absent (but detached membranes may mimic nodules) |
| Enhancement | Septal enhancement, no solid enhancing component | Septa + mural nodules enhance strongly | No enhancement | Peripheral enhancement (“rim sign”) in active cysts |
| Contents | Mucinous fluid; may be proteinaceous | Mucinous/necrotic with solid nodular tissue | Simple clear fluid | Hydatid sand, membranes, daughter cysts |
| Calcification | May occur in wall/septa | May occur, irregular | Rare | Common in wall or septa |
| Biliary Communication | Absent (usually) | Absent | Absent | Absent |
Role of Radiology
- Diagnosis: Identifying multiloculated cystic nature and septal enhancement.
- Differentiation: From benign cysts and malignant cystic tumors.
- Surgical planning: Complete excision is mandatory due to malignant potential.
- Surveillance: Detect early transformation if not excised.
Teaching Points
- Biliary cystadenoma = multiloculated cystic liver lesion with enhancing septa.
- MRI is the best modality for characterization.
- Always exclude cystadenocarcinoma if mural nodules or irregular thickening are seen.
- Differentiation from simple cysts and hydatid cysts is essential.
Conclusion
Biliary cystadenomas, though rare, must be recognized on imaging due to their premalignant potential. Radiology provides clear features — multilocularity, septal enhancement, and absence of solid nodules — that aid in accurate diagnosis and timely management.
