Management of a Cyst with 1 Internal Septation
A hepatic cyst with a single thin septation (<3 mm) is almost certainly benign and requires MRI characterization to exclude mucinous cystic neoplasm (MCN), followed by observation if no worrisome features are present. 1
Initial Diagnostic Approach
Obtain MRI immediately to characterize the septated cyst and assess for worrisome features that would distinguish a benign simple or hemorrhagic cyst from MCN. 1, 2, 3 MRI is superior to CT for this purpose, with 94-98% specificity when multiple worrisome features are present. 4
Key MRI Features to Assess
Major worrisome features that suggest MCN include: 4
- Thick septations (>2-3 mm)
- Mural nodularity or solid components
- Enhancement of septations or nodules on contrast imaging
Minor worrisome features include: 4
- Upstream biliary dilatation
- Thin septations (your case)
- Internal hemorrhage
- Perfusional changes
- Fewer than 3 coexistent hepatic cysts
Management Algorithm
If MRI Shows Worrisome Features (≥1 Major + ≥1 Minor)
Proceed directly to surgical resection with complete excision. 4, 1, 3 This combination carries 94-98% specificity for MCN, which has a 3-6% risk of invasive carcinoma and high recurrence rates with incomplete resection. 4, 3
If MRI Shows Simple Cyst with Single Thin Septation and No Other Features
Conservative management with observation is appropriate. 4, 1 A single thin septation <3 mm is considered benign with <0.4% chance of malignancy. 4
- If <10 cm: No follow-up needed in premenopausal women; consider 8-12 week follow-up in postmenopausal women 4
- If ≥10 cm: Follow-up imaging or specialist referral recommended due to slightly increased risk 4, 1
If MRI Shows Hemorrhagic Cyst
Conservative management is indicated. 4, 2 Hemorrhagic cysts present with heterogeneous hyperintense signal on both T1- and T2-weighted sequences, with fluid-fluid levels representing blood-filled lakes between septa. 4, 1 These typically show hyperintense septations on T1-weighted imaging without enhancement on contrast-enhanced sequences, distinguishing them from MCN. 2
Critical Clinical Context
Patient demographics matter significantly: MCNs predominantly occur in middle-aged women and typically present in the left liver lobe with symptoms (pain, fullness, early satiety) in 86% of cases. 4, 3 If your patient fits this profile, maintain higher suspicion even with minimal findings.
Common Pitfalls to Avoid
Do not mistake hemorrhagic septations for malignancy. 1, 2 True MCNs have thick septations with nodularity and enhancement, whereas hemorrhagic cysts show hyperintense septations without enhancement. 2
Do not use CT as the primary modality for characterizing septated cysts, as it has limited ability to assess cyst contents and differentiate benign from malignant septations. 1
Do not perform aspiration or deroofing of actively hemorrhagic cysts if hemorrhage is suspected, as conservative management is preferred. 4
Consider contrast-enhanced ultrasound as an adjunct to identify vascularized septations, which are present in malignancy but absent in benign lesions. 4, 1