What is the management approach for a 40-year-old patient with a complex septated left hepatic cyst on ultrasound, mild elevation of liver function tests, normal total bilirubin (t bili) and normal alkaline phosphatase (alp), and no other significant past medical history?

Management of Complex Septated Left Hepatic Cyst with Mild Transaminitis

This patient requires urgent MRI with contrast to assess for worrisome features of mucinous cystic neoplasm (MCN), and if ≥1 major feature (thick septations or nodularity) PLUS ≥1 minor feature are present, proceed directly to complete surgical resection. 1, 2, 3

Immediate Diagnostic Workup

Obtain MRI with contrast as the next step – this is the gold standard imaging modality for characterizing septated hepatic cysts, with 94-98% specificity for MCN diagnosis when multiple worrisome features are present. 1, 2, 3 MRI is superior to CT for assessing cyst contents, differentiating benign hemorrhagic septations from malignant features, and identifying wall enhancement. 1, 2

Key MRI Features to Assess

The 2022 EASL guidelines define a diagnostic algorithm based on major and minor worrisome features: 1

Major worrisome features (high concern for MCN):

• Thick septations (>2mm) 1, 2, 3
• Mural nodularity or solid components 1, 2, 3

Minor worrisome features:

• Upstream biliary dilatation 1, 2
• Thin septations 1, 2
• Internal hemorrhage 1, 2
• Perfusional changes 1, 2
• Fewer than 3 coexistent hepatic cysts 1, 2

The combination of ≥1 major + ≥1 minor feature carries 94-98% specificity for MCN and mandates surgical resection. 1, 2, 3

Critical Differential Diagnosis

Mucinous Cystic Neoplasm (MCN) – Highest Priority Concern

• MCNs carry a 3-6% risk of invasive carcinoma and occur predominantly in middle-aged women (86% are symptomatic with pain, fullness, or early satiety). 2, 3
• MCNs typically present in the left liver lobe (matching this patient's location). 3, 4
• Septations in MCNs arise from the cyst wall without external indentation – a highly specific feature. 1
• Recurrence rates after incomplete resection are high (0-26%), making complete excision critical. 1, 2

Hemorrhagic Simple Cyst – Benign Mimic

• Can present with septations that mimic MCN, leading to diagnostic confusion. 1
• Distinguished by heterogeneous hyperintense signal on both T1- and T2-weighted sequences with fluid-fluid levels representing blood-filled lakes between septa. 2, 3
• Internal hemorrhage is more frequent in simple cysts than MCNs and does not represent a worrisome finding in isolation. 1
• Contrast-enhanced ultrasound shows lack of enhancement in hemorrhagic cysts versus vascularized septations in MCN. 1, 2

Polycystic Liver Disease (PLD)

• Defined as >10 hepatic cysts; this patient has a solitary lesion, making PLD unlikely. 1

Management Algorithm

If MRI Shows Worrisome Features (≥1 Major + ≥1 Minor):

Proceed directly to complete surgical resection – this is the gold standard for suspected MCN with 100% consensus recommendation. 1, 2, 3

• Complete excision with free margins is mandatory; fenestration alone is associated with higher tumor recurrence rates. 1, 2
• Enucleation is acceptable for centrally located tumors. 2
• Major liver resections (including extended hemihepatectomy) may be necessary for complete removal. 2

If MRI Shows Simple Hemorrhagic Cyst:

Conservative management is appropriate with no routine follow-up imaging required. 1, 3, 4 If symptomatic from mass effect, consider laparoscopic fenestration or aspiration with sclerotherapy. 4

Addressing the Mild Transaminitis

The mild elevation of AST 40 and ALT 44 with normal bilirubin and alkaline phosphatase is likely unrelated to the cyst itself, as simple hepatic cysts rarely cause transaminase elevation unless there is significant compression of hepatic parenchyma or bile ducts. 1

• Peripheral bile duct compression can occur with centrally located cysts (segment 4), typically presenting with elevated alkaline phosphatase and jaundice – not the pattern seen here. 1
• Consider alternative causes of mild transaminitis (fatty liver, medications, alcohol) as a separate issue.

Critical Pitfalls to Avoid

Do not mistake hemorrhagic septations for malignancy – hemorrhage is more common in simple cysts than MCNs. 1, 2 The key distinguishing features are thick septations/nodularity PLUS additional minor features, not hemorrhage alone. 1

Do not use CT as the primary characterization modality – CT has limited ability to assess cyst contents and differentiate benign from malignant septations compared to MRI. 1, 2

Do not perform fenestration if MCN is suspected – this is associated with high recurrence rates and is inadequate treatment. 1, 2

Do not delay surgical referral if worrisome features are present – MCNs have malignant potential and require complete excision. 1, 2, 3