Imaging of Liver

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Liver Imaging Toolkit - Modality Mania

  • USG (Ultrasound): Initial, non-invasive. Assesses size, echotexture, focal lesions (cysts, solid), steatosis. Doppler for vascularity.
  • CT (Computed Tomography): Workhorse. Non-contrast (fat, $Ca^{2+}$, blood).

    Typical Liver Triphasic CT Enhancement:

    • Arterial Phase (~25-35s): Hypervascular lesions (HCC, FNH, adenoma, hemangioma [peripheral]).
    • Portal Venous Phase (~60-80s): Peak parenchymal enhancement; most metastases.
    • Delayed Phase (~3-5+ min): Washout (HCC); delayed enhancement (cholangiocarcinoma, hemangioma [centripetal fill-in]).
  • MRI (Magnetic Resonance Imaging): Superior soft-tissue contrast. Problem-solving. Sequences: T1, T2, DWI, hepatobiliary agents.
  • Elastography: Assesses liver stiffness (fibrosis).

Liver Steatosis MRI: In-phase, Out-of-phase, PDFFoka

Benign Bumps - Friendly Formations

  • Hemangioma: Most common benign lesion.

    • US: Hyperechoic. CT/MRI: Peripheral, discontinuous, nodular enhancement; centripetal fill-in.

    ⭐ Hemangiomas typically show peripheral, discontinuous, nodular enhancement that fills in centripetally on dynamic contrast-enhanced CT/MRI.

  • Focal Nodular Hyperplasia (FNH):

    • Arterial: Intense, homogeneous enhancement (scar may not).
    • Central scar: T2 bright, delayed enhancement.
    • Gadoxetate: Uptake (vs. adenoma).
  • Hepatic Adenoma:

    • OCP/steroid link. Risk: Hemorrhage, malignant change (rare).
    • Heterogeneous (fat/bleed). Arterial enhancement.
    • Gadoxetate: Usually no uptake.
  • Simple Cyst:

    • US: Anechoic. CT: 0-20 HU (water). T2: Markedly bright. No enhancement.

Malignant Masses - Nasty Newcomers

  • Hepatocellular Carcinoma (HCC): Most common primary. Risks: Cirrhosis, HBV, HCV.

    ⭐ HCC: Classic arterial phase hyperenhancement (APHE) & portal/delayed washout (LI-RADS major feature).

    • Other features: Capsule, mosaic pattern.
  • Cholangiocarcinoma (CCC): Intrahepatic or perihilar. Features: Delayed enhancement, capsular retraction, biliary dilatation.
  • Metastases: Most common liver malignancy overall. Appearance varies.
    • Hypovascular: e.g., Colorectal.
    • Hypervascular: e.g., NET, RCC, Melanoma. 📌 Mnemonic (Hypervascular): Melanoma, RCC, NET, Thyroid (MR. NT).
  • LI-RADS: Standardizes HCC risk reporting (e.g., LR-5 for definite HCC).

MRI Liver: APHE, Washout, and LR-5 HCC

Sick Spreads - Diffuse Dilemmas

  • Cirrhosis:

    ⭐ Imaging: Nodular surface, caudate hypertrophy, portal hypertension (splenomegaly, varices, ascites).

    • Fibrosis, regenerative nodules. Complications: HCC.
  • Hepatic Steatosis (Fatty Liver):
    • US: ↑ Echogenicity (bright liver).
    • CT: ↓ Attenuation (< 40 HU, or < spleen by 10 HU).
    • MRI: Signal loss on out-of-phase imaging.
  • Hemochromatosis (Iron Overload):
    • CT: ↑ Liver density.
    • MRI: ↓ T2/T2* signal intensity (paramagnetic effect).
  • Wilson's Disease (Copper):
    • Variable: cirrhosis, steatosis, acute hepatitis. Ultrasound: Cirrhosis with ascites

Vascular & Trauma - Flow & Fracture

  • Budd-Chiari Syndrome (BCS): Hepatic vein obstruction. CT/MRI: hepatomegaly, ascites, caudate hypertrophy, patchy enhancement ("nutmeg liver").

    ⭐ Budd-Chiari syndrome imaging often reveals hepatomegaly, ascites, and characteristic 'nutmeg liver' or 'flip-flop' enhancement pattern of the caudate lobe due to its separate venous drainage.

  • Portal Vein Thrombosis (PVT): Portal vein clot. US/CT: filling defect, cavernous transformation (chronic).
  • Liver Trauma (CT is key):
    • Lacerations: Graded (AAST).
    • Hematomas: Subcapsular, intraparenchymal.
    • Active bleed: Contrast extravasation. CT scan: Liver laceration with active contrastoka

High‑Yield Points - ⚡ Biggest Takeaways

  • HCC: Key features are arterial phase hyperenhancement and subsequent portal venous/delayed phase washout.
  • Liver Metastases: Most common malignant liver tumor; imaging appearance is highly variable.
  • Hemangioma: Most common benign liver tumor; shows peripheral nodular enhancement with centripetal fill-in.
  • FNH: Often presents with a central scar; demonstrates intense, homogeneous arterial enhancement.
  • Cirrhosis: Imaging signs include nodular liver surface, caudate lobe hypertrophy, and portal hypertension.
  • Hydatid Cyst: Characterized by pathognomonic daughter cysts or the "water lily sign".

Practice Questions: Imaging of Liver

Test your understanding with these related questions

What is the next best step for a 22-year-old with a hepatic hemangioma on ultrasound?

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Flashcards: Imaging of Liver

1/10

HCCs often appears _____vascular during the arterial phase of computed tomography (CT) studies

Hint: hypo/hyper

TAP TO REVEAL ANSWER

HCCs often appears _____vascular during the arterial phase of computed tomography (CT) studies

hyper

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