Working up a focal liver lesion

USG · CT · MRI

First and second year — the floor first, then every step

Ultrasound answers "is it there, is it solid, is the background liver abnormal" — it rarely answers "what is it".

Orient first

  • Ultrasound is the detection and surveillance tool. In a cirrhotic surveillance programme it is the study that finds the lesion; it is not the study that characterises it.
  • ECHOGENICITY is suggestive, never diagnostic. A uniformly hyperechoic lesion with posterior enhancement in a normal liver suggests haemangioma; the identical appearance in a fatty liver can be a metastasis standing out against bright background, and a small hepatocellular carcinoma can look exactly like a haemangioma.
  • A HYPOECHOIC HALO around a lesion is the finding that should raise malignancy, particularly with multiple lesions.
  • The BACKGROUND matters as much as the lesion: a coarse, nodular, shrunken liver with a recanalised umbilical vein and splenomegaly changes the differential completely before the lesion is described at all.

Acquire the study

  • Fasted where possible; intercostal and subcostal windows, both in quiet respiration and on held inspiration.
  • Place the focal zone AT the lesion depth and set the gain against a known fluid reference before judging echogenicity.
  • Assess the whole liver systematically before dwelling on one lesion — a solitary lesion and multifocal disease are different diseases.

The manoeuvre

  • Describe the background liver first: size, surface (smooth or nodular), echotexture, and deep penetration.
  • For the lesion: segment, size in three planes, echogenicity against adjacent liver at the SAME depth, margin, and a halo if present.
  • Assess posterior features — enhancement suggests fluid content, shadowing suggests calcification or fibrosis.
  • Apply colour and power Doppler at LOW-flow settings and describe the pattern: peripheral, central, basket, spoke-wheel, or absent.
  • Assess the portal vein for patency, direction of flow and any tumour thrombus — the finding that changes staging immediately.
  • Look at the spleen, for varices and for ascites, which establish portal hypertension.
  • State explicitly that characterisation requires multiphase CT or MRI, and recommend it.

What confirms it

  • A confident diagnosis needs a characteristic pattern on an ADEQUATE study, in a patient whose background risk is known.

What licenses you to exclude it

  • ⚠️ A single-phase study cannot characterise a liver lesion. If only a portal venous phase exists, report the lesion as uncharacterised and name the multiphase study needed — do not offer a differential as though it were an answer.
  • Sub-centimetre lesions in a low-risk liver are usually too small to characterise; say that rather than calling them benign.

The classic misread

  • Calling an echogenic lesion a haemangioma in a fatty liver, where the contrast is a background artefact.
  • Missing tumour thrombus by never putting colour on the portal vein.
  • Reporting a lesion without describing whether the background liver is cirrhotic.

Reference values

Each value carries the caveat that keeps it from being misused. Normal limits and diagnostic criteria are kept apart on purpose: a disease cut-off read as a normal range is the more dangerous mistake.

Normal limits

  • Liver · craniocaudal span, midclavicular lineup to 15–16 cm

    Highly habitus-dependent; a Riedel lobe is a normal variant, not hepatomegaly.

    USG · CT

  • Liver · Total and lobar liver volume — how to report it

    absolute millilitres are BSA- and formula-dependent; living-donor and resection planning uses future-liver-remnant percentage against a named software method

    A single "normal liver volume" does not exist — quote the method, the remnant percentage and the clinical threshold your HPB team uses (commonly around 20–30% remnant in a healthy liver, higher in a damaged one).

    CT · MRI

Diagnostic criteria

  • Liver · Attenuation on non-contrast CT (steatosis assessment)

    normal liver measures roughly 55–65 HU and is denser than the spleen

    Only valid on NON-CONTRAST images — portal-venous attenuation depends on timing and cannot be read against these figures. Iron, amiodarone and glycogen raise attenuation and can mask coexisting fat.

    CT

  • Liver · MRI proton-density fat fraction (PDFF)under approximately 5%

    The 5% vs 5.6% difference reflects different reference standards — state which threshold the local protocol uses. PDFF is confounded by iron overload unless the sequence corrects for R2*. Versioned criterion — verify against the current edition before clinical use.

    MRI

  • Liver · Caudate-to-right-lobe ratio (cirrhosis morphology)under 0.65

    On an axial image, the transverse width of the caudate lobe divided by the transverse width of the right lobe, using the main portal vein bifurcation and the lateral wall of the right lobe as landmarks (Harbin method).

    A ratio above about 0.65 suggests cirrhosis with caudate hypertrophy, but sensitivity is modest — morphology supports, never excludes, the diagnosis. Modified versions of the ratio use different landmarks and different cut-offs; name the method.

    CT · MRI · USG

  • Liver · Liver stiffness (elastography) — how to report it

    kPa bands are PLATFORM- and technique-specific

    A single universal kPa threshold does not exist — quoting one without naming the platform is wrong for every platform but one. Report the vendor, the technique, the number of valid measurements and the quality criteria alongside the median stiffness, and read it against that platform's published bands. Versioned criterion — verify against the current edition before clinical use.

    USG · MRI

  • Liver · Controlled attenuation parameter (CAP) — how to report it

    a named vendor parameter: dB/m bands that map onto steatosis grades are PLATFORM-specific and must be read from the device IFU or the local protocol

    Do not quote a universal CAP number — the M and XL probes do not share bands, and IQR quality criteria belong in the report with the median. MRI-PDFF is the cross-sectional counterpart (see that entry). Versioned criterion — verify against the current edition before clinical use.

    USG

  • Liver observation (cirrhotic liver) · LI-RADS categorisation — how to report it

    a named criteria set: category follows size bands (under 10 mm, 10–19 mm, 20 mm or more) combined with arterial-phase hyperenhancement, washout, capsule and threshold growth

    Applies ONLY in the defined high-risk population (cirrhosis, chronic hepatitis B, prior HCC) — applying LI-RADS to a non-cirrhotic liver is a category error. The size bands and major features table should be read from the current version, not from memory. Versioned criterion — verify against the current edition before clinical use.

    CT · MRI

See it on real cases

Direct links to Radiopaedia — the reference article and worked cases with their images. Each opens on Radiopaedia.

Key papers

Reviews and guidelines from RSNA, ESR and related journals. Each opens at its DOI.

  1. Liver Imaging Reporting and Data System (LI-RADS) Version 2018: Imaging of Hepatocellular Carcinoma in At-Risk Patients ↗Chernyak V, Fowler KJ, Kamaya A, et al. · Radiology 2018RSNA · PubMed
  2. How to Use LI-RADS to Report Liver CT and MRI Observations ↗M Cunha G, Fowler KJ, Roudenko A, et al. · RadioGraphics 2021RSNA · PubMed
  3. CT/MRI and CEUS LI-RADS Major Features Association with Hepatocellular Carcinoma: Individual Patient Data Meta-Analysis ↗van der Pol CB, McInnes MDF, Salameh JP, et al. · Radiology 2022RSNA · PubMed
  4. Hepatocellular Carcinoma in Evolution: Correlation with CEUS LI-RADS ↗Nguyen SA, Merrill CD, Burrowes DP, et al. · RadioGraphics 2022RSNA · PubMed

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