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Difficulty: HardInterpreting Imaging Results

An otherwise healthy 34-year-old female patient is evaluated by a gastroenterologist after a liver mass was incidentally discovered. She originally sought medical attention two weeks ago for mild, transient bloating, prompting an abdominal ultrasound. The ultrasound showed a 4.2-cm solid, circumscribed lesion in the right hepatic lobe. Her bloating has completely resolved without intervention. She has a history of polycystic ovary syndrome and has been using oral contraceptives for the past 10 years. She does not smoke or use illicit drugs, and she consumes approximately two alcoholic beverages per month. Her physical examination is entirely normal. Serum laboratory analysis reveals normal transaminases, alkaline phosphatase, total bilirubin, and alpha-fetoprotein levels.

A multiphasic magnetic resonance imaging (MRI) scan of the liver utilizing a hepatobiliary-specific contrast agent (gadoxetate disodium) is subsequently ordered to characterize the mass. The radiologist notes a well-circumscribed lesion demonstrating uniform, hypervascular enhancement during the arterial phase. During the delayed hepatobiliary phase (acquired 20 minutes post-injection), the lesion exhibits strong hyperintensity compared to the background liver tissue. No central scar is apparent.

Based on the interpretation of this MRI scan, which of the following is the most likely diagnosis?

  1. Focal nodular hyperplasiaAnswer
  2. B
    Hepatic adenoma
  3. C
    Hepatic hemangioma
  4. D
    Hepatocellular carcinoma
  5. E
    Hepatic metastasis

Answer

Focal nodular hyperplasia
The most likely diagnosis is focal nodular hyperplasia (FNH). FNH is a benign, hyperplastic response to a congenital vascular anomaly in the liver. On multiphasic MRI utilizing a hepatobiliary-specific contrast agent (such as gadoxetate disodium), FNH classically demonstrates intense arterial phase hyperenhancement. The critical distinguishing feature occurs during the delayed hepatobiliary phase (typically 20 minutes post-injection). Because FNH consists of functioning hepatocytes, it takes up the contrast agent via organic anion transporting polypeptides (OATPs). However, because the biliary drainage in FNH is malformed and dysfunctional, the contrast cannot be effectively excreted, leading to characteristic retention. This makes the lesion appear strongly hyperintense (or isointense) relative to the surrounding normal liver parenchyma.

Liver MassArterial PhaseDelayed Hepatobiliary Phase
Focal Nodular HyperplasiaHyperintenseHyperintense / Isointense
Hepatic AdenomaHyperintenseHypointense
Hepatocellular CarcinomaHyperintense (with washout)Hypointense
HemangiomaPeripheral nodularHypointense
Although a central scar is a classic finding in FNH, it is absent in up to 30-50% of cases and is not required for diagnosis when the contrast retention pattern is definitive.

Step-by-Step Solution

1
Analyze the patient's demographic profile and clinical history.
A 34-year-old female with long-term oral contraceptive use presents with an incidental 4.2-cm solid liver mass and normal laboratory markers.
Identifying risk factors helps prioritize the initial differential diagnosis, strongly highlighting hepatic adenoma and focal nodular hyperplasia (FNH) as the top benign possibilities.
2
Evaluate the arterial phase MRI findings.
The mass demonstrates uniform, hypervascular enhancement.
Arterial hyperenhancement is characteristic of FNH, adenoma, and hepatocellular carcinoma (HCC), distinguishing them from typical hemangiomas (which show peripheral nodular enhancement).
3
Interpret the critical delayed hepatobiliary phase MRI findings.
The mass is strongly hyperintense relative to normal liver tissue at 20 minutes post-injection.
This finding definitively distinguishes FNH from all other common solid liver masses. Functioning hepatocytes in FNH take up the contrast agent, but abnormal biliary canaliculi prevent excretion, causing contrast retention (hyperintensity). Adenomas, HCC, and metastases generally do not retain the contrast and appear hypointense.

Key Concept

Interpreting multiphasic MRI with hepatobiliary contrast to differentiate solid liver masses.
Estimated Time:1m 30s
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Topics

Interpreting Imaging Results

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