Radiation-induced liver disease

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Radiation-induced liver disease (RILD), also referred to as radiation hepatitis, represents the toxic effect of radiation therapy on normal hepatocytes.

This article will discuss liver toxicity appearances after external beam radiotherapy techniques. Please refer to the dedicated article on selective internal radiation therapy (SIRT) for further details on this matter.

Epidemiology

Liver injury tends to be more common in those patients with radiation doses greater than 30 Gy or when the whole-liver is irradiated . It is usually seen as a result of therapy to adjacent organs, such as pancreatic carcinoma, gallbladder carcinoma, retroperitoneal lymphoma, pleural mesothelioma, distal esophageal and other lower thoracic malignancies.

Clinical presentation

In most cases, where the liver is only focally irradiated, patients are asymptomatic and the hepatocytes injury is depicted on abnormal liver function tests. When there is a more severe acute hepatitis, patients may complain of right upper quadrant discomfort .

Radiographic features

CT

In the acute phase, the radiation injury typically manifests as sharply demarcated parenchymal areas of low attenuation that correlate to the radiation ports . They characteristically do not respect anatomical boundaries, eg. involving more than one segment passing through the hepatic veins. In equivocal cases, correlation with the conformal radiotherapy dose distributions maps can be helpful .

If the liver is steatotic, the injured parenchyma may present with elevated attenuation compared to the background liver .

In the late phase of cases of severe toxicity, sequela with focal liver atrophy and capsular retraction may be seen .

MRI

The demarcated areas have increased T2 signal in keeping with acute inflammation .

Nuclear medicine
PET/CT

The liver areas of low attenuation will match with high FDG avidity on PET/CT in the acute phase .

Differential diagnosis