Hepatic adenomatosis: an incidental US finding

Clinical History

History of high fever, tachypnoe and headache caused by pneumonia. A routine ultrasonography of the upper abdomen was performed.

Imaging Findings

The patient was admitted with a history of high fever, tachypnoe and headache caused by pneumonia.
Routine ultrasonography of the upper abdomen revealed multiple solid liver masses. There was no history of abdominal complaints. Further evaluation with CT scan and MRI was performed.
CT scan of the liver (fig. 1) showed on unenhanced scan (A) multiple hyperdense masses within the liver. Liver steatosis was also noted. Contrast enhanced CT scan (B) demonstrated slight but homogeneous enhancement of the lesions. MRI of the liver (fig. 2) showed on T1-weighted MR-images (A, B) multiple hyperintense lesions in the right and left liver lobes. On T1-weighted images following administration of Gadolinium (C, D) only minor enhancement of the lesions was seen. CT-guided biopsy and histological examination of one of the lesions was performed and the diagnosis of hepatic adenoma was made. As more than four identical lesions were visible on different imaging modalities, the diagnosis of hepatic adenomatosis was proposed.

Discussion

Hepatic adenoma is an uncommon benign primary liver tumor consisting of sheets of normal appearing hepatocytes but lacking the normal acinar architecture of the surrounding hepatic parenchyma. The hepatocytes may be rich in fat or glycogen, and Kupffer’s cells are occasionally present, but bile ducts and portal tracts are absent. It may be partially or completely encapsulated. Hepatic adenomatosis has been defined as more than four adenomas within an otherwise normal liver. Unlike hepatic adenoma, hepatic adenomatosis has an almost equal prevalence in men and women and is unrelated to use of oral contraceptives or anabolic steroids. Patients with glycogen storage disease are at increased risk for developing hepatic adenomatosis. Elevated serum gamma-glutamyl transpeptidase and alkaline phosphatase are commonly found. Hepatic adenoma has a tendency to undergo spontaneous hemorrhage which occurs in 25 to 50% of cases. Although patients with uncomplicated adenomas are usually asymptomatic, those with large or hemorrhagic lesions generally present with abdominal pain and/or palpable abdominal mass.
Hepatic adenomatosis has to be differentiated from other diseases causing multiple liver lesions such as metastatic disease, multifocal hepatocellular carcinoma, hemangiomas, focal nodular hyperplasia and adenomatous hyperplasia. The imaging appearance of hepatic adenoma on ultrasonography, CT scan and MRI is highly variable and nonspecific. On ultrasonography it may be visible as a well defined lesion with a variable echogenicity relative to the surrounding liver. On unenhanced CT scan the lesion may be isodense compared with normal liver parenchyma or it may be hypodense due to the presence of fat, old hemorrhage or necrosis. Large amounts of glycogen, recent hemorrhage or marked liver steatosis lowering the overall density of the liver may result in a hyperdense appearance of the lesion. Hemorrhagic adenomas are heterogeneous, whereas uncomplicated lesions are homogeneous in appearance. Following intravenous administration of iodinated contrast material, enhancement is often seen during the arterial and early portal venous phases. A thin capsula may be present.
On MRI hepatic adenoma has been reported to be isointense or more often hyperintense relative to the liver on T1-weighted images and hyperintense relative to the liver on T2-weighted images. Heterogeneous areas on either T1- or T2-weighted images are often seen as a result of differences in architecture, vascularity, necrosis, hemorrhage, or glycogen or fat deposition. The hyperintensity on T1-weighted images is often related to the presence of fat or hemorrhage in the lesion. A peripheral rim of low signal intensity on T1-weighted images, similar to that reported in cases of hepatocellular carcinoma, may be present and represents a thin fibrous capsula.
A confident distinction from hepatocellular carcinoma based on the imaging appearance is mostly not possible. Therefore, histological examination is advocated to make a definite diagnosis. Surgical resection is generally recommended in patients with solitary hepatic adenoma, but may not be possible in patients with extensive hepatic adenomatosis. In these patients periodic follow-up is recommended.

Differential Diagnosis List

Final Diagnosis

Hepatic adenomatosis

URL:	https://eurorad.org/case/1726
DOI:	10.1594/EURORAD/CASE.1726
ISSN:	1563-4086