Focal liver lesion: early hypoenhancement in CEUS does not prove malignancy -not even in a cirrhotic liver. Demonstration of a rare benign cause

Purpose: In CEUS of focal liver lesions enhancement in the arterial phase and an early outwash during the portal venous phase usually indicates malignancy, whereas almost all benign lesions display a sustained contrast enhancement up to the late phase or behave like the surrounding liver tissue. A rare cause of a benign lesion with arterial enhancement and an early hypoenhancement is reported.

Material and methods: A 75 year old patient who had suffered from epigastric pain for 3 months presented for an abdominal ultrasound. A diabetes mellitus type II and an arterial hypertension were known. The physical exam showed class 1 obesity and a slightly enlarged liver, but no abdominal pain on palpation.

Laboratory values were unremarkable. Abdominal ultrasound was performed, followed by CEUS and fine needle puncture of the lesion.

Results: Abdominal ultrasound showed an inhomogenous liver texture with a reduced elasticity, but normal vessel architecture and flow parameters and a hypoechoic liver lesion with a halo of 2.8 cm in segment III. CEUS showed a fast enhancement during the arterial and an hypoenhancement during the portal venous phase. Ultrasound guided biopsy showed a liver cirrhosis and parts of a bile duct adenoma with no signs of malignancy. After presentation in the liver tumour board a liver resection was discussed because a failed puncture of the lesion was assumed and a hepatocellular carcinoma was suspected. The patient decided against a resection and, therefore, chose to watch and wait. After four years now the lesion has not grown, the patient is still in good health.

Conclusion: Bile duct adenomas are rare benign tumours of the liver. The exact incidence is unknown. Because of the absence of portal venous vessels they show an early hypoenhancement. A single bile duct adenoma larger than 2 cm is a very rare finding.