Teaching Case

A patient was referred to the radiology department for abdominal ultrasound during health check-up.

Abdominal ultrasound of the patient revealed multiple well demarcated, tubular anechoic lesions, situated on the right liver lobe. Colour Doppler technique demonstrated the presence of flow within these structures, identifying their vascular origin. There was a communication found between these structures along with an afferent vessel originating from a branch of the portal vein and an efferent vessel draining into a hepatic vein. (Fig. 1) Spectral analysis in both the afferent and the efferent blood vessels revealed a flow with venous characteristics whereas the flow derived from the communication was turbulent. (Fig. 2)
The patient was then referred for CT to confirm the ultrasound findings. Unenhanced, arterial and venous phase contrast enhanced CT was performed. As suggested by Doppler imaging, the lesions were of vascular aetiology and were homogeneously enhanced only in the venous phase. A communication was shown between a branch of the portal vein and a hepatic vein. (Fig. 3, 4, 5)

The term Portosystemic Venous Shunt (PSVS) refers to the communication of a branch of portal vein with a systemic vein, which may be either intra- or extrahepatic. Extrahepatic PSVS can be secondary to portal hypertension due to cirrhosis whereas intrahepatic PSVS (IPSVS) is rarer and considered to be congenital. [1] IPSVS measure more than 1 mm and may be partially located outside the liver. [2] A classification of IPSVS was introduced by Park et al. Hepatic vascular malformations in general have a reported incidence of 0, 1%. [1, 3]
IPSVS may be found incidentally in asymptomatic patients but in cases with severe shunting, hepatic encephalopathy may occur. Thus, prognosis is defined by the lesion’s size, the resulting shunt ratio and patient’s age. [1] Liver tests can be elevated in some cases. [2]
IPSVS can be evaluated by US, CT and MRI. The imaging findings depend on the type of shunt. In general, imaging modalities will identify IPSVS as a single or multiple tubular or aneurysmal communication between a branch of the portal vein and a hepatic (systemic) vein. Gray-scale US reveals a single or multiple anechoic lesions within the liver parenchyma. Portal and hepatic veins may appear enlarged. It is important to use colour Doppler imaging and pulse wave technique to assess the direction and the exact waveform of the blood flow within the shunt. According to the type of vascular malformation, the flow can be arterial, portal or hepatic venous. In IPSVS, the flow has venous characteristics and is influenced by respiration or right atrial contractions. Namely, the waveform is continuous when derived from a branch of the portal vein, turbulent when corresponding to the shunt or finally biphasic when derived from a hepatic vein. [1, 3, 4, 5]
CT reveals a mass with homogeneous enhancement after contrast medium injection and the exact branches which communicate between portal and hepatic veins. MRI has similar findings but gives the opportunity to evaluate the lesion on sagittal and coronal planes and with MR venography. [1]
IPSVS need treatment only if symptomatic. Encephalopathy can be treated with dietary changes or embolisation of the shunt in more severe cases. [1, 6]
Take home message: IPSVS are rare malformations which are increasingly diagnosed thanks to progress in medical imaging. Radiologists should be aware of these entities as early diagnosis may result in treatment and prevent complications.