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British Journal of Radiology (2003) 76, 487-490
© 2003 British Institute of Radiology
doi: 10.1259/bjr/65168282
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Case report

Intrahepatic portosystemic venous shunt: diagnosis by colour/power Doppler imaging and three-dimensional ultrasound

B Oguz, MD D Akata, MD F Balkanci, MD and O Akhan, MD

Hacettepe University School of Medicine, Department of Radiology, Sihhiye, Ankara TR-06100, Turkey

Correspondence: Deniz Akata


   Abstract
Top
 Abstract
Introduction
 Case report
 Discussion
 References
 
Intrahepatic portosystemic venous shunt, considered to be a rare disease, can lead to hepatic encephalopathy. With recent advances in diagnostic imaging techniques, the number of reports of intrahepatic portosystemic venous shunts identified incidentally in patients without symptoms are increasing. We report an intrahepatic portosystemic venous shunt that was diagnosed incidentally by real-time ultrasound and colour Doppler imaging, including the use of three-dimensional ultrasound using minimum intensity projections and power Doppler.


   Introduction
Top
 Abstract
 Introduction
Case report
 Discussion
 References
 
Intrahepatic shunts between the portal and hepatic vein are rare vascular abnormalities that frequently lead to hepatic encephalopathy. It is believed that these patients become symptomatic with advancing age as the tolerance of the ageing brain to high ammonia levels diminishes [1–8]. With recent advances in diagnostic imaging techniques, such as ultrasound (US), CT, MRI and colour Doppler US, the number of reports of intrahepatic portosystemic venous shunt (IPSVS) identified incidentally in patients without definite symptoms is increasing [1, 4–12].

In this report we present the case of a congenital portohepatic venous shunt that was diagnosed incidentally by real-time US and colour Doppler imaging, and the use of three-dimensional US using minimal intensity projections and power Doppler.


   Case report
Top
 Abstract
 Introduction
 Case report
Discussion
 References
 
A 40-year-old woman was referred to our US unit for evaluation of lower quadrant pain and to rule out appendicitis. US examination was performed by a commercially available scanner (Sonoline Elegra Advanced; Siemens, Erlangen, Germany) equipped with 2–5 MHz sector transducer. Freehand image technique was used to obtain three-dimensional (3D) images. During image acquisition for 3D US, the 2D images were collected, each image originating from a unique location and orientation within the area of interest. The resulting data set was displayed by volume rendering technique, which maps voxels directly onto screen. Minimum intensity projection (MIP) method was used to display dilated tubular structures, in our case a portosystemic venous shunt. Unwanted echoes and objects were removed using editing boxes. The US study was unremarkable except for an incidental finding of an abnormal single vessel communication between left portal vein and left hepatic vein. The contour and echogenicity of the liver was normal without any focal lesions. The main portal vein was patent with antegrade flow. The left hepatic vein was prominently dilated with increased flow volume. Colour Doppler imaging as well as Doppler spectral analysis confirmed the direct communication between the left portal vein and the left hepatic vein. A high velocity continuous waveform signal was obtained at the hepatic end of the shunt and at the left hepatic vein (Figure 1aGo). The flow volume in the hepatic vein at shunt origin was 2.88 l min-1. A normal triphasic waveform was obtained in both the middle and right hepatic veins with flow volumes measuring 0.08 l min-1 and 0.06 l min-1, respectively (Figure 1bGo). To avoid portography, 3D power and minumum intensity projections of the shunt were also obtained (Figure 2Go).



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  		Figure 1. (a) Colour Doppler and duplex Doppler ultrasound shows high flow volume and continuous waveform in the hepatic venous end of the shunt, measuring 2.88 l min-1 and (b) normal triphasic waveform with flow volume measuring 0.08 l min-1 in the middle hepatic vein.

 


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  		Figure 2. (a) 3D B-mode minimum intensity projection and (b) 3D power Doppler images reveal direct communication between the left hepatic vein (LHV) and the left portal vein (LPV).

 
Physical examination and laboratory data, including liver function studies were unremarkable. Serum ammonia level was normal. There was no clinical and laboratory evidence of cirrhosis or hepatic encephalopathy. Since the patient had no symptoms and did not consent to treatment, she was followed up without intervention. The patient continued to be asymptomatic and a follow up Doppler US after 6 months was unchanged.


   Discussion
Top
 Abstract
 Introduction
 Case report
 Discussion
References
 
Although IPSVS had been thought to be uncommon, with recent advances in diagnostic imaging techniques such as US, CT and MRI, asymptomatic intrahepatic shunts have been detected in an increasing number of patients [1–12]. Since an IPSVS may cause hepatic encephalopathy, the correct radiological diagnosis and proper treatment of this unusual abnormality is important [1–8, 11].

The aetiology of IPSVS is uncertain and may be either congenital or acquired; secondary to portal hypertension due to chronic liver damage [1, 2, 4, 5, 7, 11–20]. Our case is likely to be congenital as there was no associated evidence of chronic liver disease.

To our knowledge, more than 50 cases of portohepatic venous shunts have been reported since Raskin et al first described congenital IPSVS in 1964 [1]. In most reported cases, the patients were over 50 years old [1, 4–8, 13, 18] although a few paediatric cases have been reported [9, 10, 14, 21, 22].

Park et al categorized previously published cases of portohepatic venous shunts arbitrarily into four different morphologic types [5]. Type 1 is a single large tube of constant diameter that connects the right portal vein to the inferior vena cava. Type 2 is a localized peripheral shunt in which single or multiple communications are found between peripheral branches of portal and hepatic veins in one hepatic segment. Type 3 is an aneurysmal communication between the peripheral portal and the hepatic veins. Type 4 shows multiple communications between the peripheral portal and the hepatic veins diffusely in both lobes. In a review of the literature, most examples of IPSVS are type 1 or type 2 and are located in the right lobe [5, 7, 19]. Our patient was Park's type 2 with the shunt situated in the left lobe.

Congenital IPSVS is clinically important because it can lead to hepatic encephalopathy [1–8, 11, 18]. Takako Uchino et al reviewed 51 cases of congenital portosystemic venous shunt in Japan, and in this series there were 12 patients with hepatic encephalopathy at the time of diagnosis [8]. The natural history of IPSVS depends upon the shunt ratio and on the patients age. The frequency of hepatic encephalopathy increases with age. Decreasing tolerance of brain to toxic metabolites with increasing age may explain the late clinical manifestations [1, 2].

Large intrahepatic shunts are more often associated with hepatic encephalopathy than small shunts, with the higher degree of portal venous shunting being responsible for early clinical manifestations. The shunt ratio can be determined by iodine 123-iodoamphetamine per-rectal portal scintigraphy [8]. Doppler US may also be used to determine the shunt ratio, calculated by dividing the blood flow volume of shunt by the total portal blood flow volume [8, 18]. When the shunt ratio increases, the amount of nitrogen-containing substances in the portal blood that bypass the extraction mechanism of the hepatic parenchyma rises in the systemic circulation and can lead to hepatic encephalopathy. When the shunt ratio is <30%, symptoms associated with IPSVS may not develop throughout the life time of the individual. When the shunt ratio exceeds 30%, hepatic encephalopathy may develop at any time. When the shunt ratio exceeds 60%, the risk of hepatic encephalopathy is increased [8, 18], and a portal shunt ratio more than 60%, even without encephalopathy is an indication for therapeutic intervention in non-cirrhotic patients [8, 18].

Unlike small asymptomatic shunts, large shunts causing hepatic encephalopathy require appropriate therapeutic intervention. Owing to the rarity of this disorder, the correct choice of treatment is uncertain. The literature describes surgical interventions such as shunt ligation and hepatic resection [2]. Creation of an alternative portosystemic shunt by surgery, such as a distal splenorenal shunt, or angiographic intervention may also be considered [3]. The first angiographic intervention was performed by Ohtomo in 1986 [3]. Surgery for this condition is often associated with high morbidity and mortality rates [1]. Potential complications of coil embolisation may include exacerbation of portal hypertension caused by abrupt changes in the portal haemodynamics and dislodgement of coils into the systemic circulation [6]. The long-term outcome of this treatment still needs evaluation. Coil embolisation is a potentially promising new treatment in the management of multiple large intrahepatic portohepatic venous shunts causing hepatic encephalopathy, if apart from depicting the shunt, colour Doppler US adds extra value by calculating the flow volume through the shunt and the hepatic veins, and may aid in treatment planning.

Colour Doppler imaging was first used to diagnose an iatrogenic intrahepatic portosystemic venous shunt by Bezzi et al [23]. Recent publications conclude that colour Doppler imaging combined with pulsed Doppler examination is accurate in the diagnosis of IPSVS and obviates the need for angiography. It is also able to measure shunt ratios and may be potentially useful in follow up and helping choose the appropriate therapeutic option of IPSVS, especially for those of congenital origin [18, 23, 24]. In addition, the use of 3D US of the portohepatic system may accurately delineate the IPSVS of the portohepatic venous shunt.

3D US is a relatively new technique that demonstrates anatomy and pathology as volumetric data. It has several advantages compared with 2D US. Volumetric data can be evaluated using standard anatomic orientation with planar images to obtain a simultaneous display of coronal, sagittal and axial planes. Rendering of the entire volume allows the continuity of curved structures such as a tortuous dilated abnormal vessel suggesting continuation between the portal and hepatic vein in a single image. It is also possible to evaluate the area of interest from multiple orientations by rotating the volume. In selected cases, such as in our case, it may reduce the need for further evaluation with more invasive and expensive modalities.

The major limitations of 3D US are patients' body habitus and cardiac and respiratory motion. Respiratory motion may be a problem in children and older patients. Anything diminishing 2D image quality also limits rendered image quality such as signal dropout from shadowing due to overlying structures.

In conclusion, colour Doppler US is the modality of choice for the diagnosis of IPSVS. It is also the best method to evaluate the shunt haemodynamics. 3D US promises to be a valuable adjunct to 2D image in the evaluation of IPSVS and also we believe that the additional use of 3D US may eliminate the need for angiography.

Received for publication April 5, 2002. Revision received August 27, 2002. Accepted for publication November 27, 2002.


   References
Top
 Abstract
 Introduction
 Case report
 Discussion
 References
 

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