Direct Shunt embolisation at SCVS — a novel technique for intrahepatic shunt closure
- Developed by Prof. Matthias Schneider, University Giessen, Germany
- Superior way of intrahepatic shunt closure
- SCVS is bringing this method to the UK in co-operation with Prof. Matthias Schneider
- Please contact SCVS and ask for more information
Why Direct Shunt Embolisation?
Closure of intrahepatic shunts is very complex. The three main problems are:
- Poor accesibility of the shunt due to its location
- Development of portal hypertension following shunt closure
- Formation of collateral shunt vessels following closure
Three different techniques for shunt closure are available
Surgical ligation and Stent&Coil technique usually don’t close the shunt itself. These techniques typically close the hepatic vein draining the shunt or sometimes (surgical ligation) the portal vessel itself. Closing the draining hepatic vein often triggers formation of collateral shunt vessels; closing the portal vein can lead to severe portal hypertension and complete shunt closure is therefore often not possible.
Residual shunt flow or shunt flow through newly acquired shunt connections will over time result in relapse of clinical signs and patients often require lifelong treatment with medication and / or diet.
Direct Shunt Embolisation is the only technique available, which achieves closure directly at the level of the shunt connection itself. This avoids formation of collateral shunt connection and allows complete shunt closure. Patients which have undergone Direct Shunt Embolisation typically can discontinue all medications and will transition to a completely normal diet within 1-2 years following intervention.
Portal Hypertension
Portal hypertension commonly develops following shunt closure as a consequence of poorly developed portal vasculature in the liver (little pink vessels).
Prior shunt closure a large blood volume draining from the gastrointestinal tract flows through the shunt. Following shunt closure, the blood returning from the gastrointestinal tract has to enter the liver before returning into the normal circulation. Often too little vessels entre the liver to accomodate the blood flow, resulting in high pressure in the portal vasculature (portal hypertension). If severe, the portal hypertension can be lethal.
To avoid severe portal hypertension, gradual closure of the shunt is typically required. This gradual closure over time, allows the liver to develop portal vessels to accomodate the blood flow. With surgical ligation and Stent & Coil techniques, gradual closure is often only achieved with repeated procedures. The novel Direct Shunt Embolisation achieves gradual shunt closure after only one intervention in most patients, using a unique and complex heparinisation protocol.
Formation of Collateral Shunt Vessels
Hepatic veins have pre-formed connections between each other. These connections are usually non-patent and don’t carry any blood flow in the normal circumstance. However, with increased hepatic venous pressure these connections become patent, resulting in the formation of secondary collateral shunts. Hepatic vein pressure increases if the hepatic vein instead of the shunt vessel itself is closed as this is often the case with surgical shunt ligation and the Stent&Coil technique. Direct Shunt Embolisation does not incrase hepatic vein pressure and does not carry the risk of collateral shunt vessel formation.
Formation of collateral shunt vessels explained
The intrahepatic shunt (black part of the vessel) connects the portal vein (purple vessel) with the hepatic vein (blue) and caudal vena cava. ‘Toxic’ blood reaches the systemic circulation via the shunt vessel.
The portal vein branches into the liver (thin pink vessels), but these branch vessesls are usually underdeveloped and only very few are present.
Several hepatic veins (small blue vessels) exist and drain the liver pranchyma.
There are preformed connections between all the hepatic veins (dotted lines). These remain closed and do not carry any blood flow as long as the pressure within the liver veins remains low
Closure of the draining hepatic vein (red line) will dramatically increase the pressure within the hepatic veins
Pre-formed connections between the hepatic veins open and a new shunt vessel develops
Shunt closure techniques compared
Surgical ligation:
Depending on the type and location of the intrahepatic shunt, surgical ligation is usually performed at the level of the hepatic vein or at the level of the portal vein. If ligated at the level of the hepatic vein, then very likely secondary shunt vessels will develop over time, resulting in a poor long term outcome. Ligation at the level of the portal vein impairs portal blood flow, resulting in severe portal hypertension. Especially in patients with little portal vasculature, complete shunt closure often cannot be achieved.
Stent&Coil technique
A stent is placed in the caudal vena cava. Thereafter the hepatic vein is embolised with multiple small coils. This again represents a technique which closes the hepatic vein and not the shunt vessel itself. It is therefore prone to formation of secondary shunts.
Direct Shunt embolisation (novel technique used at SCVS)
Direct Coil embolisation of the shunt positions a single large coil directly at the level of the shunt vessel. This avoids the risk of formation of secondary colateral shunts and results in a very good long term outcome for the patient.
