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Fig. 1 Spot film demonstrating transfemoral placement of IVUS probe and puncture of portal vein with modified Rosch-Uchida Portal Access set which has been placed into IVC from a transjugular route.

The IVUS (Intravascular ultrasound guided direct intrahepatic portocaval shunt) guided DIPS procedure was developed at the Dotter Institute in an attempt to improve the conventional TIPS procedure. Though used for over 10 years for the treatment of portal hypertension, the TIPS procedure suffers from two major weaknesses, one procedural, and one related to patency. Procedurally, the TIPS procedures one of the most difficult of all Interventional Radiology procedures. The single most difficult step in this procedure is the puncture from the hepatic to the portal vein. This puncture is performed without imaging guidance, and is the single step associated with the highest morbidity and long fluoroscopy times. Patency issues arise after the TIPS shunt has been successfully established. The single most common source of TIPS occlusion, malfunction and recurrent symptoms are due to development of hepatic vein stenosis in the outflow tract as blood is shunted to the IVC and heart from the portal circulation. These delayed malfunctions have led to the need for constant surveillance programs with ultrasound and repeat interventional procedures to maintain patency.

Fig. 2a IVUS image guiding the direct IVC to portal vein puncture. In this saggital, sector image, cranial is to the left, caudal to the right. The wall of the IVC is not well seen as it lies close to the IVUS transducer. The portal vein is seen in cross section as an ovoid sonolucent structure in the center of the screen. The needle is seen as a bright straight reflector as it courses from a cranial to a caudal direction as the tip of the needle begins to "tent" and enter the portal vein.
Fig. 2b IVUS image with needle tip lying in the portal vein, same orientation as the Fig. 2a. The acoustically enhanced needle tip has punctured through the wall of the portal vein, and is seen "floating" within the lumen.

The DIPS procedure eliminates these two major weaknesses of the TIPS procedure. Procedurally, the "blind portal vein puncture" is replaced by a puncture directly from the IVC to the portal vein, guided with real-time IVUS. As the shunt is performed directly from the IVC to the portal vein, the hepatic veins are excluded from the shunt, and hepatic veins obstruction are eliminated. The goal of the DIPS procedure are to increase the speed, safety, and efficacy of shunt creation and to increase the patency of the shunt. If these goals are realized, this may decrease or eliminate the need for shunt surveillance and repeat interventional procedures required to maintain patency. It could eventually expand the clinical use of the percutaneous portal decompression procedure and replace the surgical portocaval shunt.

Fig. 3 Preliminary portogram performed before DIPS. The portosystemic gradient measured 29 mm Hg. Note filling of coronary vein and small varices.

To construct the DIPS, an IVUS probe is placed into the IVC from a transfemoral approach. A modified Rosch-Uchida Portal Access set is then placed into the IVC from a transjugular approach (Fig. 1). Using the IVUS probe to guide the needle of a slightly modified Rosch-Uchida set, the needle is thrust directly from the IVC (Fig. 2), through the caudate lobe of the liver and into the portal vein. Then using conventional catheter and guidewire techniques, a shunt is constructed from the IVC to the portal vein using a PTFE covered balloon expandable stent-graft (Fig. 2 and 3). This balloon expandable stent-graft has the advantage over self expanding stent-gtafts of being able to precisely control the diameter of the shunt. By controlling the shunt diameter, one can obtain very precise portosystemic gradients and optimal portal shunting to treat patient symptoms and yet limit encephalophathy.

Thus far we have performed the DIPS procedure in more than 150 patients. All procedures were successfully performed with no significant complications. In the majority of patients, only one and only occasionaly two puncture attempts were needed for portal vein entrance. The majority of patients (89%) had long term primary DIPS patency and stable gradients. Those with ascites recurrence or an elevated gradient were treated with stent graft dilation or additional stent placement with 100% secondary patency. The longest follow-up has been 48 months.

Fig. 4 Final portogram after DIPS. Note shunting of blood directly into IVC through the shunt. There is no filling of varices. This shunt was places for ascites and has been patent for 12 months with a stable portosystemic gradient of 10 mm Hg.

We can conclude that a direct puncture from the IVC to the portal vein can be safely and reliably accomplished with real-time IVUS guidance, and that a shunt can be constructed from a PTFE covered stent-graft to cover this tract. There are advantages with DIPS over the conventional TIPS. The use of IVUS is an advantage.