Portacaval space anatomy: potential implications for percutaneous portacaval shunts

Application of transmesenteric vein extrahepatic portosystemic shunt in treatment of symptomatic portal hypertension with cavernous transformation of portal vein

Purpose

To evaluate the feasibility and efficacy of a transmesenteric vein extrahepatic portosystemic shunt (TmEPS) for the treatment of cavernous transformation of the portal vein (CTPV).

Materials and methods

The clinical data of 20 patients with CTPV who underwent TmEPS between December 2020 and January 2022 ​at Henan Provincial People's Hospital were retrospectively collected. The superior mesenteric vein (SMV) trunk was patent or partially occluded in these patients. An extrahepatic portosystemic shunt between the inferior vena cava and the SMV was established using a stent graft through an infraumbilical median longitudinal mini-laparotomy. The technical success, efficacy, and complication rates were evaluated, and the pre- and postoperative SMV pressures were compared. Patients' clinical outcomes and shunt patency were assessed.

Results

TmEPS was successfully performed in 20 patients. The initial puncture success rate of the balloon-assisted puncture technique is 95%. The mean SMV pressure decreased from 29.1 ​± ​2.9 ​mmHg to 15.6 ​± ​3.3 ​mmHg (p ​< ​0.001). All symptoms of portal hypertension resolved. No fatal procedural complications occurred. During the follow-up period, hepatic encephalopathy occurred in two patients. The remaining patients remained asymptomatic. All shunts were patent.

Conclusions

TmEPS is a feasible, safe, and effective treatment option for patients with CTPV.

Twenty-five years after the first TIPS in Spain

The incorporation, 25 years ago, of transjugular intrahepatic portosystemic shunting, better known by the acronym TIPS, represents an indisputable improvement in the treatment and management of patients with symptoms due to portal hypertension. This article discusses the origins of the technique and the technical innovations that have been progressively added through the years. The implantation of coated stents, which protect the stent from processes in the parenchymal track that can lead to stenosis, have helped ensure long-term patency, thus reducing the need for reintervention. Solid evidence from valuable publications has situated TIPS at the forefront of the treatment options in a wide variety of clinical situations associated with portal hypertension.

Intervascular Anastomoses Created by an Endovascular Approach: Technical Aspects and Initial Results in an Animal Study

PURPOSE

The current article describes the initial results after the creation of intervascular connections with use of an exclusively endovascular approach. Connections of two vessels were performed in the thoracic and abdominal areas with use of a kinematic needle without traversing a solid organ. The materials developed specifically for this technique are described.

MATERIALS AND METHODS

The procedure was carried out in 11 animals and consisted of bringing together two vascular structures with use of magnets, performing a puncture from the lumen of one vessel to that of the other, and inserting a prosthesis between the two. The prosthesis has a biconical morphology and is made with a 0.016-inch monofilament of nitinol. Its most outstanding feature is that, when it is dilated with a balloon, it shortens and "rolls up," flattening its ends. This allows good fixation to the vessel wall, avoiding the protrusion of metal into the lumen of the native vessel.

RESULTS

On four occasions, the aorta was connected to another nearby vessel: the abdominal aorta to the inferior vena cava (IVC; n = 1), the ascending aorta to the trunk of the pulmonary artery (n = 1), and the descending aorta to the left pulmonary artery (n = 2). On another four occasions, two veins were connected: the portal vein and the IVC. Finally, on three occasions, the right pulmonary artery was connected to the superior vena cava. The connection was safely and accurately performed with passage of a guide wire in all cases. In two experiments, the prosthesis was too short and leakage with massive bleeding was observed after a successful initial deployment of the prosthesis

CONCLUSION

Intervascular anastomoses created by an endovascular approach are feasible in the authors' experimental model for several different vessel pairings.

Percutaneous MR imaging-guided transvascular access of mesenteric venous system: study in swine model

PURPOSE

To determine if, with use of magnetic resonance (MR) imaging guidance alone, transcaval puncture of the superior mesenteric vein (SMV) and/or portal vein is feasible with a percutaneous femoral vein approach.

MATERIALS AND METHODS

The Institutional Animal Care and Use Committee approved the animal studies. Ten inferior vena cava (IVC)-SMV punctures were performed in six pigs. An active MR intravascular needle system was used for all transvascular punctures, and all procedures were performed with a 1.5-T MR unit. The needle was introduced via a 12-F femoral vein sheath and advanced into the IVC by using a real-time gradient-recalled-echo sequence (3.4/1.2 [repetition time msec/echo time msec], 45 degrees flip angle, and six to eight frames per second). Fast transverse spoiled gradient-recalled acquisition in the steady state (SPGR) (6.0/1.5, 60 degrees flip angle, one frame per second) was performed to confirm needle trajectory. The needle system was advanced under real-time MR imaging to puncture the SMV. The location of the needle tip was confirmed with a fast spin-echo sequence (1904/4.5, 36-cm field of view). A direct MR portogram was obtained after the administration of gadopentetate dimeglumine at a concentration of 25% with fast SPGR (6/1.3, 90 degrees flip angle, no section selection, three frames per second). Success was defined as entry into the mesenteric venous system without traversal of any retroperitoneal organs or adjacent vasculature.

RESULTS

Successful MR imaging-guided IVC-SMV punctures were performed in all 10 procedures (100%). The needle was fully visualized as it traversed the retroperitoneum and entered the SMV. MR portograms were successfully obtained following all punctures through the needle. Conventional transverse MR imaging helped confirm that the needle did not traverse any retroperitoneal organs or vessels.

CONCLUSION

With use of only MR imaging guidance and an active MR imaging intravascular needle system, the authors were able to successfully puncture the SMV from the IVC with direct visualization of the needle and all retroperitoneal structures.

Experimental Percutaneous Extrahepatic Portacaval Shunt Creation by Transjugular Approach in Swine

The purpose of the study was to evaluate the feasibility of the creation of a percutaneous extrahepatic portacaval shunt (PEPS) in swine by a transjugular approach and to find a suitable stent-graft to use in PEPS. In 12 swine, the extrahepatic portal vein (PV) was entered from the inferior vena cava (IVC) by a needle system introduced from the transjugular approach. A catheter introduced through the transhepatic approach served as a target. Five types of stent-graft consisting of homemade Z stents and a polytetrafluoethylene cover were explored for PEPS creation. Eight animals had follow-up venograms up to 6 weeks or until the shunt became severely stenotic. Gross and histologic examinations were performed after the final follow-up venography. The PV punctures and stent-graft placement were difficult, but the PEPS was established in all animals. In four animals, the stent-graft failed to adequately cover the tract, causing severe hemorrhage. Only two shunts remained patent up to 6 weeks. The other shunts exhibited severe stenosis or occlusion. At gross examination, all shunts traversed the liver parenchyma of the caudate lobe surrounding the IVC. The extravascular PEPS portion was 4 mm to 2 cm long. All shunts entered the PV close to the splenomesenteric junction and exhibited neointimal formation. Shunt stenoses were caused by neointimal hyperplasia and occlusions by a superimposed thrombus. PEPS can be created by the transjugular approach in swine, but only the PV shunt entrance is extrahepatic. None of the tested rigid stent-grafts were suitable for PEPS creation. A short flexible stent-graft with flanged ends is suggested for further exploration.

Transvenous Extrahepatic Portacaval Shunt with Use of a Modified Prototype Stent-Graft: Experimental Study in Animals

PURPOSE

To evaluate the safety and short-term patency of an experimental transvenous extrahepatic portacaval shunt (TEPS) in an animal model.

MATERIALS AND METHODS

With use of intravascular ultrasound (IVUS) guidance, the main portal vein (PV) was accessed from the inferior vena cava in six pigs and a TEPS was created with use of a prototype flanged stent-graft. Partial PV embolization was then performed to increase the post-TEPS PV pressure. Baseline and postprocedural hemoglobin and hematocrit measurements were obtained and liver function studies were conducted. Immediate postprocedural computed tomography (CT) of the abdomen was used to identify procedural complications. Follow-up venography was performed at 2, 4, and 12 weeks to assess short-term patency. Necropsy was performed at 3 months.

RESULTS

IVUS-guided PV access was accomplished with a mean of two punctures per animal (range, 1-4). TEPS creation was successful in five of six animals. One animal was killed immediately after unsuccessful shunt creation after stent-graft misdeployment and hemorrhage. A second animal required the insertion of a conventional stent coaxially because portions of the leading arms were inadvertently deployed in the portacaval space and the initial flow through the shunt was venographically suboptimal. CT images obtained after successful TEPS creation (n = 5) revealed no evidence of hemoperitoneum, and there was no decrease in hemoglobin or hematocrit levels from baseline values. All five TEPSs were widely patent at 2-week and 4-week venography with only mild pseudointimal hyperplasia (<50% diameter stenosis) identified in one shunt. Twelve-week venography and necropsy demonstrated no evidence of shunt stenosis in one animal, less than 50% diameter stenosis in one animal, 50%-75% diameter stenosis in two animals, and shunt occlusion in one animal.

CONCLUSION

Early results with TEPS with use of a modified prototype flanged stent-graft are promising as a potentially safe alternative means of portal decompression. Additional refinements of the stent-graft delivery process are needed to improve the accuracy of deployment.

Percutaneous Extrahepatic Portacaval Shunt with Covered Prostheses: Feasibility Study

PURPOSE

To assess the anatomic feasibility of creating a percutaneous extrahepatic portosystemic shunt (PEPS) between the main portal vein (MPV) and the inferior vena cava (IVC) in patients with cirrhosis and to evaluate the feasibility of this approach in an animal model.

MATERIALS AND METHODS

In human studies, computed tomographic (CT) scans from 34 patients with cirrhosis were reviewed to assess the distance and anatomic structures found between the MPV and IVC. The MPV was divided into upper, middle, and lower thirds for analysis. In the experimental model, PEPS were created in 10 beagle dogs by placing between the MPV and IVC a tubular polyurethane-covered prosthesis with flared ends designed for this study. Different approaches, devices, and prostheses were assayed.

RESULTS

In human studies, the shortest mean distance between the IVC and the MPV was found in the lower third of the MPV (1.18 cm +/- 0.6). The lower third, the nearest to the confluence of splenic and superior mesenteric veins, also presented fewer intervening structures, and the spatial relationship between the veins at this level was predictable. In the experimental model, direct portography was performed, with a small mesenteric vein catheterized through a minilaparotomy and a transjugular access to the IVC. A needle was advanced from the MPV to the IVC, and a polyurethane cone-shaped covered prosthesis was placed to bridge the path between the veins. Six of 10 animals died from bleeding that occurred either because several punctures were made during the procedure or because the prosthesis became dislodged when the mesentery was moved before suturing the minilaparotomy. The remaining four were kept alive for 1, 5, 60, and 90 days after the procedure.

CONCLUSIONS

PEPS creation in patients with cirrhosis is anatomically possible. The lower third of the MPV should be the most suitable level at which to create the shunt. Preliminary studies carried out in beagle dogs support the feasibility of this approach. However, further work is needed to improve the efficacy of this technique.

Transvenous extrahepatic portacaval shunt: feasibility study in a Swine model

PURPOSE

To evaluate the feasibility of intravascular ultrasonography (US)-guided access to the extrahepatic segment of the main portal vein (PV) to create a transvenous extrahepatic portacaval shunt (TEPS) as an easier and more durable alternative to transjugular intrahepatic portosystemic shunt.

MATERIALS AND METHODS

PV access from the inferior vena cava (IVC) to the main PV was performed in eight pigs by using intravascular US guidance. Either a prototype stent-graft (n = 6) or Wallgraft (n = 2) was used to create the shunt. Intravascular US demonstrated the main PV to be in direct contact with the IVC in all animals. A mean of 1.75 needle passes were needed to enter the PV. Immediate postprocedure computed tomography (CT) of the abdomen helped identify and quantify the presence of hemoperitoneum. Shunt venography was performed at 2 weeks, followed by necropsy.

RESULTS

PV access and TEPS creation were successful in all animals. Contrast medium extravasation, due to inadequate coverage of the portacaval tract, was identified in four procedures and addressed by the placement of additional devices in three cases and prolonged balloon inflation in one. Abdominal CT demonstrated small amounts of hemoperitoneum in five animals and moderate to large amounts in three. Two animals did not live to the 2-week follow-up study. One animal was sacrificed on the day of the procedure owing to intraperitoneal hemorrhage; the second died of intussusception-related bowel necrosis 10 days after TEPS creation. Shunts were occluded or severely stenotic at venography and necropsy in the remaining six animals.

CONCLUSION

TEPS is technically feasible after intravascular US-guided PV access.

Percutaneous inferior vena cava-to-portal vein shunt (PIPS) using a stent-graft: preliminary results

PURPOSE

To present preliminary results of an inferior vena cava (IVC)-to-portal vein shunt (PIPS) that is created through the caudate lobe of the liver.

METHODS

Sixteen patients (13 men; mean age 50 years, range 32-63) were referred for PIPS procedures because of bleeding varices (n = 11), intractable ascites (n = 4), and hepatorenal syndrome (n = 1). The severity of liver disease was Child's B in 2 and Child's C in 14. The PIPS was created by a transhepatic puncture through the IVC and the portal vein; an endograft made of polytetrafluoroethylene sutured to a Palmaz stent was placed through a jugular approach.

RESULTS

In 13 (81%) patients, the portal vein-to-IVC tracts were successfully created. The postprocedural portal vein-IVC gradients varied from 1 to 9 mm Hg (mean 5). There were 2 deaths in the 30-day periprocedural period from adult respiratory distress syndrome and hepatorenal syndrome. A third patient died at 31 days from liver failure owing to continuing alcohol abuse. In addition, there was 1 case of peritoneal bleeding treated with blood product replacement. The follow-up period ranged from 14 to 671 days (mean 343). None of the patients treated for variceal bleeding had another bleeding episode, but 2 patients who had a PIPS procedure for refractory ascites did not benefit from the procedure. Postprocedure, 46% (6/13) of the patients had hepatic encephalopathy, which was unchanged from baseline. The primary and secondary patency rates at 365 days were 60% and 65%, respectively.

CONCLUSIONS

The preliminary results using a stent-graft to create an IVC-portal vein shunt are encouraging and support further work to better determine the role of this procedure.

Main portal vein access in transjugular intrahepatic portosystemic shunt procedures: use of three-dimensional ultrasound to ensure safety

PURPOSE

To document the safety of main portal vein (PV) access to create transjugular portosystemic intrahepatic shunts (TIPS), provided that three-dimensional ultrasonography (3D US) can document the puncture to have entered a surface of the PV suitable for tamponade.

MATERIALS AND METHODS

In 11 patients who underwent conventional TIPS creation (n = 10) or a transjugular portacaval shunt procedure (n = 1), the puncture was found angiographically to enter the main PV. In seven cases, this occurred at the PV bifurcation and, in four, it occurred in the superior third of the PV. 3D US was used to determine whether the point of PV entry was functionally intrahepatic or extrahepatic. The puncture site was deemed to be intrahepatic if liver covered the puncture site on all three orthogonal imaging planes (sagittal, coronal, and transverse). If the puncture site was surrounded by liver, the access was used to deploy a metallic stent (uncovered, n = 10; covered, n = 1). Medical records and follow-up cross-sectional imaging studies were reviewed for evidence of hemorrhage complications. Pathologic correlation was performed in one explanted liver and autopsy specimens in five other patients.

RESULTS

In nine of 11 patients, 3D US was diagnostic and confidently verified that liver completely covered the portal vein access site. In two patients with diagnostically uncertain 3D US results, transcatheter injection of contrast medium documented no extravasation. All TIPS and direct portacaval shunt procedures were technically successful. No hemorrhagic complications occurred. Examination of pathologic specimens documented this portion of the portal vein to be extraperitoneal, but attached to the superior surface of the caudate lobe with fibrous tissue and small portal vein branches.

CONCLUSIONS

The bifurcation and posterior aspect of the superior third of the main PV can be safely used for TIPS procedures, provided access is proven to be surrounded by liver. 3D US can usually confidently determine if the PV entry site is functionally intrahepatic.

Adjunctive 3D US for achieving portal vein access during transjugular intrahepatic portosystemic shunt procedures

PURPOSE

To evaluate the usefulness of information provided by three-dimensional ultrasound (3D US) and to determine whether 3D US decreased the number of passes required to obtain portal vein (PV) access during creation of transjugular intrahepatic portosystemic shunts (TIPS).

MATERIALS AND METHODS

Intermittent 3D US volume acquisitions were obtained during creation of TIPS in 20 patients. Useful information provided by 3D US was tabulated. The number of passes required to achieve PV access was recorded and results were compared retrospectively to 25 patients who underwent TIPS without 3D US.

RESULTS

3D US documented that the operator's opinion of which hepatic vein had been selected was incorrect in nine patients (45%), detected unfavorable PV anatomy that required modification of equipment or technique in seven patients (35%), permitted estimation of the trajectory required to access the targeted PV in all patients (100%), assisted in selecting the optimal point along the hepatic vein for origination of the needle pass in 11 patients (55%), allowed avoidance of a large hepatocellular carcinoma in one patient (5%), and confirmed that access into the main PV was intrahepatic in four patients (20%). The mean number of needle passes decreased from 10.4 in the historic control group to 4.6 in the 3D US group (P = .0001).

CONCLUSION

3D US provided imaging information that detected technical errors and altered anatomy, and provided positional and directional information to significantly improve needle pass efficiency.

Adjunctive 3D US for achieving portal vein access during transjugular intrahepatic portosystemic shunt procedures

PURPOSE

To evaluate the usefulness of information provided by three-dimensional ultrasound (3D US) and to determine whether 3D US decreased the number of passes required to obtain portal vein (PV) access during creation of transjugular intrahepatic portosystemic shunts (TIPS).

MATERIALS AND METHODS

Intermittent 3D US volume acquisitions were obtained during creation of TIPS in 20 patients. Useful information provided by 3D US was tabulated. The number of passes required to achieve PV access was recorded and results were compared retrospectively to 25 patients who underwent TIPS without 3D US.

RESULTS

3D US documented that the operator's opinion of which hepatic vein had been selected was incorrect in nine patients (45%), detected unfavorable PV anatomy that required modification of equipment or technique in seven patients (35%), permitted estimation of the trajectory required to access the targeted PV in all patients (100%), assisted in selecting the optimal point along the hepatic vein for origination of the needle pass in 11 patients (55%), allowed avoidance of a large hepatocellular carcinoma in one patient (5%), and confirmed that access into the main PV was intrahepatic in four patients (20%). The mean number of needle passes decreased from 10.4 in the historic control group to 4.6 in the 3D US group (P = .0001).

CONCLUSION

3D US provided imaging information that detected technical errors and altered anatomy, and provided positional and directional information to significantly improve needle pass efficiency.