EXPERIMENTAL AND CLINICAL TRANSPLANTATION

Objectives: Portal vein stenosis is a relatively rare complication after liver transplant but has severe consequences. We evaluated the efficacy and long-term results of the endovascular treatment methods for portal vein stenosis.
Materials and Methods: From October 2011 to October 2022, we treated 22 patients (5 female, 17 male) with portal vein stenosis using endovascular methods. Doppler ultrasonography was used for initial diagnosis, with consideration of flow rate increase over stenosis, absence of flow, or reduced anastomotic segment size (>50%). Angiography served as the gold standard, with a pressure gradient above 5 mm Hg indicating the need for treatment. Technical success criteria were defined as <50% stenosis remaining and/or a pressure gradient <5 mm Hg. The transhepatic approach was used for all patients. Balloon angioplasty was initially performed, and stents were reserved for patients in the early postoperative period or those unresponsive to balloon angioplasty.
Results: The technical success rate was 100%. Mean age was 27.1 years (SD 22.4; range, 4 months to 63 years). Mean time from transplant to intervention was 317 days (range, 0-3135 days). Angioplasty was successful for 7 patients (13.8%). Of 15 patients who underwent stent placement, 9 (40.9%) were in the early postoperative period; in the other 6 patients (27%), results of angioplasty were not satisfactory, and stents were placed. Within 3 months of transplant, 3 patients died because of other complications. Among patients with stents, 2 required reintervention, resulting in reestablishment of good portal venous flow. During the mean follow-up of 24 months (range, 15 days to 9 years), 19 patients (86%) had portal flows within reference limits.
Conclusions: The endovascular approach is a safe and effective treatment option for management of portal vein stenosis in both adult and pediatric liver transplant recipients in the early or late period.

Key words : Endovascular treatment, Liver transplantation, Percutaneous transluminal angioplasty

Portal vein stenosis (PVS) is a relatively rare complication but has severe consequences in patients who have had liver transplant. Transplant patients with portal vein complications have increased likelihood to develop liver dysfunction and portal hypertension, which may lead to liver failure.¹ The reported incidence of PVS is between 2% and 8% in the literature but may be as high as 7% to 27% in the pediatric liver transplant population, especially for patients with split-graft liver transplants.^2-6

The treatment of choice for PVS has traditionally been surgery, but it is now mostly managed with the endovascular approach using percutaneous transluminal angioplasty (PTA) and stents because of the low periprocedural morbidity and less invasive technique.^1,7,8 Previous studies have reported better long-term outcomes for primary stent placement than PTA alone.^9-11 However, there is still no consensus regarding whether to use stents as a primary treatment or as a rescue treatment, especially in pediatric patients.¹¹

We evaluated the efficacy of the endovascular approach for management of PVS in liver transplant patients, focusing on both adult and pediatric populations during both the early and late postoperative periods.

Materials and Methods

From October 2011 to October 2022, 22 patients (5 female, 17 male) with PVS after liver transplant were treated with endovascular approach. Initial diagnosis of PVS was by Doppler ultrasonography (US). Upon suspected results for PVS on Doppler US, such as more than 3-fold flow rate increase over stenotic segment, absence of flow, or >50% reduction of anastomotic segment size, computed tomography or splenoportography is performed according to the patient’s condition. Angiography is considered the gold standard treatment, with a pressure gradient exceeding 5 mm Hg over the stenotic segment indicating the need for treatment. Patients were subsequently monitored every 6 months using Doppler US, unless they exhibited symptoms. This study was approved by the institutional ethics review board and conducted in accordance with the Declaration of Helsinki.

Splenoportography percutaneous transluminal angioplasty and stent placement

Transhepatic portal vein access is gained under sonographic and fluoroscopic guidance with 21G needle (Accustick Introducer System; Boston Scientific, Watertown, MA, USA) at the most peripheral branch with enough diameter. A 0.021-inch guidewire is advanced to the main portal vein and exchanged to 0.035-inch hydrophilic guidewire (Glidewire, Terumo Interventional Systems), and then a 6F to 8F vascular sheath is inserted. The PVS is negotiated with a 0.035-inch hydrophilic guidewire and 4F to 5F catheters; arterioportography or splenic puncture is performed if the stenosis cannot be crossed from portal side. After crossing the lesion, splenoportography is performed, and the pressure gradient is measured across the stenosis. If the pressure gradient is greater than 5 mm Hg, then intervention is planned.

For our patients, treatment consisted of PTA (n = 7; 31.8%) and stenting (n = 15; 68.2%). Initially, PTA was performed with a balloon dilatation catheter (Mustang; Boston Scientific), and the balloon size was adjusted to the prestenotic portal vein. Pressure measurements and venography were repeated after angioplasty. Less than 50% stenosis and/or less than 5 mm Hg pressure gradient was considered a technical success. Stenting is preferred in cases of residual stenosis, persistent significant pressure gradient, or early restenosis. Stents with the same size or 10% larger diameter than the nonstenotic portal vein were used. Primary stenting is preferred in the early postoperative period to avoid rupture risk, and subsequent angioplasty is performed in cases of residual stenosis. Self-expandable bare stents (EPIC; Boston Scientific) are preferred in adults, whereas balloon-expandable stents (BES) (Visi-Pro; Medtronic) are preferred in pediatric patients because BES allow for subsequent dilatation to a larger diameter if required. After the procedure, the transhepatic access route was embolized using coil, N-butyl-2-cyanoacrylate with iodized oil, or sterile compressed sponge (Gelfoam).

Mean age of participants was 27.1 years (SD 22.4 years; range, 4 months to 63 years), with 11 patients (50%) in the pediatric age group. Mean transplant-to-intervention time was 317 days (range, 0-3135 days). The technical success rate was 100%. Seven patients (13.8%) underwent PTA and did not require further intervention during follow-up. Nine patients (40.9%) required intervention in the first 2 weeks after surgery. All 9 patients in the early postoperative period were treated with stent placement. In the other 6 patients (27%), results of PTA did not meet the success criteria, so stents were placed in the same session. In 1 patient, the stenotic segment could not be crossed from the hepatic side, so trans-splenic access was required. There were no procedure-related major complications. Mean follow-up time was 24 months (range, 15 days to 9 years).

Two patients with stents required reinterventions. One patient required reintervention after 16 months, and another patient required 3 reinterventions due to thrombosis. Portal vein patency was reestablished in both of these patients. Three other patients died from other reasons within 3 months of transplant. One patient had splenic steal syndrome and underwent partial splenic artery embolization during the same session. One patient had extensive varices and underwent coil embolization simultaneous with portal vein stenting. Two patients experienced biliary strictures, which were treated by percutaneous biliary drainage. The portal venous flows of the other patients (n = 19; 86%) were within reference limits in Doppler US and did not require any reintervention regarding PVS during the follow-up period. Detailed patient information is provided in Table 1. Two of the cases are illustrated in Figure 1 and Figure 2.

Surgical repair of anastomosis or retransplant were once the primary methods for treatment of PVS, but these have largely been superseded by endovascular treatments, due to the lower morbidity and minimally invasive nature of endovascular procedures.^7,8,12,13

In our study, none of the 7 patients who underwent PTA alone required reintervention, and patency was maintained during the mean follow-up period of 44 months. Stent placement was reserved for cases unresponsive to PTA, cases with a pressure gradient higher than 5 mm Hg even after repeated PTA, or cases of early restenosis. Among the 15 patients who underwent stent placement, only 2 required reintervention. Nine patients were in the early postoperative period (within 2 weeks of surgery), and all received stent placement to avoid rupture risk. Stenting is also justified in these patients because in the early postoperative period PVS could be caused by kinking or outside pressure, both of which would require stenting.

A debate remains regarding the primary use of stents, especially in the pediatric population. A major concern in children, particularly infants, is that stents do not grow with the child and may lead to the future complication known as fixed stenosis.^6,14 Another concern is that a future retransplant (if required) could be complicated by a previously place metallic stent in the proximal portal vein.¹⁵ Although long-term data is limited, some studies have shown favorable results with stent placement.^9,13,15-17 Funaki and colleagues¹³ reported that 7 of 11 patients treated with angioplasty alone developed recurrent stenosis during follow-up (mean 6.3 months), whereas none of the 12 patients with stents developed recurrent stenosis during follow-up. Kim and colleagues¹⁸ reported 82% patency rate for PTA and 100% patency for stent placement at the 5-year follow-up. On the other hand, Shim and colleagues¹⁵ found no significant difference between stent placement and angioplasty alone in terms of the long-term primary patency and suggested that angioplasty should be considered as a first treatment choice for pediatric liver transplant patients.

There is no consensus or conclusive study regarding the choice of balloon-expandable versus self-expandable stents in pediatric patients. Gao and colleagues7 advocated for the use of BES due to the shorter length, which could avoid complications during a future retransplant surgery and facilitates accurate positioning and good radial force. However, other authors have favored self-expandable stents.^15,18 We prefer BES in pediatric patients for the aforementioned reasons and because use of BES allows for a subsequent dilatation if required.

Despite the strengths of our study, including a relatively long follow-up period and the inclusion of pediatric patients comprising half of the population, we acknowledge several limitations. This was a retrospective study with a relatively small number of patients, so risk factor analysis and comparative analysis could not be performed. Nevertheless, these findings contribute valuable insights into the management of PVS in liver transplant recipients.

The endovascular approach is a safe and effective treatment option for management of PVS in liver transplant recipients, with high technical success and long-term patency rates observed in both adult and pediatric populations during the early and late postoperative periods.

Volume: 22 Issue: 1 January 2024 - Supplement - 1

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