Portal vein (PV) hypoplasia is frequently accompanied by biliary atresia. Interposition of a homologous vein conduit has been shown to be effective for PV reconstruction in pediatric patients with PV hypoplasia undergoing liver transplantation (LT) [1-4]. While iliac vein homografts can be used as alternative interposition vein conduits for PV reconstruction, various conduit-associated complications, including aneurysm, stricture, and thrombosis, have been reported [4,5]. These conduit-associated PV complications have been observed after cryopreserved vein grafts, but they can occur after the use of cold-preserved fresh vein grafts. Interventional treatment for PV complications is much more difficult in pediatric than in adult LT recipients because pediatric patients have smaller-sized PVs, and because their physical growth is ongoing [6-10]. We herein present a case of pediatric living-donor liver transplantation (LDLT) showing late-onset stenosis of the interposed PV conduit, which was treated by endovascular stenting.

The patient was a 11-month-old 7.8 kg-weighing female infant with hepatoblastoma. She was born at 39 weeks through normal full-term spontaneous delivery. At 7 months after birth, a series study on gastrointestinal symptoms led to the diagnosis of hepatoblastoma. This tumor was classified as pediatric liver tumor staging (PRETEXT grouping system) stage IV. She underwent systemic chemotherapy and the tumor size was gradually reduced (Fig. 1). However, some parts of the tumor remained as partial response, hence we decided to perform LDLT to remove the tumor completely. The recipient native PV appeared hypoplastic on pretransplant imaging studies (Fig. 2).

Figure 1. Pretransplant computed tomography findings of the recipient. (A) At five months before transplantation, huge multiple tumors occupied the whole liver. (B) At one month before liver transplantation, the tumor size was markedly reduced.

Figure 2. Pretransplant computed tomography findings of the recipient. (A) The portal vein appears hypoplastic. (B) Relative underdevelopment of the splanchnic venous system was identified.

The donor was the 34-year-old mother of the patient. Donor operation was performed to procure the left lateral section (LLS) graft. After parenchymal transection, the LLS volume was assessed by manual palpation, and in situ non-anatomical size reduction was performed to remove the flat lateral portion. The reduced LLS graft was harvested according to the standard procedure. The weight of the graft was 235 g, which was equivalent to a graft-to-recipient weight ratio of 3.0%. The graft hepatic vein was enlarged through incision-and-patch plasty using a small patch of iliac vein homograft.

Recipient liver dissection was performed according to the standard procedures of pediatric LDLT. Recipient hepatectomy was performed according to the standard procedures of pediatric LDLT. An external iliac vein conduit homograft was anastomosed to the hypoplastic recipient PV.

After finishing venoplasty in the recipient and the graft, the reduced LLS graft was temporarily placed at the abdomen to determine the implantation location. The graft was partially accommodated in the right subphrenic fossa, hence we decided to perform dextroplantation of the graft. Graft implantation was performed in the order of hepatic vein, portal vein, hepatic artery, and Roux-en-Y hepaticojejunostomy. The graft portal vein was anastomosed with the interposed external iliac vein conduit homograft (Fig. 3). The abdominal wall wound was primarily closed under minimal tension. The resected liver specimen showed multiple viable hepatoblastomas measuring up to 5 cm in size.

Figure 3. Intraoperative photographs showing dextroplantation of the reduced left lateral section graft. (A, B) The portal vein is reconstructed with the interposed vein homograft. (C) The flat lateral part of the graft was resected and a small medial portion of segment III was removed. (D) The graft is partially accommodated in the right subphrenic fossa through dextro-rotation.

The patient recovered uneventfully. Computed tomography images taken at four days after the transplantation revealed that the reduced LLS graft was well accommodated within the right subphrenic fossa with visualization of smooth PV reconstruction (Fig. 4). She had undergone scheduled adjuvant chemotherapy.

Figure 4. Posttransplant computed tomography findings taken at four days after transplantation. The elongated interposed portal vein is visualized (arrow) without vascular complication.

At 4 months after transplantation, the liver was firmly palpated, thus she was readmitted for work-up. Imaging studies revealed luminal obliteration of the interposed PV conduit (Fig. 5). Because percutaneous radiologic intervention did not appear to be feasible considering the small body size, we performed open laparotomy. A small superior mesenteric vein branch was isolated and a cannula was inserted. The interposed PV graft was nearly completely obliterated, hence meticulous dilatation using balloons of 7 mm and 5 mm was performed (Fig. 6). Follow-up Doppler ultrasonography showed the persistence of PV stenosis. At 4 days after balloon dilatation, the abdomen was opened again, and a 10 mm×40 mm-sized endovascular stent was inserted (Fig. 7). The patient has been doing well for 3 years 6 months after transplantation with patent PV flow on follow-up Doppler ultrasonography (Fig. 8).

Figure 5. Posttransplant computed tomography findings taken at four months after transplantation. (A) The interposed portal vein conduit is completely obliterated (arrow). (B) Some collateral veins are developed (arrow).

Figure 6. Procedures of open balloon dilatation. (A) A small superior mesenteric vein branch was isolated and a cannula was inserted across the obliterated portal vein conduit. (B, C) Meticulous dilatation using balloons of 7 mm and 5 mm was performed. (D) The portal vein conduit was opened, but significant luminal stenosis was left.

Figure 7. Procedures of open endovascular stenting. (A) A cannula was inserted across the stenotic conduit. (B, C) A 10 mm×40 mm-sized endovascular wall stent was inserted. (D) The portal vein conduit was widely expanded.

Figure 8. Posttransplant Doppler ultrasonography taken at three years after transplantation showing good flow within the portal vein endovascular stent.

PV reconstruction is one of the most important procedures in pediatric LT because most patients with biliary atresia have PV hypoplasia. Various venoplasty techniques using vein patches and conduits have been developed for reconstruction of stenotic PVs [1,3]. PV reconstruction with an iliac vein homograft conduit is an effective method of PV reconstruction in pediatric recipients with severe PV hypoplasia. The interposed vein homograft provides wide tolerance to anastomotic stenosis and twisting of the PV.

Meanwhile, PV complications have been observed in a small proportion of pediatric recipients during long-term follow-up [1,3]. Although radiologic intervention such as balloon dilatation combined with wall stenting is an effective treatment for PV complications in adult recipients, it is not effective in pediatric recipients, especially in infants. PV stenting in infants is a critical risk factor of PV flow insufficiency leading to retransplantation because a small-caliber wall stent cannot expand sufficiently during the physical growth of the patient [6-10]. To induce full expansion of PV stent with patient’s growth, a 10 mm-sized wall stent was inserted in the present case.

Interposition of PV conduit has the risk of PV stenosis regardless of fresh cold storage or cryopreservation of the vein homografts. We have occasionally experienced late-onset stenosis of the interposed vein conduit, as shown in the present case. Our conventional technique for PV conduit reconstruction included using the native PV wall as the distal one-third of the reconstructed PV conduit, thereby creating a smooth streamlined cone-shaped transition between the superior mesenteric vein-splenic vein confluence and an iliac vein conduit. The distal two-thirds of the PV conduit consisted only of the iliac vein homograft [3]. We presume that such structure might be closely associated with conduit degeneration.

After experiencing a few pediatric patients with interventional balloon dilatation for late-onset stenosis of PV conduit, including the present case, we think that it is necessary to make some technical modifications to reduce the risk of PV conduit stenosis. One of our current solutions is inclusion of the native PV wall at the PV conduit, similar to longitudinal patch venoplasty. Because the native PV was fully preserved as a part of the posterior PV wall, longitudinal redundancy and unwanted rotation of the reconstruct PV would be effectively prevented.

In conclusion, interposition of PV conduit carries the risk of PV conduit stenosis, hence it is necessary to perform regular follow-up studies for PV patency for prolonged period. Radiological intervention is the only therapeutic treatment for such PV conduit stenosis.

There was no funding related to this study.

All authors have no conflicts of interest to declare.

Conceptualization: JMN, SH. Data curation: All. Formal analysis: JMN, SH. Investigation: All. Methodology: All. Supervision: SH. Writing - original draft: All. Writing - review & editing: JMN.