Portal vein (PV) hypoplasia is frequently accompanied by biliary atresia. Although various surgical techniques have been developed for the reconstruction of these stenotic PVs, PV complications can still occur [1-7]. Interposition of a homologous vein conduit has been found to be effective for PV reconstruction in pediatric patients with severe PV hypoplasia undergoing liver transplantation (LT) [1,3]. Cold-preserved fresh iliofemoral vein homografts are the best material for interposition vein conduits, but their time of availability is very limited during LT, even in patients undergoing split LT [2]. Although cryopreserved iliac veins can be used as alternative interposition vein conduits for PV reconstruction, various conduit-associated complications, including aneurysm, stricture, and thrombosis, have been reported [8-10]. Thus, interposition using a cryopreserved iliac vein is not recommended for PV reconstruction.

Interventional treatment for PV complications is much more difficult in pediatric than in adult LT recipients because pediatric patients have smaller PVs, and because their physical growth is ongoing [11-15]. Thus, the use of cryopreserved iliac veins is generally not recommended for pediatric LT. However, if a recipient’s PV is severely stenotic, and only cryopreserved vein grafts are available, cryopreserved iliac veins should be considered for use despite the potential risk of PV complications. These conduit-associated complications involving the PV have also been observed after use of cold-preserved fresh vein grafts.

To reduce the risk of these PV complications, a modified patch venoplasty technique was developed, combining the native PV wall and a vein homograft conduit, a technique called modified patch-conduit venoplasty (MPCV). The surgical technique for MPCV was optimized by virtual simulation and applied to pediatric patients undergoing LT for biliary atresia with PV hypoplasia.

This study was performed in accordance with the ethical guidelines of the World Medical Association Declaration of Helsinki 2013. The study protocol was approved by the Institutional Review Board of Asan Medical Center (IRB No. 2023-0527). Informed consent was waived by the IRB.

This study was designed to technically refine venoplasty for conduit interposition during pediatric LT. This study included three parts: a simulation analysis regarding the degeneration sequences of PV conduit veins, virtual optimization of surgical techniques for MPCV, and clinical application of this technique to pediatric patients with biliary atresia.

First, conventional techniques for PV conduit interposition were analyzed, and the process of conduit degeneration was assessed through a virtual simulation. Second, simulation studies were performed to modify current surgical techniques to alleviate the risk of conduit degeneration. Finally, the MPCV technique was applied to pediatric patients with biliary atresia undergoing LT.

Simulation Analysis of the Degeneration of Interposed Conduit Veins Following Conventional PV Reconstruction

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 (Fig. 1A). Because the native PV wall was often too long for such an anastomosis, part of the distal PV wall around the PV bifurcation portion was excised (Fig. 2). As a result, the distal two-thirds of the PV conduit consisted only of the iliac vein homograft, making it vulnerable to degeneration (Fig. 1B). In the present study, we hypothesized that full-length longitudinal inclusion of the native PV wall would buttress the thin-walled homograft conduit, thus providing additional strength resistant to vascular degeneration (Fig. 1B).

Figure 1. Illustration of portal vein (PV) conduit reconstruction. (A) Conventional technique for PV conduit reconstruction. ⓐ Longitudinal incision of the native PV with an inverted-Y shaped extension to the superior mesenteric vein-splenic vein confluence. ⓑ Creation of a small longitudinal slit at the vein conduit. ⓒ Anastomosis of the opened native PV stump and a vein conduit with continuous running sutures. (B) Virtual simulation of the process of vein conduit degeneration. ⓐ Conventional technique with insertion of a triangular native PV wall showing marked shrinkage at the mid-portion of the conduit. ⓑ Modified technique, showing that the inserted rectangular native PV wall works as a buttress to prevent excessive shrinkage at the mid-portion of the PV conduit. (C) Simulation of the procedures for modified patch-conduit venoplasty. ⓐ Full-length longitudinal incision of the native PV to the superior mesenteric vein-splenic vein confluence. ⓑ Complete longitudinal incision of the vein conduit portion to make a rectangular patch. ⓒ Anastomosis of the opened native PV stump and opened vein conduit with continuous running sutures. The native PV wall was inserted into the incised vein conduit like a longitudinal patch. (D) Comparison of the reconstructed PV diameter according to the size of vein patch. ⓐ A narrow patch can enlarge the PV diameter only by 50% or less. ⓑ A patch greater than 1 cm can enlarge the PV diameter two-fold.

Figure 2. Intraoperative photographs showing the conventional technique of portal vein (PV) conduit reconstruction. (A) Deep clamping and (B) longitudinal incision of the native PV to the superior mesenteric vein-splenic vein confluence. (C, D) Anastomosis of the opened native PV stump and a vein conduit with continuous running sutures. (D, E) Some of the distal part of the native PV was not included at the anastomosis to make the conduit suitable for short-length interposition (arrow). (F) Excision of the redundant PV stump.

The native PV wall was incised until the confluence of the superior mesenteric vein and splenic vein was reached. The incised native PV wall was subsequently stretched to act as a backbone. A sizable vein conduit was anastomosed to the proximal border of the PV wall incision. The posterior wall of the vein conduit was incised to open the vein conduit, resulting in a long rectangular patch. The diameter of the reconstructed PV conduit was roughly designed, and the lateral edges of the native PV wall were anastomosed to the incised vein conduit wall (Fig. 1C). The enlarged PV conduit was anastomosed to the graft PV stump. Because this PV reconstruction method was equivalent to a combination of longitudinal patch venoplasty and vein conduit interposition, it was called MPCV.

Clinical Application of Modified Patch-Conduit Venoplasty

MPCV was applied to seven pediatric patients with biliary atresia undergoing LT from April 2022 to March 2023. Their clinical profiles are described in Table 1. A cold-stored fresh iliofemoral vein homograft was used in five patients (e.g., Case 1), a cryopreserved femoral vein homograft was used in one patient (Case 2), and a cryopreserved inferior vena cava patch homograft was used in one patient (Case 3). No patient has experienced any PV complications to date. The surgical procedures applied to the first four patients are described in detail.

Table 1. Profiles of pediatric patients who underwent liver transplantation for biliary atresia with portal vein hyperplasia

Parameter	Value
Recipient
Sex (male:female)	2:5
Age at Kasai portoenterostomy (mo)	1.0 (0.5–2.1)
Age at transplantation (mo)	13 (8–61)
Body weight at transplantation (kg)	10.2 (7.8–18.0)
Preoperative laboratory findings
Total bilirubin (mg/dL)	14.2 (0.9–38.8)
Albumin (g/dL)	2.4 (1.6–3.5)
Prothrombin time (international normalized ratio)	1.38 (0.95–4.30)
Pediatric end-stage liver disease score	9 (4–34)
Donor
Sex (male:female)	2:5
Age (yr)	31 (21–44)
Graft type
Living-donor left lateral section graft	4 (57.1)
Living-donor left liver graft	1 (14.3)
Deceased-donor split left lateral section graft	2 (28.6)
Graft weight (g)	321 (212–432)
Graft-to-recipient weight ratio (%)	2.9 (2.2–4.0)

Values are presented as median (range) or number (%).

Case 1: application to a 5-year-old female patient with biliary atresia and severely stenotic PV

This patient had severe PV hypoplasia and coronary collateral veins due to progression of biliary atresia (Fig. 3). She underwent living-donor LT (LDLT) using a left liver graft from her mother. Although a cold-stored fresh iliac vein conduit 1 cm in diameter was available, it appeared too small for conventional conduit interposition. Thus, MPCV was performed. The recipient PV was longitudinally opened, and the cylindrical iliac vein graft was anastomosed to the proximal border of the PV wall incision. The posterior central wall of the vein conduit was incised to open the vein conduit, thus making a large rectangular patch. The edges of the native PV wall were anastomosed with the incised vein conduit wall. The posterior one-third of the circumference of the PV wall consisted of the native PV wall, whereas the remaining two-thirds of the circumference consisted of the iliac vein homograft. The enlarged recipient PV stump was anastomosed to the graft PV stump (Fig. 3). Early posttransplant computed tomography (CT) showed uneventful PV reconstruction. This patient has been doing well for 12 months after transplantation.

Figure 3. Portal vein (PV) reconstruction in Case 1. Peritransplant computed tomography (CT) findings of the recipient. (A) CT angiography 1 month before transplantation, showing marked shrinkage of the PV (arrow). (B) CT angiography 4 days after transplantation, showing uneventful reconstruction of the PV conduit (arrow); intraoperative photographs of the recipient. (C) The native PV was longitudinally incised, and a vein conduit was anastomosed at the superior mesenteric vein-splenic vein confluence portion. (D) The conduit vein was incised longitudinally (arrow). (E) Running sutures were continued toward the PV bifurcation portion. (F) The redundant conduit portion was excised (dotted line). (G) The reconstructed PV stump was anastomosed with the graft PV. (H) The native PV became the posterior wall of the reconstructed PV (arrow).

Case 2: application to an 8-month-old female patient with biliary atresia and moderately stenotic PV

The PV hypoplasia in this patient was primarily due to underdevelopment of the splanchnic venous system (Fig. 4). She underwent LDLT using a left lateral section graft from her mother. Because the diameter of the recipient PV was much smaller than that of the graft PV, MPCV was performed using a cryopreserved femoral vein homograft. The reconstruction technique described for Case 1 was applied to this patient (Fig. 4). Early posttransplant CT showed uneventful PV reconstruction (Fig. 4). This patient has been doing well for 11 months after transplantation

Figure 4. Portal vein (PV) reconstruction in Case 2. Peritransplant computed tomography (CT) findings of the recipient. (A, B) CT angiography 1 month before transplantation, showing moderate hypoplasia of the PV with underdevelopment of the splanchnic venous system. (C) CT angiography 4 days after transplantation, showing stretching of the reconstructed PV with anastomotic stenosis (arrow). (D) CT angiography 14 days after transplantation, showing smooth streamlined expansion of the reconstructed PV (arrow). Intraoperative photographs of the recipient: (E, F) apparent stretching of the reconstructed PV, consisting of a combination of the native PV wall and a cryopreserved femoral vein. (G) Rightward placement of the graft to assess the degree of PV stretching. This position appeared acceptable for graft accommodation.

Case 3: application to a 20-month-old female patient with biliary atresia and moderately stenotic PV

This patient, who had moderately hypoplastic PV due to biliary atresia, underwent LDLT using a left liver graft from her mother. Because the diameter of the recipient PV was much smaller than that of the graft PV, and because no iliac vein graft was available at the time of operation, MPCV was performed. To enlarge the PV diameter sufficiently large (Fig. 1D), a patch of the cryopreserved inferior vena cava homograft was used. A 1.5-cm-wide rectangular patch was anastomosed from the proximal border of the PV wall incision. The posterior half of the PV wall circumference consisted of the native PV wall, whereas the anterior half consisted of the inferior vena cava homograft (Fig. 5). Early posttransplant CT showed uneventful PV reconstruction. This patient has been doing well for 8 months after transplantation.

Figure 5. Intraoperative photographs of the recipient. (A–B) Case 3. (A) longitudinal incision of the native portal vein (PV). (B) Anastomosis of a cryopreserved inferior vena cava patch (arrow) to the native PV wall and reconstruction of the PV to the graft PV. (C–E) Case 4. (C) The native PV portion (arrow). (D) The native PV became the posterior wall of the PV conduit (arrow). (E) The interposed vein conduit patch became the anterior wall of the PV conduit (arrow).

Case 4: application to a 19-month-old male patient with biliary atresia and moderately stenotic PV

This patient underwent deceased-donor split LT using a left lateral section graft. Because the diameter of the recipient PV was much smaller than that of the graft PV, MPCV was performed. The same MPCV technique used in Case 1 was performed. An iliac vein homograft was recovered from the same deceased donor. The posterior half circumference of the PV wall consisted of the native PV wall, whereas the remaining half circumference consisted of the iliac vein homograft (Fig. 5). Early posttransplant CT showed uneventful PV reconstruction. This patient has been doing well for 7 months after transplantation.

PV reconstruction is one of the most important procedures in pediatric LT because most patients with biliary atresia have PV hypoplasia. To date, several venoplasty techniques using vein patches and conduits, as well as modified reconstruction techniques including oblique or side anastomoses, have been developed for the reconstruction of stenotic PVs [1,3]. Despite these efforts, PV complications have been observed in a considerable proportion of pediatric recipients during long-term follow-up [1,3]. Although radiologic interventions, such as balloon dilatation combined with wall stenting, are effective treatments for PV complications in adult recipients, they are not effective in pediatric recipients, especially in infants. PV stenting in infants is a critical risk factor for PV flow insufficiency, which can lead to retransplantation, because a small-caliber wall stent cannot expand sufficiently during the patient’s physical growth [11-15].

PV reconstruction with an iliac vein homograft conduit is an effective method of PV reconstruction in pediatric recipients with severe PV hypoplasia. We have preferentially used cold-preserved fresh iliofemoral vein homografts because of their high long-term patency rates [2,3]. However, the supply of these fresh homografts is very limited in most transplantation centers worldwide. LDLT has often been postponed at our center until the availability of deceased donors capable of providing fresh vein homografts. A timely supply of fresh vein homografts is not simple, even during split LT, because the left lateral section graft is usually recovered in advance, as in LDLT, in most Korean centers [16].

Although our center has used cryopreserved iliac vein homografts for middle hepatic vein reconstruction during LDLT using a modified right liver graft [17], cryopreserved iliac vein grafts have rarely been used for PV reconstruction in either adult or pediatric recipients because of the risk of various conduit-associated complications, such as aneurysm, stricture, and thrombosis. The use of cryopreserved iliac vein grafts should be considered, however, in recipients with severely stenotic PVs when only cryopreserved iliac vein grafts are available. Because the walls of cryopreserved iliofemoral vein grafts are weakened during the freeze-thaw process, these grafts are vulnerable to degeneration, leading to luminal stenosis [18]. The native femoral vein portion has a relatively thick wall because it is located at the inguinal area, permitting leg flexion-extension. Thus, a cryopreserved femoral vein would be preferable to a cryopreserved iliac vein for PV interposition. The same preference is applicable to fresh iliofemoral vein homografts, as shown in the patients described in this series.

PV interposition grafts carry the risk of PV stenosis regardless of fresh cold storage or cryopreservation. After experiencing a few patients with interventional balloon dilatation for late-onset stenosis of the PV conduit, we thought that technical modifications were necessary to reduce the risk of PV conduit stenosis. This realization prompted the development of the MPCV technique.

The results of this study suggest that the current anastomosis technique at the proximal PV portion is satisfactory; thus, no technical modification was required [3]. The simulation study regarding the sequence of vein conduit degeneration indicated that full-length inclusion of the native PV wall could help prevent vascular degeneration. The basic concept of longitudinal inclusion of a rectangular patch is similar to that of conventional patch venoplasty. In the MCPV technique described in this study, the native PV wall was converted into a long rectangular patch, which acts as a backbone of the reconstructed PV conduit. A longitudinal incision on the vein conduit converted the cylindrical vein into a large-sized vein patch. Thus, both cylindrical veins and opened vein patches could be similarly useful for MCPV. Because the native PV was fully preserved as a part of the posterior PV wall, longitudinal redundancy and unwanted rotation of the reconstructed PV were effectively prevented in MCPV, similar to native PV without stenosis.

Although patch venoplasty for a stenotic PV is one of the standard techniques [1,19], it is necessary to evaluate its effectiveness. Many illustrations and intraoperative photographs have depicted the insertion of a narrow rectangular patch [1], but such a narrow patch can increase the PV diameter only by one-third of the patch width because it becomes a part of the PV circumference. A wide patch is required to increase the PV diameter sufficiently, as shown above in Case 3. Even in pediatric LT, a vein patch wider than 1 cm should be used for patch venoplasty of the recipient PV.

Vein allografts have been used in the present study. In contrast, a Chinese high-volume pediatric LT center presented a technique for autogenous PV patch plasty [19]. Vessel patches were procured from the left branch or the bifurcation of the right branch and left branch of the PV in the native liver. Then, the PVs were enlarged by suturing the patches along the longitudinal axis from the confluence of the PV and coronary vein. Fifteen out of 16 patients showed good PV flow during operation, while one patient required stent placement, and no PV complications were detected at a median follow-up of 11 months [19]. However, in real-world practice, it is difficult to obtain a wide PV patch from the native liver. If a vein allograft is available, its use would be more practical than using an autogenous PV patch.

To date, MCPV has been applied to seven patients during 1 year, with none experiencing PV complications. Although the number of patients is too small and the follow-up period too short to show that MCPV is superior to conventional PV interposition, preservation of the entire native PV wall likely has theoretical advantages, including greater resistance to vascular degeneration, maintained alignment of the native PV axis, and prevention of PV redundancy. Our LT center has therefore adopted MCPV as the primary technique for PV reconstruction in pediatric recipients with PV hypoplasia.

This study has some limitations of note. First, the number of study patients was small and the follow-up period was relatively short considering the long-term growth of the pediatric patients. Second, the mechanisms of conduit stenosis were based on virtual simulative analysis instead of imaging study-based visualization primarily due to the infrequent performance of dynamic CT scans in young pediatric patients.

In conclusion, this study describes a newly devised surgical technique for MCPV that can replace the conventional PV interposition technique for pediatric patients with PV hypoplasia. Although the development of this technique was based on a virtual simulation analysis, and the number of patients treated to date with this technique was small, MCPV has replaced the conventional PV interposition technique at our LT center. These findings suggest that MCPV can be a surgical option for reliable PV reconstruction using either fresh or cryopreserved vein homografts in pediatric patients undergoing LT.

Conflict of Interest

No potential conflict of interest relevant to this article was reported.

Funding/Support

This study was supported by research grant from the Korean Society for Transplantation (2023-00-01002-009).

Author Contributions

Conceptualization: SH. Data curation: JMN, GCP, HK, SG, JP. Formal analysis: SH, JMN. Methodology: JMN, SH, KMK, SHO. Project administration: SH. Visualization: SH. Writing–original draft: SH, JMN. Writing–review & editing: SH. All authors read and approved the final manuscript.