Congenital absence of the portal vein (CAPV) is a rare venous malformation in which the mesenteric venous blood drains directly into the systemic circulation. The majority of CAPV patients show no signs or symptoms of portosystemic encephalopathy. They only show slightly abnormal liver function test results. Liver transplantation (LT) is indicated for patients with symptomatic CAPV refractory to medical treatment [1-4].

Congenital portocaval shunt (PCS) drains the entire mesenteric venous blood either directly into the inferior vena cava (IVC) or through the left renal vein via the splenorenal shunt, therefore preventing portal hypertension and collateral circulation [3-5]. However, some CAPV patients show evidence of portal hypertension, such as esophageal varix. If a patient does not respond to medical treatment, LT should be taken into account. Liver function profiles of patients with CAPV are not severely impaired, thus usually show low Pediatric End-stage Liver Disease scores. Because of the very low chances of deceased donor liver transplantation in the current Korean setting, patients with CAPV need to be prioritized for living donor liver transplantation (LDLT). We herein present a case of pediatric LDLT using a modified right liver graft with direct collateral portal vein anastomosis for CAPV.

A 12-year-old boy was referred to our hospital due to abdominal pain and splenomegaly. He was born in full-term spontaneous vaginal delivery. He had been doing well after birth until the age of 11 years. Imaging studies showed cavernous transformation of the portal vein (PV) trunk and intrahepatic portal veins, splenomegaly and esophageal varices, suggesting CAPV (Fig. 1). Endoscopic gastroduodenoscopy showed esophageal and gastric fundus varices. Endoscopic band ligation of the esophageal varix was performed uneventfully (Fig. 2). He was also diagnosed with hepatopulmonary syndrome grade 1.

Figure 1. Pretransplant computed tomography findings of the recipient. (A–C) The native portal vein was absent with the development of cavernous, transformed collateral veins. (D) The hepatic arteries were normal without anatomical variation.

Figure 2. Preoperative endoscopic varix ligation performed at three months before transplantation. (A, B) Esophageal and gastric fundic varices were identified. (C) Endoscopic band ligation of the esophageal varix was performed. (D) Regression of varix was identified at 1 week after band ligation.

Timely allocation for deceased donor LT was not expected in the Korean setting due to the low Pediatric End-stage Liver Disease score. Thus, we decided to perform LDLT at the age of 12 years with a body weight of 44 kg and a height of 150 cm.

The donor was the 41-year-old father of the patient. The right and left hemiliver volumes were determined as 795 mL and 538 mL, respectively, on computed tomography volumetry (Fig. 3). Considering the anatomical features of the cavernous-transformed portal vein collateral and two left hepatic arteries, we decided to use a modified right liver graft.

Figure 3. Computed tomography findings of the donor before donation surgery (A) and at one week after right liver donation (B).

The recipient’s operation was performed according to the standard procedure of pediatric LDLT. During hepatic hilar dissection, the recipient’s native PV was absent with cavernous-transformed portal vein collaterals (Fig. 4). The recipient hepatic artery branches were meticulously dissected.

Figure 4. Intraoperative photographs of recipient hilar dissection. (A) The portal cavernous collateral vein was isolated. (B, C) This collateral vein was transected with distal cutting of the collateral vein branches. (D) The transected vein was gently clamped to prevent iatrogenic injury.

A right liver graft without middle hepatic vein trunk was harvested, with a graft weight of 640 g at the back table, equivalent to a graft-to-recipient weight ratio of 1.45%. There were three small branches of the middle hepatic vein (MHV) at the graft liver cut surface. A 12-cm-long cryopreserved iliac vein graft was prepared at the institutional tissue bank. This vein allograft was used for MHV reconstruction at the back table (Fig. 5).

Figure 5. Intraoperative photographs of graft implantation. (A) The right liver graft was prepared after vein interposition of the middle hepatic vein branches and patch venoplasty of the right hepatic vein orifice. (B) The right hepatic vein was reconstructed under total clamping of the inferior vena caca. (C) The interposed vein conduit was reconstructed to the left-middle hepatic vein trunk stump. (D) A branch patch was made at the end of the portal cavernous collateral vein. (E–G) The posterior was anastomosed with a running suture with insertion of a vein patch to prevent stitch-inducing wall tearing. (H) The anterior wall was redundantly anastomosed to provide a sufficient growth factor.

The diameter and length of the recipient PV collateral vein appeared to be large and long enough to perform direct anastomosis (Fig. 4). The PV collateral vein was gently clamped with a Nelaton catheter-shoed vascular clamp to prevent iatrogenic injury, and the most proximal portions of the PV collateral vein were then transected to use as a branch patch. After supra- and infra-hepatic clamping of the inferior vena cava, the native liver was removed. After longitudinal extension of the right hepatic vein orifice, the graft right hepatic vein was reconstructed. The interposed MHV conduit was reconstructed with the stump of the middle-left hepatic vein common trunk (Fig. 5).

The edges of the PV collateral vein were stretched with 6-0 Prolene and trimmed to use for a branch patch. Conventional PV reconstruction using a single 6-0 Prolene was started with the insertion of a vein patch at the posterior suture line to prevent stitch-inducing wall tearing. The PV anterior wall was redundantly anastomosed to provide a sufficient growth factor (Fig. 5). Thereafter, graft reperfusion was initiated. A coronary collateral vein and a splenorenal shunt vein were directly ligated after separate isolation. Surgical microscopy was used for the reconstruction of the graft right hepatic artery. Roux-en-Y hepaticojejunostomy was used for biliary reconstruction.

The pathology report of the explant liver showed marked dilatation of PVs with herniation into hepatic lobules, consistent with porto-sinusoidal vascular disease (hepatoportal sclerosis; Fig. 6). These findings were consistent with the pathologic changes associated with CAPV.

Figure 6. Gross photograph of the explant liver.

The patient and donor recovered from the LDLT operation. The reconstructed graft hepatic vein and portal vein were maintained well without hemodynamic abnormality (Fig. 7). This patient has been doing well for 2 months after the LDLT.

Figure 7. Posttransplant computed tomography scan taken at four days after transplantation. (A, B) Uneventful anastomosis of the graft portal vein was identified. (C, D) Unusual running course of the portal collateral vein was identified (arrows).

CAPV is a rare venous malformation in which the mesenteric venous blood drains directly into the systemic circulation. There are two types of congenital PCS: intrahepatic PCS and extrahepatic PCS. Intrahepatic PCS is localized between the PV and hepatic veins [6]. Extrahepatic PCS is divided into type I and type II according to the intrahepatic portal venous supply [7]. Type I PCS is an extrahepatic shunt without a patent intrahepatic portal vein. Thus, the entire mesenteric venous blood flow drains directly into the systemic veins such as the inferior vena cava and the left renal vein. This type is called CAPV. Type II PCS is an extrahepatic shunt with a patent intrahepatic PV. Our present patient had type I PCS with noticeable development of variceal collateral veins.

The standard treatment for CAPV has not yet been established. Although PCS can be accompanied by hyperammonemia, the majority of the patients with PCS show no signs of encephalopathy. Such patients only show slightly abnormal liver function test results. Our present patient showed only mild elevation of liver enzymes. The majority of patients with CAPV receive conservative medical treatment for hyperammonemia, while only a small portion of patients with CAPV require surgical treatments, including LT. Surgical treatment is indicated when hyperammonemia or portosystemic encephalopathy is refractory to medical treatment [8,9].

Pretransplant imaging studies in CAPV patients demonstrate a large communication vein to the IVC through the splenorenal shunt, thus no evidence of portal hypertension has been observed in the imaging studies or intraoperative findings. However, we have previously reported two atypical cases of CAPV showing portal hypertension with gastric and esophageal varix [10,11]. In the present case, as in our previous cases, portal hypertension and collateral veins were observed. To prevent variceal bleeding, endoscopic variceal ligation was performed in the present patient, as in the usual adult patients with advanced liver cirrhosis [12].

Since surgical reconstruction of the portal vein structures of the native liver is impossible, LT is indicated for most patients with type I PCS. Although LT for symptomatic CAPV has been reported in the literature [1-3,5,9,11-16], techniques for portal vein reconstruction have not yet been well established. There are two methods of PV reconstruction in LT for CAPV. The first method is to anastomose the PCS directly to the graft portal vein in an end-to-end fashion [2,14]. The second method is to use a venous interposition graft through an end-to-side anastomosis to the PCS [3,5]. In our four CAPV cases, the PV stump was absent [10,12,13,17], thus direct anastomosis was technically impossible. Therefore, we used vein conduit interposition as an end-to-side anastomosis to the PCS. The prerequisite for reconstruction with a vein conduit is the availability of an adequate vein homograft. Meanwhile, in the present case, the length of the PV collateral vein was rather long enough for direct anastomosis, so the interposition of a vein allograft segment was not necessary.

In the present case, we did not perform intra-operative cine-portography because collateral veins were directly ligated after identification of these vessels at the pretransplant computed tomography images. Intraoperative splanchnic venogram works as an accurate roadmap to design the PV reconstruction and interruption of collateral drainage [11,18].

In conclusion, since CAPV patients show various types of PCS, individualized PV reconstruction with or without homograft vein interposition should be performed after thorough anatomical assessment before and during the LT operation.

There was no funding related to this study.

All authors have no conflicts of interest to declare.

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