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 treatments, especially those with hyperammonemia, portosystemic encephalopathy, hepatopulmonary syndrome, hepatic tumors, or intractable complications [1-4].

The 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]. Since a liver with CAPV does not have sufficient portal inflow, the hepatic arterial flow is the main blood inflow. 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 with resultant low pediatric end-stage liver disease (PELD) scores. Therefore, with very low chances of deceased donor liver transplantation (DDLT) 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 left liver graft for CAPV with splenorenal shunt.

A 6-year-old boy was referred to our hospital due to the diagnosis of CAPV with portal hypertension. At the 1 year of age, abdominal distension and pancytopenia were observed. Subsequent imaging studies showed cavernous transformation of the portal vein with multiple collateral veins, splenomegaly, and heterogeneous attenuation of the hepatic parenchyma (Fig. 1A). At the age of 3 years, esophageal varix occurred with aggravation of splenomegaly. The patient could not have a Rex shunt operation due to poor development of the intrahepatic portal vein system (Fig. 1B, C). Thus, this patient was enrolled on the DDLT waitlist under outpatient clinic follow-up. At the age of 6 years, endoscopic gastroduodenoscopy showed aggravation of esophageal and gastric varix. Imaging studies also showed portal hypertension progression (Fig. 1D). Considering the low PELD score (0.9 points) in the pandemic era of coronavirus-19 (COVID-19), it was difficult to expect timely performance of DDLT. Thus, we decided to perform LDLT at the age of 6 years with a bodyweight of 25 kg.

Figure 1. Pretransplant computed tomography findings of the recipient. Congenital absence of the portal vein was identified at the age of 1 year (A), and portal hypertension with collateral formation and splenomegaly was progressed at the age of 2 years (B), 4 years (C), and 6 years (D).

The donor was the 31-year-old mother of the patient. The left liver volume was determined as 450 mL on computed tomography volumetry. The recipient’s operation was initiated with intraoperative cine-portogram (IOCP) through the inferior mesenteric vein to identify the splanchnic venous system. The initial IOCP showed weak hepatopetal flow through the variceal collaterals and the majority of blood flow was drained into the well-developed splenorenal shunt (Fig. 2). During hepatic hilar dissection, the recipient’s native portal vein was not identified and there was development of variceal collaterals around the common bile duct (Fig. 3). The donor’s left liver graft had two hepatic arteries, thus the recipient hepatic artery branches were meticulously dissected. The splenic vein was isolated just distal to the insertion site of the inferior mesenteric vein (Fig. 4). The left renal vein was also dissected and encircled with a vessel loop.

Figure 2. First intraoperative cine-portogram. It was taken through the inferior mesenteric vein (A). A weak hepatopetal flow through the variceal collateral was identified (B), and the majority of splanchnic blood flow was drained into the splenorenal shunt (B–D).

Figure 3. Intraoperative photographs for hepatoduodenal ligament dissection and formation of new portal vein conduit. (A) There were variceal collaterals around the common bile duct without native portal vein. (B) The common bile duct (arrow) was transected and weak venous outflow was drained from the collateral veins. (C) The largest collateral vein exposed at the common bile duct was side-clamped. (D) A 4-cm-long iliac vein homograft was anastomosed to the collateral vein as an end-to-side fashion.

Figure 4. Intraoperative photographs of the hepatic vein venoplasty and reconstruction. (A, B) The graft hepatic vein was enlarged through unification venoplasty with a small superficial left hepatic vein. (C, D) The hepatic vein orifices at the recipient inferior vena cava was unified and reconstructed by continuous sutures after size matching.

The collateral-containing common bile duct was transected to evaluate the portal vein outflow, and weak venous outflow was observed. The venous outflow was increased after proximal splenic vein clamping. A similar amount of venous outflow was also observed after left renal vein clamping. Thus, we decided to perform proximal splenic vein ligation. The collateral vein exposed at the common bile duct was the largest, thus it was used as an inflow source. A 4-cm-long iliac vein homograft was anastomosed to the collateral vein in an end-to-side fashion (Fig. 3). The venous outflow drained from the conduit was increased compared with that from the common bile duct end.

After the recipient’s operation, a left liver graft measuring 420 g at the back table was recovered, yielding a graft-to-recipient weight ratio of 1.7%. The graft hepatic vein was enlarged through unification venoplasty with a small superficial left hepatic vein (Fig. 5A, B).

Figure 5. Intraoperative photograph showing isolation of the splenic vein (arrow) just distal to the inferior mesenteric vein insertion site.

After the native liver was removed, the hepatic vein orifices at the recipient IVC were unified. The graft hepatic vein was reconstructed by continuously suturing with 5-0 polydioxanone (Fig. 5C, D). The interposed iliac vein conduit was anastomosed with the graft portal vein after distance matching after 2-cm-long excision of the conduit (Fig. 6). Thereafter, graft reperfusion was initiated. The proximal splenic vein was securely ligated, and a subsequent marked increase in the portal blood flow was observed (Fig. 7). Surgical microscopy was used for the reconstruction of the graft left and middle hepatic arteries. Second IOCP was performed through the inferior mesenteric vein, in which the portal blood flow was well maintained (Fig. 8A). Two collateral veins through the coronary collaterals were identified, thus embolization with multiple coils was performed not to leave residual collaterals (Fig. 8B–D). The splenic artery was ligated to control splenomegaly. Roux-en-Y hepaticojejunostomy was used for biliary reconstruction.

Figure 6. Intraoperative photographs of graft portal vein reconstruction. (A, B) The portal vein conduit was anastomosed with the graft portal vein after distance matching. (C, D) The length of the interposed portal vein conduit was adjusted not to be redundant.

Figure 7. Intraoperative photograph showing the fully expanded portal vein conduit.

Figure 8. Second intraoperative cine portogram. (A) Portal blood flow was well maintained. (B, C) Two collateral veins through the coronary collaterals were identified and embolization with multiple coils was performed (arrows). (D) No residual collateral was identified.

The pathology report of the explant liver showed a non-cirrhotic liver with dilatation of the portal veins with herniation into hepatic parenchyma and replacement by numerous small vein radicles, and extrahepatic portal vein thrombosis and cavernous transformation. There was absence of portal inflammation, bile duct damage, lobular inflammation, and fibrosis. These findings were suggestive of hepatoportal sclerosis (clinically idiopathic portal hypertension) associated with extrahepatic portal vein obstruction (Fig. 9).

Figure 9. Gross photographs of the explant liver.

The patient recovered from the LDLT operation. The reconstructed portal vein was maintained well without any hemodynamic abnormalities (Fig. 10, 11). This patient has been doing well for 2 months after the LDLT.

Figure 10. Fig. 10 . Posttransplant Doppler ultrasonography at 3 days after transplantation. The contour of portal vein anastomosis showed slight stenosis at the anastomosis site. The portal vein blood flow was well maintained.

Figure 11. Fig. 11 . Posttransplant scan taken at 5 days after transplantation. (A) The graft portal vein was well perfused. (B) The portal vein conduit was well visualized (arrow). The enlarged spleen was partially infarcted due to splenic artery ligation. (C, D) Splenorenal collaterals disappeared nearly completely.

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 portal and hepatic veins [6]. Extrahepatic PCS is divided into type I and type II according to intrahepatic portal venous supply [7]. Type I PCS is an extrahepatic shunt without a patent intrahepatic portal vein. Thus, the entire mesenteric venous blood drains directly into the systemic veins such as the IVC and the left renal vein. This type is called CAPV. Type II PCS is an extrahepatic shunt with a patent intrahepatic portal vein. Thus, the patent portal vein perfuses the liver and the shunt vessel drains some mesenteric venous blood into the systemic circulation. Our present patient had type I PCS. Although there were variceal collateral veins around the common bile duct, the majority of the splanchnic blood flow was drained through the splenorenal shunt.

The standard treatment for CAPV has not been established yet. Although PCS can be accompanied by hyperammonemia, the majority of the patients with PCS have no signs of encephalopathy. Such patients only show slightly abnormal liver function test results. The majority of patients with CAPV receive conservative medical treatment for hyperammonemia, and 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. Notably, CAPV might be accompanied by hepatopulmonary syndrome. Surgical treatment for CAPV can also be indicated for hepatopulmonary syndrome [8,9].

In most cases, 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 an atypical case of CAPV showing portal hypertension with gastric and esophageal varix, which was the primary cause of DDLT [10]. In our previous case that underwent LDLT for CAPV, no portal hypertension and collaterals were observed [11]. On the contrary, the present case showed noticeable portal hypertension with formation of esophageal and gastric varix, combined with marked splenomegaly although overt development of splenorenal shunts.

LT is indicated for most patients with type I PCS since surgical reconstruction of the portal vein structures of the native liver is impossible, as shown in the present patient. Although LT for symptomatic CAPV has been reported in the literature [1-3,5,9,11-14], techniques for portal vein reconstruction have not been well established yet. There are two methods of portal vein 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 [2,12]. The second method is to use a venous interposition graft through an end-to-side anastomosis to the PCS [3,5]. In our three CAPV cases, including the present case, the portal vein stump was absent [10,11], 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. In the present case, to obtain a suitable vein homograft, we had to wait for two months before the LDLT operation.

In the present case, an abundant splenorenal shunt was observed. If it was not ligated, the majority of the splanchnic blood flow would be bypassed through the splenorenal shunt, which could result in portal flow insufficiency. To restore sufficient portal blood flow, we performed ligation of the proximal splenic vein. This technique is uniquely effective when the blood flow source of the splenorenal shunt is the splenic vein. We previously presented proximal splenic vein embolization (PSVE) to interrupt complicated large splenorenal shunts in adult LDLT [15]. Ten patients underwent PSVE as an additional secondary method because of portal steal syndrome through the remaining splenorenal shunt after surgical interruption and/or embolization, and 3 patients underwent PSVE only as a primary method of splenorenal shunt interruption. In all the 13 patients, portal steal completely disappeared after PSVE. All the patients recovered with satisfactory regeneration of the partial liver graft without reappearance of the portosystemic collaterals, and there were no procedure-related complications. Thus, we think that PSVE is an effective and safe procedure for securing adequate portal flow without portal steal for patients with complicated large splenorenal shunt arising from multiple sites of the splenic vein or escaping to multiple terminal ends [15].

In the present case, we performed direct IOCP through the inferior mesenteric vein just after laparotomy. Such a splanchnic venogram worked as an accurate roadmap to design the portal vein reconstruction and interruption of collateral drainage. We directly exposed the splenic vein and a test clamp was performed to check the portal outflow from the interposed portal vein conduit. The amount of portal blood outflow was comparable between the splenic vein clamping and left renal vein clamping. Proximal splenic vein ligation is more physiologic than left renal vein ligation [15,16], therefore splenic vein was securely ligated just distal to the inferior mesenteric vein insertion site. The splenic artery was also ligated to decompress splenomegaly. After portal reperfusion, the second IOCP showed the presence of coronary collateral around the gastric lesser curvature, which was interrupted with coil embolization. IOCP is a useful method for identifying and embolizing residual portosystemic collateral veins in young pediatric patients who undergo LT [17].

In conclusion, since CAPV patients can have several vascular anomalies, such combined vascular anomalies should be thoroughly assessed before and during the LT operation. Individualized portal vein reconstruction with homograft vein interposition combined with IOCP is an effective technique with satisfactory results.

There was no funding related to this study.

All authors have no conflicts of interest to declare.

Conceptualization: JMN, S Hwang. Data curation: All. Methodology: JMN, S Hwang, GCP, KMK. Visualization: JMN, S Hwang. Writing - original draft: All. Writing - review & editing: All.