EXPERIMENTAL AND CLINICAL TRANSPLANTATION

In patients with biliary atresia, portal vein problems may cause challenges for liver transplant. Interposition grafts have been used for vascular anastomoses in transplant recipients with varied success. A cryopreserved iliac artery graft was used for the reconstruction of the portal vein in a 29-month-old infant with biliary atresia. At 17 months after transplant, she developed upper gastrointestinal bleeding that was caused by portal vein occlusion because of vascular calcifications in the graft. Upper gastrointestinal endoscopy showed esophageal varices with fresh bleeding, and the varices were band ligated. At 3 months after the bleeding episode, the patient was asymptomatic and biochemical tests were normal. In summary, liver transplant with cryopreserved iliac artery graft may be complicated by calcifications and portal vein occlusion, and caution is advised in using this graft material for portal vein anastomoses.

Key words : Biliary atresia, Complications, Hepatic failure, Pediatric

Biliary atresia is the most common indication for liver transplant in children.¹ Living-donor liver transplant is a lifesaving procedure for these children who otherwise would have to wait for a deceased-donor organ, with the risk of death while waiting. The major size mismatch between adult graft vessels and the native vessels of pediatric recipients, many who have undergone previous surgery, may cause technical difficulties in the reconstruction of arterial and portal flow. Biliary atresia also can present in the syndromic form, and anatomic anomalies of the portal vein may cause technical problems that are not associated with previous surgery.²

Various graft materials have been used to establish flow in patients with native vessels that are unsuitable for anastomoses. These materials provide additional length or increased recipient vessel diameter, but the long-term patency may be a limiting factor when using these materials. A cryopreserved iliac artery graft may be used for arterial or venous reconstruction when no other suitable graft material is available.^3,4

We treated a patient with biliary atresia who had a liver transplant with a cryopreserved iliac artery graft that was complicated by postoperative calcification of the graft and portal vein obstruction.

A 29-month-old female infant who had biliary atresia and Kasai portoenterostomy at age 3 months underwent living-donor liver transplant with a left lateral segment graft from her mother. The graft-to-body weight ratio was 2.6%. There were technical difficulties including size mismatch and inability to obtain portal flow after repeated attempts at end-to end anastomosis of the graft portal vein and recipient main portal trunk. Portal flow was accomplished using a blood-type compatible cryopreserved iliac artery interposition graft between the graft portal vein and the confluence of the recipient superior mesenteric and splenic veins. Intraoperative Doppler ultrasonographic examination was performed at the end of surgery, in accordance with institutional protocol, which confirmed patency of all graft vessels. Postoperative immunosuppression included tacrolimus, mycophenolate mofetil, and methylpred-nisolone. Daily Doppler ultrasonographic examination showed good flow in the portal vein, hepatic vein, and hepatic artery. The patient recovered without any perioperative complications and was discharged on postoperative day 8 with improving laboratory values.

At outpatient follow-up, the liver biochemistry tests returned to normal levels by postoperative day 14. Biochemical and physical findings were satisfactory on subsequent regular visits to the outpatient clinic.

At 7 months after transplant, the patient was admitted to the hospital because of elevated aspartate aminotransferase (5.26 μkat/L [315 U/L]), alanine aminotransferase (4.24 μkat/L [254 U/L]), and alkaline phosphatase (24.3 μkat/L [1454 U/L]). Doppler ultrasonographic examination of the graft did not reveal any vascular abnormalities. Liver biopsy revealed no evidence of acute cellular rejection. The finding of mild lobular activity was nonspecific, and clinical correlation with signs of infection or drug toxicity was recommended. Serum Epstein-Barr virus DNA levels were 12 735 copies/μL and intravenous ganciclovir treatment was initiated (5 mg/kg every 12 h for 7 d). The patient was discharged on oral valganciclovir (total antiviral treatment, 90 d). Liver biochemistry tests returned to normal and Epstein-Barr virus DNA levels were < 2000 copies/μL by the end of antiviral treatment.

At 17 months after transplant, the patient was readmitted because of upper gastrointestinal bleeding. The serum hemoglobin level was 41 g/dL. The results of liver biochemistry tests were normal. After intensive resuscitation, upper gastrointestinal endoscopy was performed, and esophageal varices that had signs of fresh bleeding were band ligated. A contrast-enhanced computed tomography scan of the abdomen revealed occlusion of the portal vein with hyperdense material that was consistent with calcification within the iliac artery interposition graft that caused portal flow obstruction (Figure 1). Normal flow was evident in the main and segmental branches of the hepatic artery. There was no ascites, and spleen size was unchanged compared with previous examinations. After hospitalization for 6 days, the patient was discharged and had no further signs of bleeding. At 3 months after the bleeding episode, the patient was asymptomatic, and the results of her biochemical tests were normal.

Liver transplant for biliary atresia often is technically challenging for the transplant surgeon because of intraoperative difficulty with portal vein anastomosis. Recipient body size, the commonly hypoplastic portal vein, and a prior Kasai procedure can make liver transplant difficult.⁵ The use of interposition vein grafts and the branch patch techniques for portal vein reconstruction may give inconsistent results.⁶ Cryopreserved iliac artery interposition graft may be used to reconstruct the middle hepatic vein in right liver grafts and provides patency at 2 months not worse than venous conduits.⁴ A cryopreserved iliac artery may be used for arterial revascularization in liver transplant but may be associated with problems with hepatic artery patency.^3,7 A cryopreserved iliac artery graft previously has been used to establish hepatic venous drainage in living-donor liver transplant.⁸

In the present patient, blood-type compatible cryopreserved iliac artery was used for portal vein reconstruction because of technical difficulties in establishing intraoperative portal flow. The portal vein was inappropriate for anastomosis because the caliber was very small. The cryopreserved iliac artery graft was anastomosed to the confluence of the superior mesenteric and splenic veins. Venous graft material was not available. Although we routinely use polytetrafluoroethylene grafts for reconstruction of the middle hepatic vein in adult to adult living-donor liver transplant recipients, synthetic material was considered unsafe for this important anas-tomosis in this patient because acute thrombosis of the vessel could have caused graft loss or death.

Although this patient did not present with signs of portal hypertension until 17 months after transplant, it is unknown when the calcifications in the portal vein developed because the Doppler studies performed during the previous admission did not suggest portal flow obstruction.

Without pathologic examination of the specimen, it is impossible to know the exact cause of the cryopreserved iliac artery graft calcifications. It is possible that there may have been damage to the vascular endothelium because of inappropriate preservation conditions that caused calcium deposition within the lumen; however, this is unlikely because we have used cryopreserved arterial grafts previously for the reconstruction of various vessels, including jump grafts from the aorta, that had preservation with the same conditions, and there were no cases of luminal calcification. Another possibility is that the present patient may have had an immunologic response of unknown cause; although we used ABO-compatible cryopreserved iliac artery, arterial homografts may induce a strong antibody response against human leukocyte antigens similar to that observed with chronic rejection.⁹

Discouraging results previously were reported with portal vein reconstruction using cryopreserved iliac vein grafts in children.^10,11 Limited use of cryopreserved vein grafts was recommended because frequency of primary patency was 58% at 5 years in adult recipients.¹²

In summary, the present pediatric liver transplant was unusual because portal flow was established with a cryopreserved iliac artery interposition graft. Literature search showed no previous case with this reconstruction. In addition, the patient had delayed obstruction of portal flow and signs of portal hypertension because of arterial calcifications in the graft. Although we have frequent experience using polytetrafluoroethylene grafts for the reconstruction of the middle hepatic vein when short-term patency is sufficient to achieve the desired venous drainage, polytetrafluoroethylene may be unsuitable for portal reconstruction when long-term patency is important. The use of interposition grafts for portal vein reconstruction is a last resort; these grafts are used only when no other alternative method is available, and caution is advised with the use of cryopreserved iliac artery in portal vein reconstruction in pediatric liver transplant recipients.

Volume: 13 Issue: 5 October 2015

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