pediatric liver transplantation: a new biological abdominal wall
Study Background
Liver transplantation (LT) is the only definitive treatment for children with advanced liver disease. Pediatric liver transplantation has evolved significantly over the past few decades, with excellent short-term and long-term survival rates. However, graft matching challenges, especially size-matched donors, remain. Also, in young recipients, definite closure of the abdominal wall might be complicated by various factors like graft-to-recipient weight ratio (GRWR), hepatic artery thrombosis (HAT), and portal vein thrombosis (PVT). These complications increase the risk of graft loss and result in high morbidity and mortality after transplantation.
For living donor liver transplantation (LDLT), the optimal GRWR is ≥0.8% and ≤4%. Graft size with GRWR < 0.8 causes small-for-size syndrome (SFSS) characterized by hepatic dysfunction, ascites, prolonged coagulopathy, and elevated hepatic enzymes. By contrast, in large-for-size syndrome (LFSS), hepatic dysfunction occurs due to large graft size. LFSS has been observed widely in pediatric transplantation. Characteristics of LFSS include poorly perfused liver parenchyma, vascular kinking, and mechanical compression of the abdominal wall, which leads to abdominal compartment syndrome (ACS). Animal studies have shown that the large-for-size group had elevated levels of hepatic enzymes and poor graft survival compared to the control. Bowel congestion, pulmonary complications, and an increased risk for severe infection are also attributed to ACS. Therefore, closing the abdominal layer with correct tension is essential to avoid ACS in pediatric liver transplant recipients.
Several methods have been developed to achieve abdominal wall expansion and reduce the morbidity caused by ACS. The safer ones include delayed fascial closure with temporary silastic mesh, expanded polytetrafluoroethylene patches, or non-vascularized abdominal rectus muscle fascia as an allograft.
METHODS
Since 2008, 243 pediatric liver transplantations have been performed at the Department of Surgery, University Medical Center Regensburg, Regensburg, Germany. This study retrospectively analyzed six pediatric liver transplantation cases with large-for-size grafts where biologic meshes were used for abdominal wall expansion. Graft volume was measured from a CT scan using the Siemens Healthineers syngo.via program. In all six cases, a left lateral segment (LLS) graft, either from a living or deceased donor, was used for transplantation. The surgical meshes used consisted of ovine-reinforced tissue matrix (OviTex™ 1s, and OviTex™ 2s, TELA bio) or bovine acellular collagen matrix (SurgiMendR Integra). In all cases, the biological mesh was bridged as an interposition graft to close the fascia after midline laparotomy.
RESULTS
A total of 6 cases (1 male and 5 females) were eligible for this study.
Preoperative characteristics
The main underlying etiology of liver disease was biliary atresia (n = 3), followed by acute liver failure (n = 2), and Caroli syndrome (n = 1). The median age at the time of transplantation was 6 months (range = 0 – 57 months). The median height, weight, and BMI were 64cm (range 51 – 116 cm) and 6kg (range = 3.5 – 22kg), and 14.9 kg/m2 (range = 13.5 – 17.3 kg/m2), respectively. 4 cases had living donor grafts with a median GRWR of 20% (range = 1.6% – 23.4%). The median GRWR of 2 cases with deceased donor transplants was 4.8% (range = 1.5% – 8.5%).
Postoperative outcomes
The median duration of the primary transplantation was 388 min (range = 333 – 478 min). Five cases had normal anatomy with 1 arterial anastomosis, whereas the sixth patient had 2 arterial anastomoses. The standard immunosuppression regimen was based on basiliximab (days 0 and 4), prednisolone, and cyclosporin A. Heparin alone or in combination with ASS was administered as a postoperative anticoagulant. In all cases, the biological mesh was implanted 7 days after transplantation (range = 3 – 11 days). 4 patients underwent thrombectomy before mesh implantation due to being diagnosed with ACS and thromboses in their portal vein (n = 3) and artery (n = 1). In 2 cases, the bovine acellular collagen matrix was implanted as the inlay mesh, and in 4 cases an ovine-reinforced tissue matrix. Superinfection of the mesh and fever were not reported in any case. The median ICU and hospital stay after surgery were 21 (range = 7 – 32 days) and 68 (range = 55 – 104 days), respectively.
Follow-up
The median follow-up was 12.5 months (range = 4 – 28 months). All cases showed good liver perfusion and age-appropriate corporal development without any signs of abdominal wall hernia. One patient died due to fulminant graft rejection and emergency re-transplantation 11 months after the transplantation. 3 patients developed stenosis in the biliodigestive anastomosis, had bile leakage, and underwent percutaneous transhepatic cholangiodrainage (PTCD) therapy.
DISCUSSION
Liver transplantation in small infants remains challenging. Even though pediatric liver transplantation has better patient survival rates, aspects of size mismatch through postmortal or living donation have to be taken into consideration. GRWR plays an important role in estimating possible complications post-transplantation. The risk of abdominal compartment syndrome is higher when grafts exceed the recommended GRWR values of 2.5% – 4%. In this study, the authors observed the usage of large-for-size left lateral grafts with GRWR up to 8.5%, which could probably be due to failed preoperative volume prediction and the critical condition of the patient. This study reported four cases of thrombosis of the portal vein and liver artery.
In cases with a complicated perioperative course, direct abdominal wall closure increases abdominal pressure. Delayed abdominal wall closure using synthetic or biological mesh is the method of choice in such scenarios. Synthetic meshes such as polytetrafluoroethylene, polyester, and polypropylene are well-established in the literature. However, they are reported to cause unwanted adhesions, fistula, mesh contraction, pain, inflammation, and seroma. Alternatively, biologic mesh implantations are widely recognized as the safer option. In pediatric recipients, the use of biologic meshes has been described. However, case reports are low, and follow-up data is limited. Based on these, the authors retrospectively analyzed the use of biological mesh for facial closure in pediatric liver transplantation cases.
Despite the delayed biologic mesh implantation in the six patients, the authors reported that this technique could even be used in a contaminated situation. Furthermore, the possibility of graft thickness reduction through non-anatomical resection to reduce the risk of ACS is described; recipients in the reduced thickness group had positive outcomes. Nevertheless, these methods increase the risk of additional blood loss and biliary leakage. It is, therefore, important to keep the recipients in stable condition during transplantation.
No ventral hernia was observed in this study. Literature shows that resorbable biologic meshes increase the risk of developing a hernia after pediatric liver transplantation. Especially, the ones containing porcine matrix, which are reported to cause recurrence rates of up to 50% in contaminated wounds.
Biologic mesh grafts seem to be promising and a safe approach for abdominal wall expansion to achieve fascial closure after pediatric liver transplantation.
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