Treatment Strategies for Bile Leak Following Pediatric Liver Transplantation.

There are no standard management protocols for the treatment of bile leak (BL) after liver transplantation. The objective of this study is to describe treatment options for BL after pediatric LT. METHODS: Retrospective analysis (January 2010-March 2023). VARIABLES STUDIED: preoperative data, status at diagnosis, and postoperative outcome. Four groups: observation (n = 9), percutaneous transhepatic cholangiography (PTC, n = 38), ERCP (2), and surgery (n = 27). RESULTS: Nine hundred and thirty-one pediatric liver transplantation (859 LDLT and 72 DDT); 78 (8.3%) patients had BL, all in LDLT. The median (IQR) peritoneal bilirubin (PB) level and fluid-to-serum bilirubin ratio (FSBR) at diagnosis was 14.40 mg/dL (8.5-29), and 10.7 (4.1-23.7). Patients who required surgery for treatment underwent the procedure earlier, at a median of 14 days (IQR: 7-19) versus 22 days for PTC (IQR: 15-27, p = 0.002). PB and FSBR were significantly lower in the observation group. In 11 cases, conservative management had resolution of the BL in an average time of 35 days, and 38 patients underwent PTC in a median time of 22 days (15-27). Twenty-seven (34.6%) patients were reoperated as initial treatment for BL in a median time of 17 days (1-108 days); 25 (33%) patients evolved with biliary stricture, 5 (18.5%) after surgery, and 20 (52.6%) after PTC (p = 0.01). CONCLUSION: Patients with BL who were observed presented significantly lower levels of PB and FSBR versus those who underwent PTC or surgery. Patients treated with PTC presented higher rates of biliary stricture during the follow-up.

Recanalization of portal vein thrombosis after pediatric liver transplantation: Efficacy and safety of the transsplenic access.

BACKGROUND: Endovascular management of portal vein thrombosis (PVT) is challenging. Transsplenic access (TSA) is growing as an access option to the portal system but with higher rates of bleeding complications. The aim of this article is to evaluate the efficacy and safety of transsplenic portal vein recanalization (PVR) using a metallic stent after pediatric liver transplantation. MATERIALS AND METHODS: This is a retrospective review of 15 patients with chronic PVT who underwent PVR via TSA between February 2016 and December 2020. Two children who had undergone catheterization of a mesenteric vein tributary by minilaparotomy were excluded from the patency analysis but included in the splenic access analysis. The technical and clinical success of PVR and complications related to the procedure via TSA were evaluated. RESULTS: Thirteen children with PVT were treated primarily using the TSA. The mean age was 4.1 years (range, 1.5-13.7 years), and the most common clinical presentation was hypersplenism (60%). Technically successful PVR was performed in 11/13 (84.6%) children, and clinical success was achieved in 9/11 (81.8%) children. No major complications were observed, and one child presented moderate pain in the TSA (from a total of 17 TSA). The median follow-up was 48.2 months. The median primary patency was 9.9 months. Primary patency in the first 4 years was 75%, and primary assisted patency was 100% in the follow-up period. CONCLUSIONS: Transsplenic PVR is a safe and effective method for the treatment of PVT after pediatric liver transplantation.

Hepatic venous reconstruction of the left lateral segment with emphasis on anomalous hepatic vein in pediatric liver transplantation.

Left lateral segment grafts have become a suitable option in pediatric liver transplantation (PLT). The correlation between hepatic vein (HV) reconstruction and outcome is relevant when assessing the safe use of these grafts. We retrospectively reviewed the medical records prospectively collected from a pediatric living donor liver transplantation database and conducted a comparative analysis of the different left lateral segment graft types according to HV reconstruction. Donor, recipient, and intraoperative variables were analyzed. Post-transplant outcomes included vascular complications such as hepatic vein outflow obstruction, early (≤30 d) and late (>30 d) PVT, hepatic artery thrombosis, and graft survival. From February 2017 to August 2021, 303 PLTs were performed. According to venous anatomy, the distribution of the left lateral segment was as follows: single HV (type I) in 174 (57.4%), close HVs, simple venoplasty for reconstruction (type II) in 97 (32.01%), anomalous hepatic vein (AHV) with a distance between the HVs orifices that allowed simple venoplasty (type IIIA) in 25 (8.26%) and AHV with a distance between the HVs orifices requiring homologous venous graft interposition (type IIIB) in 07 (2.31%) grafts. Type IIIB grafts came from male donors ( p =0.04) and had a higher mean donor height ( p =0.008), a higher mean graft weight, and a higher graft-to-recipient weight ratio, both p =0.002. The median follow-up time was 41.4 months. The overall cumulative graft survival was 96.3%, and comparative graft survival showed no difference (log-rank p =0.61). No hepatic vein outflow obstructions were observed in this cohort study. There was no statistically significant difference in the post-transplant outcomes between the graft types. The venous reconstruction of the AHV with homologous venous graft interposition had similar outcomes in the short and long term.

Liver transplantation for hilar inflammatory myofibroblastic tumor: Case report and review of the literature.

BACKGROUND: Inflammatory myofibroblastic tumors (IMTs) of the liver are rare neoplasms. These tumors are difficult to distinguish from other neoplasms by radiological examination, have uncertain evolution, and there is no consensus on the treatment of these lesions. Hilar tumors can involve the portal vein, hepatic artery, bile duct, and spread to the branches of the portal triad, causing obstructive symptoms, occlusive phlebitis, and portal hypertension. Thus, liver transplantation (LT) is an excellent alternative for locally advanced hilar tumors, since it ensures complete tumor resection with free margins. METHODS/RESULTS: We present a literature review and a case report showing a 3-year-old boy with liver IMT invading the hepatic hilum and inferior vena cava, who underwent a successful living donor liver transplantation that required portal vein and vena cava replacement. CONCLUSION: The incidence of hilar IMTs is low and there is no well-established standard treatment. Liver transplantation for a hilar tumor with vascular invasion was acceptable in this case because the radically of the surgery was the key for the cure, and because the tumor was benign in nature.

Technical Choices in Pediatric Living Donor Liver Transplantation: The Path to Reduce Vascular Complications and Improve Survival.

Pediatric living donor liver transplantation (PLDLT) is a successful therapeutic option for children with chronic and acute liver disease. After early transplant results, many technical advancements were introduced in the field to reduce the rate of complications and improve survival. The aim of this study is to present the outcomes of 975 primary PLDLTs in 3 periods: initial practice (period 1, 29 patients, January 1995 to December 1999), second period (period 2, 331 patients, January 2000 to December 2009), and third period (period 3 [P3], 615 patients, January 2010 to September 2019). Among the technical refinements introduced in P3 are the use of hyperreduced left lateral segment grafts, abdominal wall prosthetic mesh closure, double hepatic artery anastomosis, and increased use of vascular grafts for portal vein reconstruction. The outcomes included significant reductions of hepatic artery thrombosis (HAT), early portal vein thrombosis (EPVT), and retransplantation, with better patient and graft survival in P3. Additional analyses showed that the factors independently associated with worse 90-day patient survival were HAT, EPVT, and increasing Pediatric End-Stage Liver Disease score. In conclusion, the introduction of technical refinements in P3, in addition to improvements in patient care, determined a reduction in EPVT, HAT, and retransplantation. Consequently, patient and graft survival rates increased in all time points studied.

Evaluation of plasma biomarkers of inflammation in patients with maple syrup urine disease.

Maple syrup urine disease (MSUD) is an autosomal recessive inherited disorder that affects branched-chain amino acid (BCAA) catabolism and is associated with acute and chronic brain dysfunction. Recent studies have shown that inflammation may be involved in the neuropathology of MSUD. However, these studies have mainly focused on single or small subsets of proteins or molecules. Here we performed a case-control study, including 12 treated-MSUD patients, in order to investigate the plasmatic biomarkers of inflammation, to help to establish a possible relationship between these biomarkers and the disease. Our results showed that MSUD patients in treatment with restricted protein diets have high levels of pro-inflammatory cytokines [IFN-γ, TNF-α, IL-1ß and IL-6] and cell adhesion molecules [sICAM-1 and sVCAM-1] compared to the control group. However, no significant alterations were found in the levels of IL-2, IL-4, IL-5, IL-7, IL-8, and IL-10 between healthy controls and MSUD patients. Moreover, we found a positive correlation between number of metabolic crisis and IL-1ß levels and sICAM-1 in MSUD patients. In conclusion, our findings in plasma of patients with MSUD suggest that inflammation may play an important role in the pathogenesis of MSUD, although this process is not directly associated with BCAA blood levels. Overall, data reported here are consistent with the working hypothesis that inflammation may be involved in the pathophysiological mechanism underlying the brain damage observed in MSUD patients.

Pancreas-preserving duodenectomy after living donor liver transplantation for invasive cytomegalovirus disease.

CMV infection plays an important role in the postoperative course following solid organ transplantation. We present the case of an 11-year-old male patient who underwent LDLT due to severe hepatopulmonary syndrome and biliary cirrhosis. Four weeks after LDLT, he developed persistent GI bleeding and was subjected to repeated endoscopic treatment and radiological arterial embolization to stop the bleeding from duodenal ulcers. Diagnostic workup was negative for CMV disease. Because the bleeding persisted, surgical treatment was indicated, and a pancreas-preserving duodenectomy was performed. Immunohistochemical staining of the surgical specimen demonstrated diffuse endothelial infiltration by CMV. Despite ganciclovir treatment, the patient developed new erosions in the jejunal mucosa and melena; ganciclovir was discontinued, and foscarnet was started, resulting in clinical improvement and the cessation of bleeding. This case highlights the technical aspects of performing a complex upper GI resection in a patient recently subjected to LDLT, taking care to avoid injury to the previous liver graft anastomosis and restore GI continuity. Moreover, CMV tissue-invasive disease compartmentalized in the GI tract may be difficult to diagnose, as indicated by the negative results of antigenemia and PCR assays and endoscopic superficial mucosal biopsies.

Alternatives for vascular reconstruction in pediatric living donor liver transplantation.

Many publications discuss the various strategies for vascular reconstruction (VR) in pediatric LDLT. Having knowledge of alternative techniques is helpful in planning transplants. This article presents three case reports that illustrate some of the alternative techniques for HV, PV, and HA reconstruction in pediatric LDLT. It also reviews the available alternative strategies reported for VR in pediatric LDLT. In the first case, a 13-month-old girl presented a PRETEXT III HB with invasion of the retrohepatic vena cava. An LLS graft HV was anastomosed to a DD iliac vein graft and subsequently implanted in a "standard" fashion in the recipient. In the second case, a 44-month-old boy presented with multifocal HB and portomesenteric thrombosis and the portal inflow was done through a renoportal anastomosis. In the third case, a 22-month-old child with a failed Kasai procedure had extensive HA thrombosis. The HA reconstruction was performed with an interposition of the recipient's IMV graft. The use of alternative techniques for VR in pediatric LDLT is paramount to the success of such a complex procedure. Imaging studies can help transplant surgeons outline surgical strategies and define the best technique to be used in each case.

Impact of Kasai portoenterostomy on liver transplantation outcomes: A retrospective cohort study of 347 children with biliary atresia.

Biliary atresia (BA) is the main diagnosis leading to liver transplantation (LT) in children. When diagnosed early in life, a Kasai portoenterostomy (Kasai-PE) can prevent or postpone LT. Instances of previous operations can result in difficulties during the LT. We hypothesized that a previous Kasai-PE could affect LT outcomes. A retrospective cohort study of 347 BA patients submitted to LT between 1995 and 2013 at Hospital Sírio-Libanês and A. C. Camargo Cancer Center was conducted. Patients were divided into those with a previous Kasai portoenterostomy early failure (K-EF), Kasai portoenterostomy late failure (K-LF), and those with no Kasai portoenterostomy (No-K). Primary outcomes were patient and graft survival. A total of 94 (27.1%) patients had a K-EF, 115 (33.1%) had a K-LF, and 138 (39.8%) had No-K before LT. Children in the K-LF group were older and had lower Pediatric End-Stage Liver Disease (PELD) scores. Patients in both K-EF and K-LF groups had more post-LT biliary complications. After Cox-multivariate analysis adjusting for confounding factors to determine the influence of Kasai-PE on patient and graft survival, the K-LF group had an 84% less probability of dying and a 55% less chance to undergo retransplantation. The K-LF group had a protective effect on posttransplant patient and graft survival. When properly performed, the Kasai procedure can postpone LT and positively affect outcomes. Having a K-EF and having not performed a Kasai-PE had the same effect in patient and graft survival; however, a previous Kasai-PE can increase post-LT complications as biliary complications and bowel perforations.

Ascites and serum sodium are markers of increased waiting list mortality in children with chronic liver failure.

UNLABELLED: Ascites is the most common complication of cirrhosis and in adults it is associated with 50% mortality at 5 years if patients do not receive a liver transplant. The occurrence of hyponatremia in these patients has been associated with increased mortality on the waiting list. The importance of serum sodium levels and the presence of ascites in the pediatric setting remain to be clarified. A retrospective analysis of pediatric patients with cirrhosis on the transplant list was carried out between October 2000 and February 2012. The primary objective of this study was to evaluate the association of pretransplant variables with mortality within 90 days following the inclusion of patients on the waiting list. In all, 522 patients were included in the study; 345 (66%) patients were under 1 year of age; 208 (40%) of the children presented ascites. A multivariate Cox proportional hazards analysis was conducted and total bilirubin (P < 0.001, hazard ratio [HR] = 2.09, 95% confidence interval [CI] = 1.35-3.21), international normalized ratio (INR) (P < 0.001, HR = 9.83, 95% CI = 4.51-21.45), serum sodium levels (P = 0.03, HR = 0.96, 95% CI = 0.92-0.99), ascites (P = 0.001, HR = 2.59, 95% CI = 1.44-4.64), and categorized age (0-1 versus ≥ 1 year old) (P = 0.025, HR = 2.33, 95% CI = 1.11-4.86) were independently associated with risk of death in 90 days. Malnutrition (Z score height/age, weight/age) and serum albumin (pediatric endstage liver disease [PELD] formula) were not included in the final model. CONCLUSION: The presence of ascites and serum sodium levels are important variables associated with decreased patient survival while candidates wait for a liver graft. Multicenter studies are necessary to validate these findings in order to improve current allocation policies based on the PELD score.

Analysis of factors associated with portal vein thrombosis in pediatric living donor liver transplant recipients.

The technique of vascular reconstruction plays a major role in the outcome of living donor liver transplantation (LDLT). An increased use of vascular grafts (VGs) as replacements for sclerotic portal veins has become a standard technique for our group. The aim of this study was to analyze the factors associated with portal vein thrombosis (PVT) in pediatric LDLT. We performed a retrospective analysis of 486 primary pediatric LDLT procedures performed between October 1995 and May 2013. VGs used for portal reconstruction included living donor inferior mesenteric veins, living donor ovarian veins, recipient internal jugular veins, deceased donor iliac arteries, and deceased donor iliac veins. Thirty-four patients (7.0%) developed PVT. The incidence of PVT dropped from 10.1% to 2%; the overall utilization of VGs increased from 3.5% to 37.1%. In a multivariate analysis, only the use of VGs remained an independent risk factor for the occurrence of PVT (hazard ratio = 7.2, 95% confidence interval = 2.8-18.7, P < 0.001). There was no difference in survival rates between patients with PVT and patients without PVT. No patient with PVT underwent retransplantation. In conclusion, the use of VGs was independently associated with the development of PVT. Over time, there was a reduction in the incidence of early PVT in this cohort, and there was a trend toward a reduction in total PVT. The occurrence of isolated PVT in this study was not associated with decreased patient or graft survival.

Incidence, management and outcomes in hepatic artery complications after paediatric liver transplantation: protocol of the retrospective, international, multicentre HEPATIC Registry.

INTRODUCTION: Hepatic artery complications (HACs), such as a thrombosis or stenosis, are serious causes of morbidity and mortality after paediatric liver transplantation (LT). This study will investigate the incidence, current management practices and outcomes in paediatric patients with HAC after LT, including early and late complications. METHODS AND ANALYSIS: The HEPatic Artery stenosis and Thrombosis after liver transplantation In Children (HEPATIC) Registry is an international, retrospective, multicentre, observational study. Any paediatric patient diagnosed with HAC and treated for HAC (at age <18 years) after paediatric LT within a 20-year time period will be included. The primary outcomes are graft and patient survivals. The secondary outcomes are technical success of the intervention, primary and secondary patency after HAC intervention, intraprocedural and postprocedural complications, description of current management practices, and incidence of HAC. ETHICS AND DISSEMINATION: All participating sites will obtain local ethical approval and (waiver of) informed consent following the regulations on the conduct of observational clinical studies. The results will be disseminated through scientific presentations at conferences and through publication in peer-reviewed journals. TRIAL REGISTRATION NUMBER: The HEPATIC registry is registered at the ClinicalTrials.gov website; Registry Identifier: NCT05818644.

Liver transplantation after stage II palliation for hypoplastic left heart syndrome.

The association of biliary atresia (BA) with congenital heart diseases has been extensively described, and there are a number of reports on the outcomes of patients in this group who undergo liver transplantation (LT). The intraoperative management and the timing of LT for patients with end-stage liver disease are matters of debate, especially when complex heart diseases are involved. This report describes the outcome after LT for a pediatric recipient with BA and hypoplastic left heart syndrome. The patient underwent Norwood-Sano and Glenn procedures for heart palliation before LT. He was cyanotic, was severely malnourished, and had complications secondary to chronic liver failure. At the time of transplantation, the child was 16 months old and weighed 5175 g. Despite the critical clinical scenario and the long hospitalization period, there were no cardiac, vascular, or biliary complications after LT. At the age of 48 months, the patient was awaiting the final cardiac repair. In conclusion, the presence of complex cardiac malformations may not be a contraindication to LT. An experienced surgical team and a multidisciplinary approach are key to a successful outcome.

Four hundred thirty consecutive pediatric living donor liver transplants: variables associated with posttransplant patient and graft survival.

The availability of living donors allows transplant teams to indicate living donor liver transplantation (LDLT) early in the course of liver disease before the occurrence of life-threatening complications. Late referral to transplant centers is still a problem and can compromise the success of the procedure. The aim of this study was to examine the perioperative factors associated with patient and graft survival for 430 consecutive pediatric LDLT procedures at Sirio-Libanes Hospital/A. C. Camargo Hospital (São Paulo, Brazil) between October 1995 and April 2011. The studied pretransplant variables included the following: recipient age and body weight, Pediatric End-Stage Liver Disease score, z score for height/age, bilirubin, albumin, international normalized ratio, hemoglobin, sodium, presence of ascites, and previous surgery. The analyzed technical aspects included the graft-to-recipient weight ratio and the use of vascular grafts for portal vein reconstruction. In addition, the occurrence of hepatic artery thrombosis (HAT), portal vein thrombosis (PVT), and biliary complications was also analyzed. The liver grafts included 348 left lateral segments, 5 monosegments, 51 left lobes, and 9 right lobes. In a univariate analysis, an age < 12 months, a low body weight (≤10 kg), malnutrition, hyperbilirubinemia, and HAT were associated with decreased patient and graft survival after LDLT. In a multivariate analysis, a body weight ≤ 10 kg and HAT were significantly associated with decreased patient and graft survival. The use of vascular grafts significantly increased the occurrence of PVT. In conclusion, a low body weight (≤10 kg) and the occurrence of HAT independently determined worse patient and graft survival in this large cohort of pediatric LDLT patients.

The impact of low recipient weight [≤ 7kg] on long-term outcomes in 1078 pediatric living donor liver transplantations.

BACKGROUND: infants who require liver transplantation represent a treatment challenge because chronic liver disease at this early age affects the child's growth and development during a critical phase. The aim is to compare demographics, operative data, and long-term outcomes according to recipient weight at the time of LDLT. METHODS: This retrospective study included primary LDLT analyzed in 2 groups: BW ≤ 7 kg (n = 322) and BW > 7 kg (n = 756). A historical comparison between periods was also investigated. RESULTS: BW ≤ 7 kg had significantly lower height/age and weight/age z-scores, with median PELD score of 19. Transfusion rates were higher in the BW ≤ 7 kg group (30.9 ml/kg versus 15.5 ml/kg, P < 0.001). Higher frequencies of PV complications were seen in the BW ≤ 7 kg cohort. HAT and retransplantation rates were similar. Those with BW ≤ 7 kg required longer ICU and hospital stays. Patient and graft survival were similar. Patient survival in BW≤ 7 kg was significantly better in the most recent period. CONCLUSION: Malnutrition and advanced liver disease were more frequent in BW ≤ 7 kg. Despite increased rates of PVT and longer hospital stay, patient and graft long-term survival were similar between groups.

Schistosoma mansoni infection in the liver graft: The impact on donor and recipient outcomes after transplantation.

The increasing number of transplants performed each year has led to the identification of unusual diseases in liver grafts from asymptomatic donors that were unrecognized before liver transplantation. Here we report our experience with patients who received liver grafts infected with schistosomiasis. From September 1991 to August 2010, 482 pediatric liver transplants were performed at A. C. Camargo Hospital/Sírio-Libanês Hospital (São Paulo, Brazil). For the identification of Schistosoma mansoni infections, pathology slides for the recipients were reviewed; these included postreperfusion and follow-up liver biopsy samples. We were able to identify 6 cases of schistosomiasis transmitted through infected grafts (5 of these grafts were from living donors). All living donors were confirmed to have normal liver chemistries, negative fecal tests for parasitic diseases, and normal abdominal ultrasound findings. Liver biopsy was not performed before transplantation. In all cases, features of schistosomiasis were absent in the liver explants. The living donors were treated with praziquantel and were taught to avoid risk factors for reinfection. No specific treatment for schistosomiasis was given to the recipients. There were no perioperative deaths, but 2 recipients died after living donor liver transplantation (LDLT) because of Kaposi's sarcoma and non-Hodgkin's lymphoma. In conclusion, using liver grafts infected with S. mansoni eggs did not compromise the results of LDLT in this pediatric cohort. Because of the parasite's life cycle and the therapeutic target of praziquantel, only donors should be treated for the infection. Three years of follow-up showed an uneventful recovery for the living donors.

Modified pediatric end-stage liver disease scoring system and pediatric liver transplantation in Brazil.

The Pediatric End-Stage Liver Disease (PELD) scoring system is a formula developed to provide a continuous numerical assessment of the risk of death in order to allocate livers to children in need of transplantation. The PELD scoring system was introduced in Brazil in July 2006. An important change was made in the system: the final number for listing patients less than 12 years old for transplantation was the calculated PELD score multiplied by 3. The consequences of this allocation policy were analyzed in 2 ways in this research: nationally and in the state of São Paulo (SP State). In the analysis of the national data, a comparison of the pre-PELD era (July 2003 to July 2006) and the post-PELD era (August 2006 to April 2009) showed that the total number of pediatric transplants for children under 12 years of age decreased 7%. Regionally, in SP State, there was a 62% increase in the number of deceased donor liver transplantation procedures for the pediatric population after the introduction of the modified PELD system. There was also a 6.1-fold increase in split liver transplantation as well as a statistically significant decrease in the time on the waiting list (P < 0.001). In conclusion, changing the allocation policy in Brazil in order to benefit pediatric patients on the waiting list had different results according to analyses of national and regional data. A significant increase in deceased donor liver transplantation/split liver transplantation and a shorter time on the waiting list were observed in SP State. The modified PELD scoring system is simple and optimizes the utilization of deceased donor liver grafts in centers performing pediatric transplants.

Current Practice in Immunosuppression in Pediatric Liver Transplantation.

The last decades have witnessed a significant improvement in the field of pediatric liver transplantation (LT), resulting in longer patient and graft survival; adequate graft selection, surgical refinement, the use of live donors and optimal postoperative care are among the reasons why pediatric recipients are living longer. With this new condition, pediatric recipients are now more exposed to the deleterious effects of immunosuppression, including metabolic, infectious and neoplastic complications, nephrotoxicity and neurotoxicity. Due to all those particularities, the approach to avoid overimmunosuppression or underimmunosuppression may be more difficult in children than in adult recipients. Moreover, pediatric recipients are exposed to growth issues and specific problems during adolescence, like nonadherence to immunosuppressive therapy. This article highlights the current immunosuppressive strategies for pediatric liver transplant recipients.

Carbon monoxide ameliorates renal cold ischemia-reperfusion injury with an upregulation of vascular endothelial growth factor by activation of hypoxia-inducible factor.

BACKGROUND: We have previously shown that carbon monoxide (CO) inhalation at a low concentration provides protection against cold ischemia-reperfusion (I/R) injury after kidney transplantation. As vascular endothelial growth factor (VEGF) may promote the recovery process of impaired vascular endothelial cells during I/R injury, we examined whether protective effects of CO involved VEGF induction and its upstream hypoxia-inducible factor (HIF)-1 activation. METHODS: Lewis rat kidney graft, preserved in University of Wisconsin at 4 degrees C for 24 hr, was orthotopically transplanted into syngeneic recipient. Recipients were continuously maintained in air or exposed to CO (250 ppm) for 1 hr before and 24 hr after transplant. RESULTS: Prolonged cold preservation resulted in progressive impairment of kidney graft function with early inflammatory responses. Carbon monoxide significantly protected kidney grafts from cold I/R injury, improved renal function and enhanced recipient survival. Real-time reverse transcriptase-polymerase chain reaction revealed upregulation of HIF-1alpha and VEGF in the CO-treated kidney grafts as early as 1 hr after reperfusion. Western blot showed CO significantly upregulated VEGF expression 1 to 3 hr after kidney transplantation. Considerably more VEGF-positive cells were observed mainly in tubular epithelial cells in CO-treated, but not air-exposed, kidney grafts at 3 hr after reperfusion. YC-1, HIF-1alpha inhibitor, completely abrogated the actions of CO on VEGF induction and reversed the protective effects afforded by CO. Nitric oxide production in the grafts was increased by CO, however, abolished by YC-1. CONCLUSION: These results demonstrate that the protective effect of CO against renal cold I/R injury may involve VEGF upregulation through its upstream signal, HIF-1 activation.