PVT in Liver Transplant Candidates
The characteristics of PVT and non-PVT pediatric liver transplant wait-listed candidates are displayed in . The prevalence of PVT (reported in this national database) among 5,087 candidates was 1.4% (n = 70). Candidates with PVT were more likely to be female (70.0% versus 51.0%; p=0.002) and have a lower PELD/MELD score at the time they were placed on the transplant list (9.9 ± 13.2 versus 15.3 ± 13.7; p=0.002). Age, race, Body Mass Index (BMI), dialysis, and previous transplant did not significantly differ significantly between PVT and non-PVT candidates. Diagnosis of biliary atresia was not more common among candidates with PVT, nor was survival among biliary atresia candidates significantly different from non-biliary atresia candidates. (p = 0.72)
Characteristics of pediatric liver transplant candidates in the presence or absence of portal vein thrombosis (n = 5087)
A Kaplan-Meier survival curve was created to compare survival among liver transplant candidates with and without PVT (). The unadjusted survival rate was not significantly lower among liver transplant candidates with PVT (p = 0.797).
Kaplan-Meier survival curve for PVT and non-PVT waitlisted liver transplant candidates.
We first assessed the relationship between PVT and waitlist mortality using a uni-variate Cox regression model. PVT was not significantly associated with waitlist mortality (HR = 1.1; 95% CI, 0.5–2.4; p = 0.765). In an attempt to elucidate the characteristics independently associated with waitlist mortality among all candidates, a multivariate Cox regression analysis was performed and is presented in . Once again, PVT was not significantly associated with waitlist mortality by multivariate analysis (HR = 1.4; 95% CI, 0.7–3.0; p = 0.382). Female gender was associated with a significantly decreased covariate-adjusted mortality risk (HR = 0.8; 95% CI, 0.6‒0.9; p=0.003), while candidates that were two years of age or younger showed increased mortality (HR = 2.6; 95% CI, 1.9–3.4; p <0.0001) compared to candidates between the ages of 3 and 11. In addition, both bilirubin and INR values were associated with waitlist mortality.
Figure 2 Multivariate Cox regression analysis of waitlist mortality in pediatric liver transplant candidates. PVT was not significantly correlated with waitlist mortality risk. Female candidates had a decreased mortality risk (HR = 1.055; 95% CI, 1.021–1.089; (more ...)
We then investigated the relationship between reported PVT status and transplant rate. A covariate-adjusted Cox regression was performed in an effort to determine candidate characteristics independently associated with liver transplant rate. PVT was not independently associated with the adjusted liver transplant rate (HR = 0.9, 95% CI, 0.8–1.1, p = 0.35). However, candidates were more likely to receive a transplant if they were female (HR = 1.1; 95% CI, 1.0–1.1; p = 0.001), age two years or younger (HR = 1.1, 95% CI, 1.0–1.1, p = 0.0002), or between the ages 12–18 (HR = 1.4, 95% CI, 1.3–1.5; p <0.0001) [age reference group candidates between 3 and 12]. Similarly, candidates with a blood sodium between 132–137 mEq/L had an increased rate of transplantation (HR = 1.2, 95% CI 1.1–1.2, p <0.0001), while a mean sodium below 132 mEq/L was not significantly correlated. As expected, PELD/MELD components were significantly associated with transplant rate: INR (1.13, 95% CI, 1.06–1.20, p<0.001), bilirubin (HR = 1.25, 95% CI 1.23–1.28, p<0.0001), albumin (HR = 0.63, 95% CI 0.59–0.67, p<0.0001), and dialysis (HR = 1.4, 95% CI 1.2–1.6, p<0.0001). Race and previous malignancy diagnosis was not associated with transplantation rate.
PVT in Liver Transplant Recipients
The characteristics of PVT and non-PVT pediatric liver transplant recipients and their donors are displayed in . A total of 3,630 patients received a liver transplant and of those, 3.7% (n = 136) were reported to have PVT. Graft donor characteristics, including age, weight, and donor risk index (DRI), were not significantly different between the groups. In addition, utilization of deceased donor split liver grafts and living donor grafts was similar between the two groups. PVT recipients were more likely to be female (64.7% versus 51.1%; p = 0.002). Recipient age, race, PELD score at transplant, albumin, sodium, and ascites did not differ between groups. PVT was not associated with diagnosis of biliary atresia, though this assessment was limited by small sample size. More specifically, there were 1496 recipients with biliary atresia listed at the primary diagnosis. Among these recipients, there were 40 with PVT and 4 mortalities.
Characteristics of pediatric liver transplant recipients and donors in the presence or absence of portal vein thrombosis (n = 3630)
A Kaplan-Meier survival curve was created to compare survival among liver transplant recipients with and without PVT (). The unadjusted survival rate is significantly lower in the PVT group across the post-transplant period (p = 0.01). It appears that the survival rate is particularly lower in the first few months following transplantation and then continues to trend downward in concordance with non-PVT recipients.
Kaplan-Meier survival curve for PVT and non-PVT recipients after liver transplantation
We then assessed the implications of PVT on short term post-transplant survival (30 day post-transplant survival). PVT was significantly associated with 30 day mortality (HR = 2.9; 95%CI 1.6–5.3, p = 0.001). Other covariates significantly associated with short term mortality included: creatinine (HR 4.42; 95%CI 2.8–7.1, p = 0.001), INR (HR = 1.6; 95%CI = 1.1–2.4, p=0.02), recipient age 0 – 2 years (HR = 1.7; 95%CI 1.1–2.6, p = 0.014) (compared to 3 to 12 years), and donor age (HR = 1.02; 95%CI 1.01–1.04, p = 0.01). No statistical interactions between PVT and the other covariates (including age at transplant) were noted.
A univariate regression was performed to determine the effects of PVT on overall post-transplant mortality. Recipients with PVT showed increased post-transplant mortality (HR = 1.7; 95% CI, 1.2–2.5; p = 0.007). These results were corroborated by a multivariate Cox regression analysis that revealed PVT was significantly associated with adjusted post-transplant mortality (HR = 1.6; 95% CI, 1.0–2.4; p = 0.03), as displayed in . The model was adjusted for gender, age, race, creatinine, bilirubin, INR, albumin, sodium, dialysis, previous malignancy diagnosis, graft type, and retransplantation.
Figure 4 Multivariate Cox regression analysis of posttransplant mortality in pediatric liver transplant recipients. Pediatric liver transplant recipients with PVT had a significantly increased risk of mortality versus recipients without PVT (HR = 1.661; 95% CI, (more ...)