The worldwide organ shortage has led to the search for additional sources of kidneys. Many transplant units use PEBK for transplantation from pediatric donors because of their small size. Although this provides excellent clinical outcomes, pediatric SKT would be ideal. However, there are no guidelines or established consensus regarding the allocation and use of single kidneys from small pediatric donors. In the past 5 years, we performed 85 SKTs from pediatric donors. Previous studies compared the outcomes of SKT using adult deceased kidney donors, ideal kidneys, and PEBK [6–10, 15, 22–26]. We compared the short- and intermediate-term patient survival, graft survival and death-censored graft survival of SKTs from small pediatric donors (≤8 years-old) and big pediatric donors (9–18 years-old).
Only a few studies examined SKTs from small pediatric donors (≤8 years-old), and the results varied greatly. For example, a 2006 study of small pediatric donors using data from the Scientific Registry of Transplant Recipients (SRTR) compared the risk of graft loss following PEBK, pediatric SKT, and ideal donors. These authors reported that pediatric SKT had a 78% greater risk of graft loss than PEBK . More recent SRTR data showed that recipients of pediatric SKT, ideal donors, and PEBK led to comparable patient survival and death-censored graft survival . However, the other studies which reported excellent patient and graft survival after pediatric SKT were limited by small sample sizes [8, 9, 24, 27, 28]. For instance, a 2013 single-center study examined pediatric SKT in 10 child recipients and 4 adult recipients . The children had 5-year patient and graft survivals of 100%, but the adults had a 5-year patient survival of 100% and a 5-year graft survival of 75% (1 lost graft). Mohanka et al.  reported the 1-year graft survival was 86% for SKT from small donors (≤15 kg), but only examined 14 recipients. Gröschl et al.  reported the 3-year death-censored graft survival after SKT from small donors was 100% in 15 recipients. Sharma et al.  reported the 5-year patient survival was 81% and the death-censored graft survival was 84% after SKT from small donors (mean donor weight: 27 kg) in 31 recipients. Balachandran et al.  reported that pediatric SKT (≤10 kg) in 11 recipients yielded excellent short-term outcomes, with a 2-year patient survival of 100% and graft survival of 92.5%. Although these previous results appear promising, they all examined small numbers of recipients.
We performed 38 SKTs from small pediatric donors (≤8 years-old, median body weight = 20.1 kg). Our results indicated excellent renal function in all recipients, indicating rapid compensatory hypertrophy of the small single renal allografts. The SCr level of the recipients in the SKG declined rapidly after surgery, and was nearly normal 1 month later. During the early stage after transplantation (1 month) the SCr level decreased more slowly in the SKG than the BKG, but we believe these groups will tend to have the same or similar SCr levels over time. Our two recipient groups also had similar 1-year graft survival (97.4% vs. 97.9%), 3-year graft survival (92.9% vs. 94.9%), 5-year graft survival (92.9% vs. 94.9%), and 5-year death-censored graft survival (100% vs. 97.9%). Impressively, there were no graft failures and no patients died in the SKG during the 5-year follow-up period. Thus, our results provide important clinical support regarding the effectiveness of SKT from young pediatric donors, a procedure that will make more kidneys available for transplantation.
A 2019 study of 46 SKTs from small pediatric donors reported the death-censored graft survival rate was 100% , encouraging results and in line with our results. Notably, this prior study reported the 1-year survival rate of recipients of small SKTs was 89.1%, although none of these deaths could be directly linked to the small allograft size. We should also note that the recipients of small SKTs in this prior study were carefully selected, with priority given to women who had relatively low body weight (median weight of the SKG = 46.5 kg). However, in present study we achieved a 5-year patient survival of 92.9% and a 5-year death-censored graft survival of 100% using less stringent criteria for recipient selection. Thus, the previously reported success was with low body weight recipients, but our current results apply more generally to patients with ESRD. In agreement, another large-scale analysis of SRTR data in the United States  also reported encouraging outcomes of SKT from small pediatric donors (<8 years-old, body weight < 30 kg). Thus, our data indicate high success of pediatric SKT for Chinese recipients.
The high incidence of post-transplant complications is a major cause for poor recovery following SKT [6, 30]. Although there are no prospective studies of TRAS and only a few large-scale retrospective studies, TRAS is a critical issue that deserves increased attention. In particular, TRAS is a serious complication that can occur after kidney transplantation and lead to uncontrollable hypertension and renal dysfunction. One of the most common post-transplantation complications is premature renal failure, and TRAS is a major cause of this complication. Therefore, early diagnosis and treatment of renal artery stenosis is very important. Previous studies reported the prevalence of TRAS ranged from 1–23% . Data from USRDS registry indicated the adjusted hazard ratio (aHR) for graft loss and death in patients with TRAS was 2.84 (95% CI = 1.70–4.72) .
In the present study, the overall incidence of graft renal artery stenosis was 10.6%, although TRAS was significantly more common in the SKG than the BKG (18.4% vs. 4.3%, P = 0.039). We speculate that TRAS may be related to preoperative hypertension and DGF. Moreover, recipients with DGF in the SKG may be more likely to develop this complication, as also reported previously. For example, two studies reported that the independent risk factors for TRAS were recipient BMI greater than 30 kg/m2, cytomegalovirus (CMV) infection, and DGF [32, 33]. More specifically, Hurst et al.  reported that TRAS was related to DGF (aHR: 1.34, 95% CI: 1.13–1.60, P = 0.001) but not CMV. Kamali et al.  reported that recipient BMI greater than 30 kg/m2 (relative risk [RR]: 7.97, 95% CI: 3.44–18.46, P < 0.001), CMV infection (RR: 4.29, 95% CI: 3.79–13.29, P = 0.01), and DGF (RR: 4.29, 95% CI: 3.12–13.79, P = 0.01) were significantly and independently related to TRAS. Although these two studies reported contradictory findings regarding the effect of CMV, our results showed that all patients with TRAS were negative for CMV (Table 4). This is probably due to our routine use of antiviral therapy before transplantation.
In the present study, we used end-to-end arterial anastomosis to suture the transplant renal artery and internal iliac vessels in all 9 patients who had TRAS. Thus, TRAS may be a consequence of this suture technique. Smith et al.  and Fung et al.  also reported that patients who received end-to-end arterial anastomosis were more likely to develop TRAS, but other studies found no difference in TRAS following end-to-end vs. end-to-side anastomosis [36, 37]. However, all these results were from retrospective studies that had small sample sizes. Thus, further prospective studies are needed to determine the effect of different arterial anastomosis methods on the incidence of TRAS.
Short-term complications after transplantation are one of the major reasons for hesitancy in using small pediatric SKT [6, 8, 25, 38]. Mohanka et al.  reported that DGF was 25% and acute rejection was 21% among recipients of pediatric SKT. In our SKG, the incidence of DGF was 50.0% and the incidence of acute rejection was 18.4%. Although the incidence of DGF in our SKG was higher than in the abovementioned study, our two recipient groups had no statistically significant difference in DGF. In addition, our two recipient groups also had no differences in pulmonary infection and PNF. We attribute this partly to our use of refined surgical techniques, carefully managed immunosuppressive therapy, and experience in perioperative management.
Our study had some limitations. First, it was limited by the retrospective design, so the results may be subject to bias. Second, our sample size was relatively small. In spite of these shortcomings, our data provide more evidence to support the use of SKT from small pediatric donors.
In conclusion, our study showed that excellent 1-year, 3-year, and 5-year patient and graft survival and 5-year death-censored graft survival can be achieved by SKT from small pediatric donors, and that the results were similar when the donors were 8 years-old or less or 9 to 18 years-old. Although short-term complications after transplantation were common, appropriate management led to satisfactory clinical results. In short, SKT from pediatric donors doubles the number of potential recipients. Large prospective studies of this topic are eagerly anticipated.