Bolen Erin, Stern Karen, Humphreys Mitchell, Brady Alexandra, Leavitt Todd, Zhang Nan, Keddis Mira
Mayo Clinic Alix School of Medicine, Scottsdale, AZ, USA.
Department of Urology, Mayo Clinic, Mayo Clinic College of Medicine and Science, Scottsdale, AZ, USA.
Clin Kidney J. 2021 Oct 20;15(3):500-506. doi: 10.1093/ckj/sfab208. eCollection 2022 Mar.
Nephrolithiasis in allograft kidneys is rare, but this diagnosis may lead to allograft complications and patient morbidity. Previous studies that have evaluated nephrolithiasis posttransplant have focused on surgical stone management, with limited data on urine metabolic risk factors and the presence of stones after follow-up.
We retrospectively evaluated kidney transplant recipients who were diagnosed with transplant nephrolithiasis between 2009 and 2019. Computed tomography and ultrasound imaging were used to confirm stone presence.
The incidence of allograft kidney stone formation was 0.86% of 6548 kidney transplant recipients. Of the 56 cases identified, 17 (30%) had a pretransplant history of nephrolithiasis. Only four (7%) patients received a known kidney stone at the time of allograft implantation. Of the 56 cases, 34 had a 24-h supersaturation study. The urine supersaturation study showed 32 patients (94%) had a urine citrate of <450 mg excreted in 24 h (median 124.5 mg/24 h, reference range >500 mg/24 h), along with 22 patients (61%) having a urine oxalate excretion of ≥30 mg in 24 h (median 34.4 mg/24 h, reference range <30 mg/24 h). Calcium oxalate composition was most common (91% with >1 supersaturation for calcium oxalate crystals), with normal median urine calcium levels (median urine calcium 103.5 mg/24 h, reference range <200 mg/24 h). After a 4-year follow-up, 50% ( = 28) required surgical intervention and 43 (77%) patients continued to have evidence of transplant nephrolithiasis on imaging.
This is the largest study of transplant nephrolithiasis confirming that hypocitraturia and hyperoxaluria were the most significant urine metabolic risk factors associated with allograft nephrolithiasis and that hyperoxaluria was the most prevalent driver for calcium oxalate stone composition. Our study is first to show low stone-free rates at the last follow-up and a significant proportion requiring surgical intervention.
移植肾肾结石较为罕见，但该诊断可能导致移植肾并发症及患者发病。既往评估移植后肾结石的研究主要集中在手术结石处理方面，关于尿液代谢危险因素及随访后结石存在情况的数据有限。
我们回顾性评估了2009年至2019年间被诊断为移植肾肾结石的肾移植受者。采用计算机断层扫描和超声成像来确认结石的存在。
在6548例肾移植受者中，移植肾结石形成的发生率为0.86%。在确诊的56例病例中，17例（30%）有移植前肾结石病史。仅有4例（7%）患者在移植肾植入时接受了已知的肾结石。在56例病例中，34例进行了24小时过饱和研究。尿液过饱和研究显示，32例患者（94%）24小时尿枸橼酸盐排泄量<450毫克（中位数124.5毫克/24小时，参考范围>500毫克/24小时），22例患者（61%）24小时草酸排泄量≥30毫克（中位数34.4毫克/24小时，参考范围<30毫克/24小时）。草酸钙成分最为常见（91%的草酸钙晶体过饱和度>1），尿钙水平中位数正常（尿钙中位数103.5毫克/24小时，参考范围<200毫克/24小时）。经过4年随访，50%（n = 28）需要手术干预，43例（77%）患者在影像学检查中仍有移植肾肾结石的证据。
这是关于移植肾肾结石的最大规模研究，证实了低枸橼酸尿症和高草酸尿症是与移植肾肾结石相关的最重要尿液代谢危险因素，且高草酸尿症是草酸钙结石成分最常见的驱动因素。我们的研究首次表明末次随访时结石清除率低，且有很大比例的患者需要手术干预。
