Hyperoxaluria and systemic oxalosis: current therapy and future directions

Excessive urinary oxalate excretion, termed hyperoxaluria, may arise from inherited or acquired diseases. The most severe forms are caused by increased endogenous production of oxalate related to one of several inborn errors of metabolism, termed primary hyperoxaluria. Recurrent kidney stones and progressive medullary nephrocalcinosis lead to the loss of kidney function, requiring dialysis or transplantation, accompanied by systemic oxalate deposition that is termed systemic oxalosis. For most primary hyperoxalurias, accurate diagnosis leads to the use of therapies that include pyridoxine supplementation, urinary crystallisation inhibitors, hydration with enteral fluids and, in the near future, probiotic supplementation or other innovative therapies. These therapies have varying degrees of success, and none represent a cure. Organ transplantation results in reduced patient and organ survival when compared with national statistics. Exciting new approaches under investigation include the restoration of defective enzymatic activity through the use of chemical chaperones and hepatocyte cell transplantation, or recombinant gene therapy for enzyme replacement. Such approaches give hope for a future therapeutic cure for primary hyperoxaluria that includes correction of the underlying genetic defect without exposure to the life-long dangers associated with organ transplantation.     

肾移植术后Ⅰ型原发性高草酸尿症复发致移植肾功能不全的多学科综合诊疗

目的探讨肾移植术后Ⅰ型原发性高草酸尿症(PH)复发的临床特点和多学科综合诊疗(MDT)的经验。方法对1例接受同种异体肾移植手术后不明原因移植肾功能短期内迅速下降的病例进行MDT讨论,总结MDT在诊断罕见遗传性疾病以及提高肾移植受者长期存活中的作用。结果经MDT讨论,患者确诊为Ⅰ型PH复发,排除排斥反应后恢复常规免疫抑制方案,嘱大量饮水,予优质蛋白和低磷饮食、维生素B6、钙剂等保守治疗措施并积极防治并发症。患者移植肾功能恶化延缓,但仍在肾移植术后5个月恢复规律血液透析至投稿日。结论肾移植术后Ⅰ型PH复发较为罕见,临床主要表现为复发性肾结石,移植肾功能下降,且并发症多,患者预后不良。通过MDT讨论患者病情,明确诊断,确定最佳治疗方案,延缓了病情进展,改善了患者预后。     

Combined liver‐kidney transplantation for primary hyperoxaluria type I in children: Single Center Experience

Primary hyperoxalurias are rare inborn errors of metabolism with deficiency of hepatic enzymes that lead to excessive urinary oxalate excretion and overproduction of oxalate which is deposited in various organs. Hyperoxaluria results in serious morbid‐ity, end stage kidney disease (ESKD), and mortality if left untreated. Combined liver kidney transplantation (CLKT) is recognized as a management of ESKD for children with hyperoxaluria type 1 (PH1). This study aimed to report outcome of CLKT in a pediatric cohort of PH1 patients, through retrospective analysis of data of 8 children (2 girls and 6 boys) who presented by PH1 to Wadi El Nil Pediatric Living Related Liver Transplant Unit during 2001‐2017. Mean age at transplant was 8.2 ± 4 years. Only three of the children underwent confirmatory genotyping. Three patients died prior to surgery on waiting list. The first attempt at CLKT was consecutive, and despite initial successful liver transplant, the girl died of biliary peritonitis prior to scheduled renal transplant. Of the four who underwent simultaneous CLKT, only two survived and are well, one with insignificant complications, and other suffered from abdominal Burkitt lymphoma managed by excision and resection anastomosis, four cycles of rituximab, cyclophosphamide, vincristine, and prednisone. The other two died, one due to uncontrollable bleeding within 36 hours of procedure, while the other died awaiting renal transplant after loss of renal graft to recurrent renal oxalosis 6 months post‐transplant. PH1 with ESKD is a rare disease; simultaneous CLKT offers good quality of life for afflicted children. Graft shortage and renal graft loss to oxalosis challenge the outcome.     

Glyoxylate determination in rat urine by capillary electrophoresis

Oxalate is important in the study of renal stone formation and is derived from the endogenous metabolism of glyoxylate. The aim of this study was to determine urinary glyoxylate levels by capillary electrophoresis (CE). Urine specimens were obtained from 25 male Wistar rats (16 rats intravenously injected with 10 mg or 20 mg glyoxylate and nine controls) by bladder puncture 1 h after administration of glyoxylate or saline. Urinary glyoxylate was measured by CE using an electrolyte composed of 5 mmol/L pyridinedicarboxylic acid and 0.5 mmol/L cetyltrimethylammonium bromide (pH 5.6 and 11.0). The mean +/- SD urinary glyoxylate concentration was 43.1 +/- 14.7 micromol/L in control rats, 722.8 +/- 165.5 micromol/L in rats given 10 mg of glyoxylate and 1290.0 +/- 470.8 micromol/L in rats given 20 mg of glyoxylate. The mean +/- SD recovery after spiking 675.7 micromol/L of glyoxylate into 16 urine specimens was 98.82 +/- 12.81%. When the reproducibility of urinary glyoxylate determination was assessed, the intra-assay coefficient of variation (CV) ranged from 1.38 to 2.59% and the inter-assay CV ranged from 2.94 to 6.69%. Capillary electrophoresis enables sensitive and reproducible determination of urinary glyoxylate levels in rats. This method appears to be suitable for laboratory use and has the advantage of determining glyoxylate and several other urinary anions simultaneously.