Zomorodian Alireza, Moe Orson W
Charles and Jane Pak Center for Mineral Metabolism and Clinical Research, University of Texas Southwestern Medical Center, Dallas, TX, USA.
Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX, USA.
Clin Kidney J. 2025 Aug 4;18(9):sfaf244. doi: 10.1093/ckj/sfaf244. eCollection 2025 Sep.
Citrate, a tricarboxylic acid cycle intermediate, plays a central role in renal physiology by acting as both a urinary base equivalent and a potent inhibitor of calcium stone formation. Hypocitraturia, a common metabolic abnormality in calcium nephrolithiasis, is not a binary disorder but a continuum shaped by acid-base status, diet, potassium balance, proximal tubular handling, and systemic citrate status. We provide an update on the biology of citrate, renal regulation of its excretion, clinical pathophysiology, and treatment of hypocitraturia. Identical urinary citrate levels may have different implications depending on systemic acid-base status and urinary calcium excretion. Hypocitraturia prevalence is increasing, paralleling rises in metabolic syndrome, obesity, and dietary habit changes. Experimental models confirm that systemic or intracellular acidosis, potassium deficiency, and upregulation of renal transport and metabolism of citrate reduce urinary citrate, enhancing stone risk. Potassium citrate remains the cornerstone of therapy, increasing both urinary citrate and pH. However, its use requires caution in calcium phosphate stone formers and patients with chronic kidney disease. Citrate resistance, defined as inadequate urinary citrate response despite good potassium delivery, is a therapeutic challenge. Novel interventions including sodium-dicarboxylate cotransporter-1 (NaDC-1) inhibitors and citrate analogs such as hydroxycitrate may offer future alternatives. In conclusion, urinary citrate must be interpreted within physiological and clinical contexts. Recognizing hypocitraturia as a modifiable, non-binary risk factor allows for more precise risk stratification and individualized therapy in stone prevention, particularly when lithogenicity overlaps with acid-base and renal abnormalities.
柠檬酸是三羧酸循环的中间产物，通过作为尿碱当量和钙结石形成的有效抑制剂，在肾脏生理学中发挥核心作用。低枸橼酸尿症是钙肾结石常见的代谢异常，它不是一种二元性疾病，而是一种由酸碱状态、饮食、钾平衡、近端肾小管处理和全身枸橼酸状态所塑造的连续体。我们提供了关于枸橼酸生物学、肾脏对其排泄的调节、临床病理生理学以及低枸橼酸尿症治疗的最新信息。相同的尿枸橼酸水平根据全身酸碱状态和尿钙排泄情况可能具有不同的意义。低枸橼酸尿症的患病率在上升，与代谢综合征、肥胖和饮食习惯改变同步。实验模型证实，全身或细胞内酸中毒、钾缺乏以及肾枸橼酸转运和代谢的上调会降低尿枸橼酸，增加结石风险。枸橼酸钾仍然是治疗的基石，可增加尿枸橼酸和pH值。然而，在磷酸钙结石患者和慢性肾脏病患者中使用时需要谨慎。枸橼酸抵抗是指尽管钾摄入充足但尿枸橼酸反应不足，这是一个治疗挑战。包括二羧酸钠共转运体-1（NaDC-1）抑制剂和羟基枸橼酸等枸橼酸类似物在内的新型干预措施可能提供未来的替代选择。总之，必须在生理和临床背景下解读尿枸橼酸。将低枸橼酸尿症视为一个可改变的、非二元性的风险因素，有助于在结石预防中进行更精确的风险分层和个体化治疗，特别是当致石性与酸碱和肾脏异常重叠时。
