Medline ® Abstract for Reference 94

of 'Causes and evaluation of hyperkalemia in adults'

94
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Intrarenal urea recycling leads to a higher rate of renal excretion of potassium: an hypothesis with clinical implications.
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Kamel KS, Halperin ML
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Curr Opin Nephrol Hypertens. 2011 Sep;20(5):547-54.
 
PURPOSE OF REVIEW: This review aims to illustrate why urea recycling may play an important role in potassium (K⁺) excretion and to emphasize its potential clinical implications.
RECENT FINDINGS: A quantitative analysis of the process of intrarenal urea recycling reveals that the amount of urea delivered to the distal convoluted tubule is about two-fold larger than the quantity of urea excreted in the urine. As the number of osmoles delivered to the late cortical distal nephron (CCD) determines its flow rate when aquaporin 2 water channels have been inserted in the luminal membrane of principal cells, urea recycling may play an important role in regulating the rate of excretion of K⁺when the distal delivery of electrolytes is not very high.
SUMMARY: Urea recycling aids the excretion of K⁺; this is especially important in patients with disorders or those who are taking drugs that lead to a less lumen-negative voltage in the CCD. As a large quantity of urea is reabsorbed daily in the inner medullary collecting duct, the assumptionmade in the calculation of the transtubular K concentration gradient that there is no appreciable reabsorption of osmoles downstream CCD is not valid.
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Keenan Research Centre in the Li Ka Shing Knowledge Institute, St. Michael's Hospital, Division of Nephrology, University of Toronto, Toronto, Ontario, Canada.
PMID