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Saudi Journal of Kidney Diseases and Transplantation
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Year : 2017  |  Volume : 28  |  Issue : 4  |  Page : 945-946
The importance of calciuria on sodium fractional excretion rate

1 Department of Cardiology, Rajaie Cardiovascular Medical and Research Center, University of Medical Sciences, Tehran, Iran
2 Department of Cardiology, Tabriz University of Medical Sciences, Tabriz, Iran
3 Department of Nephrology, Sevome-e-Shaban Hospital, Tehran, Iran

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Date of Web Publication21-Jul-2017

How to cite this article:
Moradian M, Ghaffari S, Malaki M. The importance of calciuria on sodium fractional excretion rate. Saudi J Kidney Dis Transpl 2017;28:945-6

How to cite this URL:
Moradian M, Ghaffari S, Malaki M. The importance of calciuria on sodium fractional excretion rate. Saudi J Kidney Dis Transpl [serial online] 2017 [cited 2022 Jan 17];28:945-6. Available from: https://www.sjkdt.org/text.asp?2017/28/4/945/211360

To the Editor,

Fractional excretion of sodium (FENa) is a well-known laboratory marker that can help to differentiate prerenal azotemia from acute tubular necrosis , an FENa of <1% indicating a prerenal cause and value >3% indicating tubular damage.[1]

Urine sodium excretion can be influenced by a phenomenon: calcium affecting on tubular function inducing natriuresis.[2] Hypercalciuria is observed in nearly half of ill children.[3]

In 40 children aged over two years who were admitted to Intensive Care Unit ward we found that FENa higher in hypercalciuric chidren (urine calcium/creatinine >0.2) than in children with normal calcium excretion (1.9 ± 2.1 vs. 0.8 ± 0.7 (P 0.03) [Table 1]. FENa is prominently higher if hypercalciuria occurs in normal hydration and with normal GFR compared to that seen in dehydrated children or those with reduced GFR (defined as <75 mL/ min/1.73 m2)[4] [Table 1]. There is also a linear correlation between urine calcium excretion and FENa (R2: 0.2, P 0.007) [Figure 1]. Earlier in 1985, FENa as a diagnostic tool has been questioned in especial clinical conditions by Zarich et al[5] after then Adami[2] explained physiologically that calcium excretion can affect sodium excretion rate if calcium sensing receptor on renal tubules are activated to inhibit both calcium and sodium reabsorption. They found that hypercalcemia leads to natriuresis and volume depletion. They also found that severe hypercalcemia and volume contraction can trigger more calcium reabsorbtion aggravating the hypercalcemia. Kovacevic et al[6] found that sodium and phosphate excretion lead to hypercalciuria. Adami[2] and Kovacevic et al[6] show that calcium can induce natriuresis and sodium can also induce hypercalciuria. Our result show these mechanisms can be activated in normal glomerular filtration rate (GFR) situations (GFR >75 mL/min/ 1.73 m2.
Table 1: Sodium fractional excretion of sodium in two groups of normal calcium excretion and hypercalciuria groups in different conditions.

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Figure 1: Relation of fractional excretion of sodium and urine calcium (calcium/creatinine randomly).

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Hypercalciuria is a common finding in ill immobilized children and has strongly related to FENa , this effect being more prominent in normal GFR; There is also a linear relationship between urine calcium excretion level and FENa. Thus, FENa is not a reliable laboratory test to detect and differentiate renal tubular function in conditions of hypercalciuria.

   Acknowledgement Top

We dedicate this study to our leader Dr. Mohammad Mosadegh, god bless his soul.

Conflict of interest: None declared.

   References Top

Espinel CH. The FENa test. Use in the differential diagnosis of acute renal failure. JAMA 1976;236:579-81.  Back to cited text no. 1
Adami S, Parfitt AM. Calcium-induced natriuresis: Physiologic and clinical implications. Calcif Tissue Int 2000;66:425-9.  Back to cited text no. 2
Malaki M. Renal leak; mechanism of hypercalciuria in short-term immobilization. Int J Crit Illn Inj Sci 2015;5:216-7.  Back to cited text no. 3
[PUBMED]  [Full text]  
Pottel H, Hoste L, Delanaye P. Abnormal glomerular filtration rate in children, adolescents and young adults starts below 75 mL/min/1.73 m2. J Int Pediatr Nephrol Assoc 2015;30:821-8.  Back to cited text no. 4
Zarich S, Fang LS, Diamond JR. Fractional excretion of sodium. Exceptions to its diagnostic value. Arch Intern Med 1985;145:108-12.  Back to cited text no. 5
Kovacevic L, Kovacevic S, Smoljanic Z, et al. Renal tubular function in children with hypercalciuria. Srp Arh Celok Lek 1998;126:223-7.  Back to cited text no. 6

Correspondence Address:
Majid Malaki
Department of Nephrology, Sevome-e-Shaban Hospital, Tehran
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PMID: 28748905

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