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Kidney function tests: Difference between revisions
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<section begin="clinical biochemistry" />Several laboratory tests can be used to estimate the kidney function. These are important in the evaluation of [[chronic kidney disease]] (CKD) and [[acute kidney injury]] (AKI). The most common one is using the serum creatinine level to calculate the estimated [[glomerular filtration rate]] (eGFR). | <section begin="urology" /><section begin="clinical biochemistry" />Several laboratory tests can be used to estimate the kidney function. These are important in the evaluation of [[chronic kidney disease]] (CKD) and [[acute kidney injury]] (AKI). The most common one is using the serum creatinine level to calculate the estimated [[glomerular filtration rate]] (eGFR). The normal GFR is approximately 120 mL/min for a person with 1,73 m2 of body surface. | ||
== Serum creatinine == | == Serum creatinine == | ||
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In chronic kidney disease, several toxic compounds accumulate as the kidney cannot eliminate them. The level of urea in the serum correlates to the level of these toxic compounds, in addition to being a toxic compound itself, although it is uncertain how toxic urea actually is ''in vivo''. | In chronic kidney disease, several toxic compounds accumulate as the kidney cannot eliminate them. The level of urea in the serum correlates to the level of these toxic compounds, in addition to being a toxic compound itself, although it is uncertain how toxic urea actually is ''in vivo''. | ||
Urea also accumulates in acute kidney injury. In prerenal and postrenal AKI, urea increases more than creatinine. In intrarenal AKI, the creatinine increases more than the urea. | Urea also accumulates in acute kidney injury. In prerenal and postrenal AKI, urea increases more than creatinine. In intrarenal AKI, the creatinine increases more than the urea. The "rule" that (for American units) a blood urea nitrogen (BUN) to creatinine ratio of > 20:1 indicates a prerenal AKI, while a ratio of < 10:1 indicates intrarenal cause of AKI, but studies have not shown this to be reliable on its own to determine the type of AKI. | ||
Urea can also be elevated from other causes, including [[gastrointestinal bleeding]] and increased protein catabolism. | Urea can also be elevated from other causes, including [[gastrointestinal bleeding]] and increased protein catabolism. | ||
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== Tubular function == | == Tubular function == | ||
There is no serum marker for tubular function. To evaluate function of the kidney tubules, one must examine the urine. Low urine osmolality, high urinary sodium concentration, and [[proteinuria]] are typical features of kidney tubule dysfunction or injury. This may reflect tubulointerstitial AKI or CKD. | There is no serum marker for tubular function. To evaluate function of the kidney tubules, one must examine the urine. Low urine osmolality, high urinary sodium concentration, and [[proteinuria]] are typical features of kidney tubule dysfunction or injury. This may reflect tubulointerstitial AKI or CKD. | ||
<section end="clinical biochemistry" /> | <section end="clinical biochemistry" /><section end="urology" /> | ||
== References == | == References == | ||
<references /> | <references /> | ||
[[Category:Laboratory Medicine]] | [[Category:Laboratory Medicine]] | ||