Prerenal azotemia

Azotemia (azot, 'nitrogen' + -emia, 'blood condition') is a medical condition characterized by abnormally high levels of nitrogen-containing compounds (such as urea, creatinine, various body waste compounds, and other nitrogen-rich compounds) in the blood. It is largely related to insufficient or dysfunctional filtering of blood by the kidneys. It can lead to uremia and acute kidney injury (kidney failure) if not controlled. Azotemia (azot, 'nitrogen' + -emia, 'blood condition') is a medical condition characterized by abnormally high levels of nitrogen-containing compounds (such as urea, creatinine, various body waste compounds, and other nitrogen-rich compounds) in the blood. It is largely related to insufficient or dysfunctional filtering of blood by the kidneys. It can lead to uremia and acute kidney injury (kidney failure) if not controlled. A urinalysis will typically show a decreased urine sodium level, a high urine creatinine-to-serum creatinine ratio, a high urine urea-to-serum urea ratio, and concentrated urine (determined by osmolality and specific gravity). None of these is particularly useful in diagnosis. In pre-renal and post-renal azotemias, elevation of the BUN exceeds that of the creatinine (i.e., BUN>12*creatinine). This is because BUN is readily reabsorbed by the kidneys while creatinine is not. In congestive heart failure (a cause of pre-renal azotemia) or any other condition that causes poor perfusion of kidneys, the sluggish flow of glomerular filtrate results in excessive absorption of BUN and elevation of its value in blood. Creatinine, however, is not absorbable and therefore does not rise significantly. Stasis of urine in post-renal azotemia has the same effect.