Editing Azotemia (section)

===Postrenal azotemia===
[[hydronephrosis|Blockage of urine flow]] in an area below the kidneys results in postrenal azotemia. It can be caused by [[congenital abnormalities]] such as [[vesicoureteral reflux]], blockage of the [[ureter]]s by [[kidney stone]]s, [[pregnancy]], compression of the ureters by [[cancer]], [[prostatic hyperplasia]], or blockage of the [[urethra]] by kidney or [[bladder stone]]s.<ref name=robbins7 /> Like in prerenal azotemia, there is no inherent renal disease. The increased resistance to urine flow can cause back up into the kidneys, leading to [[hydronephrosis]].<ref name=goljanpath />

The BUN:Cr in postrenal azotemia is initially >15. The increased [[nephron]] tubular pressure (due to fluid back-up) causes increased reabsorption of urea, elevating it abnormally relative to creatinine.<ref name="goljanpath" /> Persistent obstruction damages the tubular epithelium over time, and renal azotemia will result with a decreased BUN:Cr ratio.<ref>{{cite web|url=http://www.consultation.ayurvediccure.com/types-of-azotemia/|title=Types of Azotemia|website=AyurvedicCure.com|access-date=2010-10-20|archive-url=https://web.archive.org/web/20160316004603/http://www.consultation.ayurvediccure.com/types-of-azotemia/|archive-date=2016-03-16|url-status=dead}}</ref>