ATN-INVESTIGATIONS

SUMMARY

1. BUN:Cr ratio is 10-15:1.
2. Urine osmolality is usually < 350 because tubules cannot concentrate the urine.

3. Urine Na+ is > 40 (however, if reabsorption of water is significantly affected, the urine Na+ becomes dilute).

4. FENa is > 2%. However, FENa can be low in contrast induced nephropathy.

5. Casts in the urine are the hallmark finding: muddy brown, "dirty" granular casts (nonspecific but very sensitive) and epithelial cell casts.

Reference(s)

Wilkinson, I. (2017). Oxford handbook of clinical medicine. Oxford: Oxford University Press.
Hannaman, R. A., Bullock, L., Hatchell, C. A., & Yoffe, M. (2016). Internal medicine review core curriculum, 2017-2018. CO Springs, CO: MedStudy.
Therapeutic Guidelines. Melbourne: Therapeutic Guidelines Limited. https://www.tg.org.au [Accessed 2021].