Yesterday we focused on the oliguric patient. I will provide the essence of that chalk talk.
For the purpose of this talk, we define oliguria as < 500 cc / day or 20 cc / hr
- Always consider obstruction first. Pass a urinary catheter. If small amount of urine, remove it. You still need to consider a renal ultrasound. I have seen a patient with bilateral painless kidney stones.
- Once obstruction is excluded, please send urine Na and creatinine. If the patient has received a diuretic also order a urine urea.
- If you want to try things – diuretics or volume, you may – if you have sent off the urine values already.
- Calculate FeNa &/or FeUrea (see previous note) I like Nephromatic for the calculations.
- If low FeNa, then the patient is prerenal. The possibilities include volume contraction, CHF, cirrhosis, or …
- If the numbers are prerenal and none of the above is obvious think more broadly. Glomerulonephritis can cause prerenal numbers. Renal artery obstructions can do it – think aortic aneurysm or clot.
- If the FeNa is high, then the patient likely has ATN – call renal.
The most important things to remember are:
r/o obstruction
send urine chemistries
You cannot afford to miss obstruction. If you get the numbers prior to trying treatments, then you can always reconstruct the etiology.
