I spend a lot of time talking about how incredible the kidney is but then sometimes you see kidneys that just don’t do anything. I was in the hospital and we had a patient develop acute on chronic kidney disease. Following a few days of anuria they started to make urine so we checked urine creatinine to see how well the kidney was recovering.
Not good, Bob.
The patient had among the lowest urine creatinines I had ever seen. Compare the urine creatinine of 14 to the serum creatinine of 10 and you see the laziest nephron ever. It is barely altering the composition of the urine at all.
The patient also had the highly unusual situation with urine Na greater than serum Na. I think I have only ever seen that in cases of severe hyponatremia due to SIADH.
This patient had a fractional excretion of Na of 70%. Amazing. Normally the kidney reabsorbs 99% of the filtered sodium, here 70% of the filtered sodium just flies by.
This helped our discussions on the patient’s renal prognosis. The urine they were making was a useless gasp of a dying organ.
