Is A Low-grade Kidney Infection Possible Given The Creatinine And GFR Results?

Is there such a thing as a low-grade kidney infection? My nephrologist told me there is not. That any kind of kidney infection would either hospitalize me or wreak such horrific pain that I would be calling 911. This is very important, as I am in renal failure, and my creatin recently went, abruptly, from 2.71 to 3.3 and GFR from 20 to 13. She does not attribute this to tripled dosage of metanazole, but to bactrim given by another doctor for urinary tract infection. I was actually better in terms of urine outpout after taking three doses of bactrim, and ... well, you get the picture.