The first thing that disappears in renal failure is the ability of the kidney to concentrate urine. This
occurs before Cr/BUN think about increasing, or even having renal tubular casts. Example: taking
urine in the morning and doing the specific gravity of the urine and seeing what it is. B/c, specific
gravity can tell you if it is concentrated or dilute urine. If the specific gravity is greater than 1.023,
this means that the pt is concentrating urine and that the kidneys are ABSOLUTELY NORMAL (this is
a CHEAP test). Example: let’s say I did a specific gravity of urine overnight and it is 1.010 – this is
very hypotonic urine, and it means that the pt could not concentrate, and that the pt is in renal
failure. (BUN/Cr will not help determine this). The urine that should be concentrated is from a pt
that is sleeping overnight.
Hyaline cast – cast of a protein; mostly b9/harmless (all other casts have pathological significance).
Uric acid crystal – looks like a star; pH of the urine has to be acidic to form a uric acid crystal. Pt
with gout – want to stop crystals from forming, and you know they form in low pH, what do you
want to do with the urine? Alkalinize it. How can you do that? Carbonic Anhidrase inhibitor
(acetazolamide). By blocking bicarbonate reclamation will alkalinize the urine, and prevent stones
from forming. So, simple manipulation of the pH can prevent urate nephropathy.
Calcium Oxalate crystal – look like the back of an envelope; why is this imp to know? Example:
street person comes in, stupurous, has increased anion gap metabolic acidosis. Do a urinalysis, and
see bunch of calcium oxalate stones – what did he drink? Ethylene glycol. What is the MC stone we
pass? Ca oxalate. So if you have a Ca Oxalate stone, you will have crystals associated with it.
Horse kidney –joined at their lower poles. Will ask what is restricting the movement of the kidney?
IMA – it traps the kidney.
Cystic dz of the kidney –
A. Infantile polycystic kidney dz,
which is auto recessive; therefore it is present at birth. Do you think this baby is urinating? No,
therefore has oligohydramnios (decrease