Part 3: Polyuria/Polydipsia disorders ctd--> Guidelines for interpreting USGref
Why do animals lose renal concentrating ability in chronic renal failure?
there are less functional nephrons, so each nephron that is working is forced to handle more and more solute, which means that the problem is that of SOLUTE DIURESIS. THEN, Medullary hypertonicity is not maintained (ie, reduced gradient), which is usually due to Damaged medullary tissue or poor blood flow--> dec Na and Cl xport in the ascending LOH, and then the distal tubules are less responsive to ADH (so, overall, Too much H2O gets past the proximal tubes, and Defective ability to conserve H2O in loop and distal nephron)
explain how a graph of osmolality looks when it's plotting chronic renal failure. why does it look like this?
basically a flat line which stays within the bounds of isosthenuria (1.007-1.013), because there is an impared ability to concentrate AND dilute
how do cats/dogs/horses+cattle compare in their concentrating ability?
cats have the best ability to concentrate (they can get up to >1.080), where dogs are in the middle, and horses+cattle has the least ability (max 1.045). This means they all have different "cut-offs"
if you have a dehydrated animal with a USGref of apprx greater than 1.030, what would you think?
normal response, the dehydration is not because of a renal problem
if you have a dehydrated animal with a USGref of 1.014-1.030, what would you think?
the animal has an IMPAIRED ABILITY TO CONCENTRATE which implies renal failure. OR it could imply diabetes mellitus (glucosuria-->solute diuresis), or hypoadrenocorticism (dec in ADH stimulus), or diabetes insipidus (central causing dec in ADH, or renal due to pyometra, inc [tCa2+], liver failure, etc)
if you had a dehydrated animal with a USGref of 1.007 –1.013, what would you think, and what would you look for next to determine what?
this is in the ISOSTHENURIC range. So next you would see if there is AZOTEMIA. If there is azotemia, it indicates renal insufficiency/failure. If there ISNT, then it's prolly hypoadrenocorticism(which is responsible for directly decreasing ADH)
if you have a dehydrated animal with a USGref of < 1.007 what do you think?
NOT A RENAL PROBLEM, because this is in the hyposthenuric range which means the kidney is DILUTING. what causes dehydration and diluted urine? either (1) Diabetes insipidus (central: dec in ADH due to pituitary disease, hyperadrenocort(inc in cortisol so dec in ADH), etc) (renal: (pyometra, inc [tCa2+], liver failure, etc) OR (2) hypoadrenocorticism (inc in dec in Na and Cl conc which dec stimulus for ADH to be released)
what is Oliguric?
dec output of urine (think renal failure)
if you have an oliguric animal with a USGref 1.014 –1.030 what do you think?
Suspect acute renal failure (should be azotemic)
if you have an oliguric animal with a USGref 1.007 –1.013 what do you think?
isosthenuric range! Oliguric chronic or acute renal failure
if you have a Glucosuric animal with a USGref> 1.020, versus a USGref 1.007 –1.020, what is the difference?
in >1.020, the kidney is trying to concentrate, but the glucose is causing a solute diuresis. a USGref 1.007 –1.020, means there is diabetes mellitus (solute diuresis) AND medullary washout, and has the implication of Chronic renal disease / failure
the the animal has Hyponatremia & hypochloremia, and has a USGref > 1.020, what do you think is going on?
trying to concentrate. probably Hypoadrenocorticism & dehydrated
the the animal has Hyponatremia & hypochloremia, and has a USGref1.007 –1.013, what do you think is going on?
Urinary Protein to Creatinine Ratio (Prot:Crt)u is aka?
what should you know about creatinine levels (key concept)
Basically a CONSTANT amount of crt is produced by muscle each day(via degradation of creatine), and that constant amount is excreted by the kidneys each day. HOWEVER, the amount of H2O excreted by the kidneys on any given day changes, so, the [crt] that is excreted varies with amount of H2O excreted.
under physiological conditions, if Crt is dec, what should you think about protein? If there is renal damage, THEN what does the prot:crt ratio look like?
under normal circumstances, if creatinine clearance decreases, then protein should be decreased too (bc crt readily passes filtration barrier). If more protein enters urine through damaged glomeruli then rate of glomerular protein excretion is increased compared to Crt
so, in short, Urinary excretion of protein can be assessed by comparing.... ?
urine protein & creatinine concentrations
what do you use the (Prot:crt)u ratio to determine? what stipulations must you follow?
you can determine the severity of the glomerular proteinuria ( severity of protein loss due to glomerular leakage of plasma proteins) BUT!!!!!!!! you need to exclude ALL OTHER CAUSES OF PROTEINURIA, such as prerenal, tubular, hemorrhagic))
what is the (Prot:crt)u for healthy dogs? border line values? Glomerular proteinuria?