Clinical Approach and Lab Eval of Renal Dz Flashcards
(44 cards)
What are some ddx for edema and ascites when it comes to renal disease?
- nephrotic syndrome
- overhydration in cats with AKI
At what systolic pressure fundic exam should be highly encourage?
> 160mm Hg
What are some pre-renal causes of azotemia that can also have a low USG?
- lack of medullary hypertonicity. Ex. hypoadrenocorticism, very protein restricted diet
- interference of tubular function (ex. diuretics)
- interference of collecting duct function (ex. diabetes insipidus)
What lab test can be used to confirm uroabdomen?
if the creatinine in the abdominal/ peritoneal fluid is >2 higher than creatinine in blood
How is urea produced?
- produced from ammonia
- derived from amino acids as part of the ornithine cycle in the liver
- can be on endogenous or exogenous protein source
What are some non-renal differentials for increased urea?
- hypovolemia, dehydration
- any conditions that have increased protein catabolism: infection, burns, fever, starvation, hyperthyroidism)
- upper GI bleeding = important cause
What are some conditions that can lower urea concentration?
- liver dysfunction
- portosystemic shunt
- low protein diet
How is creatinine made?
dehydration of creatin and desphosphorylation of phosphocreatine in muscle
How is urea metabolized by the kidneys?
- filtered through the glomerulus, and passively reabsorbed in the tubules
- reabsorption is increased with decreased tubular flow rate - ex. hypovolemia, dehydration
How is creatinine metabolized by the kidneys?
- freely filtered in the glomerulus
- clinically negligible secretion into the tubules
What are some non-renal conditions that can increase the creatinine level?
- young kittens
Which dog/ cat breeds have increased creatinine?
Greyhounds
Birmans
What conditions can lead to a decrease in creatinine serum concentration?
- decreased muscle mass
- young animals… but young kittens have relatively high serum creatinine
How sensitive is creatinine level regarding GFR?
creatinine level and GFR have an exponential relationship
- at near normal GFR, a change in GFR will only result in relatively small change in creatinine
Does the magnitude of the creatinine elevation provide chronicity/ reversibility info?
No
- also won’t know if it’s pre-renal, renal, or post-renal
What’s the advantage of measuring serum SDMA?
- it’s a derived from L-arginine metabolism
- primarily excreted via filtration
- correlates well with creatinine concentration
- but less affected by muscle mass than creatinine
- may be a more sensitive marker in early renal disease in cats
Where would the abnormalities within the kidney be for proteinuria?
Glomerular: change in structure or function of the glomerular filtration barrier leading to excessive protein been filtered through
Tubular: inability for the proximal tubule to reabsorb the proteins
What are some pre- and post-renal causes of proteinurea?
Pre: Bence-Jones protein
Post: UTI
What happens to proteins with adequate renal function?
There is a limit on the medium/higher molecular weight protein that can be filtered through the glomerulus. Larger proteins are retained in the blood
What are the pros/ cons of urine dipstick for proteinuria?
- very sensitive (>80%) but low specificity, especially in cats
- false positive: alkaline, highly concentrated urine, more so in cats
- false negatively: dilute, acidic urine. Can’t detect Bence Jones protein
What are some advantages of UPC ratio?
- reflects proteinuria in the past 24h
- high sensitivity (84.6%) and specificity (81.8%)
- free catch/ mid stream/ cystocentesis = all comparable
- not influenced by hematuria unless is gross hematuria (>250cell/hpf)
What UPCR is considered significant?
Dog: > 0.5
Cat: > 0.4
>2.0 = highly suggestive of glomerular disease
How much changes must be noted on UPCR
- must change by ~35% if UPC > 12 or by 80% for UPC > 0.5 for it to be more than just daily variation
What are some indications for renal biopsy?
- primary glomerular disease
- persistent UPCR > 3.5
- unresponsive to anti-proteinuric therapy
- progressive proteinuria or decline in renal function despite appropriate therapy
