Clinical Approach and Lab Eval of Renal Dz Flashcards
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
What are some contraindications for renal biopsy?
- bleeding disorder
- ISIS stage 4
- primarily tubulointerstitial disease
- hydronephrosis, pyelonephritis, hemostatic disorders, abscess
- amyloidosis or hereditary nephropathy
What’s the % of satisfactory renal biopsy samples?
86.2% in cats and 87.6% in dogs
What’s the min samples that should be obtained from renal biopsy with TruCut?
2 x 10mm
min 18G needle, up to 14G if bigger patient
What’s the complication rate of renal biopsy?
cat: 18.9%
dog: 13.4%
risk factors = severe azotemia, small patient size
What’s the most common complication of renal biopsy?
bleeding - dogs = 9.9% dogs, cats = 16.9%
- hematuria 4.2% dogs, 3.1% cats (micro hematuria is more common)
- hydronephrosis 0.4% dogs, 3.1% cats
- death 2.5% dogs, 3.1% cats
What’s nephrotic syndrome?
- hypercholesterolemia
- proteinuria
- cavitary effusion or peripheral edema
Which transporter is mainly responsible for reabsorption of glucose in the proximal tubule?
SGLT2
Does hypoalbuminemia equate to hypercoagulability?
no, used to think that antithrombin III is also lost with proteinuria/ hypalbuminemia, but more recent study showed that these parameters were not related to hypercoagulability
What’s the function of ADH?
induces more aquaporin at the collecting duct to facilitate reabsorption of waterW
Where is the majority of water reabsorbed?
proximal collecting tubule, loop and Henle, and early distal convoluted collecting tubule
Where in the kidney is responsible for reabsorption of H+ and bicarbonate ion?
proximal tubule
Where in the kidney is responsible for secretion of H+ and urine pH
distal tubule
When assessing origin of blood cells, which characteristic tips off to renal origin (vs lower urinary tract)
casts
What the cylindruria mean?
- presence of cast in urine
- implies renal damage –> ascending limb of the loop of Henle and the collecting duct
What’s hyaline cast?
- colourless, proteinaceous cast
- can be normal in low numbers, after extreme exercise or fever
- most common associated with proteinuria
What’s the significance of granular casts?
partial degradation of the cellular component of the cast
- ischemic or nephrotoxic renal tubular insult
What’s the significance of epithelial casts?
direct tubular cellular damage
What’s the significance of erythrocyte casts?
renal hemorrahge
What’s the significance of white blood cell casts?
renal inflammation or acute tubular necrosis
