Clinical Approach and Lab Eval of Renal Dz

Question 1

What are some ddx for edema and ascites when it comes to renal disease?

Answer 1

• nephrotic syndrome
• overhydration in cats with AKI

Question 2

At what systolic pressure fundic exam should be highly encourage?

Answer 2

> 160mm Hg

Question 3

What are some pre-renal causes of azotemia that can also have a low USG?

Answer 3

1. lack of medullary hypertonicity. Ex. hypoadrenocorticism, very protein restricted diet
2. interference of tubular function (ex. diuretics)
3. interference of collecting duct function (ex. diabetes insipidus)

Question 4

What lab test can be used to confirm uroabdomen?

Answer 4

if the creatinine in the abdominal/ peritoneal fluid is >2 higher than creatinine in blood

Question 5

How is urea produced?

Answer 5

• produced from ammonia
• derived from amino acids as part of the ornithine cycle in the liver
• can be on endogenous or exogenous protein source

Question 6

What are some non-renal differentials for increased urea?

Answer 6

• hypovolemia, dehydration
• any conditions that have increased protein catabolism: infection, burns, fever, starvation, hyperthyroidism)
• upper GI bleeding = important cause

Question 7

What are some conditions that can lower urea concentration?

Answer 7

• liver dysfunction
• portosystemic shunt
• low protein diet

Question 8

How is creatinine made?

Answer 8

dehydration of creatin and desphosphorylation of phosphocreatine in muscle

Question 9

How is urea metabolized by the kidneys?

Answer 9

• filtered through the glomerulus, and passively reabsorbed in the tubules
• reabsorption is increased with decreased tubular flow rate - ex. hypovolemia, dehydration

Question 10

How is creatinine metabolized by the kidneys?

Answer 10

• freely filtered in the glomerulus
• clinically negligible secretion into the tubules

Question 11

What are some non-renal conditions that can increase the creatinine level?

Answer 11

• young kittens

Question 12

Which dog/ cat breeds have increased creatinine?

Answer 12

Greyhounds
Birmans

Question 13

What conditions can lead to a decrease in creatinine serum concentration?

Answer 13

• decreased muscle mass
• young animals… but young kittens have relatively high serum creatinine

Question 14

How sensitive is creatinine level regarding GFR?

Answer 14

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

Question 15

Does the magnitude of the creatinine elevation provide chronicity/ reversibility info?

Answer 15

No
- also won’t know if it’s pre-renal, renal, or post-renal

Question 16

What’s the advantage of measuring serum SDMA?

Answer 16

• 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

Question 17

Where would the abnormalities within the kidney be for proteinuria?

Answer 17

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

Question 18

What are some pre- and post-renal causes of proteinurea?

Answer 18

Pre: Bence-Jones protein
Post: UTI

Question 19

What happens to proteins with adequate renal function?

Answer 19

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

Question 20

What are the pros/ cons of urine dipstick for proteinuria?

Answer 20

• 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

Question 21

What are some advantages of UPC ratio?

Answer 21

• 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)

Question 22

What UPCR is considered significant?

Answer 22

Dog: > 0.5
Cat: > 0.4
>2.0 = highly suggestive of glomerular disease

Question 23

How much changes must be noted on UPCR

Answer 23

• must change by ~35% if UPC > 12 or by 80% for UPC > 0.5 for it to be more than just daily variation

Question 24

What are some indications for renal biopsy?

Answer 24

• primary glomerular disease
• persistent UPCR > 3.5
• unresponsive to anti-proteinuric therapy
• progressive proteinuria or decline in renal function despite appropriate therapy

Question 25

What are some contraindications for renal biopsy?

Answer 25

• bleeding disorder
• ISIS stage 4
• primarily tubulointerstitial disease
• hydronephrosis, pyelonephritis, hemostatic disorders, abscess
• amyloidosis or hereditary nephropathy

Question 26

What’s the % of satisfactory renal biopsy samples?

Answer 26

86.2% in cats and 87.6% in dogs

Question 27

What’s the min samples that should be obtained from renal biopsy with TruCut?

Answer 27

2 x 10mm
min 18G needle, up to 14G if bigger patient

Question 28

What’s the complication rate of renal biopsy?

Answer 28

cat: 18.9%
dog: 13.4%
risk factors = severe azotemia, small patient size

Question 29

What’s the most common complication of renal biopsy?

Answer 29

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

Question 30

What’s nephrotic syndrome?

Answer 30

• hypercholesterolemia
• proteinuria
• cavitary effusion or peripheral edema

Question 31

Which transporter is mainly responsible for reabsorption of glucose in the proximal tubule?

Answer 31

SGLT2

Question 32

Does hypoalbuminemia equate to hypercoagulability?

Answer 32

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

Question 33

What’s the function of ADH?

Answer 33

induces more aquaporin at the collecting duct to facilitate reabsorption of waterW

Question 34

Where is the majority of water reabsorbed?

Answer 34

proximal collecting tubule, loop and Henle, and early distal convoluted collecting tubule

Question 35

Where in the kidney is responsible for reabsorption of H+ and bicarbonate ion?

Answer 35

proximal tubule

Question 36

Where in the kidney is responsible for secretion of H+ and urine pH

Answer 36

distal tubule

Question 37

When assessing origin of blood cells, which characteristic tips off to renal origin (vs lower urinary tract)

Answer 37

casts

Question 38

What the cylindruria mean?

Answer 38

• presence of cast in urine
• implies renal damage –> ascending limb of the loop of Henle and the collecting duct

Question 39

What’s hyaline cast?

Answer 39

• colourless, proteinaceous cast
• can be normal in low numbers, after extreme exercise or fever
• most common associated with proteinuria

Question 40

What’s the significance of granular casts?

Answer 40

partial degradation of the cellular component of the cast
- ischemic or nephrotoxic renal tubular insult

Question 41

What’s the significance of epithelial casts?

Answer 41

direct tubular cellular damage

Question 42

What’s the significance of erythrocyte casts?

Answer 42

renal hemorrahge

Question 43

What’s the significance of white blood cell casts?

Answer 43

renal inflammation or acute tubular necrosis