Unit 3 - Renal Flashcards
What are the jobs for the kidney?
Acid-base status, electrolyte homeostasis, fluid homeostasis, blood pressure management, and toxin excretion
What can be done to evaluate renal function in a hose?
Blood work, urine color, USG, reagent strips, sediment exam, and CR and elyte clearance
What is creatinine a product of?
muscle breakdown
Where is creatinine filtered?
The kidneys
What is BUN a biproduct of?
processing ammonia by the liver
Where is BUN excreted?
the kidneys
What are the three categories for increased creatinine?
Pre-renal, renal, and post-renal
Creatinine is specific but very ______ for renal damage.
insensitive
When do you need to have a reduction in GFR before an elevation in creatinine above the baseline?
75% reduction of GFR
What will the BUN:Creat ratio be in patients with AKI?
<10:1
What will the BUN:Creat ratio be in patients with CKD?
> 10:1
Typically, if elevations in creatinine are due to pre-renal causes the electrolytes are largely ______.
unchanged
With AKI approaching ARF you will see what in the serum electrolytes?
Decreased sodium and chloride
With CKD, what will the electrolyte levels look like?
Increased Ca and P
Can SDMA be used in horses like they can be in dogs and cats?
No - at this time it is not more sensitive than BUN and creatinine
In cases of renal injury, does creatinine or BUN rise quicker?
Creatinine
When collecting urine in horses, when should samples be analyzed?
ASAP - if not analyzed within 1-2 hours then refrigerate
What is hematuria?
Presence of blood in the urine - will pellet when centrifugued
What does hematuria indicate?
There is bleeding within the URT or LRT
What causes hemoglobinuria?
intravascular hemolysis
What will hemoglobinuria look like after it is centrifuged?
It will be the same color
What is myoglobinuria due to?
Myopathy - breakdown of muscle tissue
USG is a surrogate for urine ________ i.e. a measurement of urine ______.
osmolality; tonicity
What can falsely affect USG?
glucosuria or proteinuria
What does a USG of <1.008 indicate in a horse?
it is hyposthenuric
What does a USG of 1.008-1.014 indicate in a horse?
it is isosthenuric
What does a USG of >1.014 indicate in a horse?
it is concentrated
What % loss in GFR is needed to get an isosthenuric USG?
50%
True or False: USG is more sensitive than creatinine/BUN for loss of GFR/nephron function.
True
If a patients USG is 1.008 - 1.014 can you give fluid therapy?
No
Should you give fluid therapy to a patient with a USG of <1.008?
No - the urine is dilute, likely providing fluid in excess
Should you give fluid therapy to a patient with a USG of 1.014-1.040?
No - the patient is just right
Should you give fluid therapy to a patient with a USG of >1.040?
Yes - the patient is dehydrated
Glomerular capillary wall is only permeable to substances < ________ Daltons.
20,000
What are the ‘normal’ urine proteins?
Albumin, serum globulins, and proteins secreted by the nephron
What proteins do reagent strips identify?
albumin
Normal ______ equine urine can yield a false positive trace protein.
alkaline
What should positive results of a protein reagent strip be followed up with?
Urine protein: Creatinine Ratio
Normal equine urine should be acidic/alkaline.
alkaline
What are the causes for aciduria?
Strenuous exercise, metabolic acidosis, urease producing bacteria, and horses with gastric reflux
What causes the aciduria in horses with gastric reflux?
Increase distal tubular H+ excretion in exchange for conserving K+
What does the blood test reagent test for?
perioxidase activity of red blood cells
True or False: The blood test reagent strip can differentiate between hematuria, myoglobinuria, or hemoglobinuria
False - it cannot
Is the USG test reagent accurate in the horse?
no
Where is glucose typically reabsorbed?
the proximal tubule - almost completely reabsorbed
When does glucosuria typically occur in the horse?
When the filtered load exceeds what the tubules can reabsorb
What is the renal threshold in the horse?
~160-180 mg/dl
Glucosuria without hyperglycemia is indicative of what?
Proximal tubule dysfunction
What does the kidney look like on US in cases of AKI/ARF?
Renomegaly, hyperechoic, thickened cortices, distinct corticomedullary differentiation, and perirenal edema
It is the ‘pretty kidney’
What will the kidney look like on US in cases of CKD and nephroliths?
Increased echogenicity and shadowing from a nephrolith
What is the hallmark for a nephrolith on US?
A stone is the bright spot with a shadow
Why is the left kidney difficult to find in the horse?
Because it is deep to the spleen
What is AKI?
An acute insult or injury that the kidney may recover from or may progress to ARF of CKD
What acute injury can cause AKI?
Hypovolemia, hypotension, and administration of nephrotoxic medication
What nephrotoxic medication can cause AKI?
Aminoglycosides
What form of azotemia is associated with AKI?
pre-renal azotemia
What will the USG be like in patients with AKI?
> 1.040
What may you find in the urine in AKI patients (on sediment)?
blood and casts
What is the good news with AKI?
The kidney still has concentrating abilities
What is the bad news with AKI?
The kidney needs your help and cannot wait much longer
What will the BUN and creatinine levels be like in patients with AKI and isosthenuria due to receiving a nephrotoxic medication?
They will be normal
True or False: A horse with AKI and isosthenuria due to receiving a nephrotoxic medication is euvolemic and urinating.
True
What is the good news about AKI with isosthenuria due to nephrotoxic medication?
You caught it quickly because you were monitoring
What is the bad news about AKI with isosthenuria due to nephrotoxic medication?
You have <50% of nephron function
How is AKI treated?
Restore euvolemia if necessary, remove or limit nephrotoxic medications if possible, prevent/educate the client about limiting future insults to the kidney
What clinical pathologic changes are associated with ARF?
Creatinine/BUN will be elevated, isosthenuria, and oliguria or anuria in the face of euhydration
In ARF, the kidney is literally failing to do its basic job which is to do what?
make urine
How do you treat ARF?
Remove the insult Careful, judicious, fluid boluses Furosemide \+/- Dopamine \+/- Renal replacement therapy
What is the prognosis for ARF?
poor
True or False: Treatment is better than prevention in cases of ARF
False -Prevention
True or False: CKD is likely underdiagnosed and recognized in horses
True
Define CKD.
The presence of isosthenuria and/or azotemia in the face of euhydration without an acute insult
When are horses with CKD asymptomatic? When do they become symptomatic?
If they have access to free choice water
When their creatinine is >4 mg/dL and BUN is >50 mg/dl
What type of insult may the first diagnosis of CKD be?
During an ‘acute-on-chronic’ insult i.e. a horse with CKD has diarrhea and cannot keep up with the losses
How is CKD treated?
Eliminate nephrotoxic medications
Ensure adequate access to water
+/- Omega 3 Fatty acids (not proven)
Palatable feed and ‘low protein diet’
What is the hypothesis for the cause of nephrolithiasis?
Unknown, but may be due to nidus such as previous AKI resulting in necrosis - may be associated with infection
How is nephrolithiasis diagnosed?
Since most horses are asymptomatic this is often an incidental finding
Some horses will display signs of colic or develop pyelonephritis
If you diagnose a cystolith or urethrolith, what should you do?
Look at the kidneys because there may be more
How do you treat nephrolithiasis?
Consider nephrectomy, antimocrobials to treat a concurrent infeciton, possibly benign neglect if incidental (they were fine before…)
What complication is a nephrectomy associated with?
Secondary infections - abx is indiated
If you have a patient with hematuria, what will the supernatant of the PCV tube be when you spin down the urine sample? What will the color serum be in the PCV tube if you spin down the blood from this patient?
They will both be clear
If you have a patient with hemoglobinuria, what will the supernatant of the PCV tube be when you spin down the urine sample? What will the color serum be in the PCV tube if you spin down the blood from this patient?
they will both be pink
If you have a patient with myoglobinuria, what will the supernatant of the PCV tube be when you spin down the urine sample? What will the color serum be in the PCV tube if you spin down the blood from this patient?
The serum will be clear and the supernatant will be pink
