ALL the renal/urinalysis Flashcards
Renal disease
morphologic or functional lesions of any size, distribution, or etiology involving one or both kiendys
- +/- accompanied by renal failure
- tells nothing about function
Renal failure
accumulation of nitrogenous wastes & alteration in water/electrolyte/acid-base status due to reduced functional renal mass
- may eventually lead to uremia
Azotemia
an increase in NPN compounds in blood
- does NOT imply presence of clinical signs
Uremia
azotemic renal failure with the presence of clinical signs
Renal insufficiency
when loss of functional nephron mass is more than 66.6% but less than 75%
- animal is polyuric b/c can no longer concentrate urine, but not yet azotemic
What is the first course of action when presented with an azotemic patient?
determine source of azotemia (pre-renal, renal, post-renal)
When does pre-renal azotemia occur?
- reduced renal perfusion
- decreased delivery of blood to kidneys
- congestive heart failure
- decr. effective arterial blood volume
- IV voume loss or shift to ECF (hemorrhage, severe burns, pancreatitis, hypoadrenocorticism, shock)
- Extravascular fluid loss (vomiting, diarrhea)
- increased vascular capacity (sepsis)
- decreased delivery of blood to kidneys
- increased urea production/protein catabolism
- high protein diet
- GI bleed
- starvation
- infection
- azathioprine
- tetracyclines
- exogenous corticosteroids
- fever
- burns
USG of dog/cats with pre-renal azotemia
CONCENTRATED
dog >1.030
cat>1.35
What type of urine sediment is associated with pre-renal azotemia?
inactive
Renal excretion of urea
- glomerular filtration
- tubular reabsorption
How does tubular flow rate affect reabsorption?
slower tubular flow rates = greater reabsorption
Differentials for decreased BUN
- liver failure, low protein diets (i.e. decreased production)
- diuresis (i.e. increased excretion…due to decreased tubular reabsorption)
Give an example of a normal case of lower serum creatinine
puppies (don’t yet have a large muscle mass)
How is creatinine excreted?
- glomerlular filtration (almost exclusively)
What is a good indicator of GFR?
creatinine clearance
What species might have minimal tubular secretion of creatinine?
dog
When might you have false elevations of creatinine and why?
Diabetic ketoacidosis
- acetoacetate is a non-creatinine chromagen which contributes to serum creatinine
When do creatinine/BUN levels change most: early in renal disease with a large decrease in GFR or late in renal disease with small decrease in GFR?
Later in renal disease with small decrease in GFR
renal azotemia occurs with ____% of nephron loss
75% & greater
When does post-renal azotemia occur?
- obstruction to urine outflow
- calculi
- stricture
- foreign body
- tumor
- urinary tract rupture
What type of urine sediment is associated with post-renal azotemia?
active
What form of azotemia is hyperkalemia possibly associated with?
post-renal
USG associated with post-renal azotemia
USG can be variable-because the kideys are still functioning at first
What are two diagnostic methods that might be used when post-renal azotemia is suspected?
- abdominal ultrasound-preferred over rads
- abdominal fluid creatinine - with ruptured bladder, fluid creatinine will be > serum creatinine
Once pre and post-renal causes of azotemia are eliminated, how is renal azotemia confirmed? What are two exceptions?
Azotemia + isosthenuria or minimally concentrated urine
Exceptions:
- cats (can concentrate late into renal disease)
- glomerular disease
clinical findings that support renal azotemia
- glucosuria w/o hyperglycemia
- mod./severe proteinuria
- mod./severe cylindruria
- alkalinuria with concurrent systemic acidosis
- non-regenerative anemia
How do kidneys in ARI vs. CKD differ on ultrasound?
ARI-normal to large kidneys
CKD-small, irregular kidneys
Which form of renal disease is likely to be associated with anemia?
CKD
List common causes of ARI
- ethylene glycol toxicity
- drugs (aminoglycosides)
- hypercalcemia
- hypokalemia (cats)
- volume depletion
- sepsis
- pancreatitis
- infectious causes
- bacterial pylelonephtritis
- leptospirosis
- multiple disorders (18%)
- unknown cause (22%)
Risk factors for ARI
- advanced age
- preexisting renal disease
- dehydration/reduced renal perfusion
- hypokalemia, hypercalcemia
- diuretics, nephrotoxic drugs
- liver disease-possibly
- any factor known to cause renal failure
What is a common cause of CKD in older cats?
pyelonephritis
Clinical signs of urine outflow obstruction
- dysuria
- hematuria
- paradoxical incontinence
- fluctuations in urine volume
- markedly distended bladder
- inability to pass urinary catheter
- renomegaly if hydronephrosis present
- uremic signs
Things to consider if azotemia is persistent after obstruction is relieved
- not enough fluids are being given to make up for fluid losses due to post-obstructive diuresis
- preexisting renal disease has led to renal failure
- the obstruction was long-standing and caused renal failure
How can you evaluate for post-obstructive diuresis? Within what timeframe should this resolve?
- measuring urine volume every four hours
- should resolve in 48-72 hours
What species is more prone to post-obstruction diuresis?
cat
Clearance
the volume of a substance removed from the plasma per unit time
The clearance of substances such as Na, Cl, and Ca is _________ (greater or less) than GFR
less
(these are reabsorbed only-no tubular secretion)
Clearance of PAH is ________(greater/less) than GFR
greater
substance is secreted, but not reabsorbed
How is uric acid handled by the kidneys?
it is both secreted and reabsorbed
How is creatinine handled by the kidney?
filtered by glomerulus and not substantially reabsorbed or secreted
Most appropriate test for determinng reneal excretory function when non-azotemic renal failure (renal insufficiency) is suspected
exogenous creatinine clearance
What are the advantages of radioisotope studies?
- not time consuming
- don’t require urine collection
Disadvantage of radioisotope studies
- must be performed at referral institution
Tests of glomerular function:
- endogenous creatinine clearance
- exogenous creatinine clearance
- radioisotope studies
- plasma clearance of iohexol
Easiest & most reliable method available for calculating GFR
plasma clearance of iohexol
Contraindications for water deprivation test
animal with renal failure or insufficiency
Tests of tubular function
- USG, urine osmolality
- fractional clearances of electrolytes
- ammonia challenge tests
- (water deprivation tests)-technically a test of renal tubular concentrating ability but don’t us in animal with renal failure/insufficiency
Ammonia challenge tests are used for what?
- assessing urinary acidifying ability when evaluating renal tubular disorders, specifically renal tubular acidosis
What are two potential values of doing a renal biopsy in an animal with AKI?
- establish etiologic dx
- facilitate prognostication via evaluation of overall appearance of renal tissue and integrity of tubular basement membrane
What is the primary purpose of a renal biopsy when the animal has PLN?
determine whether or not to use immunosuppressive drugs
Contraindications to renal biopsy
- uncontrolled coagulopathy
- severe hydroephrosis
- large renal cysts
- perirenal abscess
- extensive peylonephritis
- solitary or extremely small kidney
- end-stage renal disease
- inexperienced operator
- incomplete patient immobilization
What region of the kidney is biopsied?
cortex
Why should the corticomedullary junction and medulla be avoided when performing a renal biopsy?
large renal vessels are present
Three methods for renal biopsy are:
- percutaneous
- laparoscopic
- laparotomy
What are some advantages to using laparotomy to perform a renal biopsy?
- both kidneys can be visualized with the midline approach
- hemorrhage can be controlled
- can ensure adequate biopsy
Complications occur in ___% of dogs & cats undergoing renal biopsy
17
What is the most common complication that occurs from renal biopsy?
hemorrhage
How is severe hemorrhage defined?
PCV<20%
What is the likely cause of hydronephrosis after a biopsy?
obstruction of the ureter with blood clots
Polydipsia definition
water consumption >100 ml/kg/day
Polyuria definition
urine production greater than 50 ml/kg/day
Oliguria definition
production of less than 1.0 ml/kg/hour of urine
Hx/PE abnormalities suggestive of renal failure
- changes in urine volume
- GI abnormalities
- abnormal kidney size/contour/texture or pain on palpation of kidneys
- hematopoietic abnormalities
- skeletal abnormalities-“rubber jaw”
- cardiopulmonary & vascular abnormalities
- neurologic abnormalities
- non-specific signs
- anorexia
- chronic progressive weight loss
- lethargy
What size should the kidneys be?
- 2.5-3.5x the length of the second lumbar vertebral body in dogs
- 1.5x the length of the second lumbar vertebral body in the cat
Abnormal fluid retention might be related to _____
PLN
Common causes of CKD
- most often undetermined
- glomerulonephritis
- prior ARI episode
- pyelonephritis (often older cats)
- familial
Four therapeutic goals for renal failure
- avoid stress
- if animal stops drinking->pre-renal azotemia
- provide unlimited fresh water
- avoid nephrotoxic agents
- allow for adequate exercise
Risk factors for ARI
- advanced age
- pre-existing renal disease
- dehydration or other causes of decreased renal perfusion
- hypokalemia
- hypercalcemia
- concurrent use of diuretics or nephrotoxic drugs
- liver disease (MAYBE)
- presence of other factors known to cause renal injury
Causes of infectious ARI (“nephritis)
- bacterial pyelonephritis
- leptospirosis
- rickettsial diseases
- RMSF
- ehrlichiosis
- “lyme nephritis”
Phases of ARI
- induction (initiation)
- maintenance
- recovery
What is often given in cases of ethylene glycol ingestion?
4-MP (fomepizole)
What are some reasons the kidneys may be large instead of small, as is expected with CKD?
- renal neoplasia
- hydronephrosis
- compensatory hypertrophy of solitary surviving kidney
- renal cysts
- renal abscesses
- FIP
- renal amyloidosis
- membranous glomerulonephropathy–cats
ARI therapeutic goals
- prevent further damage
- remove inciting cause
- remove pre & post-renal factors
- production of diuresis
- sustain patient’s life during recovery
Why is production of diuresis in ARI relevant?
polyuric patients have better prognosis
CKD therapeutic goals
- alleviate clinical signs
- reduce rate of progression
- eliminate obvious factors causing acute deterioration
- implement factors known to slow progression
- keep current knowledge base!
- work w/in owner comfort zone
FACTORS KNOWN TO SLOW PROGRESSION OF CKD IN DOGS & CATS
HAD2P
- manage Hypertension
- mange Anemia
- feed renal Diet
- manage renal 2ndary hyperparathyroidism
- reduce magnitude of Proteinuria
Factors impacting morbidity of CKD
- UTI
- hypertension
- hypokalemia (primarily cats)
- ureteroliths(primarily cats)
- gastroenteritis
- dehydration
Staging CKD is based on _____
Substaging CKD is based on _______
Staging-CREATININE
Substage-PROTEINURIA, HYPERTENSION
When does uremia occur?
- severe AKI
- stage IV CKD
Restoration of euvolemia should occur within what timeframe?
6 hours
Signs of severe overhydration
- weight gain
- edema
- distended jugular veins
What is the first method you should try in a patient to try to remedy oliguria?
Fluid diuresis (not effective if already overhydrated)
What drug is synergistic with furosemide?
dopamine
When is chronic fluid therapy appropriate to initiate?
- Stage 4 CKD
- sometimes used in recovering ARI
How should alkalinization be approached in an ARI patient vs. CKD?
ARI
- sodium bicarb IV
CKD-stage 4
- sodium bicarb PO
- potassium citrate PO-often in cats for added potassium benefit
What parameters indicate alkalinization is appropriate?
pH<7.20 or TCO2<12
Is hyperkalemia more common in ARI or CKD?
ARI
When is hyperkalemia seen in CKD patients?
CKD patients on ACE inhibitors or those with oliguria/anuria
Appropriate treatment for hyperkalemia >8mEq/L or if arrythmias are present
- sodium bicarbonate
- insulin & dextrose
- calcium gluconate
How can you prevent hypokalemia from occurring during forced diuresis?
add KCl to fluids
What are some consequences of hypokalemia to be aware of?
- renal vasoconstriction
- K+ depleted cells are more susceptible to necrosis
- downregulation of aquaporin-2 (inhibits ADH)
Renal diets improved MST by how much in dogs? cats?
dogs: 3x
cats: 2.4x
What is one drawback to renal diets?
caloric density contributes to obesity
What is the phosphate binder that is usually used when renal diets alone are not enough to control hyperphosphatemia?
aluminum hydroxide
How is anemia generally treated in ARI vs. CKD?
- ARI–>Whole Blood Transfusion
- CKD–>epoetin, darbepoetin
What are some ways GI distress can be managed?
- dietary protein restriction
- H2 blockers
- Cimetidine, Ranitidine, famotidine
- Proton pump inhibitors
- omeprazole, esomeprazole
- antimetics as needed in ARI or acute exacerbation of CKD
Uncotrolled hypertension ocular effects
- retinal, vitreal, or anterior chamber hemorrhage
- retinal detachment & atrophy
- retinal edema
- perivasculitis
- retinal vessel tortuosity
- glaucoma
How much can an ACE inhibitor be expected to lower blood pressure when used by itself?
15%
Enalapril and Benzapril are used for what?
ACE inhibitors used for treating hypertension
ACE inhibitors are used for managing hypertension but have what added benefit?
reduce proteinuria
In early stages of AKI, what parameters should be measured daily/several times a day?
- BUN/Creatinine daily
- PCV/TS several times a day
Paramenters to be monitored and how often with CKD
- PE, hx: 2-4x per year
- panel, PCV/TS, UA: 2-4x per year
- urine culture: 2x per year
- blood pressure: every visit
Uncontrolled hypertension effects on the heart
- left ventricular hypertrophy with secondary valvular insufficiency
Uncontrolled hypertension effects on kidney
- progressive renal decline of renal disease
Uncontrolled hypertension effects on brain
- cerebrovascular hemorrhage
- may manifest as head tilt
- depression
- seizures
Clinical signs of renal disease can vary depending on:
- etiology of disease
- severity of disease
- duration of disease
- rate of progression of primary dz process
Why are clinical signs often more severe in an animal with ARI than an animal with CKD that has the same level of renal dysfunction?
Animals with ARI have not had time to adapt to the physiologic changes asssociated with renal failure
What laboratory finding would suggest ethylene glycol toxicosis?
hippurate or CaOx crystals
What are some clinical signs that occur in CKD that may allow differentiation from ARI?
- long hx of weight loss & PU/PD
- poor BCS
- non-regenerative anemia
- small, irregular kidneys
- fibrous osteodystrophy
- gastric or other tissue mineralization
Renal diet characteristics
- mod. protein restriction
- phosphorous restriction
- sodium restriction
- Omega 3:omega 6 ratio enhanced
- high in water soluble vitamins
- increased caloric density
- increased fiber content
- added K+ in feline diets
What might happen if a diet is too restricted in protein?
- aggravate anemia, acidosis
- protein depletion & muscle wasting
- worsen renal hemodynamics
When is amlodipine indicated?
In hypertension cases that aren’t responding enough to an ACE inhibitor alone
What UPC value is associated with more rapid progression of CKD in dogs? cats?
dogs: UPC>1
cats: UPC>0.4
Clinical signs of hypokalemia often develop when serum potassium is less than what value?
2.5 mEq/L
How does increased GFR affect protein passage through glomerulus?
increase
How does decreased renal plasma flow affect protein passage through the glomerulus?
increase
How does decreased GFR affect protein passage through the glomerulus?
decrease
How does increased renal plasma flow affect protein passage through the glomerulus?
decrease
What are the components of normal urine?
- albumin (40-60% of total urine protein)
- low molecular weight proteins-small amounts
- Peptide hormones (insulin, PTH, GH), enzymes (lysozyme), Ig fragments
- Tamm-Horsfall Protein
How much protein is found in normal dog urine?
5-10ug/dl
Post-renal proteinuria is associated with hemorrhage or inflammation of:
- ureter
- bladder
- urethra
- prostate
- prepuce
- vagina
3 subtypes of renal proteinuria
- functional/physiologic
- tubular
- glomerular
What does a persistently elevated urine protein content indicate?
proteinuria associated with glomerular disease
Causes of glomerular proteinuria
- glomerulonephritis (membranoproliferative or proliferative)
- membranous glomerulonephropathy
- amyloidosis
- glomerulosclerosis-including focal segmental glomerulosclerosis
- minimal change disease
- hereditary nephritis
Causes of tubular proteinuria
- acute tubular necrosis
- Fanconi
- drug/toxin-induced proximal tubular damage
- aminoglycosides
- NSAIDs
- heavy metals
- ethylene glycol
- hypercalcemia
- hypokalemic nephropathy
- tubulointerstitial disease
50-90% of dogs with chronic renal failure have ______
glomerular disease
What is the most common cause of proteinuria?
post-renal
With tubular proteinuria, what is the expected USG?
isosthenuric-minimally concentrated range
What is the expected USG with glomerular proteinuria?
normally concentrated unless late in disease
Three most common causes of glomerular proteinuria
- amyloidosis
- glomerulonephritis
- focal segmental glomerulonephritis
The urine dipstick is what type of test?
qualitative
What protein is the urine dipstick most sensitive to?
albumin
What circumstances can yield false positives with a urine dipstick?
- highly alkaline urine (pH>8-9)
- dipstick immersed for long periods of time
- urine is contaminated with quaternary ammonium compounds(e.g. cleaning agents)
Under what circumstances do false negatives occur with a urine dipstick?
- dilute urine
False positives may occur with what circumstances when using the bumintest?
- organic iodides(radiographic contrast dyes)
- large amounts of penicillins, sulfisoxazole, or thymol(urine preservative)
Highly alkaline or dilute urine may produce false _______ with the bumintest
negatives
When is a quantitative test indicated?
- when animal is hypoalbuminemic
- repeat positive screening tests and a normal urine sediment examination
- absence of pre & post-renal causes of proteinuria
What is the gold standard for measuring urine protein losses?
24 hour urine protein content
What test correlates well with the 24 hour urine protein content in both cats and dogs?
UPC
Normal UPC values in cat & dog
dog: <0.5
cat: <0.4
What are two diseases that are considered with especially high UPC ratios?
- glomerulonephritis
- amyloidosis
What should you do if you detect proteinuria in a dog or cat with mild to moderate pyuria?
reevaluate a urine sample after the cause of pyuria is eliminated
What test characterizes protein fractions in urine samples, thereby allowing for the determination of relative contribution of albumin and globulin to total urine protein content?
urine protein electrophoresis
The usefulness of urine protein electrophoresis is limited to what two situations?
- detection of low molecular weight proteinuria associated with overload proteinuria
- identification of albuminuria as the cause of hypoalbuminemia in animals with LUT hemorrhage or inflammation that is not responsive to therapy
What is the point-of-care RIA that is used to detect microalbuminemia?
E.R.D.-HealthScreen
Factors that lead you to suspect glomerular proteinuria
- hypoalbuminemia
- concurrent systemic infectious or inflammatory disease
- patient has renal azotemia but NOT isostheunuric (pre or post renal causes of azotemia have been excluded)
Factors that would lead you to suspect tubular disease
- normal serum albumin
- other abnormalities suggestive of tubular disease
- glucosuria w/o hyperglycemia
- isosthenuria
What is pathognomonic for glomerular disease?
Nephrotic syndrome
Nephrotic syndrome
- hypoproteinemia(hypoalbuminemia)
- proteinuria
- hypercholesterolemia
- edema