Renal Flashcards
Outline the 7 areas to evaluate when trying to distinguish between acute and chronic kidney disease and outline the more advanced methods further.
What level of creatinine in abdominal fluid indicates urinary tract rupture?
> 2x that of serum
IRIS staging of CKD in dogs and cats.
n.b. main difference is for stage 2 (>125mml/L dog, >140mmol/L cat). Otherwise values are essentialy the same
Outline the IRIS AKI Grading criteria
Normal GFR values for dog and cat
- Dog: 3.5-4.5ml/min/kg
- Cat: 2.5-3.4ml/min/kg
4 characteristics for makers that are required to allow GFR measurement
- Freely filtered at the glomerulus
- Not circulate bound to plasma proteins
- Not undergo resorption or secretion by renal tubules
- Must not alter GFR or cause renal toxicity
What is the definition of urinary clearance vs. plasma clearance?
Renal = The rate at which a filtered substance is cleared from a given volume of plasma by the kidneys into the urine. It can be expressed as the amount of substance in the urine appearing per a unit of time.
Plasma = he rate at which a substance is cleared from a given volume of plasma per unit time.
Which feline breed has a higher creatinine?
Birmans, n.b. that kittens have a higher creatinine than adults until about 8 weeks of age
What is the role of cystatin C in evaluating GFR?
Cystatin C should be reabsorped by the proximal tubules so if elevated concentrations are found in the urine this could be a marker of tubular injury. However, clinical studies in dogs and cats have not been overly promising.
What is the predominant urine protein detected on the dipstick?
Albumin
What is the lower limit of detection for a urine protein dipstick?
30mg/dL albumin
What are the factors that can lead to false negatives on the urine dipstick vs. false positives?
- False negatives with:
- Bence-jones proteinuria
- Dilute urine
- Acidic urine
- False positivies with
- Haematuria
- Pyuria
- Concentrated urine
- Alkaline urine
What is the clinical definition of microalbuminuria?
albuin >1mg/dL but <30mg/dL
What are the ‘normal’ limits of UPC in dogs vs. cats and what do these values indicate?
Cat > 0.4
Dog >0.5
These indicate a urine albumin of >30mg/dL.
Values ≥0.2 indicate microalbuminuria
How many samples need to be taken to consider UPC abdnormal?
≥3 samples taken ≥2 weeks apare
What are the 6 factors that can affect UPC measurement and their actual impact on measurements
- Sample method
- No difference between cysto, midstream or free-catch
- Environment
- Higher in hospital vs. home
- Haematuria
- Only gross haematuria (>250 RBC/HPF)
- Pyuria
- Minimal
- Bacturia
- Minimal as ‘post-renal’ proteinuria is really a result of leakage of proteins from the blood from the inflammation in response to bacteria
- Day-today variability
- Can be very high particulary in patients that are markedly proteinuric
- If UPC <4.0 then day-to-day variability is likely less important
- If UPC >4.0 then a pooled urine sample is likely to be a good idea
- Equivolume of urine over 3 measurements
Wat degree of proteinuria should prompt consideration for a renal biopsy
UPC >3.5 that is persistent
How long should anti-thrombotic therapy be discontinued prior to renal biopsy?
72h
What sample medium should be used when collecting a renal biopsy?
- Post-biopsy handling
- Put into physiological saline
- Divide samples:
- Light microscopy (formalin fixed)
- Transmission electron microscopy (TEM, gluteraldehyde)
- Immunoflourescence (Michel’s medium)
What light microscopy stains should be applied to identify the following in renal biopsy specimens:
a) General tissue architechture
b) Collagen
c) Junctions between compartments
d) Glomerular basement membrane to evaluate for immune complex deposition
e) Amyloid
a) H&E
b) Masson’s trichrome
c) PAS
d) Jones metanamine silver
e) Congo red
Which IFA markers should be evaluated on a renal biopsy (6)?
IgG
IgA
IgM
C1q
C3
Lamda and kappa light chains
What are the main risk factors for the development of complications during/following renal biopsy
<5kg size
Severe azotaemia (Cr. >442mmol/L)
Haemostatic disorders
What are the components of nephrotic syndrome
- Proteinuria
- Hypoalbuminaemia
- Hypercholesterolaemia
- Peripheral oedema or cavitary effusion
What endogenous (2) and exogenous (3) factors can impact on USG and approximate increases with these
- Severe proteinura
- 1g per dL increases USG by 0.003 - 0.005
- Severe glycosuria
- 1g per dL increases USG by 0.004 - 0.005 (urine dipstick is about 100mg per increment so only 0.1g => very little effect)
- Colloids
- Manitol
- Iohexol
Which antibiotic classess can cause false positives on urine dipstic measurements?
Fluroquinolones (part. ciprofloxacin) (glucose oxidase methods)
Penicillins and cephalosporins (copper sulfate methods)
Equation for calculation of FE of electrolytes
What is the distribution of uinary epithelial cells in the urinary tract
Squamous = urethra or vagina
Transitional = all the way from the renal pelvis to the urethra
What does this picture indicate?
Granular cast
What does this picture indicate?
Waxy cast - later stage of granular cast
What ketones are detected on the urine dipstick?
Acetone and acetoacetic acid (NOT BHB)
What can cause ketonuria in animals, other than DKA
Prolonged fasting
Low carbohydrate diet in cats
What is a relatively specific feature of renal lymphoma on ultrasonography?
Hypoechoic subcapsular thickening, this can mimic peri-renal fluid
What are perinephric pseudocyts and with what disease are they associated?
Fluid filled sacs without an epithelial lining (as would be the case for a true cyst). They are associated with CKD in cats.
Most common nephrotoxins in dogs vs. cats
Dogs: Ethylene glycol, NSAIDS, Cholecalciferol, aminoglycosides
Cats: Ethylene glycol, cholecalciferol, lillies
What are the four phases of AKI?
- Initiation
- Extension - hypoxia and inflammation promote ATP depletion, impairement of NA/KATPase and cellular swelling
- Maintenance
- Recovery
How can FE sodium help in determining the cause of an AKI
FE <1% indicates a pre-renal component only as in this scenario the body is trying to conserve sodium and water.
Which antibiotics are directly nephrotoxic?
Aminoglycosides
Expired tratracyclines - causes a fanconi-like syndrome
Sulfonamides - intra-tubular crystal formation
What is the mechansm of action of fendolopam?
It is a D1 agonist. D1 agonism will dilate renal arteries and therefore increase renal blood flow, theoretically, inhibit ANG II and ADH. It does not have any D2 or adrenergic effects
What is the amount of insensible loss from the respiratory tract in dogs?
22ml/kg/d
Outline how to approach fluid therapy for a patient with AKI. Include how you would approach the oliguric or anuric scenario
- Assess and correct hypovolaemia within the first 6 hours
- Rehydrate the animal using nomal calculation
- Subtract any fluid boluses from 1
- If not clinically dehydrated and not overydrated then assume a 5% dehydration rate - Once hypovolaemia and hydration have been corrected then use ins and outs:
- 1. Add 22ml/kg/d for insensible losses
- 2. Add in urinary losses
- 3. Add in any ongoing losses
Anuric patients: only administer insensible losses
Overhydrated patients: withold fluids until euvolaemic
Overhydrated anuric/oliguric patients should ideally have dialysis
When to use frusemide in AKI?
Only if there are clinical signs of volume overload as it has actually been associated with worse outcome.s
What is the lower end of blood pressure that is tolerable for renal autoregulation?
60 - 80 MAP or 80 - 100mmHg systolic
What are the definitions of oliguria?
In a well hydrated pet <1ml/kg/h is relative oliguria and 1 - 2 ml/kg/h would be considered relative oliguria in a patient receiving aggressive fluid therapy.
Antidotes for ethylene glycol toxicity?
4-methylpyrazole or ethanol given within 8 hours of exposure
Aminoglycoside antidotes
Tircacillin
Cabenicillin
What hypothesis is applicable to the progression of CKD in dogs and cats?
The trade off hypothesis
What canine breeds MAY CKD be more likely in?
Cocker spaniels and CKCS
Compare and contrast the differences in primary histopathologic findings in CKD between dogs and cats
Chronic tubulointerstitial nephritis is the most common in both dogs and cats and the second most common is glomerulonephropathy with an increased prevalence in dogs. The third most common cause in dogs is amyloidosis and lymphoma in cats.
Compare and contrast negative prognostic factors for CKD in dogs vs. cats
Factors in both:
- IRIS Stage
- Proteinuria
Dogs only:
- Feeding a renal diet
- Hypertension
- Decreased BCS
Cats only:
- Serum phosphorus
- Anaemia
Which species is uraemic gastropathy more common in?
Dogs
Explain the pathophysiology of renal secondary hyperparathyroidism
- PO4 is increased due to declining GFR –> increased PTH
- FGF23 increases in response to increased phosphorus –> inhibition of 1-alpha hydroxylase leading to reduced vitamin D –> increased PTH
- Uraemia also inhibits calcitriols negative feedback on the parathyroid gland
- Net result is a reduced resorption of calcium from the gastrointestinal tract
What alterations in CKD may predispose to a metabolic acidosis?
Decreased ability of renal tubular cells to synthesise ammonia (from glutamine)
Decreased ability to secrete hydrogen ions
Decreased excretion of phosphate buffers
In addition to RSHP what mechanisms may reduce total calcium in CKD?
Increased inorganic ions such as citrate, phosphate and sulfates may occur in the blood
Targets for phosphate restriction in CKD
How long after starting a phosphate restricted diet or phosphate binder can serum phosphate be re-evaluated?
4 - 6 weeks after a change
What are the four agents that can bind dietary phosphates, their risks and administration considerations, if applicable.
Aluminium hydroxide - risks of neuromuscular toxicity and microcytosis
Calcium containing - likely to increase calcium, do not give alongside calcitriol
Lanthanum - few side effects
Sevalamer - can cause metabolic acidosis and hypercalcaemia (from the acidosis maybe?)
Treatment for metabolic acidosis due to CKD?
Renal diet
Potassium citrate
Sodium HCO3
What percetage of CKD dogs and cats treated with EPO will develop EPO antibodies?
25 - 30% cats and 50% dogs
When can the use of calcitriol therapy be considered and what conditions apply to its use?
Theory - it may reduce PTH levels (although this has not been proven to be prognostic)
There is no evidence for its use in cats
There is some evidence to suggest its use in dogs in stage ≥III CKD with evidence fo improved mortality
Do not use if there are alterations in serum phosphorus or calcium as it will lead to absorption of BOTH of these in the GIT.
What is the most important determinant of passage of substances across the glomerulus?
Size - 60 - 70kDa is the upper limit
Other factor is charge selectivity (negative charges are resisted by the BM)
Which breeds of dog seem to be predisposed to glomerular disease in general?
Labradors and golden retrievers
What combination of azotaemia and concentrating ability of the urine is a hallmark of glomerular disease?
Renal azotaemia with intact concentrating ability is suggestive of glomerular disease (as if you think about it the glomerulus has nothing to do with concentrating ability).
What are the four components of nephrotic syndrome
Hypoalbuminaemia
Proteinuria
Hypercholesterolaemia
Oedema formation
Outline the classification of glomerular diseases in dogs/cats
Main categories:
- Glomerulosclerosis (incl. FSGS and Global)
- Immune complex glomerulonephritis (membranous, membranoproliferative, lupus, proliferative, cresentric, IgA)
- Amyloidosis
- Hereditary nephritis
- Mimimal change glomerulopathy
What are the most common forms of glomerular disease?
ICGN (around 50% cases historically), glomeruloschlerosis and amyloiodosis
What glomerular disease is associated with lyme borreliosis?
Membranoproliferative glomerulonephritis
What findings suggest a primary vs. secondary ICGN?
Complement and Ig binding to the endothelial side is more suggestive of a secondary disease process wheras binding on the urinary side may suggest more of a primary process (e.g. membranous nephritis)
Which ICGN seems to be more of a primary disease?
Membranous nephritis - this is the most common glomerular disease in cats and often presents with quite severe proteinuria.