Renal/Urinary Clinical Flashcards
Most common canine uroliths and sex predisposition
CaOx = male Struvite = female
Breed predisposition to rate and cysteine stones?
EBD = urate + cysteine Dalmation = urate
What size urolith can be removed by voiding urohydropropulsion?
<3mm stones
Which stones are amenable to medical dissolution?
Struvite, urate, xanthine, cysteine
Dietary management of CaOx prevention.
Dilute USG
Maintain pH >8.0
Consider KCi, Hydrochlorathiazide
Avoid high sodium, protein
Avoid phosphorus restriction
Urease producing organisms
Streptococcus
Proteus
Ureoplasma
Corynebacterium
Klebsiella
Drugs that can be used to acidify urine in dogs with struvite urolithiasis
L-methionine
Ammonium chloride
Genetic defect of breeds that form urate stones
SLC2A9 (urate transporter)
Purine degredation pathway
Urine pH to aim for for xanthine and urate dissolution?
Alkaline
Urine pH to aim for for cysteine uroliths
Alkaline
CaOx monohydrate crystals
Dumbells and pickets
CaOx dihydrate crystals
Struvite crystals
Urate crystals
Amorphous, speculated globules with and without spicules
Cysteine crystals
Xanthine crystals
Crystals that may be amorphous
Calcium phosphate carbonate
Brushite
Calcium phosphate apetite
Stones that may be spikey
Calcium oxalate dihydrate can be spiculated
Silica is the other one.
Radiolucent stones
Lucency of:
Cysteine, urate, xanthine
Dumbells and pickets
CaOx monohydrate crystals
CaOx dihydrate crystals
Struvite crystals
Amorphous, speculated globules with and without spicules
Urate crystals
Cysteine crystals
Xanthine crystals
Lucency of:
Cysteine, urate, xanthine
Radiolucent stones
Amino acids involved in abnormal cysteine transporters
COLA
Cystine
Ornithine
Lysine
Arginine
Genetic basis of abnormal cysteine transport
genetically heterogeneous (autosomal recessive- SLC3A1, autosomal dominant-SLC3A1 & SLC7A9, and sex linked/androgen responsive
Three genetic groups
Type 1 (autosomal recessive) = Labrador, Newfoundland, Landseers, Scottish Terriers = SLC3A1, autosomal recessive
Type 2 (autosomal dominant) = Australian cattle dogs (SLC3A1) and mn pinschers (SLC7A9)
Type 3 (androgen responsive) = Mastiff, Bulldogs, Kromfohrländer and Irish Terrier
Innervation of the bladder and urethral sphincters
Pelvic nerve (S1-S3) = parasymphathetic innervation to the bladder (muscarinic receptors)
Hypogastric nerve (L1-L4) = syphathetic innervation to the bladder (beta3) and internal urethreal sphincter (alpha)
Pudendal nerve (S1-S2) = somatic.
Where is the micturition centre located?
In the pons.
Which nerve is the main afferent (sensory) nerve in the urinary tract?
The pelvic nerve.
How to tell the difference between UMN bladder and detrusor atony?
UMN bladder is difficult to express
Detruser atony will also have a large bladder but should be easily expressed.
Tiopronin
Indications
MoA
Side effects/Contraindications
Indication = treatment for cysteine urolithiasis when medical management and castration have failed
MoA = chelates cysteine
Side effects: agranulocytosis, aplastic anaemia, thrombocytopenia, IMHA, proteinuria
AVOID IN CATS
Potassium Citrate
Indications
MoA
side effects
Alkalinisation of urine, treatment of metabolic acidosis
MoA: - citrate converts to HCO3 in the liver, citrate can also complex with calcium
Side Effects: GI, hyperkalaemia, bitter taste
Phenylpropanolamine
MoA
Side effects
Indirect stimulation of alpha receptors (and to some degree beta) through release of nEP and inhibition of nEP re-uptake within the synapse.
Side effects:
- Hypertension (mild and transient)
- can also get all the signs you would expect with a phaeo
Bethanecol
Indications
MoA
Side effects
Detrusor atony, may also reduce urethral resistance in some conditions. Can also be used as a upper GI prokinetic (reduces LES tone)
MoA = muscarinic stimulation.
Side effects: cholinergic (SLUDG-M)
Prazosin
Indications
Indications: reflex dysnergia, urethral spasm,
Alpha-1 antagonist
Side effects - hypotension is the main one to worry about
Tamsulosin
Also urethral spasm (reflex dysnergia)
alpha-1a antagonist (may be more specific to the urethra than Prazosin)
Baclofen
Centrally acting skeletal muscle relaxant
GABAb agonist.
Care in cats or seizure disorders
Cholinergic side effects
SLUDGE-M
Salivation
Lacrimation
Urination
Defecation
GI disress
Emesis
Miosis
Basic categories of DDx causing PU/PD
Primary PD
CDI
NDI; primary
NDI;secondary
Osmotic
Reduced medullary tonicity
Other/Unknown
At what bodyweight loss is maximum ADH release stimulated?
5%
Why does hypoadrenocorticsm cause PU/PD?
There is a lack of urinary sodium reabsorption and resultant medullary washout.
How does hyperadrenocorticism result in PU/PD?
Psychogenic
Alters release and action of ADH
Polyuria in AKI?
Reduced sodium resorption. Attempt to eliminate retained solutes.
Why does PU occur in CKD?
There is a disruption of normal medullary architecture.
Remaining nephrons suffer from osmotic diuresis.
Which urinary crystals are associated with ethylene glycol toxicity>
Calcium oxalate monohydrate
What miscellaneous tools can help you to deterimine AKI from CKD?
X-ray of the mandible to look for lamina dura loss
US of PT to look for hypertrophy
Measure carbamylated haemoglobin (theorhetical)
Renal biopsy
In what circumstances may dogs and cats be azotaemic but retain urine concentrating ability even when a renal cause for the azotaemia is present?
Cats can just do this with CKD
Dogs with glomerular disease may retain concentrating ability but be azotaemic
IRIS CKD Staging (dogs and cats)
IRIS AKI grading
Calculation for urinary clearance
Clearance = (Urine flow rate x Concentration of solute in the urine)/concentration of solute in plasma.
Plasma clearance
Dose of substance/AUC*
*The auc is determined by taking several times measurements.
How are the following substances handled by the kidneys?
Urea
Creatinine
SDMA
Cystatin C
- Urea = freely filtered and passively reabsorbed
- Creatinine = freely filtered, small amount is secreted
- SDMA = moslty freely filtered (=> more linear relationship with GFR)
Cystatin C = freely filtered, actively reabsorbed (should be low concentration in the urine)
What protein is mainly detected by the urine dipstick? What is the lower limit of detection?
Albumin, lower limit is 30mg/dL (0.3g/L)
Reasons for false negative and false positive positive dipstick results
False positive:
- Alkaline urine
- Haematuria
- Pyuria
- Concentrated urine
False negative:
- Acidic urine
- Dilute urine
- Bence-jones proteinuria
What is the definition of microalbuminuria?
Urine albumin >1mg/dL but < the 30mg/dL on the dipstick.
Why are the cut offs for UPC the numbers that they are? What are they and what does this mean?
Cat > 0.4, Dog >0.5 = 30mg/dL of albumin
>0.2 = microalbuminuria
How many samples need to be taken for proteinuria to be considered persistent?
>3 samples > 2 weeks apart.
What are the relationships between the following parameters and proteinuria?
Sample method
Environment
Haematuria
Pyuria
Bacturia
Day-today variability
No difference between cysto, midstream or free-catch
Higher in hospital vs. home
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: not of concern if <0.4.
What sample media should be used for a renal biopsy?
- Formalin = light microscopy
- Gluteraldehyde = TEM
- Michel’s medium = immunoflourescence
Initially the specimen should be put into physiologic saline before being divided.
What are the hallmark;s of the nephrotic syndrome?
Proteinuria
Hypoalbuminaemia
Hypercholesterolaemia
Peripheral oedema or cavitary effusion
What do the following casts indicate?
Epithelial
Granular
Hyaline
Waxy
RBC
Epithelial = can be normal in low numbers, often come from the urethra etc.
- Squamous = from the lower urethra and beyond
- Transitional = from the renal pelvis up to the urethra
Granular = indicate partial cellular degeneration so tubular injury
Hyaline = usually from proteinaceous urine (protein that is present in the tubule so not post-renal)
Waxy = complete cellular degeneration
RBC = may indicate haemorrhage
It is possible that cellular, granular and waxy casts are different stages of the same problem.
Which ketones are detected by the urine dipstick?
Acetoacetate (more sensitive to this - this is the first ketone produced)
Acetone
What renal ultrasound finding is likely to reflect EG toxicity?
Very bright, large kidneys.
What molecule likely contributes to hyaline casts in glomerular disease?
Tamm-Horsfall mucoprotein
What is the approximate prevalence of IMGN in canine glomerular disease?
50%
What type of glomerulonephritis is assocaited with Borrelia bungdorferi?
Membranoproliferative (MPGN)
Components of Fanconi syndrome
Glucosuria
Aminoaciduria
Proteinuria
Phosphaturia
Hypophosphatemia
What percentage of renal bicarbonate is reapsorbed by the proximal tubule?
80-90%
Pathologic mechanism of proximal vs. distal RTA
Proximal = failure of basolateral Na/HCO3 echanger resulting in loss of HCO3
DIstal = failure of H+ ATPase most likely
Main ways to differentiate proximal vs. distal RTA
Proximal = milder hyperchloraemic metabolic acidosis with appropriately acidic pH
Distal = more marked metabolic acidosis with paradoscially alkaline urine
Ammonium chloride challenge test
What is the therapy for RTA?
Alkali therapy such as potassium or sodium citrate.
How can assessing urea:creatinine ratio help in distinguishing causes of Azotaemia?
Urea:creatinine will be elevated if pre-renal due to the handling of these biomarkers in dehydration.
