Lab Dx Urinary Dz Flashcards
What affects GFR?
Renal perfusion and plasma flow
Define azotaemia
- increase in non-protein nitrongenous compounds (usually urea nitrogen (UN) and or creatinine or uric acid (birds)) in the blood
Define uraemia?
Uraemia = sick from azotaemia (every urea mic animal is azotaemic but NOT vice versa)
Clinical signs of uraemia
- anorexia
- VD+
- GI haemorrhage
- ulcerative stomatitis
- bruxism in ruminants
What causes loss of kidney function?
Loss of number of functioning nephrons (not a decrease function of each individual)
Which biochem parameters are related to renal function?
- UN
- creatinine
- phosphorus
- calcium
- sodium
- chloride
- potassium
- acid base
- protein
Which 2 diagnostics are more important for evaluating renal function?
Serum/plasma chemistry and urinalysis CONCURRENTLY
Most important biochem results
> UN (urea nitrogen)
creatinine
- indicate GFR (^conc in blood if GFR v)
Where is urea produced and where does it travels?
- urea produced in liver from ammonia (ammonia very toxic, urea bit less toxic)
- excreted by kidney
- levels affected by liver function and protein levels
What affects creatinine levels
Derived from creatine in muscles, influenced by muscle mass
What causes ^ urea
Protein meal or decrased filtration (GFR)
Is urea excreted in feaces?
NO
How does excretion of urea and creatinine differ?
Creatinine not reabsorption
- urea can reabsorb in collecting duct
Does urea equilibrate in body?
Once in vascular diffuses through body water in 90mins
How is UN excreted?
- Renal excretion most important route
- passively filtered by glomerulus (conc filtrate same as blood)
- passively diffuses with water from tubular luman back into blood
- amount absorbed inversely proportional to urine flow (v urine flow ^ absoroption and ^ blood levels)
Is Urea measurement reliable in ruminants ?
- NO (Use creatinine)
- cattle severe renal dz can compensate urea levels as excreted into rumen and used to produce protein
- if anorectiv all urea will be excreted via GIT not kidneys
Creatinine sources - what influences levels? How easily does this equilibrate?
- non-enzymatic conversion of creatine stores ini muscle
- constant rate of conversion (influenced by muscle mass and disease)
- will distribute in body water but very slowly cf. urea
How do creatinine and urea levels change with a ruptured bladder?
- abdo fluid concentrations creatinine > serum levels
- difference with serunm lasts longer cf. differneces in urea levels
Is creatinine a sensitive indicator of kidney function?
NO 3/4 nephrons lost before parameters change
- more sensitive cows and horse
- not at all sensitive birds
whY IS Creatinine such a poor indicator in birds ?
- uric acid produced instead
- hyperuriceamia does occour but not very sensitive
- may also occour during ovulation and after meal
3 types of azotaemia
> prerenal azotaemia
- v GFR d/t v renal perfusion (poor BP -> vasoconstriction and ULTIMATELY ischaemia)
- or ^ protein catabolism
renal
- v GFR d/t non functioning nephrons
postrenal
- interference with excretion of urine (obstruction/postrenal leakage)
How can prerenal azotaemia be Dx?
Urine SG low shows no functioning nephrons and poor concentration
- if urine SG normal then must be pre renal
Causes of prerenal azotaemia
- ^protein catabolism
- gastric or SI haemorrhage / necrosis / starvation / corticosteroids / high protein diet
- reduced renal perfusion == haemoconcentration MOST COMMON CAUSE
- dz causing pre/post renal azotaemia 2* affect the kidneys -> renal azotaemia
- USG high d/t ADH response occouring -> concentration of urine
Why dos USG increase with pre-renal azotaemia?
- ADH response -> kidney concentrates urine
Causes of Post renal azotaemia. CLinical signs?
- obstruction/post rental leakage
- oliguria/anuria clinically
- USG may vary
- UN and creatinine return to normal once obstruction releved
What is USG compared with?
Creatinine and urine on serum /plasma
What is USG and what is it a measure of?
- ratio of refractive index urine cf. ater
- depends on particle size, weight and number
- refractomter
- reflects osmolality (very expensive machine needed to measure this!)
- falsely increased by glucose and protein
What is a normal USG?
No reference interval
- based on expectation
- range 1.001 - 1.065 in healthy animals (1.080 in cats)
- concentrating ability neonates is poor
What may falsely increase USG?
- glucose (some effect on osmolality but not much)
- protein (no effect on osmolality but 3+ increase ~= 0.004 change)
With azotaemia, what should USG be?
Minimum - 1.03 dog - 1.035 cat - 1.025 horse or ruminant > if less than these = decreased concentrating ability and renal failure
Define isosthenuria and hyposthenuria. What implications do these have?
> isosthenuria - fixed USG 1.010 (1.008-1.012) - kidney not concentrating or diluting - osmolality = GFiltrate > hyposthenuria - USG
Component of biochem useful for renal function?
- Na, K, Cl
- P
- Ca
- protein/albumin
- anylase/lipase
Where is the majority of Sodium and how are levels regulated/
- main ion ECF
- 75% filtered Na resorbed PCT
- aldosterone stimulated Na resortopin in collecting ducts
- ^ Na may be d/t ^ intake, ^ water loss or v water intake
- v Na d/t ^ loss or ^ H20 intake
What do changes in Chloride usually mirror?
- Na
- if not mirroring Na, suspect changes in acid/base status
- interference from bromide and iodine salts
WHere is Potassium found? What is it regulated by?
- intracellular space
- levels regulated by aldosterone (CDs)
ASSESS ACID BASE CHANGES FIRST - ^ d/t renal failure esp with anuria or oliguria present
- v d/t loss (renal/VD+) or decreased intake,
also affected by..
> leakage from cells thombrocytosis, leukaemia, tissue damage
> hypoadrenocorticism
What is potassium linked in with?
Acid base balance (can be swapped into cells for H+)
How are kidneys related to Acid base balance
- Kidney conseve filtered bicarb
- renal failure -> metabolic acidosis
- assessing acid base from serum biochem not reliable, check blood gas
What forms of Calcium can be measured? What are Ca levels affected by?
- free ca (50%)
- bound calcium: albumin (45%)
- Ca related to albumin, if albumin lost, Ca v)
- bound ca: nonpretein anions (5%)
Calcium levels regulated by…
- PTH, vit D, calcitonin
- renal failure -> hypo or normocalcaemia in cats, dogs and cows
- HORSES will be HYPERcalceamic as kidney major excretor of Ca
What causes ^/v levels of Phosphorus
- Decreased GFR (so levels will ^ in animals with renal dz)
- EXCEPT in HORSES phosphorus levels v with renal dz
- ^ elvels with young growing anmals alongside ^ ca and ^ ALP
Outline how Secondary renal hyoerparathyroidism occorus
- v GFR -> ^P
- v 1,25DHCC (Vit D?)
- v Ca absorption from intestine and bone, ^ PTH
- v Ca -> ^ 1,35DHCC -> ^ Ca absorption
- ^ PTH promotes phosphaturia
> Ca, P, Vit D all within ref range
> BUT concurrent ^ PTH
How may protein and albumin be affected by renal dz?
- 1* glomerular dz severe hypoproteinaemia d/t hypoalbumenaemia
What may be affected concurrently with protein changes (hypoproteinaemia)?
- hyperlipidaemia and hypercholesterolemia
- proteinuria and very high protein:creatinine ratio
Which enzymes may be affected by renal dz?
- amylase and lipase
- pancreatic enzymes cleared by kidney so ^ moderately with renal dz
- TLI also ^ with v GFR
What may be seen on haematology with renal disease?
> anaemia
- mild (HCT >30%)
- normovytic, normochromic, non regeneratice
- 2* to lack of EPO and complicated by haemorrhage and direct BM suppression
What is cytology useful for with kidneys? When is cytology not useful and what is performed instead?
- lymphoma renal
- bladder neoplasia (histopath or urine cytology, not sediment)
> biopsy for all other diseases (assess architecture)
What can be used to monitor GFR?
Creatinine, inulin
What affects urine pH?
> diet
- protein (and fasting in ruminants) v pH
- vegetables ^ pH
will become alkaline on standing
cystitis ^ pH (urease producing bacteria -> ammonia)
What does urine pH affect?
types of crystals that form
4 types of proteinuria?
- prerenal
- glomerular
- tubular
- haemorrhagic or inflammaotry (post renal)
What are the threshold levels of glucose reabsorption?
> 9mmol/L dogs
> 14mmol/L cats
What may glycosuria be seen?
- hyperglycaemic glucosuria (DM)
- renal glucosuria
- stressed cats
What do ketones indicate? Ketones in the urine?
- excessive fat degradation rather than using glucose as an energy source
> ketone bodies - acetoacetate, B-hydroxybutyrate, acetone
- reagant strip detects mainly acetoacetate
> ketones in the urine - poorly controlled diabetics
- starvation
When is bilirubin seen in the urine? How may this be noted?
- overspill in haemolytic anaemia
- liver dz with cholestasis, gall bladder/bile duct obstruction
> threshold lower in dogs cf. cats - small amount in dogs not a concern but any in cats concerning
> urine may be bright yellow and stain things
Normal no. red and white cells per 40x high power field?
When are ammonium biurate crystals seen?
- neutral - alkali pH
- Portosystemic shunt
When are bilirubin crystal seen?
- most common dogs
- in low numbers not clinically significant in dogs
- often significant in cats and horses
When are calcium oxalate crystals seen?
- any pH > 2 forms - monohydrate (ethylene glycol toxicity) - dihydrate (found in normal urine) > horses have low numbers normally
When are struvite crystals seen?
- most common crystal in cats and dogs
- may be seen in normal urine
- neutral - alkaline pH
When are calcium carbonate crystal seen?
- normal horse urine
Where are all casts derived from?
Renal tubular epithelium
- appearance depends on transit time down tubule
- in high numbers indicate tubular damage
