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Flashcards in Lab Dx Urinary Dz Deck (61)

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?



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?

- 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


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)
- ^ 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