Lab 11 - Kidney Function Flashcards
Water intake during different renal problems
acute: decreased(oliguria)
chronic: increased(polyuria)
Dog: 20-40 ml/kg body weight/day
Cat: 10-20
Horse: 5-15 l/day
cattle: 20-40 l/day
Azotaemia
(prerenal, renal or postrenal, see later) accumulation of nitrogen containing protein breakdown products in the blood (for example: urea).
Ureamia
(prerenal, renal, or postrenal) severe increase in the level of nitrogen containing protein breakdown products and toxins in the blood, leading to obvious clinical signs (anorexia, depression, vomiting, diarrhea, lethargy, stomatitis, gastritis, etc.)
Tests for examining the glomerular function
1️⃣Plasma urea 2️⃣plasma creatinine 3️⃣ urea/creatinine ratio(plasma) 4️⃣urine total protein:creatinine 5️⃣ GFR💙 6️⃣ SDMA 7️⃣ iP
Determination of blood urea
First always urease to split urea into two NH3 mols, then:
1️⃣ urea-color test
2️⃣ enzymatic urea method
Urea-colour test
1️⃣NH3 in water forms NH4+. NH4+ forms green colour in alkalytic pH with Na-hypochloride and salycilic acid.
2️⃣Green colour can be measured spectrophotometrically.
3️⃣It is an end point reaction and it is linear (the result is reliable) till 24.97 mmol/l urea concentration.
Enzymatic urea method
1️⃣ NH3 is used in a reaction to Change of NADH + H+ 2 NAD+ 2️⃣ causing light emission change and it is measurable spectrophotometrically
3️⃣ (the speed of absorbancy decrease is in correlation with urea concentration of the blood sample)
4️⃣ After 30 seconds of preincubation, the extinction change is measured within 1 min.
5️⃣ It is a kinetic reaction and it is linear till 65 mmol/l urea concentration. (Bigger reliable normal range than urea color test!)
Normal value: 8-10 mmol/l
Causes of ⬆️ blood urea concentration (prerenal factors)
1️⃣ incr protein intake
2️⃣ RU: low energy status (carbs needed for bacteria to resynth NH3 to aa) - nh3 accumulation, absorbed then to liver for urea production
3️⃣ incr bacterial activity incr the protein catabolism to NH3 so it indicates small int bacterial overgrowth (SIBO)
4️⃣ int/gastric bleeding: blood proteins are catabolised in intestines💙
5️⃣ haemolysis: catabolism of tissues own protein💙
6️⃣ hyperthyroidism
7️⃣ starving
8️⃣ fever, hypothermia
9️⃣decr blood perfusion of the kidneys:
🔺shock,
🔺decr bp,
🔺cardiac failure,
🔺a. Renalis strangulation
Causes of ⬆️ blood urea concentration (renal factors)
1️⃣ embolism
2️⃣ chronic kidney diseases
3️⃣ fibrosis
4️⃣ inherited: hypoplasia, fe polycystic kidney disease
5️⃣ amyloidosis
6️⃣ nutrition neoplasia (tumor)
7️⃣ glomerular-, interstitional-, tubular nephritis
8️⃣ toxin: ethylene glycol, NSAID’s, mycotoxins
Causes of ⬆️ blood urea concentration (postrenal factors)
1️⃣ obstruction of the pelvis, urether, bladder or urethra (“retention azotaemia”)
2️⃣ Rupture of the kidneys, urether, urinary bladder, or urethra: “uroperitoneum” (urine is in the abdominal cavity, toxic materials and metabolites are easily and quickly reabsorbed from it to the blood through the peritoneal blood vessels),
Life threatening emergency situation, immediate diagnosis and surgical intervention is required to save the life of the animal!!
Causes of Decreased urea concentration
1️⃣ Impaired liver function: decreased urea synthesis in the liver cells from NH3, leading to increased NH3 level.
2️⃣ Haemodilution (hyperhydration)
3️⃣ decreased protein intake (starvation, anorexia)
Determination of creatinine in blood plasma
Jaffe method(kinetic reaction measured by spectrophotometry) - More common! But influenced by jaundice and hemolysis!(bc spectroph.)
enzymatic method: also a kinetic reaction measured by spectrophotometry, measure before and after reaction. Give linear result at bigger ranges!
Jaffe method
Creatinine forms yellow-orange complex with picric acid on alkalytic pH, Speed of complex formation is dependent on the creatinine concentration.
There are other mols which can react too, so there are competition btw. them, though creatinine is the fastest.
Measure within 2mins
Enzymatic method
1️⃣Reagent 1 and sample should be preincubated for 5 minutes together and measured (E1)
2️⃣then Reagent 2 should be added and measured (E2).
3️⃣The change should be measured for standard and sample.
Blood creatinine depends on:
1️⃣ by change in dietary intake but MORE by incr muscle mass, which is the long term effect of high prot intake. 2️⃣muscle necrosis 3️⃣injury, 4️⃣myositis 5️⃣ cachexia (causes decreased creatinine level due to decreased muscle mass) 6️⃣ rhabdomyolysis 7️⃣ rhabdomyosarcoma 8️⃣ decr blood perfusion of the kidneys: 🔺shock, 🔺decr bp, 🔺cardiac failure, 🔺a. Renalis strangulation 9️⃣ starving 1️⃣0️⃣ fever, hypothermia 1️⃣1️⃣ post-renal urea incr!! 1️⃣2️⃣ renal urea incr!!
Normal value creatinine
50-200 μmol/l
When do we use the Plasma urea (mmol/l) / plasma creatinine (μmol/l) ratio? Normal range?
if both parameters are increased in the blood and we are interested in the cause of the increase.
0.1-0.06 (or 6-10%)
Urea/creatinine ratio more than 0.06 which renal diseases
prerenal kidney failure - decreased blood supply of the kidney:
1️⃣ shock, dehydration, hypotension,
obstruction. compression of kidney (glomerular) arteries , vasoconstriction of kidney (glomerular) vessels
3️⃣ postrenal causes
ureter, urethra, urinary bladder (neck) obstruction, compression
4️⃣ extrarenal causes
not renal increase of urea concentration in blood plasma
Urea/creatinine ratio less than 0.06 which renal diseases
renal (sometimes postrenal causes)
Since many factors influence the plasma urea concentration, the plasma urea:creatinine ratio has limited reliability and give only orientative suggestion about the cause.
What are the non renal reasons for ⬆️ urea, and ⬇️↔️ creatinine?
High urea: 1️⃣ increased protein intake 2️⃣ gastrointestinal bleeding 3️⃣ fever (hemolysis - increased protein catabolism) 4️⃣ tetracycline, steroid treatment 5️⃣ haemolysis 6️⃣ necrotic processes 7️⃣ hyperthyroidism (increased protein catabolism) 8️⃣ catabolic drugs (amphetamine)
Low, normal creatinine 1️⃣ cachexia
2️⃣ chronic muscle atrophy
What are the non renal reasons for ⬇️↔️ urea, and ⬆️ creatinine?
Low, normal urea: 1️⃣ liver failure, portosystemic shunt 2️⃣ polyuria-polydypsia 3️⃣ low protein intake 4️⃣ anabolic steroids
High creatinine: 1️⃣ inflammation of muscles (myocarditis, rhabdomyolysis) 2️⃣ rhabdomyosarcoma 3️⃣ muscle trauma 4️⃣ increased meat intake
Name the parameters for polyuria
1️⃣ Creatinine clearance
2️⃣ Urinary total protein concentration and Urinary total protein / urinary creatinine ratio
3️⃣ Radioisotopic methods
4️⃣C-inulin clearance
5️⃣H-tetraaethyl-ammonium-chloride clearance
💙GFR! Creatinine clearance, normal range
When the GFR decrease the creatinine concentration of blood will increase. C=U•V/P
norm.: 2.4-5 (dog), 1.9-5 (cat)
How do we analyse urinary total protein?
1️⃣ Objective protein measurements (Biuret reaction, ultrasensitive protein measurements)
2️⃣ Specific protein determination - electrophoresis, immune-electrophoresis, Western-blot analysis
3️⃣ Proteinuria/day less than 20 mg/kgbw/day (how much is excreted)
4️⃣ Urinary protein/creatinine (ratio less than 1)
Explain the results of the Urinary total protein / urinary creatinine ratio?
Physiological is less than 1
🔺More than 1 is pathological: a 20kg dog passes about a gram a day of proteins
🔺 btw 1-5: proteinurea is usually prerenal
🔺 glomerulonephropathy: protein loss increases and the creatinine excretion does not show change, the value of the ratio becomes increased.
🔺 tubulonephropathy protein loss does not show change, the creatinine excretion becomes decreased, the value of the ratio is also increased (>5)
Why do we examine the Urinary total protein / urinary creatinine ratio?
When we have a high total protein conc in the urine for an unknown reason, this ratio is not influenced by the other substances in the urine(specific gravity), while creatinine alone is.
What do we have to do when we examine the Urinary total protein / urinary creatinine ratio?
1️⃣ dilute urine sample 10 or 100 times
2️⃣ standardise units to g/l
What are the tests when we analyse tubular function?
Basic test: 1️⃣ Specific gravity 💙 2️⃣ Urinary sediment analysis 3️⃣ Fractional electrolyte clearance % Generally in case of tubular damage, Na+ reabsorption decreases, and usually K+ reabsorption increases 4️⃣ Analysis of enzymuria 5️⃣ Tubular clearance examinations: PHA 6️⃣ Water deprivation test(If suspecting polyuria or polydipsia(incr thirst/drinking) 7️⃣ Urine osmolality at 5% dehydration
1️⃣2️⃣About water reabsorption, are routine
3️⃣4️⃣ check if tubules can reabs electrolites - need ionogram!
Analysis of enzymuria
Certain enzymes are released by the tubular cells(not into blood), these are increased in case of ACUTE/PERACUTE tubular DAMAGE (for example in case of oxalate-nephrosis)
Values must be reffered to the creatinine levels to exclude misdiagnosis of highly concentrated urine!
Tubular clearance examinations:
para-amino-hyppuric acid (PAH), diodrast, phenolred clearance. These molecules are only secreted in the tubules, not reabsorbed.
How do we Analysis postrenal kidney failure
1️⃣Analysis of creatinine and urea concentration in ascites fluid (uroperitoneum!!)
2️⃣ Urinary sediment analysis
