Kidney function and NPNs Flashcards
Main functions of the kidneys:
- Excretory function - remove unwanted waste product and excess water
- Regulatory function - regulation of fluid and acid-base balance; conservation of nutrients
- Endocrine function - ADH and aldosterone
Basic process in urine formation: filtration, reabsorption, secretion:
Filtration: only small (can be any charge) and larger (+ve/neutral) molecules pass by hydrostatic pressure.
Reabsorption: most filtered elements are reabsorbed. prevents loss of water
Secretion: removal of further waste products, regulate acid-base balance
ADH: water
Aldosterone: water and NaCl
Main causes of kidney disease:
- Disruption of blood flow (low filtration, low GFR)
- Disruption of urine flow
- Nephron damage
Other name for glomerulonephritis:
Acute nephritic syndrome
What disease have an increase in glomerular permeability:
Nephrotic syndrome
What does nephrotic syndrome entails?
Passage of molecules like proteins to pass (esp. albumin) resulting in proteinuria, low albumin in plasma, lipiduria. Big molecules are NOT passing.
What does acute nephritic syndrome entails?
Altered permeability and decreased filtration allowing bigger molecules to pass through like cells and proteins. They accumulate in blood (low filtration) and can result in hematuria, proteinuria, pyuria.
Where within the nephron is electrolyte and water reabsorption controlled by aldosterone and ADH?
DCT and collecting duct
What effect would hyperproteinemia likely have on filtration (increase or decrease) and why?
Decreased; high proteins in capillaries, will want to keep fluid to equalize osmotic pressure .
Other causes for kidney disease:
Tubular disease
Interstitial disease
Vascular disease (less blood flow)
What would constitute a good component for a clearance test?
- Not reabsorbed
- Freely filtered
- Not secreted
Principle of Jaffe reaction:
creatinine + picric acid (in alkaline) = color
Interferences for Jaffe reaction and what can be done to be corrected:
Hemolysis: RBC release substance which reacts with rgt
Bilirubin: false neg; interfere with rgt
Bacteria: false neg; slows down reaction
Kinetic reaction is used: rate of change in abs in measured btw a certain window of time.
Rules for specimens collection for creatinine:
No ammonium (no NH anticoagulants) Separate cells (RBC and ammonia production)
What are NPNS?
Non-protein nitrogenous compounds - good indicator for renal function
Why pre-renal, renal and post-renal conditions associated with high blood creatinine/urea/uric acid?
Pre-renal: decreased blood flow and filtration (low GFR) = increase in blood
Renal: kidney disease = less filtration
Post-renal: urinary obstruction, increased reab
Urea is the breakdown of
Protein
What can cause a low urea to creatinine ratio?
Decreased GFR, high reab = more in blood
Low protein intake (decrease in urea, not creat)
Severe liver disease
Starvation
What can cause a high urea to creatinine ratio with normal creatinine?
high urea/N creatinine
Increased protein breakdown (more urea)
Increased protein intake
What can cause a high urea to creatinine ration with high creatinine?
Decreased GFR with increased reabsorption of urea (very high urea with high cret due to low GFR) = hypoperfusion
Uric acid is a breakdown of:
Nucleic acid and purines
Main concern with high uric acid?
Gout: insoluble deposition of urate = crystals
Specimen rules for urea collection
No fluoride (inhibits urease) No ammonium
Principle of uric acid:
Uric acid broken down by uricase gives H2O2. Then Trinder’s reaction
Specimen rules for uric acid collection
No fluoride or EDTA
Interferences for Trinder’s
Reducing substances (ascorbic acid) : compete with chromogen (false low) Oxidizing substances: oxidize with chromogen (can change its color) (false high)
Specimen rules for ammonia collection
PLASMA Minimize contact with air Transport on ice No contact with smocking or exogenous ammonia Separate quickly (RBC have ammonia) Bacteria
What happens in MAU?
Levelled increased but not detectable by routine testing. Indicate increased permeability which reflect indicator for kidney dmg.
What urine specimen is preferred for MAU
and why?
24h random (or timed)
Creatinine and albumin are measured for albumin to creatinine ratio where it compensates for urine concentration in the day.
