Glossary of 4. Kidney and Clearance Products
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- List the 6 functions of the kidneys:
- 1. Urine formation
2. Fluid/electrolyte balance
3. Acid-base balance
4. Waste excretion
5. Hormone function
6. Protein conservation
- What 3 processes occur to allow urine formation?
- What 3 waste products are removed by the kidneys?
- 1. Urea
3. Uric acid
- What 3 hormones are regulated by the kidneys?
- 1. Vitamin D - active form is produced
2. Renin - produced
- How much blood supplies the kidneys?
what %body wt are the kidneys?
- -25% of cardiac output
- What transport occurs in the proximal convoluted tubule?
- 1. Active transport of Glucose, amino acids, Na, K.
2. Water follows
3. Passive reabsorption of negative ions
- What transport occurs in the loop of Henle?
- Active transport of Cl-
- What transport occurs in the distal convoluted tubule?
- Active transport of Na, K, H.
- What controls Na/K/H2O transport in the distal tubule?
- What is the tonicity of filtrate as it leaves the distal tubule?
- Isotonic to hypotonic
- What happens to the filtrate tonicity when it enters the collecting duct?
- Becomes hypertonic - H2O gets reabsorbed so the ion concentration increases.
- What allows the filtrate to become hypertonic in the collecting duct? What controls this?
- -The reabsorption of Water from the filtrate.
-Controlled by ADH
- What is the function of ADH?
- Increased permeability of collecting duct to H2O
- How does the kidney buffer body pH?
- -Excretion of organic acids and H+
- What exactly is Urea?
- Major nitrogen waste product from protein breakdown
- How is Urea formed?
- -Liver deaminates a. acids
-Intest bacteria degrade NH3
- What is the name of the chemistry test for Urea?
- BUN - blood urea nitrogen
- How is Urea excreted?
- 1. Glomerulus filters it at a constant rate
2. 40% is reabsorbed passively
3. Final excretion amt depends on protein diet and metabolism.
- How do these physiological factors affect the BUN?
-High protein diet
- Liver dis: decreased BUN
Hi-protein diet: increased BUN
Starvation: increased plasma urea
Dehydration: increased BUN
Kidney disease: increased BUN
- what is azotemia?
- Increased urea waste products in the serum
- What are 6 pre-renal causes of azotemia?
- What are 4 renal causes of azotemia?
- 1. Vascular - arteriosclerosis
2. Glomerular disease
3. Acute tubular necrosis
- What causes post-renal azotemia?
- Obstruction of urine flow - through ureters, bladder or urethra.
- List 4 causes of a decreased BUN:
- 1. Liver disease
3. Decreased protein diet
- What is Creatinine formed from?
- Muscle creatine and phosphocreatine
- How closely does Urine creatinine measurement approximate the GFR?
- Close, but it overestimates it b/c about 10% is excreted.
- Does creatinine fluctuate much in normal individuals?
- No; it is relatively constant b/c it's a muscle byproduct.
- How much of the body creatinine is filtered by the glomerulus?
- About 90%
- How do the urine Creat and the BUN change with decreasing Renal function?
- They both increase
- what is the normal Creat ref range?
- 0.6-1.2 mg/dl
- what is the normal BUN ref range?
- 7-18 mg/dl
- how high do the creat and bun get in renal failure?
- Creat = about 10 mg/dl
BUN = about 35-110 mg/dl
- how high do the creat and bun get in uremic syndrome?
- Creat = >8 mg/dl
BUN = >80 mg/dl
- List 3 tests for glomerular function:
- 1. Creatinine clearance
2. Inulin clearance
3. Urea clearance
- How is the Creatinine clearance calculated?
- see flashcard.
- How is inulin clearance different from creatinine?
- Inulin is given exogenously.
- Which clearance test more accurately parralels the GFR?
- Urea clearance
- List 4 tests for evaluating Tubular Function:
- 1. Phenolsulfonphthalein (PSP)
2. Specific gravity
4. Concentration tests
- What is the principle of the PSP test?
- -Dye is given exogenously, the secretion is measured to determine how well the tubules function.
- What is the definition of urine specific gravity?
- The weight of dissolved solutes in the urine compared to water.
- What is a normal specific gravity?
- Above 1.000 (sp gr of H2O) up to about 1.030
- What is a dilute Sp gr?
- What 3 methods are used for measuring specific gravity?
- 1. Densitometry
2. T-S meter (refractometer)
- How is osmolality different from specific gravity?
- It takes into account the number of molecules, not just the weight.
- What is the normal serum osmolality?
- 285-300 mOsm/kg
- What is the normal urine osmolality?
- App. 600 mOsm/kg
- What is the normal Urine:Serum osmolality ratio?
- After 12 hrs of fluid restriction what is the Urine:serum osmol. ratio?
- Increased; 3-4.7
- How does Urine:serum osmolality ratio change with:
-Renal tubular deficiency?
- Ren. tubular. def: decreased
Diabetes insipidus: 0.2-.7
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