Title: Renal Physiology and Function
1Renal Physiology and Function
Ricki Otten MT(ASCP)SC uotten_at_unmc.edu
2Objectives
- Please review the objectives located on page 1 of
the lecture handout
3Kidney Function
- Form urine (excretory function)
- Maintain acid-base balance
- Regulates body water balance
- Maintain electrolyte balance
- Aids in maintaining BP
- Excrete toxic (and) waste products
- Reabsorb essential substances
- Hormonal function
- Target organ for aldosterone, ADH
- Secretes renin (an enzyme)
- Erythropoietin, vitamin D
4Kidney Function
- Depends upon proper
- Renal blood flow (20-25 cardiac output)
- Glomerular filtration
- Tubular absorption
- Tubular secretion
5Urinary System
- Each kidney about the
- size of your fist
6Inflammation/Infection
Pyelonephritis
Cystitis
Urethritis
7Nephron
- Functional unit of kidney
- 1.5 million per kidney
- Components
- Glomerulus
- Tubules
- (PCT, Loop of Henle, DCT)
- Collecting ducts/tubules
- Functions to form urine
- Filtration
- Reabsorption
- Secretion
8Glomerulus
- Capillary tuft
- Bowmans space
- Bowmans Capsule
- Afferent arteriole
- Efferent arteriole
- Empties into PCT
9Glomerulus
- Function Filtration of blood
- Allows passage of water, electrolytes and low
molecular weight substances (lt70,000) - Filtration based on solutes size and charge
- Difference between glomerular filtrate and blood
is absence of - Protein
- Protein-bound substances bilirubin, drugs
- Cells (RBC, WBC)
10Glomerular Filtrate
- Specific Gravity
- 1.010
- Ultrafiltrate volume
- 120 ml/min
11Glomerular Filtration
- Dependent upon
- Basement membrane
- cell structure
- Hydrostatic pressure
- Oncotic pressure
- RAA system
12Glomerular Filtration
- Dependent upon
- Basement membrane
- cell structure
- Hydrostatic pressure
- Oncotic pressure
- RAA system
13Renin-Angiotensin-Aldosterone
14Renal Tubules
- PCT
- Loop of Henle
- Descending limb
- Ascending limb
- Not permeable to water
- DCT
- ADH (controls water)
- Aldosterone (controls Na)
- Collecting ducts/tubules
- ADH (controls water)
15Renal Tubules
- Functions
- Reabsorption of essential substances
- Secretion of waste, toxins, metabolites, drugs,
protein-bound substances, etc - Final urine output 1 ml/min
- Range 0.3 15 ml/min (dependent on hydration
status)
16Tubular Transport Mechanisms
- Active transport energy is required
- Passive transport simple diffusion
- Renal Threshold
- Glucose 160-180 mg/dl (plasma)
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18Normal Urine Composition
- Water 94
- Solutes 6
- Urea
- Sodium
- Chloride
19Normal Urine Composition
- Water 94
- Solutes 6
- Urea
- Sodium
- Chloride
Urea end product of protein metabolism Creatinin
e end product of muscle metabolism Uric acid
end product of purine metabolism
20Factors Influencing Concentration of Substances
- Dietary intake
- Physical activity
- Body metabolism
- Endocrine function (ADH, Aldosterone)
- Body position (orthostatic proteinuria)
21Urine Output
- Average 24 hour volume
- Normal 1500 2000 ml/24 hour
- Extreme 600 2500 ml/24 hours
- Factors that influence urine output (volume)
- Fluid intake
- Non-renal loss (vomiting, diarrhea, sweating)
- Secretion of ADH (too little, too much)
- Bodys need to excrete solutes (glucose)
22Abnormal Urine Output
- Polyuria gt2500 ml/24 hr
- Artificially induced by suppression of ADH
- (diuretics, caffeine, alcohol)
- Diabetes mellitus plasma glucose exceeds renal
threshold - Diabetes insipidus
- Neurogenic DI lack of ADH
- Nephrogenic DI tubules unable to respond to ADH
23Abnormal Urine Output
- Oliguria (low)
- Anuria (absence)
- Nocturia
24Renal Function Tests
- Tubular Reabsorption
- Glomerular Filtration
- Renal Blood Flow
- Tubular Secretion
25Tubular Reabsorption Tests
- Can the kidneys concentrate urine
- Concentration Tests control of fluid intake
important in interpretation of test - Fluid deprivation
- Free water clearance
26Tubular Reabsorption Tests
- Laboratory
- Specific gravity (number and density)
- Refractometer
- Reagent strip
- Osmolality (number of particles in solution)
- Better test
- More accurate
27Glomerular Filtration Tests
- Assess filtering ability of glomerulus
- Clearance tests
- Measures the RATE at which kidneys can clear a
filterable substance from the blood - This substance must not be reabsorbed or secreted
by the tubules - GFR glomerular filtration rate
28Glomerular Filtration Tests
- Specimen requirements
- Timed urine specimen 24 hour collection
- Plasma sample
- Clearance calculation UV ml/min
- P
29Glomerular Filtration Tests
- Endogenous
- Creatinine (most common)
- Exogenous
- Inulin (considered the standard)
30Glomerular Filtration Tests
- Creatinine clearance test
- Endogenous substance (found in the body)
- Produced at a steady rate
- Dependent on muscle mass (male, female, child,
adult) - Thus normalized to body surface area using a
nomogram - Children
- Obese
31Glomerular Filtration Tests
- Calculate creatinine clearance UV
- P
-
- Urine creatinine (U) 185 mg/dl
- Plasma creatinine (P) 0.9 mg/dl
- Urine volume (V) 1250 ml/24 hr
- Height 60
- Weight 260 lb
32Calculate Creatinine Clearance
33Calculate Creatinine Clearance
- UV 185 mg/dl x 1250 ml x 1 hour
178.4 - P 0.9 mg/dl 24 hours 60 min
-
- CrCl 178 ml/min
34Calculate Creatinine Clearance
- UV 185 mg/dl x 1250 ml x 1 hour
178.4 - P 0.9 mg/dl 24 hours 60 min
-
- CrCl 178 ml/min
- Is this normal for a 20 year old male?
35Calculate Creatinine Clearance
- UV 185 mg/dl x 1250 ml x 1 hour
178.4 - P 0.9 mg/dl 24 hours 60 min
-
- CrCl 178 ml/min
- Is this normal for a 20 year old male?
- No, it is increased
- Correct value for body surface area
36Corrected Creatinine Clearance
- CrCl 178 ml/min
- Corrected CrCl
- CrCl x 1.73m2 178 ml/min x 1.73
- BSA 2.39
- 128.8 129 ml/min
37Corrected Creatinine Clearance
- CrCl 178 ml/min
- Corrected CrCl 129 ml/min
- Is this normal for a 20 year old male?
38Corrected Creatinine Clearance
- CrCl 178 ml/min
- Corrected CrCl 129 ml/min
- Is this normal for a 20 year old male? Yes
39Renal Reserve
- Large margin of reserve in renal function
- Greater than 50 of kidney function must be lost
before - Clinical symptoms apparent
- Biochemical abnormalities evident
- Thus, not useful for screening for early renal
disease
40- Renal Blood Flow
- Tubular Secretion
No objectives
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