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Anatomy of the nephron (p.1-2)
- Each kidney contains approximately 1 million nephrons
- Each nephron contains:
- o Glomerulus – coiled within Bowman’s capsule
- o Proximal convoluted tubule
- o Loop of Henle
- o Distal convoluted tubule
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Specific functions of the nephron:
- Filtration- glomerular capillaries
- Reabsorption - tubules and peritubular capillaries
- Secretion - tubules and peritubular capillaries
- Excretion - collecting duct
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Primary functions of kidney:
- o Removal of waste products
- o Maintenance of fluid and electrolyte balance
- o Acid-base balance
- o Secretion of hormones and autocoids
- o Regulation of BP
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Blood flow to kidneys accounts for what percent of cardiac output? (p.5)
- 25% of cardiac output
- (4-6 L/min)
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What is the normal GFR/minute or per day? (p.2-3)
- GFR/minute = 90-130 mL/min (average = 110 mL/min)
- GFR/hr = average 6600 mL/hr
- GRF/24 hours = 158 L/day
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What is the blood threshold for appearance of glucose in urine? (p.5)
225 mg/min
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Renal: Urine pH
- Normal = 4.5 - 8.0
- Increased = Alkalosis
- Decreased = Acidosis, intrarenal ARF
- Notes: Should be on acidotic side to discourage bacterial overgrowth
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Renal: Specific gravity of urine
- Normal = 1.003 - 1.030
- Increased = volume deficit, glycosuria, proteinuria, prerenal ARF (>1.020)
- Decreased = volume overload
- Notes: measure of concentration of urine. Closer to 1 = more dilute
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Renal: Osmolality of urine
- Normal = 300 - 1200 mOsm/kg
- Increased = volume deficit, prerenal ARF (urine osmol > serum osmol)
- Decreased = volume excess, intrarenal ARF (urine osmol < serum osmol)
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Renal: Protein in urine
- Normal = 30 - 150 mg/day
- Increased = trauma, infection, intrarenal ARF, transient with exercise, glomerulonephritis
- Notes:
- Does not belong in urine. If seen, think problem with glomerulus. Does not filter due to electrical charge and large size.
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Renal: Sodium in urine
- Normal = 27 - 287 mEq/day
- Increased = High sodium diet, intrarenal ARF
- Decreased = prerenal ARF
- Notes: Help differentiate between injury and failure
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Renal: Creatinine in urine
Normal = 1 - 2 g/day
- Decreased = intrarenal ARF, CRF
- Notes: Less creatinine in urine is problem in tubular system
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Renal: Urea in urine
- Normal = 6 - 17 g/day
- Decreased = Intrarenal ARF, CRF
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Renal: Myoglobin in urine
- Normal = Absent
- Increased = crush injury, rhabdomyolysis
- Notes: from muscle cells, nephrotoxic, and giant clogging tubules; seen with trauma
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Renal: RBCs in urine
- Normal = 0 - 5
- Increased = trauma, intrarenal ARF, strenuous exercise, renal artery thrombus
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Renal: WBCs in urine
- Normal = 0 - 5
- Increased = infection
- Notes: look for leukocyte esterase (more sensitive than WBC)
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Renal: Bacteria in urine
- Normal = none - few
- Increased = Infection
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Renal: Casts in urine
- Normal = none - few
- Increased:
- RBC = glomerular disease
- WBC = pyelonephritis, glomerular disease, nephrotic syndrome
- Epithelial = glomerular disease
- Broad waxy casts = longstanding kidney dysfunction (very negative)
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Review the renin-angiotensin-aldosterone mechanism (p.4)
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