KIDNEY FUNCTION AND URINE FORMATION Functions of the Kidneys
"A WET BED"
KEY FUNCTIONS
A - Acid-base balance
Urine Formation: Filtration, reabsorption, W - Water removal
secretion, and excretion of water, electrolytes, and E - Erythropoiesis waste.
Waste Elimination: (production of red blood
Endogenous: Urea (BUN), bilirubin, creatinine. cells)
Exogenous: Medications. T - Toxin removal
INDICATORS OF KIDNEY FUNCTION B - Blood pressure control
E - Electrolyte balance
Tests: Urea and creatinine levels.
D - Vitamin D activation
High Levels:
Both high: Potential kidney problems.
High urea, normal creatinine: Dehydration.
High creatinine, normal urea: Kidney injury.
KIDNEY'S ROLE IN HOMEOSTASIS
Regulates fluid, electrolyte, and acid-base balance.
RENAL ANATOMY
Renal Parenchyma: Includes renal pelvis, cortex, and medulla.
Nephron: Functional unit; ~1 million per kidney.
Glomerular Filtration: Begins at the glomerulus; normal GFR ~125 mL/min.
Arterial System: Causes of Acute Kidney
Afferent Arteriole: Brings blood to glomerulus Injury
Efferent Arteriole: Carries blood away "PRERENAL"
IV Contrast: Can affect kidney function; avoid in AKI P - Perfusion issues (e.g.,
Nephron Components: hypovolemia)
Bowman's Capsule: Filters blood into renal tubules. R - Renal artery stenosis
Renal Tubules: Reabsorb fluids/electrolytes, excrete waste. E - Embolism
R - Reduced cardiac
Diuretics:
output
Lasix (Furosemide): Loop diuretic; decreases K+ and BP.
E - Endotoxins
Bumex: More potent than Lasix; similar precautions. N - NSAIDs
Thiazide Diuretics: Act on distal tubule; used for A - ACE inhibitors
hypertension.
RAAS System:
Renin: Activates RAAS; increases BP via vasoconstriction and Na+/H2O retention.
Hormones and Vitamins:
Erythropoietin (EPO): Stimulates RBC production; reduced in kidney failure.
Vitamin D: Activated by kidneys; essential for calcium absorption.
Metabolism:
Insulin: Metabolized by kidneys; dysfunction can lead to hyperinsulinemia.
Bicarbonate: Released to neutralize blood acidity.
Impacts of Chronic Kidney Failure:
Anemia, BP issues, bone problems, acidosis.
ACUTE KIDNEY INJURY (AKI) OVERVIEW
Definition: Sudden decline in kidney function.
Indicators: Elevated BUN (azotemia), creatinine, and potassium; decreased GFR.
Types of AKI
PRERENAL AKI
Cause: Reduced blood flow to kidneys.
Common Causes:
Decreased cardiac output (e.g., heart failure, MI, dysrhythmias).
Systemic vasodilation (e.g., sepsis, certain medications).
Intravascular volume deficit (e.g., dehydration).
Note: Accounts for 50% of AKI cases; can progress to intrarenal AKI.
"A WET BED"
KEY FUNCTIONS
A - Acid-base balance
Urine Formation: Filtration, reabsorption, W - Water removal
secretion, and excretion of water, electrolytes, and E - Erythropoiesis waste.
Waste Elimination: (production of red blood
Endogenous: Urea (BUN), bilirubin, creatinine. cells)
Exogenous: Medications. T - Toxin removal
INDICATORS OF KIDNEY FUNCTION B - Blood pressure control
E - Electrolyte balance
Tests: Urea and creatinine levels.
D - Vitamin D activation
High Levels:
Both high: Potential kidney problems.
High urea, normal creatinine: Dehydration.
High creatinine, normal urea: Kidney injury.
KIDNEY'S ROLE IN HOMEOSTASIS
Regulates fluid, electrolyte, and acid-base balance.
RENAL ANATOMY
Renal Parenchyma: Includes renal pelvis, cortex, and medulla.
Nephron: Functional unit; ~1 million per kidney.
Glomerular Filtration: Begins at the glomerulus; normal GFR ~125 mL/min.
Arterial System: Causes of Acute Kidney
Afferent Arteriole: Brings blood to glomerulus Injury
Efferent Arteriole: Carries blood away "PRERENAL"
IV Contrast: Can affect kidney function; avoid in AKI P - Perfusion issues (e.g.,
Nephron Components: hypovolemia)
Bowman's Capsule: Filters blood into renal tubules. R - Renal artery stenosis
Renal Tubules: Reabsorb fluids/electrolytes, excrete waste. E - Embolism
R - Reduced cardiac
Diuretics:
output
Lasix (Furosemide): Loop diuretic; decreases K+ and BP.
E - Endotoxins
Bumex: More potent than Lasix; similar precautions. N - NSAIDs
Thiazide Diuretics: Act on distal tubule; used for A - ACE inhibitors
hypertension.
RAAS System:
Renin: Activates RAAS; increases BP via vasoconstriction and Na+/H2O retention.
Hormones and Vitamins:
Erythropoietin (EPO): Stimulates RBC production; reduced in kidney failure.
Vitamin D: Activated by kidneys; essential for calcium absorption.
Metabolism:
Insulin: Metabolized by kidneys; dysfunction can lead to hyperinsulinemia.
Bicarbonate: Released to neutralize blood acidity.
Impacts of Chronic Kidney Failure:
Anemia, BP issues, bone problems, acidosis.
ACUTE KIDNEY INJURY (AKI) OVERVIEW
Definition: Sudden decline in kidney function.
Indicators: Elevated BUN (azotemia), creatinine, and potassium; decreased GFR.
Types of AKI
PRERENAL AKI
Cause: Reduced blood flow to kidneys.
Common Causes:
Decreased cardiac output (e.g., heart failure, MI, dysrhythmias).
Systemic vasodilation (e.g., sepsis, certain medications).
Intravascular volume deficit (e.g., dehydration).
Note: Accounts for 50% of AKI cases; can progress to intrarenal AKI.
