Kidney Anatomy and Function Quiz

Kidney Anatomy and Function

• Kidney weight is less than 0.5% of total body weight.
• Kidney location spans from the 12th thoracic vertebra to the 3rd lumbar vertebra.
• Kidneys receive 20% of cardiac output.
• Each kidney contains approximately 1 million nephrons.
• Normal GFR (Glomerular Filtration Rate): Males ~120 ± 25 mL/min; Females ~95 ± 20 mL/min (using creatinine clearance).
• Normal serum creatinine range is 0.8 to 1.3 mg/dL.
• Normal serum osmolality is 280-290 mOsm/kg.
• Urine osmolality ranges from 50-100 mOsm/kg (diluted) to 900-1200 mOsm/kg (concentrated).
• PCT (Proximal Convoluted Tubule) reabsorbs 67% of the filtered load.
• Thick ascending loop of Henle reabsorbs 25% of the filtered load.
• DCT (Distal Convoluted Tubule) reabsorbs 5% of the filtered load.
• Collecting tubule reabsorbs 3% of the filtered load.
• 0.4% of the filtered load remains to be excreted in urine.
• Normal daily sodium intake/excretion is balanced at 80-250 mEq/day.

Electrolytes and Osmolality

• Normal plasma sodium concentration: 135-145 mEq/L.
• Normal serum osmolality: 280-290 mOsm/kg.
• Normal plasma potassium concentration: 3.5-5.0 mmol/L.
• Intracellular potassium concentration: 135-145 mmol/L.
• Urine osmolality in response to hypernatremia: 1000-1200 mOsm/kg.

Acid-Base Balance

• pH range compatible with survival: 6.8-7.8.
• Hydrogen concentration range compatible with survival: 16-120 nEq/L.
• Minimum urine pH: 4.5.
• Daily hydrogen excretion by kidneys: 50-100 mEq.
• Daily CO2 production: 15,000 mmol.
• Daily non-carbonic acid production: 50-100 mEq.
• Normal daily dietary potassium intake: 80-120 mmol.

GFR and Creatinine

• Normal GFR range: 80-120 mL/min.
• Normal serum creatinine: 0.8-1.3 mg/dL.
• Normal GFR for young adults: ~120 mL/min/1.73 m².
• Normal urine output: 0.5 mL/kg/hour.
• Normal BUN (Blood Urea Nitrogen) range: 6-20 mg/dL.
• Normal GFR for males ~120± 25mL/min & for females ~95 ± 20 mL/min (using creatinine clearance).

Acute Kidney Injury (AKI) Criteria

• Increase in serum creatinine by over 0.3 mg/dL within 48 hours.
• Increase in serum creatinine over 50% compared to baseline within 7 hours.
• Urine volume less than 0.5 mL/kg/hr for 6 hours.

Chronic Kidney Disease (CKD) Stages

• Based on GFR (mL/min):
  • Stage 1: GFR >90
  • Stage 2: GFR 60-89
  • Stage 3: GFR 30-59
  • Stage 4: GFR 15-29
  • Stage 5: GFR <15

Body Water Distribution

• Total body water is about 60% of body weight.
• Two-thirds of total body water is intracellular fluid, one-third is extracellular fluid.
• One-quarter of extracellular fluid is intravascular volume, three-quarters is interstitial fluid.

Hyponatremia and Hypernatremia

• Hyponatremia: Sodium concentration below 135 mEq/L.
• Hypernatremia: Sodium concentration above 145-147 mEq/L.
• Urine osmolality in hyponatremia due to primary polydipsia: below 100 mOsm/kg.
• Urine sodium concentration in hyponatremia due to effective circulating volume depletion: less than 25 mEq/L.
• Urine sodium concentration in SIADH (Syndrome of Inappropriate Antidiuretic Hormone): usually above 40 mEq/L.

Calculations

• Ideal Body Weight (IBW) for males: 50 kg + 2.3 kg for each inch over 5 feet.
• Ideal Body Weight (IBW) for females: 45.5 kg + 2.3 kg for each inch over 5 feet.
• Adjusted Body Weight (AdjBW): IBW + 0.4 x (Total Body Water - IBW); used when BMI ≥ 25 or TBW ≥ 20% over IBW.

Test your knowledge of kidney anatomy, nephron structure, and the functions they perform. This quiz covers key concepts such as glomerular filtration rates, tubular reabsorption, and electrolyte balance. Perfect for students studying renal physiology!