Renal Function (Ch. 33)-- Definition First

Question 1

• Amount of urea in blood
  
  • Waste product of metabolism
• Not specific to kidneys
  
  • Influenced by protein intake, GI bleed, dehydration
• Included on Basic Metabolic Panel (BMP)

Answer 1

Blood Urea Nitrogen (BUN)

Question 2

• Filter blood and reabsorb substances
  
  • Electrolytes
• Regulate pH
  
  • Conserve or eliminate HCO3- & H+
• Regulate osmolality of ECF & urine
  
  • ADH
  • Aldosterone (RAAS)
• Endocrine functions
  
  • Renin
  • Erythropoietin
  • Vitamin D

Answer 2

Functions of the Kidneys

Question 3

• Average urinary output: 125 mL/hr
• Neural & humoral mechanisms
  
  • SANS, ADH, & Angiotensin II (RAAS) → Vasoconstriction
    
    • ⇣ renal blood flow
  • Dopamine & NO → Vasodilation
    
    • ⇡ renal blood flow

Answer 3

Renal Regulation

Question 4

• Urinary obstruction
  
  • Renal pelvis
    
    • Renal calculi (kidney stones)
    • Pregnancy
  • Ureter
    
    • Neurogenic bladder
    • Uretovesicle junction stricture
  • Bladder & urethra
    
    • Bladder stones
    • BPH

Answer 4

Obstructive Disorders of Renal Function

Question 5

• Volume of plasma filtered per minute
• BEST index of kidney function

Answer 5

Glomerular Filtration Rate (GFR)

Question 6

Supersaturation → Solute precipitates → Stone formation

Urinary stasis → Crystal aggregation (around organic material) → Stone formation

Answer 6

Renal Calculi Mechanisms

Question 7

• PAIN
  
  • Renal colic
    
    • Acute, intermittent, excruciating
    • N/V
  • Non-colicky
    
    • Dull, deep, continuous ache
    • Mild → Severe

Answer 7

Renal Calculi Clinical Manifestations

Question 8

Drug exposure (NSAIDS, contrast media, diuretics, immunosuppressants) → Structural or functional changes in kidneys

NSAIDS/ASA → ⇣ PGs (renoprotective) → ⇣ Renal blood flow

Hypersensitivity (Methicillin + Furosemide/Thiazide Diuretic) → Tubulointerstitial nephritis

• High blood flow and filtration pressure in kidneys
  
  • Exposed to toxins in blood
• Kidneys involved in metabolism of drugs
  
  • Exposed to toxic drug metabolites
• Tolerance factors:
  
  • Age
    
    • ⇡ Risk: Elderly
  • Renal function
  • Hydration status
  • Blood pressure
  • Urinary pH

Answer 8

Drug-Related Nephropathies

Question 9

• [Solutes] in urine
  
  • Normal range: 1.010-1.025
    
    • High– Dehydration
    • Low– ⇣ Renal function

Answer 9

Specific Gravity

Question 10

• Abrupt onset of shaking, chills, or fever
• Constant ache in lower back
  
  • Unilateral or bilateral
• Malaise
• N/V
• Abdominal pain
• Lower urinary tract symptoms
  
  • Dysuria
  • Increased urinary frequency
  • Urgency

Answer 10

Acute Pyelonephritis Clinical Manifestations

Question 11

• Calcium salts → Calcium stones (oxalate or phosphate)
  
  • 70-80%
  • Hyperparathyroidism, High fructose beverages
• Uric acid → Uric acid stones
  
  • Gout, Tumor lysis syndrome, High purine diet
• Magnesium ammonium phosphate → Struvite
  
  • Alkaline urine, Bacteria that split urea → ammonia & CO2
    
    • Normal urine pH: 4.5-8
• Cystine → Cystine stones
  
  • Cystinuria (autosomal recessive genetic defect)
    
    • ⇡ Cystine resorption

Answer 11

Types of Renal Calculi

Question 12

Expansion of the kidney with urine

• ⇡ Pressure inside renal capsule
• Compartment syndrome
  
  • Blood vessels compressed
• Renal ischemia
  
  • Necrosis of tissue
  • Chronic renal failure

Answer 12

Hydronephrosis

Question 13

• Hematuria w/ red cell casts
  
  • Sudden onset
• Oliguria
  
  • <20 mL/hr
• ⇣ GFR
• Azotemia
  
  • ⇡ BUN
• Cola-colored urine

Answer 13

Acute Nephritic Syndrome Clinical Manifestations

Question 14

• Acute nephritic syndrome
• Rapidly progressive glomerulonephritis
  
  • Goodpasture Syndrome
• Nephrotic Syndrome

Answer 14

Disorders of Glomerular Function

Question 15

Determined by site, degree, and duration of obstruction

Urinary stasis → Infection & Renal Calculi

Dilation of renal collecting ducts → Hydronephrosis → Renal ischemia → Necrosis of kidney tissue

Acute emergency → Chronic renal failure

Answer 15

Urinary Obstruction Mechanisms

Question 16

Lupus

Type III Hypersensitivity

Systemic lupus erythematosus→ Antigen-antibody complexes trapped in glomerular membrane → Inflammation → Lupus Nephritis

Diabetes

T1DM/T2DM → Diabetic glomerulosclerosis (thickening/scarring of basement membrane) → CKD → Renal failure, proteinuria, or nephrotic syndrome

• Mechanisms
  
  • ⇡ BG → ⇡ GFR & glomerular pressure → Capillary pores enlarge
    
    • Angiotensin II-mediated
  • Improper synthesis of basement membrane
• Manifestations
  
  • Glomerular lesions
  • Non-nephrotic proteinuria
  • Microalbuminuria
    
    • 30-300 mg urinary albumin in 24hrs.
• Nephrotic syndrome

Answer 16

Systemic Causes of Glomerularnephritis

Question 17

Crescent-shaped structures destroy the Bowman space

• Occurs over several months
• Immunologic disorders
  
  • Systemic lupus erythematosus
  • Goodpasture syndrome
    
    • Antibodies to glomerular basement membrane → Inflammation
    • Cross-react w/ pulmonary basement membrane
    • Renal failure + Pulmonary hemorrhage

Answer 17

Rapidly Progressive Glomerulonephritis

Question 18

Glomerular basement membrane disturbed → ⇡ Permeability → Protein and lipids in urine

Filtration of proteins > Tubular reabsorption

Answer 18

Nephrotic Syndrome

Question 19

Acute inflammation of the kidney caused by bacterial infection

Infection → Outflow obstruction + Vesicoureteral orifice incompetence → Vesicoureteral reflux

E. Coli, Klebsiella, Proteus

• Route of bacteria to kidney
  
  • Ascending infection from lower urinary tract
    
    • UTI
      
      • ⇡ Risk– Short intravesical ureter
  • Through the bloodstream
    
    • Staphylococcus aureus in blood (sepsis)
    • Infective endocarditis

Answer 19

Acute Pyelonephritis

Question 20

• Fluid & solutes filtered from capillary into Bowman space (filtrate)
  
  • IN through AFFERENT
  • OUT through EFFERENT
• Capillary membrane
  
  • Endothelial layer
  • Basement membrane
  • Capsular epithelial layer
    
    • Podocytes
    • Particles move through “gaps”
  • Selectively permeable
    
    • Water and small particles leave blood
    • Larger particles prevented from leaving blood
      
      • WBCs, RBCs, glucose, proteins…
  • ⇡ Permeability w/ inflammation
    
    • Glomerular damage

Answer 20

Glomerulus

Question 21

• Protein in the urine
  
  • Indicates glomerular damage
• Urinalysis

Answer 21

Proteinuria

Question 22

Inflammation → Damage to capillary wall

• Acute post-infectious glomerulonephritis
  
  • Group A Beta-Hemolytic Streptococci
• Deposition of immune complexes
  
  • IgG & Complement

Answer 22

Acute Nephritic Syndrome

Question 23

• Proteinuria>3.5 g protein in urine/day
• Loss of serum protein
  
  • ⇣ Albumin → Edema
  • ⇣ Ig’s & complement → Immune suppression
  • ⇣ Binding proteins → Low ions & hormones
  • ⇣ Clotting/anticlotting factors → Thrombosis
  • Hyperlipidemia
    
    • Liver preoccupied with protein synthesis to compensate for hypoproteinemia

Answer 23

Nephrotic Syndrome Clinical Manifestations

Question 24

• Waste products produced by muscles
  
  • Not specific to kidneys
• Measures ability of kidney to filter
  
  • Reflects GFR
• Included on Basic Metabolic Panel (BMP)

Answer 24

Serum Creatinine (SCr)