Renal

Key Facts to Keep in Mind:

• Normal BUN: 10-23
• Normal Creatinine (Cr): 0.6-1.4
• Normal Urine Specific Gravity: 1.010-1.020
• Best GFR Indicator: 24-hour urine collection
• Metabolic Acidosis: Associated with intrarenal failure
• Nephrotoxic substances: Antibiotics, NSAIDs, ACE/ARBs, contrast agents, and excessive diuretic use

Prerenal Failure

• Cause: Reduced perfusion without damage to the renal tubules.
• Most common type of kidney failure.
• BUN:Cr ratio: 20-40:1
• Signs/Symptoms: Concentrated urine, increased specific gravity, low urine sodium
• Treatment: Responds to LASIX (diuretic therapy)

Intrarenal Failure

• Cause: Decreased blood flow to the kidneys with damage to tubular membranes.
• May require dialysis.
• BUN:Cr ratio: 10-15:1
• Signs/Symptoms: Diluted urine, decreased specific gravity, increased urine sodium
• Treatment: Prevent uremia and initiate early dialysis.

Acute Tubular Necrosis (ATN)

• Cause: Damage to the tubular basement membrane, often due to prolonged low blood flow, infection, or contrast dye.

Postrenal Failure

• Cause: Obstruction anywhere from the collecting ducts to the external urethra.
• Treatment: Remove the obstruction to restore function.

Contrast Medium Nephropathy

• Higher risk for those on: Metformin, NSAIDs, or ACE inhibitors
• Prevention: Hydrate before and after contrast use with adequate fluids.

Rhabdomyolysis

• Cause: Breakdown of muscle tissue, releasing potassium, creatine kinase (CK), and myoglobin, which may block renal tubules.
• Common causes: Crush injuries, prolonged immobility.
• Signs/Symptoms: Muscle pain, weakness, decreased urine output, tea-colored urine, increased CK levels
• Treatment: Hydrate aggressively with fluids and bicarbonate, treat high potassium levels.

Hemodialysis

• Used as a last resort when other treatments fail.
• Indications:
  • Acidosis
  • Electrolyte imbalances (especially high potassium)
  • Intoxication (e.g., aspirin or methanol)
  • Overload (e.g., heart failure)
  • Uremia (elevated BUN)
• CRRT (Continuous Renal Replacement Therapy): Recommended for unstable patients who cannot tolerate rapid fluid shifts.