Acute Kidney Injury (AKI) Overview

Introduction

• Acute Kidney Injury (AKI), also known as Acute Renal Failure, is a rapid decrease in kidney function.
• Causes build-up of waste (e.g., BUN, creatinine) and fluid in the body.
• Potentially reversible if diagnosed early and treated.

Causes of AKI

• Prerenal Causes

  • Issues before reaching the kidneys, often due to decreased kidney perfusion.
  • Examples: Cardiac issues (e.g., myocardial infarction), massive bleeding, dehydration, burns.

• Intrarenal Causes

  • Damage within the kidneys, affecting nephrons.
  • Examples: Nephrotoxic drugs (NSAIDs, aminoglycosides), infections (e.g., glomerulonephritis).

• Postrenal Causes

  • Obstructions in urine outflow after the kidneys.
  • Examples: Kidney stones, enlarged prostate, neurogenic bladder issues.

Kidney Function Basics

• Kidneys filter waste, balance electrolytes, and maintain fluid balance.
• Normal urine output: 1-2 liters/day.
• Key waste products: Urea (BUN), creatinine.
• Creatinine
  • Indicator of kidney function, normal range: 0.6-1.2 mg/dL.
• Glomerular Filtration Rate (GFR)
  • Measures blood flow through the kidneys; normal is 90+ mL/min.

Stages of AKI

1. Initiation Stage

   • Triggered by an initial injury.
   • Early intervention can prevent progression.

2. Oliguric Stage

   • Urine output <400 mL/day.
   • Signs: Increased BUN/creatinine, azotemia, hyperkalemia, fluid overload.
   • Treatment: Monitor protein intake, restrict potassium, manage fluid status.

3. Diuresis Stage

   • Increased urine output, 3-6 liters/day due to osmotic diuresis.
   • Risks: Hypovolemia, electrolyte imbalances (e.g., hypokalemia).
   • Management: Maintain fluid balance, replace electrolytes.

4. Recovery Stage

   • GFR returns to normal.
   • Normal urine output and electrolyte balance.
   • Recovery time varies; may take up to a year.

Laboratory Tests and Indicators

• BUN (Blood Urea Nitrogen): Measures urea level, indicates kidney function.
• Creatinine Clearance: Indicates blood volume free of creatinine per minute.
• GFR (Glomerular Filtration Rate): Overall kidney function.
• Urine Specific Gravity: Indicates urine concentration.

Potential Complications

• Metabolic Acidosis: Due to decreased hydrogen ion excretion.
• Hyperkalemia: Risk of cardiac issues; monitor closely.
• Hyponatremia and electrolyte imbalances.

Conclusion

• Early detection and management of AKI are crucial for recovery.
• Ongoing assessment of labs and symptoms guides treatment.
• Some patients may progress to chronic kidney disease requiring long-term management.