Summary of "Acute Kidney Injury (AKI) | Clinical Medicine"

Main Ideas and Concepts

Definition of Acute Kidney Injury (AKI)
AKI is characterized by an abrupt decline in urine output and a rise in serum creatinine levels. Defined as:
- An increase in serum creatinine of ≥0.3 mg/dL within 48 hours.
- An increase of ≥1.5 times the baseline creatinine within 7 days.
- Oliguria defined as urine output of ≤0.5 cc/kg/hour for ≥6 hours.
Classification of AKI
- Pre-renal AKI: Due to reduced blood flow to the kidneys, often from factors like dehydration or heart failure.
- Intrarenal AKI: Caused by damage to the kidney structures, particularly the nephrons, due to toxins or ischemia.
- Postrenal AKI: Results from urinary tract obstruction, which can occur at various points from the kidney to the bladder.
Pathophysiology
Pre-renal AKI results from decreased renal perfusion, leading to reduced glomerular filtration rate (GFR). Intrarenal AKI involves nephron injury, which can be due to ischemia (acute tubular necrosis) or nephrotoxins (medications, pigments). Postrenal AKI is caused by obstruction, leading to back pressure and impaired GFR.
Diagnosis
Diagnosis involves assessing serum creatinine levels and urine output. Urinalysis and fractional excretion of sodium (FENa) help differentiate between pre-renal and intrarenal causes. Imaging studies (e.g., renal ultrasound) are used to identify obstructions in Postrenal AKI.
Complications
Common complications of AKI include:
- Metabolic acidosis
- Hyperkalemia (high potassium levels)
- Uremia (accumulation of waste products)
- Fluid overload leading to pulmonary edema and peripheral edema.
Treatment Strategies
- Pre-renal AKI: Administer IV fluids to restore blood volume and improve renal perfusion.
- Intrarenal AKI: Supportive care, discontinuation of nephrotoxic agents, and monitoring for potential dialysis.
- Postrenal AKI: Removal of obstructions via catheterization or surgical intervention.

Methodology and Instructions

Assessment:
- Monitor urine output and serum creatinine levels.
- Conduct urinalysis to evaluate FENa and urine osmolality.
- Use imaging to check for obstructions.
Treatment:
- For Pre-renal AKI:
  - Administer IV fluids (e.g., normal saline, lactated Ringer's).
- For Intrarenal AKI:
  - Discontinue nephrotoxic medications.
  - Consider dialysis if indicated.
- For Postrenal AKI:
  - Insert a Foley catheter for bladder decompression.
  - Consider stenting or nephrostomy for proximal obstructions.