Acute Kidney Injury Overview

Study Notes

AKI (Acute Kidney Injury)

Characterized by a sudden loss of renal function, often reversible.
Can be classified into three categories: prerenal, intrarenal, and postrenal.

Prerenal AKI

Characterized by decreased renal perfusion due to factors like:
- Extremely low blood pressure or blood volume
- Heart dysfunction (e.g., myocardial infarction, heart failure)
- Liver disease with portal hypertension

Intrarenal AKI

Involves direct damage to the kidney structures.
Can be further categorized into:
- Vascular disease:
  - Reduced blood supply within the kidney (e.g., atherosclerosis, renal vein thrombosis, renal aneurysm, aortic dissection)
- Glomerular disease:
  - Conditions like glomerulonephritis and acute interstitial nephritis (often linked to allergic reactions to nephrotoxic medications)
- Tubular and interstitial disease:
  - Tubular disorders and toxic injury

Postrenal AKI

Occurs when urine excretion is interfered with due to:
- Bilateral ureter obstruction (e.g., kidney stones, tumors)
- Bladder obstruction and dysfunction (e.g., benign prostatic hyperplasia, tumors, nerve innervation disruption)

Acute Tubular Necrosis (ATN)

A common cause of intrarenal AKI.
Often triggered by ischemia (reduced blood flow) due to decreased renal perfusion and sepsis.
Exposure to nephrotoxic drugs can also contribute.
Process involves:
- Nephron injury leading to reduced blood flow and increased vascular permeability.
- Inflammatory response with activation of leukocytes, macrophages, and complement.
- Impaired sodium, water, and other substance transport in the kidney.
- Tubular shedding and obstruction, leading to pressure buildup within the lumen.
- Necrosis in multiple areas of the tubule.

Phases of AKI

Initial phase: Often asymptomatic, renal damage is occurring, functioning nephrons compensate.
Oliguric phase: Impaired glomerular filtration leads to solute and water reabsorption, waste products accumulate (uremia).
- Characterized by decreased urine output, electrolyte disturbances, fluid volume excess, azotemia (elevated nitrogenous waste in the blood), and metabolic acidosis.
- Lasts for days to weeks.
Diuretic phase: Gradual return of renal function, cell regeneration occurs.
- Tubular damage impairs urine concentration, leading to excessive diuresis (increased urine production - up to 5L/day).
- Can lead to dehydration and electrolyte imbalances.
Recovery phase: Gradual restoration of normal glomerular function and resolution of symptoms.
- Can persist for 3 to 12 months.

Description

Explore the critical aspects of Acute Kidney Injury (AKI), including its categories: prerenal, intrarenal, and postrenal. Understand the causes, symptoms, and treatment options for each type of AKI. Enhance your knowledge on how these factors influence renal function.