Acute Kidney Injury (AKI)

Definition

Acute Kidney Injury (AKI) is a sudden decline in kidney function over hours to days. It leads to an accumulation of waste products, electrolyte imbalances, and fluid overload.

Causes of AKI

AKI is classified into three categories based on the site of injury:

1. Prerenal AKI (Decreased Blood Flow to Kidneys)

  • Hypovolemia (e.g., hemorrhage, severe dehydration, burns)
  • Decreased cardiac output (e.g., heart failure, myocardial infarction)
  • Systemic vasodilation (e.g., sepsis, anaphylaxis)
  • Renal artery stenosis

Use of NSAIDs or ACE inhibitors (which impair renal perfusion)

2. Intrinsic AKI (Direct Damage to Kidney Tissue)

  • Acute tubular necrosis (ATN) due to ischemia or toxins (e.g., contrast media, aminoglycosides, rhabdomyolysis)
  • Glomerulonephritis (immune-mediated damage)
  • Acute interstitial nephritis (often drug-induced, e.g., penicillins, NSAIDs)
  • Thrombotic microangiopathies (e.g., hemolytic uremic syndrome, disseminated intravascular coagulation)

3. Postrenal AKI (Obstruction of Urinary Flow)

  • Kidney stones
  • Prostate hypertrophy or cancer
  • Ureteral strictures
  • Neurogenic bladder
  • Malignancies compressing the urinary tract
  • Classification of AKI

RIFLE Criteria

  • Risk: GFR decrease by 25% or creatinine increase x1.5
  • Injury: GFR decrease by 50% or creatinine increase x2
  • Failure: GFR decrease by 75% or creatinine increase x3
  • Loss: Persistent kidney failure > 4 weeks
  • End-stage: Complete loss of function > 3 months

AKIN Criteria

Stage 1: Increase in creatinine ≥ 0.3 mg/dL or 1.5–2 times baseline

Stage 2: Increase in creatinine 2–3 times baseline

Stage 3: Increase in creatinine >3 times baseline or need for dialysis

Signs and Symptoms of AKI

  • Oliguria (< 400 mL/day) or anuria
  • Edema
  • Fatigue and confusion
  • Hyperkalemia (leading to arrhythmias)
  • Metabolic acidosis
  • Uremia (nausea, pruritus, encephalopathy)

Diagnosis of AKI

  • Serum creatinine and BUN levels
  • Urine output monitoring
  • Urinalysis (casts, proteinuria, haematuria)
  • Renal ultrasound (assess obstruction or structural abnormalities)
  • Fractional excretion of sodium (FENa)

Management of AKI

  • Identify and treat the cause (e.g., stop nephrotoxic drugs, treat infections, restore perfusion)
  • Fluid resuscitation in prerenal AKI (balanced approach to avoid overload)
  • Diuretics in fluid-overloaded patients (cautiously used)
  • Electrolyte correction, especially hyperkalemia (calcium gluconate, insulin-glucose, sodium bicarbonate)
  • Renal replacement therapy (RRT) if severe metabolic disturbances or volume overload

Chronic Kidney Disease (CKD)

Definition

CKD is a progressive loss of kidney function over months to years, leading to end-stage renal disease (ESRD) if untreated.

Causes of CKD

  • Diabetes mellitus (most common cause)
  • Hypertension (chronic high blood pressure damages glomeruli)
  • Glomerulonephritis (chronic inflammation of glomeruli)
  • Polycystic kidney disease (genetic disorder)
  • Obstructive uropathy (prolonged obstruction of urinary flow)
  • Autoimmune diseases (e.g., lupus nephritis)

Stages of CKD (Based on GFR)

Stage 1: GFR ≥ 90 mL/min (kidney damage with normal function)

Stage 2: GFR 60-89 mL/min (mild reduction)

Stage 3a: GFR 45-59 mL/min (mild to moderate reduction)

Stage 3b: GFR 30-44 mL/min (moderate to severe reduction)

Stage 4: GFR 15-29 mL/min (severe reduction)

Stage 5: GFR < 15 mL/min (end-stage renal disease)

Signs and Symptoms of CKD

  • Fatigue
  • Anemia (due to decreased erythropoietin production)
  • Hypertension
  • Edema (fluid retention)
  • Hyperkalemia
  • Bone disease (due to altered calcium and phosphorus metabolism)
  • Uraemic Frost
  • Uraemic symptoms (nausea, pruritus, confusion)

Diagnosis of CKD

  • Serum creatinine and estimated GFR
  • Urinalysis (proteinuria, hematuria)
  • Renal ultrasound (small, shrunken kidneys in advanced disease)
  • Renal biopsy (if unclear cause)

Management of CKD

  • Control underlying causes (e.g., diabetes, hypertension)
  • Blood pressure control (ACE inhibitors, ARBs)
  • Dietary modifications (low sodium, potassium, phosphorus, protein restriction)
  • Anaemia management (erythropoiesis-stimulating agents, iron supplements)
  • Bone mineral disorder management (calcium, vitamin D, phosphate binders)
  • Dialysis initiation when GFR < 10-15 mL/min or symptomatic uraemia
  • Kidney transplantation in eligible patients