Chronic kidney disease

Background

Definition

• Structural or functional kidney disorder lasting at least [3 months]

KDIGO Classification

• Defined as 3 or more months of either GFR < 60 or 1 or more marker of kidney damage:
  • Proteinuria
  • Urine sediments
  • Tubular electrolyte disorder
  • Kidney transplant
  • Structural disease
• Categories & grades:
  • Grade 1: GFR ≥90 (normal) with a marker of kidney disease
  • Grade 2: GFR 60-89 with a marker of kidney disease
  • Grade 3a: GFR 45-59
  • Grade 3b: GFR 30-44
  • Grade 4: GFR 15-29
  • Grade 5: GFR <15, ESRD

Epidemiology

• 8% of population have GFR < 60
• 4% of population have proteinuria despite normal GFR

Differential Diagnosis

• Diabetes
• Cardiovascular disease/HTN
  • Ischemic nephropathy
  • Nephrosclerosis
• Glomerulonephritis
• PCKD
• Drugs, especially lithium, cyclosporine, tacrolimus, tenofivir
• Other disease associations
  • Inflammatory bowel disease: oxalate nephropathy
  • Rheumatoid arthritis: amyloidosis
  • Cirrhosis: Type 2 hepatorenal syndrome
  • Solid tumours: membranous nephropathy
  • Severe CHF: cardiorenal syndrome
  • Post-AKI: incomplete recovery of ATN in hospital

Investigations

Laboratory

• GFR
  • MDRD underestimates the GFR in healthy patients
  • CKD-Epi is the newer equation and possibly more accurate
  • Radioisotopic GFR is the gold standard, inulin clearance is the gold standard for research
  • Cystatin C may complement or replace creatinine in the future
• Urinalysis, though "protein" only picks up albumin
• Urine ACR and PCR

Imaging

• Abdominal ultrasound

Management

• Education re: dialysis and transplant
• Refer to nephrology when:
  • GFR drops by 5+ per year
  • Acute on chronic kidney injury
  • eGFR < 30 (Stage 4)
  • Proteinuria >1g/day
  • Difficulty controlling BP
• BP control
  • ACEi + CCB + diuretic
  • If albuminuria, target <130/80, else <140/90
• Proteinuria
  • If proteinuria >500mg/d or ACR>30mg/mmol, start ACEi/ARB regardless of BP
  • If diabetes and microalbuminuria, start ACEi/ARB
• Metabolic acidosis (normal anion gap)
  • Oral sodium bicarbonate 0.5-1 mEq/kg/d to maintain bicarb between 23-29 mmol/L
• Hold ACEi/ARB when AKI, any illness causing dehydration, surgery, contrast study, planning pregnancy
• Avoid nephrotoxic mediation like NSAIDs

Complications

• Anemia: treat iron deficiency before adding Epo, targetting 105-115
• Hypocalcemia: give calcium between meals or rocaltrol (if the hyperphosphatemia is treated)
• Hyperphosphatemia: give a phosphate binder like calcium or Renagel with meals
• Metabolic bone disease: maintain normal phosphate with diet, binders, and vitamin D
• Acidosis: supplement bicarb when < 22
• Hyperkalemia from poor GFR, ACEi, DM
• Pruritis: moisturizers, steroids, antihistamines

Prognosis

• GFR declines linearly over time
• Progression predicted by
  • Previous rate of progression
  • Hypertension **
  • Proteinuria **
  • Metabolic acidosis
• High risk of cardiovascular mortality compared to general population
  • 30 year olds on dialysis have same risk as 80 year olds in the general population
  • Risk increases with a decreasing GFR