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
