Chronic Kidney Disease (CKD)/ ACR

What is Chronic Kidney Disease (CKD)?

CKD means reduced kidney function or kidney damage that lasts more than 3 months.

  • eGFR < 60 on at least 2 tests, 3 months apart
  • Or normal eGFR with evidence of kidney damage (e.g. raised urine ACR, persistent blood in urine, abnormal imaging) for > 3 months

Common Causes

  • Diabetes mellitus
  • Hypertension
  • Glomerulonephritis
  • Polycystic kidney disease
  • Obstructive uropathy (e.g. BPH, stones)
  • Recurrent urinary tract infections
  • Medications (e.g. NSAIDs, lithium)

Stepwise Primary Care Approach

Step 1: Confirm CKD

  • Repeat eGFR in 3 months if new finding and patient well
  • Check urine ACR and urine dip (blood/protein)
  • Rule out AKI: ask about vomiting/diarrhoea, infection, new medications, reduced urine

Step 2: Classify CKD Stage

  • G1: eGFR ≥ 90 with evidence of damage
  • G2: eGFR 60-89 with evidence of damage
  • G3a: eGFR 45-59
  • G3b: eGFR 30-44
  • G4: eGFR 15-29
  • G5: eGFR < 15

Albuminuria: A1 (< 3 mg/mmol), A2 (3-30), A3 (> 30)

Step 3: Initial Investigations

  • Urine ACR
  • Urine dip for blood and protein
  • U&Es and eGFR (baseline)
  • FBC (anaemia)
  • HbA1c (diabetes)
  • Calcium (and phosphate if CKD stage 3b or worse)
  • Blood pressure measurement
  • Renal ultrasound if:
    • eGFR < 45
    • Persistent haematuria
    • Suspected obstruction
    • Suspected polycystic kidney disease

Step 4: Management in Primary Care

  • Blood pressure target:
    • < 140/90 if ACR < 30
    • < 130/80 if ACR ≥ 30
  • ACE inhibitor or ARB: try if ACR ≥ 3 (especially diabetes or hypertension)
  • Diabetes: aim for individualised HbA1c target
  • Statin: try atorvastatin 20 mg nocte for CKD (primary prevention is usually recommended)
  • Avoid harm: avoid NSAIDs and review nephrotoxic medicines
  • Vaccines: try annual flu vaccine, and pneumococcal vaccine as appropriate
  • Diet advice: reduce salt intake, avoid high salt processed foods

Step 5: Monitoring (Simple and Practical)

  • G1-G2: monitor based on ACR and risk factors
  • G3a with A1: repeat U&Es and ACR yearly
  • G3a with A2/A3: repeat every 6 months
  • G3b: repeat every 3-6 months
  • G4: repeat every 3 months (often shared care with nephrology)
  • Always recheck U&Es 1-2 weeks after starting or increasing ACE inhibitor or ARB

Step 6: When to Refer to Nephrology

  • eGFR < 30 (G4-G5)
  • ACR ≥ 70 mg/mmol unless clearly due to diabetes and already optimised
  • Persistent haematuria with proteinuria
  • Rapid decline in kidney function:
    • eGFR drop ≥ 5 in 1 year
    • or ≥ 10 within 5 years
  • Resistant hypertension despite 4 drugs
  • Suspected systemic or inflammatory renal disease
  • Structural abnormality on imaging (e.g. hydronephrosis, polycystic disease)

What is ACR?

Albumin:creatinine ratio (ACR) detects and quantifies protein (albumin) loss in urine. It is a key test in diagnosing and monitoring CKD, especially in people with diabetes or hypertension.

Reference Ranges (Spot Urine Sample)

  • < 3 mg/mmol: no action needed
  • 3 - 70 mg/mmol: repeat ACR within 3 months
  • > 70 mg/mmol: indicates significant proteinuria - no repeat needed, proceed with CKD workup

Stepwise Clinical Approach

Step 1: First Sample

Request early morning urine ACR sample. Avoid samples during menstruation or UTI.

Step 2: If ACR ≥ 3 mg/mmol

  • Repeat 2 additional early morning samples within 3 months
  • Diagnosis of proteinuria confirmed if 2 out of 3 ACR results ≥ 3 mg/mmol
  • Use PCR (protein:creatinine ratio) if ACR > 70 mg/mmol or to monitor treatment

Step 3: Rule Out Transient Causes

  • Exclude UTI (send MSU if dipstick positive)
  • Post-exercise, fever, or upright posture may temporarily raise ACR

Step 4: Check for CKD

  • Repeat eGFR and ACR 3 months apart
  • CKD is diagnosed if ACR ≥ 3 mg/mmol or eGFR < 60 for > 3 months
  • Classify CKD based on ACR and eGFR together

Step 5: Additional Investigations

  • BP, HbA1c, lipid profile, BMI, and dipstick for haematuria
  • Renal ultrasound if: structural abnormalities suspected, family history of polycystic kidney disease, or aged > 20

Step 6: When to Refer to Nephrology

  • ACR persistently > 70 mg/mmol (even with normal eGFR)
  • ACR 30 - 70 mg/mmol with haematuria or reduced eGFR
  • Progressive decline in eGFR or uncontrolled hypertension
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