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Approach to an abnormal eGFR in primary care

Approach to an abnormal eGFR in primary care. Hugh Gallagher Consultant Nephrologist SW Thames Renal Unit. Changes in the way we measure kidney function eGFR Total protein-creatinine ratio Chronic kidney disease (CKD), classification, clinical features and consequences

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Approach to an abnormal eGFR in primary care

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  1. Approach to an abnormal eGFR in primary care Hugh Gallagher Consultant Nephrologist SW Thames Renal Unit

  2. Changes in the way we measure kidney function • eGFR • Total protein-creatinine ratio • Chronic kidney disease (CKD), classification, clinical features and consequences • Approach to an abnormal eGFR in primary care • The management of CKD in primary care

  3. Changes in the way we measure kidney function • eGFR • Total protein-creatinine ratio • Chronic kidney disease (CKD), classification, clinical features and consequences • Approach to an abnormal eGFR in primary care • The management of CKD in primary care

  4. “Local health organisations can work with pathology services and networks to develop protocols for measuring kidney function by serum creatinine concentration together with a formula-based estimation of glomerular filtration rate (eGFR), calculated and reported automatically by all clinical biochemistry laboratories.” Renal NSF Part 2, Dept of Health, 2004

  5. The problem with creatinine…. • Affected by muscle mass (age/sex/weight) so poor surrogate for GFR • Insensitive – can lose 50% of renal function before serum creatinine rises • Therefore poor marker of early renal disease

  6. GFR = Glomerular filtration rate “Normal” = 80-120 ml/min Therefore see as “% renal function” Calculate 1) Actual – iohexol/EDTA clearance 2) Estimated – using formula

  7. Formulae in use • *MDRD formula • Age • Sex • Creatinine • Ethnicity (black vs. non-black) • Cockcroft-Gault formula • Age • Sex • Creatinine • Weight

  8. Cockcroft Gault & MDRD Formula

  9. Age Sex Weight Serum Estimated (kg) creatinine GFR ( mol/L) (ml/min) μ 60 M 70 150

  10. Age Sex Weight Serum Estimated (kg) creatinine GFR ( mol/L) (ml/min) μ 60 M 70 150 46

  11. Age Sex Weight Serum Estimated (kg) creatinine GFR ( mol/L) (ml/min) μ 60 M 70 150 46 80 M 60 170

  12. Age Sex Weight Serum Estimated (kg) creatinine GFR ( mol/L) (ml/min) μ 60 M 70 150 46 80 M 60 170 26

  13. Age Sex Weight Serum Estimated (kg) creatinine GFR ( mol/L) (ml/min) μ 60 M 70 150 46 80 M 60 170 26 80 F 60 170

  14. Age Sex Weight Serum Estimated (kg) creatinine GFR ( mol/L) (ml/min) μ 60 M 70 150 46 80 M 60 170 26 80 F 60 170 22

  15. The introduction of eGFR will allow early identification of CKD and Will result in increased awareness of advanced CKD previously not recognised as such

  16. The “normal” eGFR is age related

  17. Urine total protein:creatinine ratio • Replaces timed 24 hour urine collections for protein • Random spot urine (preferably early morning, but not essential) • Result in mg/mmol (mg of protein per mmol of creatinine) • Multiply by 10 = total daily protein excretion in mg

  18. Total protein:creatinine ratio

  19. Urine total protein:creatinine ratio Urine protein = 500 mg/l Urine creatinine = 5 mmol/l Therefore TPCR = 500/5 = 100 mg/mmol Therefore daily protein excretion = 100 x 10 = 1000 mg = 1 g

  20. Not to be confused with…. Urine albumin:creatinine ratio NOT for quantifying urine total protein excretion BUT simply to diagnose the earliest stage of diabetic nephropathy Raised ACR = treat with ACEI/ARB (even if normotensive) and address CV risk

  21. Changes in the way we measure kidney function • eGFR • Total protein-creatinine ratio • Chronic kidney disease (CKD), classification, clinical features and consequences • Approach to an abnormal eGFR in primary care • The management of CKD in primary care

  22. K-DOQI Classification of CKD Chronic kidney disease is defined as either kidney damage or GFR < 60 ml/min for > 3 months. 1 Kidney damage is defined as pathological abnormalities or markers of damage, including abnormalities in urinalysis or imaging

  23. K-DOQI Classification of CKD Chronic kidney disease is defined as either kidney damage or GFR < 60 ml/min for > 3 months. 1 Kidney damage is defined as pathological abnormalities or markers of damage, including abnormalities in urinalysis or imaging

  24. In real money... • GP practice 10,000 patients • Stage 3 CKD: 500 patients • Stage 4 CKD: 20 patients • Stage 5 CKD: 20 patients • Unreferred stage 4 and 5: 28 patients • Renal unit, serving 1.8 million population • Unreferred stage 4 and stage 5: 5,100 patients

  25. Functional consequences of CKD • Hypertension (all stages) • Anaemia (stage 4-5, earlier in DM) • Disorders of Ca/Pi/PTH metabolism (stage 4-5) • renal osteodystrophy • vascular calcification

  26. Causes of CKD in the elderly

  27. Snapshot of a CKD population in primary care • GFR estimated on patients from 12 practices in Surrey, Kent and Greater Manchester • 19% of sample (5% population) stage 3-5 CKD • mean age 74 years (control 57 years) • 75% stage 3-5 (22% control) co-existing circulatory disease • 25% stage 3-5 (men) prostatic disease • 15% stage 3-5 anaemic by WHO (4% requiring treatment by European Best Practice guidelines) • 3% recorded as having a renal disease

  28. Comorbidities in CKD

  29. Cardiovascular diseases in CKD Damage to the heart (Uraemic cardiomyopathy) Damage to the arteries (Uraemic arteriopathy)

  30. Cardiovascular Mortality Rates are Higher among Dialysis Patients 100 10 1 Dialysis: male Dialysis: female 0.1 General population: male 0.01 General population: female 0.001 Adapted from Levey AS et al. Am J Kidney Dis 1998; 32: 853-906.

  31. The Kaiser Permanante experience Derangements in renal function are independently associated with a graded increase in (cardiovascular) risk. This effect is seen even with relatively minor impairments in function. Go, A. S. et al. N Engl J Med 2004;351:1296-1305

  32. John, RI et al. AJKD 43:825-835; 2004

  33. ESRD is the tip of an iceberg DIALYSIS DEPENDENT 0.04% PROGRESSIVE STAGE 4 CKD 0.05% STABLE STAGE 4 CKD 0.15% STAGE 3 CKD 4%

  34. 3 Key Messages • Most patients with CKD are elderly • The majority have stable disease and die of CV causes well before they reach ESRD • Their management is therefore that of their CV risk

  35. Changes in the way we measure kidney function • eGFR • Total protein-creatinine ratio • Chronic kidney disease (CKD), classification, clinical features and consequences • Approach to an abnormal eGFR in primary care • The management of CKD in primary care

  36. Questions to ask with a newly detected abnormal eGFR (< 60 ml/min) • Is this acute renal failure? • Historical records • Repeat within 1/52 • Is it in the context of intercurrent illness? • Repeat after illness treated • Is there suspicion of obstruction? • Renal tract US (not otherwise) • Are there abnormalities on urinalysis? • Dipstick urine, send simultaneous MSU/TPCR • Should the patient be referred?

  37. Urinanalysis and the patient with a newly detected abnormal eGFR (< 60 ml/min) • Nephrology referral is indicated in the presence of persistent microscopic haematuria (if age > 45 then urological malignancy should be excluded first) • Nephrology referral is also indicated (in the presence or absence of microscopic haematuria) if total protein-creatinine ratio > 100 mg/mmol (1 g proteinuria) • Nephrology referral is not required (in the absence of microscopic haematuria) for lower levels of proteinuria, although these patients should be labelled as Stage 3 CKD and entered into appropriate care pathway

  38. Should the patient with newly detected eGFR < 60 ml/min be referred? • Not in the majority of cases • ARF • Obstruction (urology) • Abnormalities on urinalysis • For those patients with previously abnormal creatinine/eGFR, treat as CKD

  39. What about referral indication in patients with eGFR > 60 ml/min? • Proteinuria > 1g/day (TPCR > 100 mg/mmol) • Proteinuria > TPCR 45 mg/mmol plus microscopic haematuria • Multisystem disease with evidence of kidney damage • Accelerated hypertension with evidence of kidney damage • Suspicion of renal artery stenosis • New diagnosis of APKD

  40. Changes in the way we measure kidney function • eGFR • Total protein-creatinine ratio • Chronic kidney disease (CKD), classification, clinical features and consequences • Approach to an abnormal eGFR in primary care • The management of CKD in primary care

  41. General management of CKD • Blood pressure • Home meter • 140/90 threshold • 130/80 target (125/75 if TPCR > 100 mg/mmol) • ACEI/ARB if MA/proteinuria/heart failure • Refer if >150/90 despite 3 complementary drugs • Lipid management • JBS guidelines • Other • Aspirin if 10 year CV risk > 20% • Influenza/pneumococcal vaccination • Smoking/weight • Medication review

  42. Frequency of monitoring

  43. Specific management of Stage 3 CKD • Renal US only if: • Refractory hypertension • Lower tract symptoms • 50% dose reduction metformin if eGFR < 45 ml/min • Refer if: • Progressive (fall in eGFR > 10 % over 1 year) • Functional haematological/biochemical consequences: • Hb < 11 • K > 6 • Ca < 2.1, Pi > 1.5, PTH > 7 pmol/l • Poorly controlled hypertension

  44. Specific management of Stage 4 CKD • Discuss with nephrology • Renal US • Stop metformin • Refer if: • Diabetic • Progressive (fall in eGFR > 15 % over 1 year) • eGFR < 20 ml/min • Functional haematological/biochemical consequences: • Hb < 11 • K > 6 • Ca < 2.1, Pi > 1.5, PTH > 11 pmol/l • Poorly controlled hypertension

  45. Specific management of Stage 5 CKD • Refer

  46. Take home messages • eGFR as a “% kidney function” • 0.5-1%/year lost from 40+ • Most CKD patients are stable and management is that of CV risk • CKD patients that should be referred are those: • With progressive disease • With advanced disease (Stage 5 +/- Stage 4) • With functional consequences of disease

  47. The nephrologist’s view

  48. The GP’s view

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