Chronic kidney disease

Contributed by Professor A. Meguid El Nahas, consultant renal physician, Sheffield Kidney Institute, and professor of nephrology at the University of Sheffield.

1. EPIDEMIOLOGY

In the UK, the annual incidence of established renal failure (ERF) is about 100 new patients per million population. This has doubled over the past decade and is expected to continue to rise by 5-8 per cent annually, at a considerable healthcare cost.

The number of patients receiving renal replacement therapy in the UK is rising and is not expected to reach a steady state for another 25 years.

The rise in ERF patients worldwide most likely reflects the ageing of the population and the global epidemic of obesity and type-2 diabetes mellitus.

Patients with ERF make up only a small percentage of all chronic kidney disease (CKD) patients; the total number may be 50 times higher. Population-based studies show between 6 and 7 per cent of the population have microalbuminuria and about 0.6-0.7 per cent have overt proteinuria. Patients with CKD are at a significantly higher risk of cardiovascular disease (CVD) than the general population.

Screening

Recently, a set of comprehensive guidelines were instigated by the joint speciality committee of the Royal College of Physicians and the British Renal Association, and developed together with the RCGP and others. The guidelines are aimed at identifying patients with CKD, reducing associated risk factors and identifying patients who would benefit from referral to specialist renal services.

The guidelines recommend that screening should identify and target those at highest risk, including patients with hypertension and diabetes. Other at-risk groups such as the obese, relatives of CKD patients, the elderly and those with underlying disease or medication predisposing to CKD, should also be screened.

Screening with dipsticks for albuminuria/proteinuria is acceptable as long as it is confirmed by quantitative spot urine, preferably early morning, analysis for albumin:creatinine ratio (ACR) or protein:creatinine ratio (PCR) to avoid false positives. These methods are preferable to 24-hour urine collection-based analysis in view of the inaccuracies in prolonged urine collections.

Definitions

Albuminuria (microalbuminuria) is defined as an ACR level of 2.5-30mg/mmol in men and 3.5-30mg/mmol in women or the equivalent of 20-200mg/24h and 30-300mg/24h respectively.

Proteinuria is defined as an ACR >30mg/mmol, or PCR >45 mg/mmol or >300 mg/24h equivalent.

2. PREVENTION

Serum creatinine is a readily available and reliable indicator of CKD but is affected by a variety of factors and renal function can be significantly impaired before serum creatinine levels are raised.

Classification

The DoH has recommended the implementation of routine estimated glomerular filtration rate (eGFR) reporting by all NHS Clinical Biochemistry laboratories from 1 April 2006. This is derived from an equation put forward by the Modification of Diet in Renal Disease group in the US.

Such formulation allows the classification of CKD patients into five stages. Stage one has a normal GFR (>90ml/min) with other evidence of chronic kidney damage such as persistent microalbuminuria or proteinuria, haematuria, biopsy-proven glomerulonephritis or structural abnormalities.

Stage two has GFR 60-90ml/min with other evidence of kidney damage; stage three is defined as GFR 30-59ml/min; stage four has GFR 15-29ml/min and stage five is defined as GFR <15ml/min.

Prevention Primary prevention programmes based on the reduction of CKD and cardiovascular risk factors are a major healthcare priority. As CKD and CVD share common risk factors such as diabetes, hypertension, dyslipidemia, obesity and smoking, primary prevention based on lifestyle modifications, including diet, exercise and weight loss, are most likely to reduce the incidence of both conditions.

Secondary prevention in CKD patients involves tight BP control with BP 1g/24h). The use of ACE inhibitors and angiotensin receptor blockers (ARBs) are recommended to concomitantly reduce proteinuria (<1g/24h).

Strict diabetes control, HbA1c about 7%, is recommended. Statins may benefit patients with CKD in terms of renal and cardiovascular protection.

Smoking cessation and weight loss should be encouraged.

Such a multifactorial risk reduction approach has been reported to slow or even reverse the decline in CKD.

References

- http://www.renal.org/CKDguide/ckd.html

- http://www.renal.org/CKDguide/full/Conciseguid141205.pdf

- http://www.renal.org/eGFR/eguide.html

3. MANAGEMENT

Models for the management of CKD include conventional shared care, specialist GPs, specialist nurses and computer-based shared care. Recommendations for referral are summarised in the table to the top right. The new GMS quality domain for CKD, which came into effect on 1 April 2006, is expected to influence the way care is delivered.

Check-ups

CKD primary care programmes for patients with isolated microscopic haematuria, those with low-level proteinuria and those with stable CKD discharged from hospital follow-up should include regular BP measurement, urinalysis and serum creatinine (eGFR) estimation.

The frequency of such check-ups is 12-monthly for stage one to two, six-monthly (12-monthly if stable) for stage three, three-monthly (six-monthly if stable) in nephrology unit for stage four and one to three check-ups monthly in nephrology unit for stage five.

Complications

The aim is to delay the progression of established CKD (eGFR<60ml/min) (see table, right).

Finally, CKD complications such as CVD, anaemia, renal bone disease and undernutrition are often late manifestations of CKD, and are probably best managed, at least initially, in the nephrology tertiary setting.

RECOMMENDED REFERRAL PATTERNS
ParameterDefinitionNeed for referral
eGFR

30-59ml/min
15-29ml/min
<15ml/min

Routine referral for assessment
Semi-urgent referral
Urgent referral to consider RRT
ProteinuriaPCR<100mg/mmol (<1k/24h) without haematuria with normal eGFR
PCR <100 with either haematuria or impaired eGFR<60ml/min
PCR >100mg/mmol
CKD primary care programme
Refer for assessment
Refer for assessment
HaematuriaMacroscopic
Microscopic. Age >50 year
Microscopic after exclusion of urological cause
Haematuria + proteinuria or + eGFR <60ml/min
Fast-track urological referral
Refer to urology
CKD primary care programme
Refer to nephrology

 


GUIDELINES FOR MANAGEMENT OF CKD
Risk factorTargetManagement
BP

<130/80mmHg
<125/75mmHg in those with diabetes and those with proteinuria >100mg/mmol (1g/24h)

Preferably start with ACE inhibitors or ARBs: caution in the elderly and those with atherslerosis
Close monitoring of eGFR
ProteinuriaPCR< 100mg/mmol (<1g/24h)ACE inhibitors/ARBs
+ low salt diet
+ diuretics
Cholesterol<5mmol/l
Statins
Smoking
STOP
 
Alcohol
<2 units/day
 

 

 

 

 

 

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