Chronic Kidney Disease
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Classification of Chronic Kidney Disease (CKD)

The publication of the second part of the Renal NSF has highlighted the importance of a structured approach to the management of chronic kidney disease. Central to the organisation of care is the utilization of a modified form of the kDOQI classification of chronic kidney disease. The classification is based on measuring serum creatinine, translating this measure into an estimated GFR and then grading the stage of CKD. This then allows the stratification of assessment, modulation and treatment of patients.

Stage GFR (corrected for surface area) mls/min/1.73 m2 Description Management Prevalence**
1* 90+ Normal kidney function but other markers of renal damage Monitor, guidance here 5.9%
2* 60-89 Mildly reduced kidney function and other markers of renal damage Monitor, guidance here 4.0%
3 30-59 Moderately reduced kidney function Management of progression and complications 4.3%
4 15-29 Severely reduced kidney function Planning for end stage renal failure 0.2%
5 <15 or RRT Very severe or end stage kidney failure Renal replacement therapy 0.2%

* with other markers of renal damage

** data taken from NHANES III (1988-1994) for stages 1-4 and USRDS (1998) for stage 5. Data for guidance only.

The interpretation of eGFR has a number of caveats, especially in patients with normal or near normal function and is discussed here. Moreover, the staging is only applicable if the abnormality has been present for more than 3 months.  However, it is a useful serial measurement and is helpfully in guiding investigation and treatment. The UK CKD guidelines (Royal College of Physicians) therefore note that CKD Stages 1 and 2 should be used with caution. The Royal College of General Practitioners has produced this leaflet for guidance, which can be downloaded and printed out:

How to use this

The pathology reports will report an estimated GFR on all patients in whom a serum creatinine is measured (although eGFR > 60 will be reported as > 60 mls/min). Consult the above table and follow the guidance link for suggested management. For a patient with previously unrecognised CKD the flow chart here can be helpful (taken from the St Helier guidelines)

Given that a large proportion of the population have CKD should all patients be screened? The answer is NO. However high risk populations should have regular assessment of their renal function.

High risk groups include:

        - those with diabetes (test at least annually)

        - those with hypertension and/or cardiovascular disease (test eGFR at least annually)

        - those with a family history of kidney disease (test at least 2 yearly)

It is unclear whether the elderly should be considered a high risk group, but those on potential nephrotoxic drug regimes should probably be monitored.

Stage 1 and 2 CKD

This is a difficult area. The management of stage 1 and 2 is identical and relies on other markers of renal disease to truly classify someone within this staging. It is impractical to test the urine every time a serum creatinine is requested. So unless a person is at high risk of renal disease (diabetes, hypertension or cardiovascular disease), or there is a clinical index of suspicion, a urine dip is probably not required. If a urine has been done on a stable patient in the last year, again it is probably not required, especially if the urine dip was negative for protein. To turn this around patients should not be labelled as having CKD 1 or 2 unless there is clear evidence of renal pathology.