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Key questions: chronic kidney disease

Key questions: chronic kidney disease

Key points

  • It is important to differentiate transient, acute impairments (such as acute kidney injury from dehydration or drugs) from CKD
  • CKD is classified according to level of albuminuria in mg/mmol (A1 to A3) and eGFR, this combination of factors being predictive of risk of CVD and kidney failure
  • All patients with CKD should be offered 20mg atorvastatin daily for the primary prevention of CVD 
  • BP targets are stringent and vary depending on the ACR
  • ACE inhibitors or ARBs and, in certain circumstances, SGLT2s, have a role to play in patients with microalbuminuria
  • Any anaemia is unlikely to be caused by the CKD itself if the eGFR is greater than 60 ml/min/1.73m2
  • One criterion for referral to secondary care is a greater than 5% risk of renal replacement therapy (RRT) within five years – this can be calculated via a Kidney Failure Risk Equation

Professor Debasish Banerjee is a professor of clinical practice in renal medicine and a consultant, Dr Souradip Mookerjee and Dr Ella Tumelty are academic foundation trainees at St George’s University Hospitals NHS Foundation Trust

Q: Possible chronic kidney disease (CKD) is often found in primary care on ‘routine’ blood testing in a non-acute situation. In these circumstances, how soon should the test be repeated, and how many times should it be done to confirm CKD?

A: CKD is defined as either damage to kidney structure or reduction in kidney function present for more than three months, with implications for health. Often, routine blood tests can highlight impaired renal function through estimated glomerular filtration rate (eGFR) – eGFR less than 60ml/min/1.73m2. This is done through measurement of serum creatinine levels (and then calculated eGFR/creatinine clearance) in the non-acute situation. It is important to differentiate transient, acute impairments (such as acute kidney injury [AKI] from dehydration or drugs) from CKD.

NICE recommends repeating the measurement within two weeks. If the results are still low, repeat a third time within three months.  

Also, organise an early morning urine sample to measure the albumin-to-creatinine ratio (ACR), to look for proteinuria. If this returns a value less than 3mg/mmol, no further action is required. If the value is above 70mg/mmol, this can be interpreted as clinically significant proteinuria. If the ACR reading lies between these values, arrange for a repeat test within three months and if it remains above 3mg/mmol, this is clinically significant. Note that many other benign causes can result in transient increases of urine ACR. 

NICE does not recommend the use of urine dipsticks to assess proteinuria in suspected CKD, unless the strip can measure albumin at low levels and express this as an ACR. Most reagent strips will give false negative results because they don’t detect clinically significant proteinuria, or false positive results due to haematuria, or concentrated or alkaline urine. Measurement of albuminuria identifies patients with high risk of progression and cardiovascular events, who will benefit from strict BP control and use of renin-angiotensin-aldosterone system (RAAS) inhibitors and sodium glucose cotransporter-2 (SGLT2) inhibitors.

You can accurately diagnose CKD if there is evidence of persistent renal dysfunction (eGFR below 60ml/min/1.73m2) or proteinuria (urinary ACR above 3mg/mmol) for at least three months.

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