What is CKD?

Our kidney has lot of physiologically important functions like removal of waste products, production of urine and etc. However, there are some instances when your kidneys fail to achieve the expected level of functions. The long-term inability to achieve such is defined as CKD. Although there may be structural abnormality of kidneys in Chronic Kidney Disease, CKD is commonly the functional abnormality. However later you would have structural changes too.

What is GFR and eGFR?

GFR – Glomerular Filtration Rate is the key indicator of someones kidney functions. This indicate the average rate of solute filtration from the glomeruli. It is calculated by the filtration rate of Creatinine. Therefore GFR is depend on someones age, sex and race. eGFR is a mathematically calculated glomerular filtration rate. The calculated eGFR value is used for the eGFR staging of CKD.

The calculation of eGFR is done with the help of standard calculation formulae. It uses age, gender and race for this calculations. The result is given for the body surface area. The normal eGFR is more than 90ml/min/1.73m² .

eGFR Staging of CKD (Chronic Kidney Disease)

The usual CKD staging has 5 main stages. It is stage 1 to stage 5. The stage 1 having minimum or no reduction of kidney functions while stage 5 has almost zero kidney function.

Normal eGFR

Usually eGFR for normal person is above 90 (>90ml/min/1.73m2). If you have normal eGFR, you have a good kidney function. However the normal GFR is vary according to age. Usually the normal level of GFR reduce with age.

20–29 116

  30–39 107

  40–49 99

 50–59 93

  60–69 85

  70+ 75

Stage 1 CKD

Stage 1 CKD is also can called “Early stage CKD”. Here there may be some features of Chronic Kidney Diasese, however the eGFR remains above the level of 90. These patients may have albumin urea while they maintain the normal eGFR levels.

Stage 2 CKD

When you have stage 2 CKD, there is a minimum reduction in kidney functions. The GFR is between 60 to 89. Although the impairment of kidney function is minimal, there may be features of microalbunurea.

Stage 3 CKD

Stage 3 CKD indicate a moderate to severe impairment of renal functions. When you have stage 3, the glomerular filtration rate remain between 30 to 60. There is a chance of oedema. At the stage 3 CKD you need a care of a Nephrologist. According to the eGFR staging of CKD, stage 3 is seperated to two sub stages. Those are stage 3A and stage 3B.

Stage 3A

Chronic Kidney Disease of Stage 3A have GFR between 45 to 60. In this stage of CKD, the reduction of kidney function remains in mild to moderate levels.

Stage 3B

Stage 3B CKD has a Glomerular Filtration Rate of 30 to 44. At the stage 3B CKD, you disease getting irreversible and there is a rapid deterioration of renal functions. Therefore you need a proper care by a Nephrology team at this stage.

Stage 4

CKD stage 4 is defined as severe limitation of renal functions. The range of glomerular filtation is 15 to 29. Usually there is a significant reduction of urine out put. There is a gross oedema and other features of CKD. Then a patient diagnosed with stage 4 CKD, they need to counselling on future dialysis or other renal replacement therapy options.In addition they may need to send for creation of vascular access, if they plan to proceed with haemodialysis.

Stage 5

According to the eGFR staging of CKD, stage 5 Chronic Kidney Disease has GFR of less than 15. These patients have severe impairment of renal functions. Some patients have almost nil urine output. According to the guidelines of management of CKD, stage 5 CKD patients need dialysis.

End Stage Kidney Disease – ESKD

What is the End stage kidney diases (ESKD) according to the eGFR staging of CKD? This is other common question among kidney disease patients. Usually the stage 5 CKD is define as end stage kidney failure. However in some situations stage 4 also consider as end stage renal disease.

eGFR EPI staging of CKD

GFR is not always a reliable indicator in normal method of calculation. Therefore there is a recently introduced method of eGFR staging of CKD called eGFR EPI. eGFR epi indicates complex formula of epidemiological collaboration. This is more reliable method of CKD staging.

How to Check the eGFR levels

The diagnosis is Chronic kidney disease is done with assessment of kidney functions in two separate occasions in 3 months gap. The main investigation to diagnosis of chronic renal impairment is Serum Creatinine (S Cr) with eGFR test. This blood test will give you the amount of Serum creatinine and mathematically calculated eGFR. In addition we can perform a urine test to identify the red blood cells (RBC) and urine albumin levels.

Except for the grossly reduced eGFR values you cant diagnose CKD with high amount of serum creatinine levels.

Reference

1. Levey AS, Stevens LA, Schmid CH, et al. A new equation to estimate glomerular filtration rate [published correction appears in Ann Intern Med. 2011 Sep 20;155(6):408]. Ann Intern Med. 2009;150(9):604-612. doi:10.7326/0003-4819-150-9-200905050-00006