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Tuesday, April 2, 2013

What is "Chronic Kidney Disease", or CKD?


In my previous post, I had talked about how physicians check your kidney function, as well as the concept of glomerular filtration rate (a measure of your kidneys' function, or more accurately, its filtration capacity), or GFR. I want to talk today about an entity that you might have heard before: chronic kidney disease, or CKD. 

CKD is a generic, umbrella term. Nephrologists define it as "kidney damage or reduction in kidney function that persists for 3 or more months". The definition does not include the cause of kidney disease. In other words, whether you have reduction in kidney function from diabetes, or high blood pressure, or a genetic cause, you could still carry a common diagnosis of CKD. This diagnosis is then further subdivided in to stages 1 thru 5, depending on the disease severity. This is where the concept of GFR that I talked about before becomes useful. 

 

Take a look at the above picture (courtesy of The National Kidney Disease Education Program). Now think of GFR as a "meter of your kidney function".
If you have normal kidneys, your GFR should fall between 60 and 120 (the units for these numbers are expressed as ml/min per 1.73 m2)

If you have indications of kidney damage in spite of a GFR that is over 60, you may have CKD stages 1 or 2. The other stages, based on your GFR are as follows:

  • CKD Stage 3: GFR between 30 to 59
  • CKD Stage 4: GFR between 15 to 29
  • CKD stage 5:  GFR less than 15 (this is when many patients might require dialysis or kidney transplant)
In other words, stages 1 thru 5 represent increasing severity of CKD.  What is the need to divide CKD in to these stages, you might ask? Well, it is not that nephrologists want to scare you or other physicians. This staging system actually helps in delineating a specific management plan for the patient. For instance, patients in early stage 3 CKD might need to focus on eating right, avoiding medications that are toxic to the kidneys, and blood pressure control alone; whereas, advanced stage 4 CKD patients might need preparation to be started on dialysis in addition to all the measures that are instituted to treat stage 3 CKD. Remember, it is relatively easier to prevent the decline in GFR. Once the GFR is chronically low, it is unlikely that you would be able to increase it. The needle on the meter usually only goes one way! The rate of progression from a lower to higher stage depends on the cause of CKD, your genetic predisposition, ethnicity, presence of  other comorbid conditions like heart disease, your socioeconomic status, and possibly, even on how early/late  are you referred to a nephrologist. 

The last point that I would like to emphasize is that reduced GFR is not the only way to diagnose CKD. You could receive a diagnosis of CKD (even with a "normal" GFR), if you have abnormalities in the urine (protein, blood, white cells), or if your kidneys look abnormal on biopsy or imaging.

2 comments:

  1. Thank you so much for all this information, Doctor Chauhan! I was diagnosed with stage 3 CKD 7 years ago but only just found out that I'm supposed to be limiting my protein, K & P intakes along with Na. My GP is terrific, but CKD is not her "specialty" and I had to ask to be referred to a renal dietician. My husband & I have since been scouring the internet for more information about how these things effect me and this is how we came to find your blog. Please, keep up the good work! It has been a bounty of valuable information for us!

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