Chronic kidney disease (CKD) has traditionally been identified as stages 1-5. CGA staging is another way to classify CKD and this edition of “In the kNOW” will explain how this classification works. We’ll also examine the appropriate ICD-10-CM coding when presented with this documentation.
The long-standing classification for CKD is based on the glomerular filtration rate (GFR). An estimated or measured GFR of <60 mL/min that is present for at least three months is one definition for CKD. This is true whether or not there is kidney damage.
The following table shows the correlation between the GFR and the CKD stage.
Source: https://ckdexplained.co.uk/debates-in-nephrology-ckd-staging-system/
Stage 1-normal kidney function but there is kidney damage (N18.1)
Stage 2-Minimally reduced kidney function (N18.2)
Stage 3a-Moderately reduced kidney function (N18.31)
Stage 3b-Moderate to severe reduced kidney function (N18.32)
Stage 4-kidney function is severely reduced (N18.4)
Stage5-Most kidney function is lost; requires
dialysis or transplant (N18.5)
Let us identify here that coded for CKD 4 and 5 are considered CCs, while N18.6 for end-stage CKD is considered an MCC. The other stages carry no impact on DRG assignment.
The CGA methodology is also related to the GFR but also includes the cause and albuminuria (Cause, GFR, Albuminuria). This definition also takes into account kidney damage that is evident whether or not there is decreased GFR, and again must be present for at least three months. The kidney damage can be due to an abnormal kidney structure (seen on ultrasound), a pathological abnormality (found on biopsy), findings of protein in urine, or hematuria unrelated to a urological cause.
Source: https://hospitalhandbook.ucsf.edu/01-chronic-kidney-disease/01-chronic-kidney-disease
As you will be able to see by reviewing the table above, the staging looks slightly different in that a new component will be included. For example, a patient could have G3bA2 CKD or G5A1 CKD. This level of detail provides more clinical information is more indicative of future progression of the disease.
A Coding Clinic from First Quarter 2023 explains that coding professionals will assign ICD-10-CM codes for CKD expressed with CGA staging based on the number present after the G which is the stage. In effect, this is exactly like we are used to coding. That means that G3bA2 is coded to N13.82 with G5A1 coded to N18.5.
Returning for a moment to the three-month threshold for findings of CKD which indicates the condition is chronic rather than acute. Bear in mind, that the code for acute kidney injury (AKI) or disease is N17.9 which is a CC. It is also worth mentioning that if acute tubular necrosis is documented with the AKI, the correct ICD-10-CM assignment is N17.0 which carries the highest impact for a DRG since it is an MCC.
Now you are In the kNOW!!
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