Primary Care Coding Alert

Question: I’m confused by the new ICD-10 codes N18.31 and N18.32. I don’t see anything in the guidelines or in the instructions about how to use the N18 codes. What do I need to know?

Pennsylvania Subscriber

Answer: ICD-10 2021 introduced the following new N18.- (Chronic kidney disease (CKD)) codes:

• N18.30 (Chronic kidney disease, stage 3 unspecified)
• N18.31 (Chronic kidney disease, stage 3a)
• N18.32 (Chronic kidney disease, stage 3b)

ICD-10 guideline 1.C.14.a tells you to use these codes in documenting stage 3, or moderate, CKD. You would use N18.31 when a patient’s estimated glomerular filtration rates (eGFRs) are between 45 and 59 mL/minute, while you would assign N18.32 to a patient with eGFRs between 30 and 44 mL/minute.

However, as a coder, you cannot assign either code based on a patient’s eGFRs; code assignment can only come from a provider’s documentation. And, per another part of the guideline, you would not assign any of these codes “if both a stage of CKD and ESRD [end-stage renal disease] are documented.” Instead, you would only assign code N18.6 (End stage renal disease), but again only if your provider has documented it.