Q&A: Toxic and metabolic encephalopathy

Q: Are you able to code both toxic (G92) and metabolic (G93.41) encephalopathy on the same patient and get both MCCs?

A: Traditionally, there has been some conflicting thoughts on this. On one side, it can be thought that no, you cannot code both because the subcategories in the Official Guidelines for Coding and Reporting lead you to one code for toxic encephalopathy if there is both toxic and metabolic. If you search for toxic encephalopathy, there is the subcategory for metabolic encephalopathy, and both have the code G92. If you look for metabolic encephalopathy, it has the code G93.41 with the subcategories of drug induced and toxic, both with G92 codes.

On the other hand, it can also be looked at as yes, you can code both. Again, from the Official Guidelines, code G93.4- for the category of other and unspecified encephalopathy that metabolic encephalopathy falls under, there has been a change for toxic encephalopathy from an Excludes 1 note to an Excludes 2 note. An Excludes 1 note signifies “not coded here,” where an Excludes 2 note means “not included here.” This reading would mean that both toxic and metabolic encephalopathy may be reported separately as long as the medical documentation supports it.

Prior to the fiscal year (FY) 2021 updates, that Excludes 1 note under the subcategory G93.4- prevented the assignment of a code from that subcategory when the patient also had a diagnosis of toxic encephalopathy reported with code G92.

Because this Excludes 1 note has been changed to an Excludes 2 note for the FY 2021 update, this means you can now report both toxic encephalopathy and metabolic encephalopathy. While on first thought the change may seem benign since encephalopathy is most often a secondary diagnosis and coding two MCCs has the same effect on the MS-DRG as only reporting one MCC, there are occasions when the ability to code both may lead to a higher weighted MS-DRG. Plus, appropriately reporting both together allows us to properly represent the patient’s true severity of illness.

Editor’s note: This question and answer were adapted from a thread on the ACDIS Forum. To learn more about participating on the Forum, click here.