Learning How to Query for Acute Encephalopathy Specificity

I’ve recently encountered a couple of discussions about encephalopathy so I thought others might be interested in this topic. First up, querying for the type of encephalopathy.

I’ve noticed there is confusion about querying for metabolic encephalopathy (or toxic) when encephalopathy due to urinary tract infection (UTI) or other infection is documented. The source of much of this confusion is second quarter 2018 American Hospital Association (AHA) Coding Clinic (p. 22) that advised G93.49 Other encephalopathy be coded when “encephalopathy due to urinary tract infection” is documented.

The same edition (p. 24) includes guidance that states, “when encephalopathy is linked to a specific condition, such as stroke or urinary tract infection, it is appropriate to use the code describing ‘other encephalopathy.’ However, what some may have overlooked is this advice continues by instructing us to use G93.49, Other encephalopathy “when encephalopathy is linked to a condition, but a specific encephalopathy (e.g., metabolic, toxic, hypertensive, etc.) is not documented.” 

Ideal documentation for acute encephalopathy would be for the provider to document the type of acute encephalopathy as metabolic or toxic. The AHA Coding Handbook associated metabolic encephalopathy with a lack of glucose, oxygen or another metabolic agent, or caused by organ dysfunction.

In contrast, toxic encephalopathy is associated with exposure to toxic substances or as an adverse effect of medication. The concept of toxic encephalopathy due to external factors and as metabolic being due to an internal process was challenged with a first quarter of 2022 (p. 52) AHA Coding Clinic. It discusses the reporting of toxic encephalopathy in a patient with acute on chronic hepatic encephalopathy. This Coding Clinic explains that toxic encephalopathy is not limited to external toxins because the body can also generate toxins.

This coding clinic also cleared the way for both an acute encephalopathy (i.e., metabolic or toxic) to be reported with chronic encephalopathy when clinically supported. Additionally, both metabolic and toxic encephalopathy can be coded, when clinically supported, as confirmed by a 2024 AHA Coding Clinic (second quarter, p. 14) because they are due to two separate causes so both conditions are needed to fully capture the patient’s condition. To be fair, this was always the case due to coding conventions because under the G93.4 Other and Unspecified Encephalopathy in the tabular list, under which G93.41 metabolic encephalopathy is included, is an excludes 2 note, which means code also, for toxic encephalopathy (G92.8). I think, however, many coders have been hesitant to follow this coding convention because there is so much pushback from payers on acute metabolic or toxic encephalopathy.

Now, should you query for metabolic (or toxic) encephalopathy when the documentation supports the reporting of G93.49, Other encephalopathy? My advice for what it is worth is yes.

An underlying premise of coding is to use the most specific code available. In fact, our job as clinical documentation integrity (CD) professionals is to clarify vague or incomplete documentation.

Let’s look at this from a coding guidance perspective. The tabular list includes encephalopathy NEC as an inclusion term under G93.49, Other encephalopathy. Coding convention I.A.6b Tabular List abbreviations defines NEC as “not elsewhere classifiable.” It is used when a specific code is not available for a condition. However, there are more specific codes available for encephalopathy e.g., metabolic or toxic.

As CDI professionals, when a provider documents encephalopathy due to UTI, we should query for the type of acute encephalopathy, which is most likely to be metabolic. Remember if the provider documents metabolic encephalopathy due to UTI, metabolic encephalopathy (G93.41) would be reported instead of other encephalopathy (G93.49). If the provider did not link encephalopathy to the UTI, G93.40 Encephalopathy, unspecified would be reported. In which case, I would also encourage a query for the type of acute encephalopathy.

Most providers think they are doing the right thing by linking encephalopathy to the UTI but really, we want to know if the acute encephalopathy is metabolic (in this example toxic is unlikely). Encephalopathy is always caused by something else and when it comes to metabolic encephalopathy there is no requirement that its cause must be documented or linked to metabolic encephalopathy except in specific coding circumstances like when it represents organ failure in the setting of sepsis.

There is not a code also note, or code first note at G93.41 metabolic encephalopathy. However, septic encephalopathy is an inclusion term under metabolic encephalopathy. I think a lot of this confusion could be solved if the coding conventions linked all infections (acute encephalopathy due to [insert infection here]) to metabolic encephalopathy but it does not so we should query.  

Querying could also be avoided if the provider simply documented metabolic encephalopathy without linking it to the UTI, which is not required. This is why it is appropriate to query for the type of encephalopathy as metabolic or toxic (but it is usually metabolic) instead of reporting G93.49 Other encephalopathy.

My guess is what makes some CDI and coding professionals feel uneasy is that G93.49 is classified as a complication/comorbidity (CC) compared to metabolic encephalopathy, which is classified as a major complication/comorbidity (MCC). However, based on coding conventions, guidelines, advice, etc. this is the appropriate action to take.

I’m not sure why G93.49 Other encephalopathy and G93.40 Encephalopathy unspecified are classified as CCs and not MCCs. Maybe it is because the coders are newer? Maybe it is purposeful because they are fewer specific codes?

If so, it further supports that querying for the type of acute encephalopathy as metabolic or toxic is the most compliant action. However, the same resources would be used regardless of the type of acute encephalopathy and the MS-DRG system is supposed to be based hospital resource utilization.

My guess is due to the prevalence of encephalopathy as a secondary diagnosis it is more likely that both metabolic and toxic encephalopathy codes will be downgraded from MCCs to CCs as that is what we saw many years ago when acute kidney injury was downgraded from an MCC to a CC.

Only time will tell.