Updated on: November 21, 2016

Encephalopathy and Delirium: Tomato-Tomatoe, Potato-Potatoe

By Allen Frady, RN, BSN, CCS, CCDS, AHIMA Approved ICD-10-CM/PCS Trainer
Original story posted on: August 24, 2015

What is the difference between delirium and encephalopathy? This is a common discussion among coders and clinical documentation improvement (CDI) professionals alike.

Usually when a question like this comes up, the solution is simple: check the literature. Unfortunately, the information is somewhat contradictory, so we continue the debate while Recovery Auditors (RACs) take advantage, leveraging this confusion as a means to miraculously cure or downgrade the severity for this patient population.

Delirium and encephalopathy often are used interchangeably in the clinical setting as well as in the research and literature. Yet for the purposes of classification and severity of illness, they do not mean the same thing. Delirium, unspecified is classified in ICD-9 as non-specific alteration of mental status (780.9), while in ICD-10 the language is “disorientation” (R41.0). When further specified as a specific type, delirium is still classified in the section of ICD-9 reserved for mental and behavioral problems (located between drug-induced mental disorders and dementia, with codes ranging from 290.x to 293.x), which is an obviously inappropriate code assignment for a patient with a brain malfunction resulting from a systemic pathological problem. Another valid argument is that “delirium” is sometimes used to describe the observable manifestations of an underlying encephalopathy. When used in this manner, the change of the diagnosis to delirium imposed by the RACs would be tantamount to suggesting that chest pain is the correct diagnosis for a patient with a documented myocardial infarction. RACs get away with this, however, because the delirium codes are not straightforward sign-and-symptom codes in the classification the way chest pain is. The advice here is to avoid using delirium in this manner, as it is not the convention.

Further adding to the confusion, ICD-10 includes a code for delirium resulting from other physiological cause (F05). ICD-10 seems to classify all infective psychosis (with the exception of septic), ICU psychosis, cases of delirium superimposed on dementia, sun downing, and acute brain syndrome/acute confusional state as code F05, with metabolic encephalopathy being reserved for everything else.  Special carve-out codes are still available for hypoxic, toxic, hypertensive, alcoholic, and unspecified encephalopathy, with hepatic encephalopathy now being reported in ICD-10 only for cases of hepatic coma.

The Centers for Medicare & Medicaid Services (CMS) assigns a lower severity to the nonspecific behavioral diagnosis of delirium than for the pathophysiological diagnosis of encephalopathy.

Let’s do a quick review of the best advice from the most official sources. Per Coding Clinic, encephalopathy has not been viewed as a form of delirium since 1988. More current guidance in coding clinic is on page 58 of the edition published in the fourth quarter of 2003:

“Metabolic encephalopathy is always due to an underlying cause,” the segment reads. “There are many causes of metabolic encephalopathy, such as brain tumors, brain metastasis, cerebral infarction or hemorrhage, cerebral ischemia, uremia, poisoning, systemic infection, etc. Metabolic encephalopathy is also a common finding in 12-33 percent of patients suffering from multiple organ failure. The development of metabolic encephalopathy may be the first manifestation of a critical systemic illness and may be caused by various reasons — one of the most important being sepsis.”

Note the above definition does not allow for the reporting of encephalopathy in cases that are clearly psychiatric in nature. 

The National Institutes of Health (NIH) further defines encephalopathy as:

“Encephalopathy is a term for any diffuse disease of the brain that alters brain function or structure. Encephalopathy may be caused by infectious agent (bacteria, virus, or prion), metabolic or mitochondrial dysfunction, brain tumor or increased pressure in the skull, prolonged exposure to toxic elements (including solvents, drugs, radiation, paints, industrial chemicals, and certain metals), chronic progressive trauma, poor nutrition, or lack of oxygen or blood flow to the brain. The hallmark of encephalopathy is an altered mental state. Depending on the type and severity of encephalopathy, common neurological symptoms are progressive loss of memory and cognitive ability, subtle personality changes, inability to concentrate, lethargy, and progressive loss of consciousness.”

Once again, the above definition does not allow for the psychiatric causes to be reported as encephalopathy. The reverse is also true. We should not be reporting delirium for scenarios that clearly have a basis in an underlying medical origin, at least not with the (291.x to 293.x) codes, as that is not what these codes convey.

Recovery Auditors (RACs) have been known to reference the DSM IV as an argument for either removing the diagnosis of encephalopathy or as an argument for downgrading the condition to the diagnosis of delirium. As a psychiatric classification system, the DSM IV does not even address the medical diagnosis of encephalopathy – a fact which RACs no doubt find very convenient.

A review of the definitions of delirium on Medline and the NIH reveal similar definitions of delirium that overlap with the same causes and treatments as encephalopathy. Neurologists are perfectly fine using the two terms interchangeably, and why shouldn’t they? This only really impacts things like risk adjustment, hospital profiling, and payment, after all. 

Fortunately, we are in a transition period in which this risk adjustment also will be of concern for attending physicians. I would like to argue here that the convention is to define delirium as that which is occurring from a psychiatric origin and reserve encephalopathy for brain malfunction occurring as a result of an acute or chronic medical disease state. That is, after all, essentially how the terms are being classified when we report them to CMS and the insurance carriers. Since the two diagnoses are not reported with the same codes and have vastly different levels of expected severity, morbidity, and mortality associated with their classification, we really have no choice but to fall in line with the definitions as defined in ICD-9 and ICD-10. 

Physician advisors and physician champions should work with their staffs to provide a framework of reporting based on the severity of illness reflected in the patient’s condition. Encephalopathy should be reserved for patients who are experiencing confusion and altered mental status, etc. from an underlying pathophysiological cause. Delirium should be reserved for patients with an underlying psychiatric condition. Drug-induced mental status changes can be either, but I would advise using drug-induced delirium for mental status changes occurring as a direct result of brain chemistry due to drugs while urging encephalopathy for patients with mental status changes occurring as a result of systemic changes that have an indirect result on the functioning of the brain. Toxic encephalopathy is certainly a valid diagnosis, but unfortunately it is limited to cases of a poisoning (by drugs or external chemicals) for the purposes of reporting in ICD-9 and ICD-10. “Toxic-metabolic,” which defines patients who are essentially suffering from a buildup of natural toxins in the body due to a failure of metabolism or excretion, should be reported as simply “metabolic encephalopathy.”

Regardless of which diagnosis is chosen, the physician will need to commit to a diagnosis and stop using them interchangeably. If physicians are documenting the same condition as both delirium and encephalopathy, RACs simply will state that the documentation is “inconsistent” and either remove both diagnoses or downgrade the reporting to the lowest severity possible. It is also important to link the brain malfunction to the underlying medical cause. For example: encephalopathy due to severe hyponatremia, encephalopathy in a septic patient with severe sepsis and AKI, encephalopathy due to hypoxia with respiratory failure, encephalopathy due to poisoning from an overdose of narcotics and benzodiazepines, encephalopathy superimposed on chronic dementia in an Alzheimer’s patient with multiple metabolic disturbances, etc.

We will have to adapt to the changes suggested by the notes for F05 when ICD-10 is finally implemented, of course, but at least that will bring us a bit more clarity.

About the Author

Allen Frady is a consultant with experience in management, implementation, education and clinical practice.  With 20 years in healthcare, he provides his clients assistance in the areas of documentation, program implementation and compliance.  His background includes critical care nursing, coding, auditing, utilization review, and documentation improvement.

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Disclaimer: Every reasonable effort was made to ensure the accuracy of this information at the time it was published. However, due to the nature of industry changes over time we cannot guarantee its validity after the year it was published.

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