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PubMed This is a summary of 20 peer-reviewed journal articles Updated
Hepatology

Diagnosis and Testing: How Doctors Identify Hepatic Encephalopathy

At a Glance

Hepatic encephalopathy (HE) is diagnosed based on physical symptoms and ruling out other conditions, rather than a single blood test. Because ammonia levels can be misleading, doctors rely on specialized cognitive tests and brain imaging to accurately detect HE and guide treatment.

It is a common misconception that a simple blood test can diagnose Hepatic Encephalopathy (HE). In reality, HE is a clinical diagnosis [1]. This means doctors identify it by looking at the whole picture: the patient’s medical history, physical symptoms, and the exclusion of other possible causes of confusion [2].

Because HE can look like many other conditions—such as a stroke, a medication reaction, or a different type of brain infection—the diagnostic process is often about ruling out those other “look-alike” conditions first [3][4].

The Ammonia Confusion

If you have seen an “ammonia level” on a lab report, you may be surprised to learn that many experts consider it an unreliable way to manage HE [5]. Here is why doctors don’t rely solely on that number:

  • Handling Matters: Ammonia is very sensitive. If the blood sample isn’t processed immediately or is handled improperly, the level can appear falsely high [6][7].
  • The Number Doesn’t Match the Patient: A person can have a very high ammonia level and be completely clear-headed, while someone else might have a “normal” level and be in a coma [8].
  • Treatment Decisions: Clinical guidelines suggest that knowing the ammonia level rarely changes how a patient is treated. Doctors focus on treating the symptoms (the confusion) rather than chasing a specific lab number [9][10].

While a very low ammonia level can sometimes help a doctor rule out HE when they are uncertain, the “number” is never the whole story [11].

Testing for “Hidden” (Covert) HE

Because the early stages of HE (Covert HE) are not visible during a standard conversation, doctors use specialized “stress tests” for the brain to uncover subtle delays in processing and coordination [2].

  • EncephalApp Stroop: This is a smartphone-based test that measures how quickly a person can identify colors while being distracted by written words. It is a highly effective way to detect the mental “slowing” of early HE [12][13].
  • PHES (Psychometric Hepatic Encephalopathy Score): This is a series of paper-and-pencil tests, such as connecting dots or drawing lines, used to measure fine motor skills and attention [14][15].
  • Animal Naming Test (ANT): A simple but powerful tool where a patient is asked to name as many animals as they can in one minute. Naming fewer than 10 to 15 animals can be a red flag for HE [16].

Ruling Out Other Conditions

To be sure the symptoms are truly HE, the medical team may perform other tests to look at the brain’s physical structure and electrical activity:

  • EEG (Electroencephalogram): This test measures the brain’s electrical waves. It is particularly useful for ruling out “non-convulsive seizures,” where a person appears confused rather than having physical tremors [17][18].
  • Imaging (MRI or CT Scans): These are used to ensure the confusion isn’t caused by a brain bleed, a stroke, or a tumor [19][20].

By using these clinical tools together, the medical team can confirm that the liver is the source of the trouble and start the correct treatment [4].

Common questions in this guide

Can a simple blood test diagnose hepatic encephalopathy?
No, hepatic encephalopathy is a clinical diagnosis. Doctors look at your complete medical history, assess your physical symptoms, and rule out other conditions rather than relying on a single blood test.
Why do doctors say the ammonia blood test is unreliable for HE?
Ammonia levels can be falsely high if the blood sample is not handled perfectly. Additionally, a person with a high ammonia level might be completely clear-headed, while someone with a normal level could be severely confused.
What tests are used to find hidden or early hepatic encephalopathy?
Doctors use specialized brain tests to uncover subtle processing delays. These include smartphone apps like EncephalApp Stroop, paper-and-pencil tests, and simple exercises like the Animal Naming Test where you name as many animals as possible in one minute.
Why might my doctor order an EEG or MRI if I have liver disease?
Imaging and brain wave tests help rule out other conditions that look like hepatic encephalopathy. An EEG checks for quiet seizures, while an MRI or CT scan ensures the confusion is not caused by a stroke or brain bleed.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.If the ammonia level is 'normal' but confusion is present, what other conditions have you ruled out?
  2. 2.Are there specific psychometric tests, like the EncephalApp Stroop or PHES, that we should use to check for 'hidden' encephalopathy?
  3. 3.Should we consider an EEG to make sure these symptoms aren't being caused by quiet seizures?
  4. 4.How much weight are you giving to the lab results versus the physical symptoms you see today?
  5. 5.If symptoms aren't improving with lactulose, what is the next step in the diagnostic process?

Questions For You

Tap a prompt to share your answer — we'll use it plus this page's context to start a tailored conversation.

References

References (20)
  1. 1

    [Chinese guidelines on the management of hepatic encephalopathy in cirrhosis (2024)].

    Zhonghua gan zang bing za zhi = Zhonghua ganzangbing zazhi = Chinese journal of hepatology 2024; (32(9)):799-812 doi:10.3760/cma.j.cn501113-20240630-00309.

    PMID: 39375101
  2. 2

    Hepatic Encephalopathy: Definition, Clinical Grading and Diagnostic Principles.

    Weissenborn K

    Drugs 2019; (79(Suppl 1)):5-9 doi:10.1007/s40265-018-1018-z.

    PMID: 30706420
  3. 3

    Laboratory Abnormalities of Hepatic Encephalopathy.

    Karanfilian BV, Cheung M, Dellatore P, et al.

    Clinics in liver disease 2020; (24(2)):197-208 doi:10.1016/j.cld.2020.01.011.

    PMID: 32245527
  4. 4

    Qualifying and quantifying minimal hepatic encephalopathy.

    Morgan MY, Amodio P, Cook NA, et al.

    Metabolic brain disease 2016; (31(6)):1217-1229 doi:10.1007/s11011-015-9726-5.

    PMID: 26412229
  5. 5

    Serum ammonia use: unnecessary, frequent and costly.

    Aby E, Olson APJ, Lim N

    Frontline gastroenterology 2022; (13(4)):275-279 doi:10.1136/flgastro-2021-101837.

    PMID: 35722602
  6. 6

    Transportation and handling of blood samples prior to ammonia measurement in the real life of a large university hospital.

    Imbert-Bismut F, Payet PE, Alfaisal J, et al.

    Clinica chimica acta; international journal of clinical chemistry 2020; (510()):522-530 doi:10.1016/j.cca.2020.07.048.

    PMID: 32735981
  7. 7

    Variability and Lability of Ammonia Levels in Healthy Volunteers and Patients With Cirrhosis: Implications for Trial Design and Clinical Practice.

    Bajaj JS, Bloom PP, Chung RT, et al.

    The American journal of gastroenterology 2020; (115(5)):783-785 doi:10.14309/ajg.0000000000000384.

    PMID: 31449156
  8. 8

    Serum Ammonia in Cirrhosis: Clinical Impact of Hyperammonemia, Utility of Testing, and National Testing Trends.

    Deutsch-Link S, Moon AM, Jiang Y, et al.

    Clinical therapeutics 2022; (44(3)):e45-e57 doi:10.1016/j.clinthera.2022.01.008.

    PMID: 35125217
  9. 9

    Low-Value Levels: Ammonia Testing Does Not Improve the Outcomes of Overt Hepatic Encephalopathy.

    Tapper EB, Rahimi RS

    The American journal of gastroenterology 2020; (115(5)):685-686 doi:10.14309/ajg.0000000000000454.

    PMID: 31714365
  10. 10

    Ammonia Levels Do Not Guide Clinical Management of Patients With Hepatic Encephalopathy Caused by Cirrhosis.

    Haj M, Rockey DC

    The American journal of gastroenterology 2020; (115(5)):723-728 doi:10.14309/ajg.0000000000000343.

    PMID: 31658104
  11. 11

    The Ongoing Debate of Serum Ammonia Levels in Cirrhosis: the Good, the Bad, and the Ugly.

    Deutsch-Link S, Moon AM

    The American journal of gastroenterology 2023; (118(1)):10-13 doi:10.14309/ajg.0000000000001966.

    PMID: 36001400
  12. 12

    Utility of the EncephalApp Stroop Test for covert hepatic encephalopathy screening in Chinese cirrhotic patients.

    Zeng X, Li XX, Shi PM, et al.

    Journal of gastroenterology and hepatology 2019; (34(10)):1843-1850 doi:10.1111/jgh.14656.

    PMID: 30861191
  13. 13

    Detection of minimal hepatic encephalopathy in patients with cirrhosis based on the Stroop-CN model (NCRCID-CHESS 2106): a prospective multicenter study.

    Li X, Liu S, Guo Y, et al.

    MedComm 2024; (5(8)):e627 doi:10.1002/mco2.627.

    PMID: 39015557
  14. 14

    Psychometric methods for diagnosing and monitoring minimal hepatic encephalopathy -current validation level and practical use.

    Hansen MKG, Kjærgaard K, Eriksen LL, et al.

    Metabolic brain disease 2022; (37(3)):589-605 doi:10.1007/s11011-022-00913-w.

    PMID: 35102491
  15. 15

    PSYCHOMETRIC HEPATIC ENCEPHALOPATHY SCORE FOR THE DIAGNOSIS OF MINIMAL HEPATIC ENCEPHALOPATHY IN ROMANIAN CIRRHOTIC PATIENTS--PARTIAL RESULTS.

    Badea MA, Prelipcean CC, Mihai C, et al.

    Revista medico-chirurgicala a Societatii de Medici si Naturalisti din Iasi 2015; (119(2)):368-73.

    PMID: 26204638
  16. 16

    Animal naming test is a simple and valid tool for detecting covert hepatic encephalopathy and predicting outcomes in Chinese-speaking regions: a preliminary study.

    Huang CH, Yu TY, Tseng WJ, et al.

    Annals of medicine 2023; (55(1)):2236013 doi:10.1080/07853890.2023.2236013.

    PMID: 37494454
  17. 17

    Newly Diagnosed Hepatic Encephalopathy Presenting as Non-convulsive Status Epilepticus: A Case Report and Literature Review.

    Olivero M, Gagliardi D, Costamagna G, et al.

    Frontiers in neurology 2022; (13()):880068 doi:10.3389/fneur.2022.880068.

    PMID: 35645984
  18. 18

    Propofol pump controls nonconvulsive status epilepticus in a hepatic encephalopathy patient: A case report.

    Hor S, Chen CY, Tsai ST

    World journal of clinical cases 2019; (7(18)):2831-2837 doi:10.12998/wjcc.v7.i18.2831.

    PMID: 31616699
  19. 19

    Combined diffusion tensor imaging and magnetic resonance spectroscopy to predict neurological outcome before transjugular intrahepatic portosystemic shunt.

    Rudler M, Weiss N, Perlbarg V, et al.

    Alimentary pharmacology & therapeutics 2018; (48(8)):863-874 doi:10.1111/apt.14938.

    PMID: 30178870
  20. 20

    Brain Magnetic Resonance Imaging Abnormalities in Patients with Hereditary Hemorrhagic Telangiectasia.

    Kobayashi Z

    Internal medicine (Tokyo, Japan) 2021; (60(21)):3515 doi:10.2169/internalmedicine.7059-21.

    PMID: 34053985

This page explains how hepatic encephalopathy is diagnosed for educational purposes only. Always consult your hepatologist or medical team for an official diagnosis and treatment plan.

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