Hepatic Encephalopathy in Dogs: Signs, Causes, and Treatment

Hepatic encephalopathy (HE) is a neurological syndrome in dogs caused by the liver's failure to filter toxins — especially ammonia — from the blood. It produces a characteristic constellation of behavioral changes, seizures, and altered consciousness that require urgent veterinary evaluation.

Last reviewed: June 2026

What Is Hepatic Encephalopathy in Dogs?

Hepatic encephalopathy occurs when the liver cannot adequately detoxify substances absorbed from the gut — most critically ammonia generated by intestinal bacteria from protein metabolism. When ammonia and other toxins accumulate in the systemic circulation and cross the blood-brain barrier, they disrupt normal neuronal function and produce the neurological signs collectively called HE. As described in Ettinger's Textbook of Veterinary Internal Medicine, HE in dogs most commonly results from portosystemic shunting (either a congenital portosystemic shunt or acquired collateral circulation from advanced liver disease), severe hepatocellular failure from any cause, or urea cycle enzyme defects.

Young dogs with congenital portosystemic shunts (most often Yorkies, Maltese, and other small breeds) frequently develop HE symptoms early in life. Dogs with acquired liver disease from chronic hepatitis, cirrhosis, or hepatotoxins typically develop HE later as liver reserve is exhausted. The AAHA Canine Life Stage Guidelines, 2019 recommend annual bloodwork for adult and senior dogs to catch early liver enzyme abnormalities before HE develops.

Tivers et al., 2014, JVIM reviewed the clinical presentation, diagnosis, and outcomes in dogs with congenital portosystemic shunts and confirmed that neurological signs — including episodic weakness, head pressing, and altered behavior — are among the most common presenting complaints, often worse after high-protein meals.

Recognizing Signs of Hepatic Encephalopathy

Signs of HE are neurological and behavioral, often episodic (worse after meals), and can fluctuate dramatically in severity.

Behavioral and mental status changes:

• Apparent confusion or disorientation — staring blankly, getting "lost" in familiar spaces
• Behavioral change — aggression or marked anxiety in a previously calm dog, or unusual docility
• Circling in one direction
• Head pressing against walls or furniture — one of the most specific signs of forebrain disease
• Excessive vocalization or apparent hallucination behavior

Motor signs:

• Ataxia — wobbly, uncoordinated gait
• Weakness, especially in the hindlimbs
• Tremors

Altered consciousness:

• Lethargy progressing to stupor
• Seizures — generalized or focal; may cluster
• Coma in severe, advanced HE

Other hepatic disease signs that often accompany HE:

• Excessive drinking and urination (polyuria/polydipsia)
• Vomiting, diarrhea, or reduced appetite
• Weight loss and muscle wasting
• Jaundice (yellow tinge to skin, eyes, or gums) in some cases
• Ammonium biurate crystals or urinary tract signs — common with portosystemic shunts

Head pressing is a particularly distinctive sign — when a dog pushes its forehead against a wall or floor for extended periods, this indicates significant forebrain dysfunction and warrants immediate evaluation.

Diagnosis

Diagnosing HE requires identifying both the neurological syndrome and its hepatic source.

Diagnostic workup:

1. Serum biochemistry — low albumin, low BUN (blood urea nitrogen), elevated liver enzymes (ALP, ALT) in hepatocellular disease; hypoglycemia possible
2. Fasting and postprandial bile acids — markedly elevated bile acids confirm significant hepatic dysfunction or portosystemic shunting; the standard functional liver test
3. Blood ammonia — elevated in most dogs with active HE; sample must be processed rapidly
4. CBC — microcytosis (small red blood cells) is a classic finding in portosystemic shunts
5. Urinalysis — ammonium biurate crystals strongly support PSS in young dogs
6. Abdominal ultrasound or CT portography — identifies shunt anatomy; CT angiography is the gold standard for surgical planning

Treatment: Stabilization and Long-Term Management

Acute HE management:

• Dietary modification — transition to a reduced-protein or hepatic support diet to reduce ammonia generation; protein should not be eliminated but should come from high-quality, highly digestible sources
• Lactulose — oral acidifying agent that traps ammonia in the gut lumen for excretion; also used as a rectal enema in acute, non-eating dogs
• Antibiotics targeting gut flora (metronidazole or neomycin) — reduce bacterial ammonia production
• IV fluids, dextrose supplementation for hypoglycemia, seizure management as needed

Long-term management:

• Congenital portosystemic shunts — surgical ligation or ameroid constrictor placement is curative in most dogs; as described in Fossum's Small Animal Surgery, surgical outcomes are excellent in dogs with extrahepatic shunts, with the majority achieving normal or near-normal liver function post-operatively
• Medical management — for dogs with intrahepatic shunts or those who are poor surgical candidates: lifelong lactulose, restricted protein diet, monitoring

When to See a Vet

Call your vet today if:

• Your young small-breed dog is having episodes of apparent confusion, circling, or odd behavior — especially after meals
• Your dog is staring blankly, walking aimlessly, or seems not to recognize familiar surroundings
• Your dog is drinking and urinating much more than normal alongside any behavioral changes

Go to the ER immediately if:

• Your dog is pressing its head against the wall or floor
• Your dog has a seizure for the first time or is having multiple seizures
• Your dog is difficult to rouse, lethargic to the point of stupor, or has collapse
• Your dog is having active seizure activity that is not stopping within 2–3 minutes

Frequently Asked Questions

What does head pressing look like in a dog? Head pressing is when a dog holds its forehead or face against a wall, furniture, or floor for an extended period — not just rubbing or scratching, but sustained, stationary pressing with apparent unawareness of the behavior. It signals significant forebrain dysfunction and should prompt immediate veterinary evaluation, not watchful waiting.

Can hepatic encephalopathy be reversed? HE signs are often substantially reversible if the underlying liver disease or shunt is treated. Dogs with congenital portosystemic shunts that undergo successful surgical repair frequently recover to normal neurological function. HE secondary to severe acquired liver disease has a less predictable outcome depending on how much functional liver tissue remains. Acute HE episodes can often be stabilized with medical management while the underlying cause is addressed.

What should I feed a dog with hepatic encephalopathy? Dogs with HE benefit from high-quality, highly digestible protein rather than protein restriction — the goal is to minimize the ammonia load from undigested protein reaching gut bacteria. Veterinary hepatic support diets are formulated with appropriate protein levels and sources. Always transition diet changes gradually and under veterinary guidance — abrupt dietary changes can worsen GI upset and alter ammonia production unpredictably.

How much does hepatic encephalopathy workup and treatment cost? Initial diagnostic workup — exam, bloodwork, bile acids, urinalysis, and ultrasound — typically runs $400–900. CT portography for shunt surgery planning adds $800–1,800. Surgical shunt repair commonly costs $3,000–6,000 including hospitalization and aftercare. Medical-only management with lactulose and hepatic diet runs approximately $50–120 per month in ongoing costs, plus quarterly monitoring bloodwork.

Which dog breeds are predisposed to portosystemic shunts causing HE? Yorkshire Terriers are the most commonly affected breed, followed by Maltese, Miniature Schnauzers, Pugs, and Bichon Frises among small breeds. Irish Wolfhounds and other large breeds are the most commonly affected large-breed dogs. Any breed can develop acquired HE from liver disease, but congenital shunts have strong breed predispositions.

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