A portosystemic shunt is an abnormal blood vessel that lets blood bypass the liver, so ammonia and other toxins accumulate in the bloodstream. Cats are diagnosed less often than dogs but the signs are dramatic: young, small, slow-growing kittens with copper-colored irises, drooling, and odd neurological signs after eating. Roughly 75 percent of feline shunts are extrahepatic and surgically treatable, with reported good outcomes in most cases (Lipscomb et al., 2007, JFMS).
Last reviewed: June 2026
What a Shunt Actually Does
Normal blood from the gut enters the liver through the portal vein, where the liver detoxifies ammonia and other byproducts before the blood returns to general circulation. A shunt is a vessel that skips the liver, so ammonia, mercaptans, and other toxins enter the brain. This causes hepatic encephalopathy — drooling, head pressing, staggering, blindness, seizures, and odd behavior, often worst within a few hours of a meal.
How Affected Kittens Present
The classic kitten is small for the litter, slow to grow, and acts oddly. Copper-colored or unusual eye color is reported in a notable fraction of cases. Drooling (ptyalism) is the single most common feline sign, more so than in dogs. Other signs include staggering, blindness that comes and goes, head pressing, and seizures within a few hours of a meaty meal. Some cats have blood in the urine from ammonium biurate crystals. Adult-onset cases are less common and usually present with weight loss and chronic vomiting.
Diagnosis
Bile acid testing — fasting and 2-hour post-feeding — is the screening test. Cats with shunts usually show very high post-feeding bile acids. Bloodwork often shows low BUN, low albumin, and microcytic red cells. Abdominal ultrasound by an experienced sonographer can identify the shunt in most extrahepatic cases. CT angiography is the gold standard and is now widely available at referral centers, allowing surgical planning before opening the abdomen, as described in Ettinger's Textbook of Veterinary Internal Medicine.
Surgery vs. Medical Management
Surgical attenuation — gradually closing the shunt with an ameroid constrictor or cellophane band — is the definitive treatment for extrahepatic shunts and yields good to excellent long-term outcomes in roughly 75 percent of treated cats (Lipscomb et al., 2007, JFMS). Medical management is used while awaiting surgery or in non-surgical candidates and includes a moderately protein-restricted, high-quality diet, lactulose to trap ammonia in the gut, and antibiotics (often metronidazole or amoxicillin) to reduce ammonia-producing bacteria. Cats with intrahepatic shunts are harder to fix and usually need referral interventional radiology.
Crises and What to Do
Hepatic encephalopathy crises happen when a cat eats a high-protein meal, gets dehydrated, or develops a GI bleed. Signs are sudden stupor, head pressing, blindness, or seizures. The home plan is to give an oral lactulose enema or oral lactulose if the cat can swallow safely, withhold protein for a meal, and go to the ER. IV fluids, lactulose, and ammonia-binding therapy usually resolve a crisis within 12 to 24 hours.
When to See a Vet
Call your vet today if:
- A small, slow-growing kitten with drooling or staggering after meals
- Unusual copper-colored eyes in a kitten that also acts off
- Repeated vomiting, weight loss, or excessive thirst in a young cat
- Blood in the urine in a kitten or young cat
- Bile acid test result that is high — schedule imaging promptly
Go to the ER immediately if:
- Seizures, head pressing, or sudden blindness after a meal
- Profound lethargy or unresponsiveness
- A known shunt cat who collapses or develops black tarry stool
- Severe drooling with refusal to eat or drink for more than 12 hours
- Any post-surgical shunt cat with new neurological signs
What's going on with your pet?
Describe symptoms or snap a photo. Voyage tells you urgency, home care, and whether you need a vet.
First, tell us about your pet
Breed and age make a real difference in how Voyage interprets symptoms.
Describe the symptoms
🏆 Outperforms ChatGPT & Gemini · 🩺 Vet-grounded · 🔒 Private
Love it? See everything Voyage can do
Frequently Asked Questions
What is a liver shunt in cats?
A liver shunt, or portosystemic shunt, is an abnormal vessel that lets gut blood bypass the liver. Without filtration, ammonia builds up and poisons the brain. Most feline shunts are present at birth, but cats are diagnosed at all ages because signs can be intermittent and easy to miss.
How much does shunt diagnosis and surgery cost?
Initial exam runs $50 to $150 in the US. Bile acid testing adds $100 to $250, abdominal ultrasound is $300 to $600, and CT angiography is $1,500 to $3,000 at a referral center. Surgical attenuation by a board-certified surgeon costs $3,000 to $8,000 including hospitalization. Medical-only management runs $50 to $150 per month long term.
Can a shunt cat eat normal cat food?
Not usually. A moderately protein-restricted diet with high-quality protein (eggs and dairy are favored over red meat) is recommended for both pre- and post-surgical cats. Some commercial hepatic diets exist. Severe protein restriction is avoided because cats are obligate carnivores and need amino acids for repair.
What is the prognosis for a cat with a liver shunt?
Extrahepatic shunts attenuated surgically have good to excellent long-term outcomes in roughly 75 percent of cats. Cats managed medically only often do reasonably well for 2 to 3 years but tend to deteriorate over time. Intrahepatic shunts and acquired shunts carry a guarded prognosis.
Why are the eyes a different color in shunt kittens?
Copper-colored irises in shunt kittens are thought to reflect abnormal copper metabolism by the underdeveloped liver. It is not universal but is a recognized feature and should prompt bile acid testing in a young cat with even subtle neurological signs.
Still Not Sure if Your Cat Needs a Vet?
When you're not sure if this is wait-and-see or call-tonight, Voyage AI Vet triages in under 2 minutes. Describe what you're seeing in chat, share photos of stool, vomit if present, gum color, and abdomen, or hop on a live video call if you want a second pair of eyes. Every answer comes with citations to the actual veterinary literature it's pulling from — so you see exactly where the guidance comes from, not just a chatbot's word.