Bilirubin Crystals in Cat Urine: What They Mean

Name: Bilirubin Crystals in Cat Urine: What They Mean
Creator: Dr. Zubair Khalid

By Dr. Zubair Khalid, DVM, MS, PhD · 2026-10-03

Bilirubin crystals in urine in cats are an uncommon finding that usually points to a liver or bile duct problem instead of a bladder problem. Healthy cats normally have little or no bilirubin in their urine, so when it shows up, your veterinarian will want to look at the liver, gallbladder, and bile ducts. In some cases it reflects a partial bile duct obstruction or other liver disease that needs prompt testing.

This article is educational and is not a substitute for veterinary diagnosis or treatment.

Quick Answer

Bilirubin in cat urine is abnormal and most often signals liver disease or a blockage in the bile ducts, not a urinary tract infection.
A cat with bilirubinuria may also show jaundice (yellow gums, eyes, or skin), weight loss, lethargy, and poor appetite [1].
Your veterinarian will usually confirm the finding with blood work, including liver enzymes and bilirubin levels, plus imaging such as ultrasound.
Urine sediment should be examined on fresh urine, because crystals and cells can change or form after the sample sits [2].
Treatment depends on the underlying cause and may include surgery for a bile duct obstruction, so early evaluation matters [1].

What Bilirubin Crystals in Urine in Cats Actually Mean

Bilirubin is a yellow pigment made when the body breaks down old red blood cells. The liver processes it and sends it into bile, which flows through the bile ducts into the intestine. When this pathway is blocked or the liver is not working normally, bilirubin can spill into the bloodstream and then into the urine.

When bilirubin is present in urine, it can appear as crystals or as amorphous (shapeless) pigment on a urine sediment exam. Bilirubin crystals are not the same as the struvite or calcium oxalate crystals that form bladder stones. They are a chemical clue about what is happening upstream in the liver and biliary system.

This is why bilirubin crystals in urine in cats are treated as a liver and bile duct signal first. The urinary tract is often just the messenger.

Bilirubin Crystals vs. Other Urine Crystals

Cats commonly form two main types of urinary stones. Calcium oxalate uroliths account for about half of all uroliths in cats and most kidney stones, and they can appear anywhere in the urinary tract [3]. Struvite stones are linked to alkaline urine and low urine volume [3].

Bilirubin crystals are different. They do not usually mean a stone is forming in the bladder. They mean bilirubin, a liver product, is escaping into urine when it should not.

Signs Owners Notice

Some cats with bilirubinuria have obvious signs. Others look nearly normal at first, which is why urine and blood testing matter.

Watch for:

Yellow tint to the gums, inner eyelids, ear flaps, or skin (jaundice or icterus) [1]
Weight loss and chronic mild inappetence [1]
Lethargy or reduced activity [1]
Vomiting or diarrhea
Dark yellow, orange, or brown urine
Increased drinking and urination
Pale gums if anemia is also present

In one reported case, a cat was referred for chronic mild inappetence, lethargy, bilirubinuria, weight loss, and icterus, and imaging suggested a partial biliary tract obstruction caused by an enlarged pancreas [1]. That combination of signs is a classic reason a veterinarian starts looking at the liver and bile ducts.

If your cat has blood in the urine along with these signs, that can point to a separate urinary issue. You can read more about that in Why Is My Cat having blood in urine? UTI and Bladder Stones Diagnosis.

Causes and Risk Factors

Bilirubin in urine means the liver or bile pathway is under stress. Common causes include:

Bile duct obstruction, partial or complete
Pancreatitis or an enlarged pancreas pressing on the bile duct [1]
Cholangitis or cholangiohepatitis (inflammation of the bile ducts and liver)
Hepatic lipidosis (fatty liver)
Liver tumors or biliary tumors
Toxin exposure or certain drugs
Hemolytic disease, where red blood cells break down faster than normal

Pancreatitis is a frequent culprit because the pancreas sits right next to the bile duct. When it swells, it can squeeze the duct and block bile flow [1].

Risk factors are less well established for bilirubin crystals specifically. Cats with known liver disease, prior pancreatitis, or ongoing weight loss are the ones most likely to develop bilirubinuria.

Is This Always Liver Related?

Not always, but most of the time it is. A veterinarian will consider the whole picture, including blood work, imaging, and how your cat looks. Occasionally bilirubin can appear with severe anemia or after certain medications. Your veterinarian sorts this out with testing.

How It Is Diagnosed

Diagnosis starts with a good urine sample and a full physical exam. Your veterinarian will check for jaundice, feel the abdomen, and review your cat's history.

Urine Testing

Urine sediment exam is a core part of urinalysis. It identifies insoluble particles in the urine and helps diagnose urinary tract disease as well as some systemic diseases [2]. Fresh urine is recommended, because cell morphology, cell lysis, and crystal formation can change during storage [2].

If your cat pees on litter, be aware that polypropylene-based collection litter can affect some results. One study found leukocyte counts dropped after litter exposure and sediment backgrounds were more contaminated, though protein, pH, and red blood cell counts were not affected [4]. Collection litter is still useful for a preliminary sample, but a cleaner sample is better for accurate sediment analysis [4].

Blood Work

Blood tests are essential. Your veterinarian will look at liver enzymes, total bilirubin, and often a complete blood count. If kidney values are also being checked, this guide explains what those numbers mean: Understanding Cat Blood Tests: Interpreting Renal Markers BUN, Creatinine and SDMA.

Imaging

Ultrasound is the most common next step. It lets your veterinarian see the liver, gallbladder, bile ducts, and pancreas. In the reported case, imaging plus serum biochemistry suggested a partial biliary tract obstruction from an enlarged pancreas [1].

Advanced Testing

If the cause is still unclear, your veterinarian may recommend bile sampling, liver biopsy, or other specialized tests. These are usually done under anesthesia.

Test	What It Looks For	Why It Matters
Urine sediment exam	Bilirubin crystals, cells, bacteria, other crystals [2]	Confirms bilirubin is present and checks for urinary disease
Blood chemistry	Liver enzymes, bilirubin, kidney values	Shows how the liver is functioning
Complete blood count	Anemia, infection, inflammation	Helps identify hemolysis or infection
Abdominal ultrasound	Bile duct blockage, pancreas, liver masses	Finds structural causes of bilirubinuria [1]
Urine culture	Bacterial infection	Rules out infection as a contributor

Urine culture can be useful because bacteriuria can occur even when the sediment looks inactive. In one study, 17% of cat urine samples with inactive sediment had a positive culture [5]. That does not mean every cat with bilirubin crystals needs a culture, but your veterinarian may order one.

Treatment Options

Treatment targets the underlying cause, not the crystals themselves. There is no medication that simply removes bilirubin crystals from urine.

Medical Management

If the cause is inflammation, infection, or pancreatitis, treatment may include fluids, anti-nausea medication, pain control, liver support, and a prescription diet. Your veterinarian calculates all doses based on your cat's weight and health.

Surgical Management

If a bile duct obstruction is confirmed, surgery may be needed. In the reported case, a cholecystoduodenostomy was performed to reroute bile flow around the blockage [1]. This is a major procedure and requires careful anesthesia and monitoring [1].

Supportive Care

Many cats need appetite support, a high-moisture diet, and a low-stress environment during recovery. If your cat is not eating, that is a medical concern, not a behavioral one.

Recovery, Outlook, and Long-Term Management

Outlook depends heavily on the cause. A cat with a reversible cause, such as an infection or a mild pancreatitis flare, may recover well with treatment. A cat with a bile duct obstruction that is not corrected can become very ill.

Some liver and biliary conditions are manageable but not curable. These cats often need lifelong monitoring, periodic blood work, and prescription diets.

If your cat also has kidney involvement, long-term management may overlap with kidney care. Kidney stones in cats are a separate but sometimes related concern, covered in Kidney Stones in Cats: Diagnosing Nephroliths and Ureteroliths.

What to Expect at Follow-Up

Your veterinarian will likely repeat urine and blood tests to see if bilirubin has cleared. Improvement in appetite, energy, and gum color are good signs. If jaundice worsens or your cat stops eating, call your veterinarian right away.

Prevention

You cannot always prevent liver or bile duct disease. But you can lower some risks and catch problems earlier.

Keep your cat at a healthy weight to reduce fatty liver risk.
Feed a balanced diet and avoid sudden food changes or crash diets.
Schedule routine wellness exams with blood work, especially for senior cats.
Address dental disease and chronic inflammation early.
Watch for subtle signs like weight loss, hiding, or reduced appetite.
Provide fresh water and encourage moisture in the diet.

If your cat has a history of pancreatitis or liver disease, ask your veterinarian how often urine and blood testing should be repeated. There is no standard schedule that fits every cat.

Limitations and When to Contact a Veterinarian

Bilirubin crystals in urine are a clue, not a diagnosis. Your veterinarian needs to examine your cat and run tests to find the cause. Individual cases always need a veterinarian's assessment.

Contact your veterinarian the same day if you notice:

Yellow gums, eyes, or skin
Your cat has not eaten for 24 hours
Vomiting that will not stop
Marked lethargy or weakness
Dark orange or brown urine

Go to an emergency clinic now if your cat is:

Collapsed, unresponsive, or having trouble breathing
Having seizures
Showing severe abdominal pain (crying, pacing, hiding, reacting when touched)
Unable to stand or walk normally

Call for a routine visit if you notice mild appetite changes, occasional vomiting, or a single episode of unusual urine color. Early testing is easier on your cat and often less expensive than waiting.

Frequently Asked Questions

Do bilirubin crystals in cat urine always mean liver disease?

No, but they strongly suggest a liver or bile duct problem. Most cats with bilirubinuria have an underlying liver, gallbladder, or pancreatic issue. Your veterinarian will confirm with blood work and imaging.

Can a urinary tract infection cause bilirubin crystals?

A urinary tract infection alone does not usually cause bilirubin crystals. Infection can happen at the same time as liver disease, and urine culture may be ordered to check [5]. The crystals themselves point upstream to the liver.

Is bilirubin in urine painful for my cat?

The bilirubin itself does not cause pain. The underlying condition, such as pancreatitis or a bile duct obstruction, can be painful. Signs of pain in cats include hiding, pacing, and reacting when touched.

How is bilirubin in cat urine treated?

Treatment depends on the cause. Some cats need fluids, medication, and diet changes, while others need surgery to relieve a bile duct obstruction [1]. Your veterinarian will tailor the plan to your cat.

Can bilirubin crystals go away on their own?

They can clear if the underlying cause resolves, such as a mild inflammation that settles with treatment. They will not reliably go away without addressing the liver or bile duct problem. Follow-up testing is the only way to know if they are gone.

References

Unravelling the fatal chain: A detailed investigation into catastrophic events following anaesthesia in a feline patient. Veterinary anaesthesia and analgesia, 2025.
Urinalysis in dogs and cats, part 2: Urine sediment analysis. Tierarztliche Praxis. Ausgabe K, Kleintiere/Heimtiere, 2023.
Urolithiasis in Cats - Urinary System. Merck Veterinary Manual.
Evaluating the impact of polypropylene-based cat litter on urinalysis reliability in feline patients. Polish journal of veterinary sciences, 2025.
Evaluation of haem dipstick pad, urine protein, urine pH and urine protein:creatinine ratio results as a marker of bacteriuria in dogs and cats with inactive urine sediment. The Journal of small animal practice, 2023.