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Written by Natascha Wille

Feline Lower Urinary Tract Disease (FLUTD) is a collective term used to describe a group of problems associated with the lower urinary tract—namely, the bladder and urethra—of cats. This includes infection of the bladder by bacteria, known as Urinary Tract Infection (UTI), which is more common in female cats due to the wider anatomy of the urethra. It also includes uroliths (urinary stones), which can occur in both female and male cats, and urethral obstruction (blockage), which is more common in male cats because of the narrow shape of their urethra.

Uroliths, also known as urine stones or urinary crystals, are further divided into two main types: struvite crystals, made of magnesium-ammonium-phosphate, and oxalate stones, made of calcium oxalate. You might also hear them referred to as bladder stones, calculi, or cystoliths. The condition of having urinary or bladder stones is called urolithiasis. In contrast, the term cystitis in cats usually refers to inflammation of the bladder where no cause is identified.

Confused? You’re not alone. It’s all very overwhelming—especially if you have a male cat who’s experienced a urethral obstruction, which can be life-threatening and often leads to emergency expenses that run into the thousands, only for the issue to recur at any time. It is vitally important to get a handle on your cat’s urinary health not only in the short term to prevent pain and discomfort and potentially fatal blockage, but also help secure the future health of your cat’s kidneys. Recurring cases of FLUTD is one cause of Chronic Kidney Disease (CKD) later down the road. In some cases, kidney damage or kidney failure is an acute consequence from an urethral obstruction or urinary tract infection.

My Experience with Crystals and Blockages

Knock on wood—or perhaps it has less to do with luck—I have never had a male cat suffer from an obstructed urethra, nor any cat experience struvite crystals or oxalate stones that caused problems where I or the cat would have noticed their existence. That is in over 30 years and caring for a total of 51 cats. But, I understand how frightening it can be when it happens.

When uroliths do occur in cats, they are most commonly struvite (magnesium-ammonium-phosphate). These minerals—ammonia, magnesium, and phosphorus—are naturally present in feline urine. What causes them to crystallise is typically a combination of elevated urine pH (shifting toward alkaline), small urine volume, infrequent urination, or urine retention.

Male cats may retain urine as part of normal behavior for the purpose of territory marking, but a less intentional cause of urine retention can also occur. One often overlooked cause is dry stool in the colon pressing down on the urethra. If your cat has very dry faeces or struggles with constipation, it’s important to help the stool retain moisture. Using a laxative such as Lactulose or Restoralax may be beneficial in these cases.

Proteins in the urine and, less frequently, bacteria can contribute to the clumping of crystals by producing mucus that allows minerals crystals to stick together, or the mass of mucus itself can form a plug in the urethra.

Prevention Through Diet and Hydration

Research has shown that increasing urine volume and encouraging more frequent urination is the most effective way to prevent most struvite crystals. A high-moisture diet that increases water intake through eating promotes high urine output, which flushes small crystals from the bladder before they can grow into a problem.

Traditionally, magnesium restriction has been a cornerstone of prevention, and it remains the industry standard. Reducing dietary phosphorus and calcium can also help, since any excess of these minerals is excreted through the urine. Excreted phosphorus, together with magnesium, forms the building blocks of struvite crystals. Excreted calcium can buffer the urine and make it harder to acidify effectively.

What About Calcium Oxalate Stones?

Another type of urinary stone—calcium oxalate—is more commonly associated with overly acidic urine. This can be an unintended side effect of some prescription urinary diets. Other contributing factors include excess calcium intake, dietary oxalates (typically from vegetables), unnecessary administration of vitamin C (which cats don’t need in the diet), too much vitamin D, a deficiency in vitamin B6, or hypercalcaemia caused by kidney disease or certain tumours. Occasionally, no cause can be identified. Treatment for calcium oxalate stones is somewhat different from treatment for struvite crystals, because there is an underlying cause, while the potential for struvite cystals always exists, because all necessary elements occur naturally in urine at all times.

A Homemade Diet as Part of Prevention

The cats in my care, who eat a diet prepared with either TCfeline Original or TCfeline Special Formula, have not experienced urolithiasis. To me, this means, this is one of the decided benefits and strengths of TCfeline premix and the raw diet it prepares. Although I have no personal experience with applying TCfeline premix and this homemade diet in cases when cats have a history with urolithiasis, this homemade diet may still play a helpful part in a prevention strategy if you do not wish to—or cannot—continue using a prescription diet from your veterinarian.

I recommend using TCfeline Special Formula, as the resulting diet is low in calcium, phosphorus, and magnesium. This helps reduce the urinary mineral load and buffering of the urine pH. Use Recipe #1 in the User Guide and be sure to add the full amount of water—perhaps even an extra ¼ cup.

This diet is intentionally quite low in sodium, as it’s designed for cats with chronic kidney disease. For cats who do not have CKD, I recommend adding 1/4 teaspoon of table salt (iodised is fine) to every 20g of TCfeline Special Formula premix during food preparation.

Is Diet Enough to Acidify the Urine?

While diet alone cannot always acidify the urine enough, a high-protein diet based on animal sources does provide the acidifying sulphur-containing amino acids that help. That said, the body’s buffering systems work hard to maintain a stable pH, and results can vary from cat to cat.

The best dietary approach is one that is:

• High in moisture
• High in protein from animal sources
• Balanced with minimal but adequate levels of essential minerals

Using extra-lean cuts of meat will increase the protein content, and it is said that red meats are slightly more acidifying than poultry. It’s best to avoid all supplements—including herbal or “urinary health-enhancing” ones—unless your veterinarian approves them. Cranberries are definitely not going to help with urolithiasis. Never give potassium citrate (which Veterinarians may use to treat kidney stones or calcium oxalate stones) or sodium bicarbonate (which a Veterinarian may use to treat metabolic acidosis in cats with kidney disease or to treat an electrolyte imbalance during severe diarreah). Both are highly alkalising.

When Urine pH Remains Too High

If your cat’s urine pH does not drop enough after switching to cat food made with TCfeline Special Formula, your veterinarian may recommend a urine acidifier such as DL-methionine (an amino acid) or ammonium chloride. These supplements can be helpful when prescription diets are refused or not well tolerated.

However, they do carry risks and should:

• Only be used under veterinary supervision
• Be given at the lowest effective dose
• Be used only for the shortest necessary time

Long-term use can lead to complications, so careful monitoring is important.

Monitoring Urine pH at Home

Keeping track of your cat’s urine pH at home can be a useful tool to regulate the use of acidifiers. Your veterinarian can help recommend a reliable product or method for testing, allowing you to monitor changes and track progress effectively.

If you’ve found yourself facing urinary issues in your cat, I hope this article provides some clarity and guidance. These problems can be frightening and stressful—but they can often be managed or even prevented with the right support and informed choices.