Introduction
Urinary crystal formation is a common health issue that affects many cats. Crystals form when certain minerals become concentrated and precipitate out in the urine. While crystals themselves may not cause problems, they can lead to more serious lower urinary tract diseases like urethral obstructions or bladder stones.
Diet and water intake play an important role in urinary health for cats. Many pet owners wonder if feeding dry food contributes to crystal formation compared to wet food diets. In this article, we’ll take a closer look at the types of crystals that form in cats, symptoms to watch for, causes and risk factors, the potential role of diet, and steps you can take to prevent and treat crystals.
What Are Urinary Crystals in Cats?
Urinary crystals form when certain minerals in a cat’s urine clump together into tiny crystals that can irritate the bladder and urethra. Crystals develop when a cat’s urine is too concentrated or becomes too alkaline or acidic (source). Certain minerals like struvite, calcium oxalate, urate, xanthine and cystine tend to come out of solution in urine and form crystals easier than other minerals.
Cats prone to urinary tract infections or those fed dry food diets may be at higher risk for developing crystals. When crystals form, they can act like tiny spurs, causing pain and irritation. In severe cases, they may clump together to form bladder stones.
Types of Crystals
There are several common types of crystals that can form in a cat’s urine, the most prevalent being struvite and calcium oxalate crystals (https://www.betterpet.com/crystals-in-cat-urine/):
Struvite crystals – These crystals form in alkaline urine and are more common in female cats. They are made up of magnesium, ammonium and phosphate. Struvite crystals can form into larger stones that may block the urinary tract (https://www.comfortedkitty.com/urinary-crystals/).
Calcium oxalate crystals – These crystals form in acidic urine and are more common in male cats. They are made of calcium and oxalate. Calcium oxalate crystals tend to be smaller but can still cause irritation, inflammation and blockages.
Other less common types of crystals include urate crystals, composed of uric acid, and cystine crystals, composed of cystine amino acids. Certain breeds like Persians and Himalayans are prone to developing urate crystals while cystine crystals are genetic in some breeds (https://www.prettylitter.com/caturine).
Symptoms
Some of the most common symptoms of urinary crystals in cats include straining to urinate, frequent attempts to urinate with little success, crying out or vocalizing pain when urinating, blood in the urine, and inappropriate urination like urinating outside the litter box. Straining to urinate and blood in the urine are especially indicative of crystal formation in the urinary tract.
Male cats are at greater risk for complete urinary obstruction from crystals due to their narrow urethra. Signs of a blockage include excessive straining and crying when trying to urinate, small and frequent urinations, lethargy, and vomiting. This is a life-threatening emergency requiring immediate veterinary care.
In some cases crystals may cause no symptoms at all, especially if they are present in small amounts and are flushed out before accumulating. That’s why periodic urinalysis testing is important even in apparently healthy cats.
Causes and Risk Factors
There are several factors that can increase a cat’s risk of developing urinary crystals:
High mineral diets – Diets that are very concentrated in minerals like magnesium, phosphorus, and calcium can increase urinary crystal formation. This is especially true for struvite crystals, which form in alkaline urine.1
Genetics – Some breeds, like Persians and Himalayans, are genetically prone to developing crystals. Male cats are also at higher risk than females.2
Obesity – Overweight cats are more likely to form crystals, especially calcium oxalate stones. Carrying excess weight puts more pressure on the urinary tract.3
Other factors like not drinking enough water, urinary tract infections, bladder inflammation, and stress can also increase risk.
Dry Food and Urinary Crystals
There is some debate over whether dry food contributes to the formation of urinary crystals in cats. Some veterinarians and pet owners believe that the low moisture content of dry food may lead to concentrated urine, which allows crystals to form more easily.
One commonly cited source is an article published in 2006 titled “Effects of dietary moisture and sodium content on urine composition and calcium oxalate relative supersaturation in healthy miniature schnauzers and Labrador retrievers” (source). The study found that dogs fed a dry food diet produced more concentrated urine with higher calcium oxalate saturation compared to dogs fed a wet food diet. However, the study was done on dogs, not cats.
More research specifically looking at cats is needed. Some veterinarians argue that factors like breed, genetics, and water intake play a bigger role in crystal formation than diet moisture content alone. Anecdotal evidence of cats on dry food diets without crystals further muddies the picture.
While the alleged link between dry food and crystals remains controversial, most veterinarians recommend feeding wet food or adding water to dry food to increase moisture intake. This may help promote healthy urination patterns and reduce risk, especially for cats prone to crystals.
Prevention
There are some steps cat owners can take to help prevent urinary crystals from forming in their cats:
Increased water intake – Encouraging cats to drink more water can help dilute the urine and prevent crystal formation. Using cat fountains, adding water to wet food, feeding wet food, and placing multiple water bowls around the house can all help increase water consumption (source).
Prescription diets – Veterinarians may recommend a special veterinary therapeutic diet designed to promote dilute and acidic urine which helps prevent crystal formation. These prescription urinary or “c/d” diets are specifically formulated to promote healthy urinary tracts (source).
Increased exercise – Promoting exercise through playtime and cat towers/trees can encourage cats to drink more water. Exercise also helps cats maintain a healthy weight, which reduces risk of urinary crystals (source).
Treatment
The treatment for urinary crystals in cats depends on the type of crystals present. The goal of treatment is to dissolve the existing crystals, relieve symptoms, and prevent new crystals from forming. Some of the main treatments may include:
Fluids: Vets often recommend increased fluid intake to promote urine dilution and flow. This helps flush out crystals from the urinary tract. Intravenous fluids may be given to cats that are dehydrated or not drinking enough.[1]
Diet change: Prescription urinary or dissolution diets are commonly recommended. These diets are formulated to create the ideal urine pH and concentration of minerals to dissolve crystals. For struvite crystals, the diet helps acidify the urine. Diet therapy may persist long-term to prevent recurrence.[2]
Medications: Drugs like methionine or potassium citrate can help change the chemical composition of the urine. Antibiotics may also be prescribed if there is an accompanying urinary tract infection. Pain medications can provide relief while the crystals pass or dissolve.
Outlook and Prognosis
With prompt veterinary treatment, the prognosis for cats with urinary crystals is often good. If caught early, many cats can fully recover and not have recurrent episodes of crystal formation. Specific prognosis depends on the underlying cause and type of crystals present.
For struvite crystals, the prognosis is generally good with dietary management to promote more acidic urine. Prescription urinary or bladder health diets help prevent the crystals from forming again by altering urine pH. With prevention, struvite crystals may not recur.
The prognosis for calcium oxalate crystals depends on how advanced the condition is. In milder cases, dietary changes may be sufficient. But recurring calcium oxalate crystals often require more intensive treatment and prevention. In severe cases, bladder stones (uroliths) have formed and may require surgery for removal. After surgery, prescription diets and increased hydration can help prevent recurrence.
Overall, by following veterinary recommendations for dietary and lifestyle changes, many cats with a history of crystals can live long and healthy lives without recurrence. Annual urinalyses and checkups are advised to monitor urinary health.1
With attentive care from pet owners and vets, crystals in cats can often be successfully managed for a good long-term outlook.
1 https://www.prettylitter.com/caturine
Key Takeaways
There is a common belief that dry cat food can cause crystals to form in a cat’s bladder and urinary tract. However, research does not clearly show a direct link between dry food and crystal formation.
While decreased water intake may contribute to crystal formation, many factors beyond just dry food play a role. These include genetics, pH level of urine, inactive lifestyle, and urinary tract infections.
The most important way to help prevent crystals is to encourage increased water consumption, feed an appropriate diet for your cat’s needs, and monitor their litter habits. Wet food can help add moisture, but dry food does not directly cause crystals if your cat is hydrated.
If your cat already has crystals, treatment may include prescription diets, medications, or surgery. With proper care, most cats can fully recover and lead normal, healthy lives.
