Myths around Urinary Tract Health in Dogs and Cats

By: Dr. Doreen M. HoustonDoreen is a board certified Diplomate of the American College of Veterinary Internal Medicine (ACVIM).

Calcium Oxalate Stones

Myth 1:   Salt in urinary diets is bad.  It can lead to kidney failure, hypertension and associated heart disease, and calcium oxalate bladder and kidney stones.

Reality

Dogs and cats are not “salt sensitive” like humans.  There are many published studies that support that salt does not contribute to kidney disease; in fact there is science suggesting quite the opposite.  Low salt intake can lead to loss of potassium in the urine and this can worsen kidney failure.  By increasing the salt content of the diet, we might actually help decrease the risk of chronic renal failure.  There are a number of studies supporting that salt is not a concern in aged cats, the group most likely to develop kidney disease.  Unlike people, dogs and cats do not develop hypertension because of salt in the diet.  Salt in urinary diets causes the animal to drink more and consequently urinate more-this is good when trying to prevent significant crystal and stone disease in dogs and cats.  Salt in the diet has been shown to help prevent calcium oxalate stones in cats and dogs.

Myth 2:   Struvite crystals and stones form when the urine pH is alkaline.  Keeping the urine acidified will prevent struvite in dogs and cats.  On the other hand, calcium oxalate forms when the urine pH is acidic.   Keeping the urine alkaline (pH >7) will prevent calcium oxalate in dogs and cats.

Reality

Struvite in the majority of canine cases is due to infection.  Treating or preventing the urinary tract infection is the most important aspect of management of struvite crystals and stones in dogs.  Cats are totally different- infection does not play a role in the vast majority of cases.  A diet that maintains an average urine pH less than 6.5 and restricts the minerals that contribute to struvite formation is recommended in cats.
Calcium oxalate crystal and stone formation is not urine pH dependent in dogs or cats.  This type can form at any urine pH.  Highly acidic urine (consistently having a pH in the 5’s) may predispose a pet but otherwise, urine pH is not a key factor in the development of oxalate crystals or stones.   A diet that has undergone specific testing for oxalate crystal and stone prevention is recommended for management of oxalate in dogs and cats.

Myth 3:   Cats with blood in their urine should be placed on antibiotics for 7-14 days.

Reality

Antibiotics are not indicated unless a urinary tract infection (UTI) is confirmed with urine culture and sensitivity. Cats rarely get UTIs and it is much more likely that there is another reason for blood in their urine, such as a condition called Feline Idiopathic Cystitis! Antibiotics are rarely needed in cats with lower urinary tract problems. There is growing concern for antibiotic resistance in people and pets-antibiotics should not be given unless an infection is confirmed.

Myth 4: Ash in pet food is one of the causes of feline lower urinary tract disease. Ash can cause a male cat to suffer a blockage in the urinary system.  Cats should not be fed diets with ash.

Reality

This was a commonly held belief for many years, but has been shown not to be true. All pet foods are composed of protein, fat, carbohydrates, vitamins, minerals and water. The inorganic components of pet foods, such as the minerals and vitamins, are called “ash” because they are not incinerated when the food is burned for nutritional analysis. Ash was once thought to contribute to struvite crystals and stones in the bladder and urethra of cats, causing male cats in particular to “block”-not be able to urinate. We now know that urinary pH plays a significant role in the development of struvite crystals in cats and if the urine pH is kept lower than 6.5 and the amount of magnesium (one of the minerals in “ash”) is controlled the production of struvite crystals and stones can be prevented. In addition, it is important to know that other minerals in ash such as calcium, manganese, and selenium are critical to the cat’s health. Ash is not a bad thing!

Myth 5: Vitamin C, cranberry juice, or cranberry extracts are very good for urinary tract health-they acidify urine (lower the urine pH), are anti-inflammatory and might help treat and prevent urinary tract infections.

Reaity

Unlike people, dogs and cats make their own vitamin C. Vitamin C is broken down to oxalic acid which is excreted into the urine. Too much of this could put dogs and cats at risk for calcium oxalate crystals and calcium oxalate kidney/bladder stones. In addition, it has been shown that neither vitamin C nor cranberry are very good urinary acidifiers-there are much better ones available from your veterinarian should they be needed. In addition, vitamin C can be a bad thing for dogs and cats that have copper associated liver disorders as it is pro-inflammatory in this condition. In most cases urinary tract infections are caused by bacteria and antibiotics are needed. Cranberry is used in dogs and cats to help with certain urinary tract infections as the proanthocyanidins in cranberry (PACs) block attachment of bacteria such as E. coli to the lining of the bladder. The cranberry doesn’t stop the bug from being there in the first place but it might help lessen the clinical signs the animal experiences. Antibiotics are needed to treat bacterial infections-cranberry is supplemental therapy only!