The lower (distal) portion of the canine urinary tract comprises of the bladder and the urethra. The upper (proximal) portion consists of kidneys and ureters, a pair of thick-walled tubes that carry urine from the kidney to the urinary bladder. The prostate gland encircles the urethra in males.

The entire system barring the urethra is normally sterile. Pathogens from the environment enter through urethra, the duct through which urine is discharged in most mammals.

Certain breeds of dogs are more prone to develop urinary tract infections. In addition, proximity to human populations has lead to a situation where dogs have become more susceptible to common human ailments like UTI. In fact, urinary tract infection in dogs is far more common than it is in humans.

Urinary tract infection usually occurs at a single site – the bladder, ureters, kidneys, urethra, or the prostate glands. But it can affect more than one site at the same time also. Common signs of UTI in puppies and adult dogs are the amount, color and odor of urine along with the frequency of urination.

The structure of the urinary tract in dogs is as simple as it can be. It consists of the following:

* Kidneys that filter the daily metabolic wastes from the blood and dissolve them in as little water as possible.
* A set of two tubes called ureters that transport liquid waste to a storage area.
* The urinary bladder which is the storage area for urine.
* Urethra, the tube through which this waste is eliminated during urination.

The simplicity, however, ends here because a lot can go wrong with this simple system that is responsible for eliminating wastes. To start with, diet, water consumption, pH balance of the urine and stress can cause urinary tract problems.

In addition to this, disease causing bacteria can enter the sterile tract through the urethral opening at the end of penis (in males) or just within the vaginal vestibule (in females) and cause canine and feline urinary infection.

If the prostate gland, the seminal vesicles or the testicles are infected or inflamed in males, they can cause urinary problems as well. This is because these organs are closely associated with the urethra. The ureters are the least affected and seldom pose a problem unless damaged by injury, cancer, surgical accident, or kidney stones that pass through them.

Although there are other causes as well, dogs that do not drink enough water or those that are not allowed to urinate frequently are at a greater risk of forming bladder stones. Diet plays an important role since excess amounts of magnesium, calcium or phosphorus can lead to the formation of bladder stones.

Other causative factors are the pH balance and urinary tract infection. In dogs urine normally tends to be more acidic. Stones of different composition of minerals can form in both acidic and alkaline urine.

Many medications like diuretics, cortisone, sulpha drugs and tetracycline increase calcium levels in the urine that sets the stage for the formation of crystals and stones. Ammonium urate bladder stones are also among the many consequences of a liver shunt, a condition of abnormal blood flow to the liver.

The treatment of canine bladder stones depends upon the type, size and composition of the stones. Almost fifty percent of the bladder stones are struvite and are predominantly found in female dogs. Excessive struvite crystals are normally formed due to urinary tract infection.