I. Urinary Tract Anatomy in the Dog

The anatomy of the urinary tract in the dog is very similar to that in people. The urinary tract consists of the kidneys, the ureters, the urinary bladder, and the urethra. The kidneys make urine by filtering water and waste products out of the blood. Urine travels from the kidneys through very tiny tubes called ureters. The ureters end in the urinary bladder. The bladder is connected to the outside of the body by the urethra. In male dogs, the urethra passes through the prostate, so the prostate can be involved in urinary tract infections.

II. What is a Urinary Tract Infection?

Normally, there are no bacteria or other organisms anywhere within the urinary tract. Any time that bacteria or other organisms enter and begin to grow in the urinary tract, this is a urinary tract infection. The most common kind of urinary tract infection in dogs is a bacterial infection of the bladder. The bacteria that cause urinary tract infections usually enter the urinary tract from outside the body and ascend the urethra to enter the bladder. From there, they can continue to move up the urinary tract to the kidneys. The most common way dogs get kidney infections is by movement of bacteria from the bladder to the kidneys. In dogs with a normal urinary tract and a normal immune system, it is hard for bacteria to enter and grow. Dogs that get urinary tract infections usually have some underlying problem that predisposes them to get a urinary tract infection. Some of these include:

• Bladder or kidney stones


• Cancer in the urinary tract


• Malformation of any part of the urinary tract


• Not going to the bathroom often enough (holding urine too long in the bladder)


• Previous urinary tract surgery


• Taking immunosuppressive drugs (such as prednisone or cyclosporine)


• Any disease that decreases the concentration of the urine (for example kidney failure, Cushing’s Disease, and Diabetes)

An underlying cause is not found in all cases. Female dogs, in particular, are more likely to get bladder infections without a predisposing factor being present.

III. What to Watch for at Home – Symptoms

The most common symptoms of a bladder infection are:

• Straining to urinate


• Needing to urinate often, but only producing a small amount of urine when going


• Blood in the urine


• Pain when urinating


• Urinating in unusual places; usually this means going to the bathroom in the house.


• Foul smelling urine


• Some dogs that have been on prednisone for a long time or who have diabetes may not have any symptoms.

If bacteria continue to move up from the bladder to the kidneys, a kidney infection may occur. The symptoms of a kidney infection include:

• Depression


• Lack of energy


• Vomiting


• Not wanting to eat (anorexia)


• Fever


• Abdominal pain


• Back pain


• Some dogs with kidney infections may also have symptoms of a bladder infection


• Some dogs with kidney infections may have no symptoms

IV. The Veterinary Visit – How to Tell if a Dog has a Urinary Tract Infection

The first thing a veterinarian will want, after doing a physical examination, is a urine sample. If you can keep your dog from going to the bathroom for a few hours before the veterinary visit, this would be ideal. For dogs with urinary tract infections, this is not always possible. They usually need to go very often.There are three ways that the veterinarian can get a urine sample. The easiest way to get a urine sample is to take the dog for a walk and collect a sample when they urinate using a cup. While this is easy, a sample collected this way can sometimes provide confusing results. This is because as the urine leaves the body, it is exposed to the skin and hair around the urethral opening. This can contaminate the sample with bacteria and protein that might make the results of a urine analysis confusing. The best way to collect a urine sample is via cystocentesis. For this, a veterinarian lays a dog on its back or side and uses a syringe and needle to get a sample directly from the urinary bladder. This is not painful for the dog. The sample obtained this way is not contaminated by bacteria or protein from the outside of the body, and really represents the urine that is in the urinary tract. The third way to get a urine sample is to use a sterile urinary catheter. This produces a good urine sample, but can be very difficult to do in female dogs. The video below demostrates a cystocentesis.

The sample of urine will usually be analyzed right in the office while you wait. A small sample will be put on a strip with pads that change color if there are red blood cells, white blood cells, protein, or other abnormal substances in the urine.

A urine test strip. Color changes are compared to the bottle to get results.

Next, a small amount of urine will be spun in a centrifuge. This instrument spins tubes of fluid very rapidly causing solids that are present to sink to the bottom of the tube. The solid material from the bottom of the tube is placed on a microscope slide and examined. If a urinary tract infection is present, bacteria, blood cells, and crystals may be seen.

Crystals seen in a spun urine sample

If the veterinarian suspects, based on the physical examination, history, or symptoms of the dog, that there is an underlying problem present, some other tests might be run as well. Some of these are:

• X-rays of the abdomen – X-rays are used to look for stones in the urinary tract.


• Ultrasound of the abdomen – An ultrasound is used to look at the inside of the bladder and kidneys. It can be used to help diagnose kidney infections and tumors of the urinary tract.


• Complete Blood work – This is used to check the function of the kidneys and other organs. Diabetes can usually be diagnosed using blood work.

V. Treatment

Bacterial urinary tract infections are treated with oral antibiotics. In most cases, a bladder infection will clear up in ten to fourteen days. Kidney infections may take much longer to clear up. It is very important not to stop giving antibiotics if your dog feels better. The entire course of antibiotics must be given. When the course of antibiotics is done, a urine sample will need to be checked to make sure the urinary tract infection is gone. It is important to follow up and make sure that an infection has cleared up. Kidney infections that are not cleared up may lead to kidney failure. If an infection does not clear up, or keeps coming back, a urine cuture should be done.

If bladder or kidney stones are present, a special diet or other medication may be prescribed. These may help dissolve the stones or prevent the formation of new stones. Some dogs end up needing surgery to remove bladder stones, especially of the stones become lodged in the urethra. If the stones block the urethra, this is a medical emergency. Dogs with a blocked urethra are not able to urinate.