Your Dog’s Urinary System

The urinary tract of dogs is made of four parts:

• Kidneys (left and right) - Function to filter metabolic waste products from the blood which are excreted from the body via the urine. The kidneys are also important in regulating the balance of water and electrolytes (such as bicarbonate, sodium, and potassium) in the body.
• Ureters (left and right) - These are the tubes that connect the kidneys to the urinary bladder and through which urine passes.
• Urinary bladder - A muscular organ that stores urine.
• Urethra - The tube where urine passes from the urinary bladder to the outside of the body during urination.

What is Kidney Infection?

A kidney infection occurs when bacteria colonize one or both kidneys. It can be a primary infection characterized by a spontaneous occurrence, or it could be secondary, in which the presence of a pre-existing condition created favorable conditions for bacteria to invade, multiply, and cause infection. The most common predisposing factor of kidney infections in dogs is the migration of bacteria thru the ureters to one or both kidneys from an infection in the urinary bladder.

In some cases, affected dogs may exhibit only mild symptoms that often go unnoticed. However, kidney infections that remain undetected or untreated can have serious consequences. They warrant early detection and diagnosis so appropriate treatment can be given for a chance of a better prognosis.

Kidney Disease, Kidney Failure, Kidney Infection: Are these conditions the same?

1. Kidney Disease

This is an umbrella term for conditions that affect the function and integrity of the kidneys.

2. Kidney Failure

This is a condition in which the function of the kidneys is significantly reduced and compromised. This can affect the kidneys’ ability to filter out toxins and other metabolic wastes from the blood, as well as maintain water and electrolyte balance in the body.

Kidney disease and kidney failure are often used interchangeably. Conditions that may fall under the category include acute kidney injury (AKI) and chronic kidney (renal) disease.

Acute kidney injury (AKI) occurs when there is sudden kidney damage. Depending on the cause and severity, the symptoms can be mild to life-threatening. In addition to a sudden onset, the problem can progress rapidly. With prompt detection, diagnosis, and appropriate treatment, many cases of AKI in dogs can be reversed. Some of the most common causes of AKI include:

• Kidney infection
• Toxins (grapes, raisins, antifreeze, etc.)
• Infections (like leptospirosis and Lyme disease)
• Hypercalcemia (abnormally high calcium levels in the blood)
• Shock

Chronic kidney disease (CKD) takes time to develop, and the onset of symptoms is slow and gradual. Most pet owners don’t notice that there’s something wrong with their dogs until the problem is quite advanced and complications have already set in. Chronic kidney disease is progressive and can cause irreversible and permanent damage to the kidneys that will eventually lead to kidney failure. Affected dogs, however, can live longer and have a better quality of life with proper management that includes a special diet, medications, and maintaining fluid and electrolyte balance in the body.

3. Kidney Infection (Pyelonephritis)

This is most commonly due to ascending infections from the lower urinary tract in dogs and cats. The bacteria that are common causes of infections in the kidneys are E. coli and Staphylococcus. Other types of bacteria that have been implicated include Streptococcus, Pseudomonas, Klebsiella, Proteus, and Enterobacter. These bacteria are common causes of lower urinary tract infections but may move up into the ureters and reach the kidneys. Some fungal organisms have also been implicated in kidney infections.

The kidneys are normally protected from bacterial infection by mechanisms of immunity and flap valves. The renal medulla also has a hypoxic (low-oxygen) environment that renders unfavorable conditions for the growth and colonization of bacteria. Another protective mechanism of the kidneys is the length of the ureters and the one-way flow of urine from the kidneys to the bladder.

Factors That Can Increase a Dog’s Risk of Kidney Infection

Several conditions can increase a dog’s risk for pyelonephritis. These include:

• Renal dysplasia - A congenital abnormality in the development of the kidneys that is already present at birth.
• Ectopic ureters - The ureters are not attached to the urinary bladder properly
• Vesicoureteral reflux - A condition characterized by the backflow of urine from the urinary bladder back into the ureters.
• Diabetes mellitus - The abnormally high quantity of sugar in urine attracts bacteria
• Cushing’s disease - A condition in which a hyperactive adrenal gland produces excessive amounts of steroids in the body which can significantly decrease the resistance of the body to infection.
• Steroid medications
• Retention of urine for considerable lengths of time
• Kidney failure
• Insertion of a catheter into the urethra
• Bladder or kidney stones
• Perineal urethrostomy - A surgical procedure in which a new opening into the urethra is created.

Symptoms of Kidney Infection in Dogs

Many dogs with kidney infections don’t show any symptoms, although signs of lower urinary tract disease may be present, such as:

• Increased water intake and frequency of urination (often with only small amounts of urine)
• Difficulty in voiding urine
• Pain during urination
• Inappropriate urination (your house-trained dog may suddenly urinate anywhere inside your home)
• Fever
• Painful kidneys when touched during the physical exam

Chronic kidney infections may have slow, progressive azotemia (buildup of nitrogenous waste products that causes toxicity in the body), progressive kidney damage, and ultimately renal failure if there’s no treatment given. Blood in the urine may also be associated with bacterial pyelonephritis.

Treatment Options for Dogs with Kidney Infection

Dogs with kidney infections are usually treated without hospital confinement except when they have developed septicemia (bacteria is already present in their blood), or signs of kidney failure are evident.

The treatment regimen for kidney infection depends on the underlying cause. It may involve a special diet that is formulated to support kidney health and function.

If a dog has ectopic ureters, surgery can be performed to reposition them so urine can properly drain into the urinary bladder from the kidneys. If a stone is causing a blockage in the upper urinary tract, surgery is often necessary to remove it as soon as possible because the bacterial infection and inflammation associated with it may rapidly progress and lead to septicemia.

If urinalysis reveals the presence of bacteria in the urine, antibiotic sensitivity testing may be necessary so the appropriate antibiotics can be given. Antibiotics are usually administered for 4-6 weeks to clear up the infection. An ideal antibiotic must have the following features:

• Should kill the bacterial pathogen that is causing the infection
• Appropriate levels must be present in the blood and urine
• Should not be toxic to the kidneys

Follow-Up Care for Dogs with Kidney Infections

While the dog is undergoing antibiotic treatment, urinalysis and urine cultures are usually performed 5-7 days into treatment and 1-4 weeks after antibiotic treatment has been concluded. These tests are necessary to assess the efficacy of the treatment regimen.

Prognosis

There are several potential complications of kidney infections. These include recurrent kidney infections and kidney failure. If septicemia is present, bacteria in the blood may reach other organs of the body, such as the heart and liver, and also cause infections in these organs.

Overall, dogs with acute kidney infections have an excellent prognosis unless they also have concurrent issues affecting their kidneys, such as blockage in any part of the urinary tract, kidney stones, urinary tract cancer, or chronic kidney disease.

Dogs with recurrent or chronic kidney infections may be a challenge to cure thus making their prognosis more serious. Prompt and proper identification and appropriate treatment are necessary to prevent permanent damage to the kidneys and kidney failure.

Read more:

Common Causes of Urinary Issues in Dogs

Canine Hormone-Responsive Urinary Incontinence

What does it mean if my dog has crystals in her urine?

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