What is cystitis?
The term "cystitis" literally means inflammation of the urinary bladder. This is a generalized term and applies to any disease that inflames the urinary bladder.
What causes cystitis?
The most common cause of cystitis in dogs is an infection due to bacteria. However, other common causes include bladder stones, tumors or polyps in the bladder and diverticula.
What are the signs of cystitis?
The most common sign seen by owners is hematuria (blood in the urine). In addition, many dogs experience discomfort while urinating. They will often spend several minutes passing only a small amount of urine and may urinate more frequently than normal.
Symptoms are determined by the specific cause of cystitis. Bacterial infections usually cause hematuria and dysuria (straining to urinate). Bladder stones are often very rough and cause irritation as they rub against the bladder wall, also creating hematuria and dysuria. Tumors or polyps are usually not highly irritating to the bladder, but they can cause bleeding and mild straining to urinate. A diverticulum is a small pouch in the bladder wall that usually causes hematuria and dysuria secondary to the chronic bacterial infection that occurs. Bacteria often reside deep in the diverticulum and are nearly impossible to remove without surgery.
How is cystitis diagnosed?
A history of hematuria, dysuria and increased frequency of urination is strong evidence of some form of cystitis. When these are seen, several tests are appropriate.
The first group of tests include urinalysis, urine culture and bladder palpation (feeling with the fingers). A urinalysis consists of several tests to detect abnormalities in the urine. These are generally adequate to confirm cystitis, but may not provide enough information to determine the exact cause.
A urine culture determines whether bacteria are present and which antibiotics are likely to be effective in killing them. This is appropriate because most cases of cystitis are caused by bacteria that may be easily eliminated with antibiotics.
Bladder palpation helps to determine the size of the bladder as well as any discomfort.
Bladder palpation is the first "test" for bladder stones, since many are large enough to be felt by experienced fingers.
What is done if cystitis is present, but the culture is negative for bacteria and stones cannot be felt?
This scenario occurs about 20 percent of the time. When this happens, it is important that more tests be performed so a diagnosis can be achieved.
Radiographs (X-rays) are taken to further evaluate the bladder to detect possible stones, but they are usually not able to visualize tumors, polyps or diverticula. 
An ultrasound examination is also useful in evaluating the bladder. This technique uses sound waves to visualize stones as well as detect tumors and polyps. It may also identify other abnormalities of the bladder wall, such as thickening.
Both of these tests can be performed without sedation or anesthesia in a cooperative dog. 
Cystoscopy (placing a camera scope into the urethra and bladder) is used when the other two methods of imaging don’t find a cause. This is a highly specialized camera and performed under anesthesia with an internal medicine specialist.
Contrast radiographs are taken when plain radiographs and an ultrasound examination do not render a diagnosis. The bladder is filled with negative contrast material (usually air), positive contrast material (a special radiographic dye) and a small amount of positive contrast material against negative contrast material (double contrast study). An X-ray is taken each time the bladder is filled.
These three procedures permit visualization of otherwise unseen bladder stones, tumors and polyps, diverticula and wall thickening. It is necessary to pass a catheter into the bladder and to distend it for the scope; therefore, general anesthesia is required.
Dogs showing other signs of illness, such as fever, poor appetite or lethargy should also be evaluated for systemic diseases and bleeding disorders that may be causing hematuria. Lab work, including a chemistry profile and complete blood count (CBC), should be performed. If a clotting problem is suspected, a bleeding profile is appropriate.
How is cystitis treated?
Treatment depends on the cause. Bacterial infections are often easily treated with antibiotics. Some bladder stones can be dissolved with special diets; others require surgical removal.
Benign bladder polyps can usually be surgically removed, but malignant bladder tumors are difficult to treat successfully.
A bladder diverticulum should be removed surgically.
See Cystitis in Cats