Bladder infection in dogs – an overview

What is cystitis?

A bladder infection, medically known ascystitis, is an inflammation of the bladder wall and is one of the most common urinary tract diseases in dogs. It can affect any dog—regardless of age, breed, or lifestyle—and ranges from mild discomfort to severe pain. Typically, affected dogs suddenly need to go outside more often, pass only small amounts of urine, or appear restless when urinating.

Causes and risk factors

In dogs, bladder infections are most commonly caused by bacteria that enter the bladder via the urethra. In most cases, these areE. coli bacteria, which occur naturally in the intestines but can cause inflammation in the bladder. In rare cases, fungi or parasites are involved.

Infection is not always the cause. Bladder stones, crystals, or changes in the bladder structure—such as polyps or tumors—can also cause cystitis.
In addition, there are various factors that contribute to its occurrence. These include metabolic diseases such as diabetes mellitus or Cushing's syndrome, as they weaken the immune system or alter the composition of urine. Neurological diseases that impair bladder emptying also increase the risk. Finally, anatomical features such as a bladder diverticulum or a persistent urachus play a role because urine residues and thus bacteria can accumulate more easily there.

Differences between male and female dogs

In principle, any dog—regardless of breed, age, or gender—can develop cystitis. However, female dogs are significantly more susceptible to bacterial cystitis because their urethra is shorter, making it easier for bacteria to ascend into the bladder.

Male dogs can also develop cystitis. However, in unneutered male dogs, the prostate should always be taken into account. Inflammation of the prostate (prostatitis) can cause similar symptoms or even be the actual trigger for the symptoms. Male dogs with prostatitis often appear to be systemically ill: they show fever, reduced appetite, fatigue, or pain in the lower abdomen or pelvic area.

Recognizing signs

Cystitis can manifest itself in many different ways, but some symptoms occur particularly frequently. Many dogs suddenly need to go outside very often, but only pass small amounts of urine or even become temporarily incontinent. Some dogs show signs of pain or strain when urinating. In some cases, the urine turns reddish—sometimes clearly visible, sometimes only detectable in the laboratory.

Many affected animals lick their vulva or penis more frequently, appear restless, or adopt a protective posture due to abdominal pain.
Occasionally, fever may also occur. Overall, dogs with cystitis often appear less cheerful, calmer, or withdrawn—subtle changes that can easily be overlooked in everyday life.

Diagnosis

If you notice signs of a possible bladder infection in your dog, you should definitely consult a veterinarian. The diagnosis always begins with a thorough clinical examination and a urine analysis.

The most reliable method is to obtain a sterile urine sample directly from the bladder using cystocentesis. The major advantage of this method is that the urine is free from external contamination, enabling accurate bacterial culture and resistance testing. However, in the case of a first-time, uncomplicated bladder infection, spontaneous urine may also be sufficient—especially if cystocentesis is not possible or would be too stressful for the dog. However, since spontaneous urine is not sterile, it is less meaningful for bacteriological examination.

Imaging techniques such as ultrasound or X-rays are not absolutely necessary for a first uncomplicated episode, but can be very helpful. Ultrasound is particularly well suited for assessing the bladder wall and detecting tumors or anatomical abnormalities, while X-rays are primarily used to visualize bladder stones. In cases of recurrent bladder infections, both ultrasound and X-rays should be used, ideally supplemented by a blood test, in order to reliably identify the underlying causes.

Therapy

The treatment of cystitis always depends on the underlying cause. If there is a bacterial infection, a specific antibiotic is usually used—ideally based on the results of a bacteriological examination.

If bladder stones are responsible, the treatment depends on the type of stones. Some can be dissolved or reduced in size through a special diet, while others can only be removed surgically. Painkillers are often used to relieve symptoms and facilitate urination.

Many dogs also benefit from dietary supplements that support bladder health, as well as a change in diet—especially if they are prone to urinary crystals or stones.

In unneutered male dogs, the prostate must always be included in the treatment if it is involved in the symptoms. Prostate inflammation or enlargement can otherwise significantly impair the healing process.

It is equally important to optimize existing underlying conditions, such as metabolic disorders or neurological problems that affect bladder emptying. Only when these factors are taken into account can the risk of recurrent cystitis be effectively reduced.

New approaches

In recent years, there has been an important change in the approach to treating uncomplicated bacterial cystitis. Today, the focus is primarily on clinical healing—meaning that the decisive factor is that the dog no longer shows any symptoms. Complete bacteriological healing, i.e., urine that is completely free of bacteria, is not always necessary and is no longer routinely checked.

For this reason, it is no longer recommended to automatically repeat urine culture approximately one week after completing antibiotic therapy, provided that the dog is symptom-free. The reason for this is that dogs occasionally have what is known as subclinical bacteriuria: bacteria are found in the urine, but the dog shows no symptoms. This form does not necessarily require treatment , as it does not harm the animal and unnecessary use of antibiotics should be avoided.