Excerpt from Ask the Vet About Dogs: Easy Answers to Commonly Asked Questions
A bladder infection, also called a lower urinary tract infection, is a bacterial infection of the inside lining of the urinary bladder and the urethra (the canal through which urine flows as it leaves the body). Lower urinary tract infections are more common in female dogs. Infections can affect dogs of all ages, but older dogs have more problems, such as tumors and bladder stones, that predispose them to infection. Symptoms of a lower urinary tract infection include urinating frequent small amounts; straining to urinate; bloody or strong-smelling urine; and inability to control urination, sometimes misinterpreted as a house-training problem. Your dog can be in discomfort, so make an appointment with your veterinarian quickly. Veterinarians usually diagnose infection by a careful examination of a urine sample for the presence of blood, bacteria, and other abnormalities. Sometimes, the diagnosis is difficult to make, and the urine sample must be sent to a laboratory to be cultured.
Most lower urinary tract infections are one-time events, and antibiotic treatment cures them without complication. A lower urinary tract infection that doesn’t respond to antibiotics may be more complicated. This indicates the need for further tests such as a urine culture and X-rays of the bladder.