Blood in the urine is almost always caused by cystitis (inflammation of the bladder). There are several underlying medical issues that can cause the cystitis. The most common cause of cystitis is a bacterial infection. This is especially true for female dogs. Bacterial infections in dogs happen the same way they do in people and dogs will show similar symptoms. These symptoms include: increased frequency of urination, straining to void the bladder, and blood in the urine. Antibiotics are used to treat bladder infections
Another common cause of cystitis is bladder stones. Bladder stones are mineral deposits that form into rock-like substances. These can be as large as golf balls! The symptoms are exactly the same as with bladder infections. Occasionally, a small stone may become trapped in a male dog's urethra causing a blockage. This is a serious condition that requires emergency treatment. During the early stages of stone development, the dog will have crystals in the urine. Dogs may or may not develop symptoms of cystitis during the crystal phase. As I stated earlier, these crystals and stones are caused by mineral deposits created by the urine either being too acidic or too basic. The treatment is a change in diet that will either raise or lower the pH of the urine depending on which is needed. Surgery is usually needed to remove the stones.
A less common cause of cystitis is a bladder tumor. These typically develop in older female dogs. The tumors are typically benign.
There are other less common causes of cystitis. All causes create the same symptoms. Therefore, it is very important to take your pet to a veterinarian in order to get an accurate diagnosis.