If your dog urinates more often than normal, small amounts, there is a big chance that your dog is suffering from cystitis. The bladder wall is then inflamed and becomes very sensitive. Because of the cystitis the bladder wall contracts, with the result that the dog can no longer hold his urine. It is common for blood to be seen when urinating.
Cystitis is very common in dogs (especially in spayed bitches). The most common cause is a bacterial infection. Stones can also be a cause, as can stones, struvite, calcium oxalate, or urethral obstruction.
Common symptoms of cystitis in your dog include being unrestrained, urinating often, in small amounts, blood in the urine, pushing on the urine, pain when urinating and lethargic or sluggish behaviour. A bladder infection can be easily remedied with e.g. a supplement based on Chinese herbs.