Frequent urination is caused by many physiological conditions like anxiety, stress (submissive), drinking too much of water as well as diseases of urinary tract, liver or endocrine diseases. Pain, straining or frequent voiding of small volume of urine may be associated with lower urinary tract diseases including stones. You are suggested to visit your vet if you notice your dog having any urgency or discomfort while urinating.
Question by - MRM Nair, Trivandrum