There are multiple diseases associated with the urinary tract that could lead to blood clots. While infection is one of them, another common cause would be urinary stones (bladder and/or kidney stones).
In order to observe for this, imaging such as x-rays would be needed. If stones are not found with normal x-rays then sometimes a special x-ray using contrast material and/or ultrasound evaluation of the urinary tract are needed.
Male dogs that are not neutered are also at higher risk for prostate disease which can then cause inflammation and irritation to the urinary tract that can then lead to bleeding.
Cancer is another possible cause for blood clots, however is not as common as the other causes listed. The best thing to do would be to have your dog’s urinary tract evaluated with x-rays and possible ultrasound as these methods of testing would screen for the potential causes for blood clots.
It would also be important to have blood testing to best evaluate the health of the kidneys as they are part of the urinary tract as well. You may contact our hospital with any additional questions or to schedule an appointment so that we can help you determine the cause of his problems and help to get him feeling better soon.