Bruno, my 13-year-old Border Collie mix, had a mucous/bloody nose and sneezed constantly. We went to the vet and had an inconclusive an X-ray. Other symptoms were a high white blood cell count and bacteria in his nose culture. He was treated with Baytril for two weeks, which stopped the bloody nose. He’s been off of Baytril for two weeks and now his bloody nose has returned. One day the blood was just blood and very thin. Now the mucous/blood has returned. It is not a foxtail causing it. He is very lethargic but is eating and wags his tail. I am afraid it is a tumor.
— Karen, Southern California
In an older dog with a bloody nose, a tumor is unfortunately high on the list of possible causes. An infected tooth root can also be the culprit, so full mouth dental radiographs (X-rays) are strongly recommended as well as a thorough oral examination. If radiographs of the nose are inconclusive, advanced imaging such as a CAT scan may need to be performed to provide more detail. In addition, a scoping of the nose can be performed to examine the nasal passages for lesions. However, a biopsy of the lesion is often required for a definitive diagnosis.
Unfortunately, you have to biopsy the appropriate area in order to get the correct diagnosis, so imaging is often performed first to direct the biopsy site. Other possible causes for a persistent bloody nose are a foreign body (such as a foxtail), a fungal infection and a bleeding disorder caused by a systemic illness (such as liver disease). Blood work to rule out a systemic infection or a fungal disease can be performed before advanced imaging to help stage the diagnostics and defray some of the costs.