Panting at Night and Bright Red Blood in an Older Dog's Stool
Small amounts of bright red blood, especially near the end of a bowel movement, usually come from the large bowel (colon) rather than the stomach. Colitis is a common cause. Diet changes, stress, parasites and infections can all trigger it. A short episode often settles within a few days, but blood that keeps appearing should be checked with a stool test, a rectal exam and sometimes bloodwork or a scope, to rule out polyps, growths or inflammatory bowel disease.
Panting at night in a cool room is worth mentioning at the same visit. In a 10-year-old dog it can be a sign of pain, or of Cushing's disease, which also causes more drinking and urination, a bigger appetite and a potbelly. Night restlessness can also come with age-related cognitive changes. Notice whether she's drinking more than usual, and bring that to the vet too.
It's great that she's still playful. Older dogs often hide early illness, and changes we put down to age are often treatable. A senior checkup about every 6 months, with bloodwork and a urine test at least once a year, is a good way to catch these things early. Some dogs with colitis do better with added fiber, but ask your vet before changing her food.
See senior dog care, dog panting and blood in dog stool.
This is general information, not a diagnosis. Please follow your own vet's advice.