By Jennifer Viegas

George and Fritz -- two canine littermates -- spent their entire lives together. In the mornings they squabbled over the tastiest bowl bites. Sufficiently fueled, they then seemed to collaborate on clever schemes, like stealing tennis shoe laces or sneaking into forbidden places. They went on walks together, played and napped side by side.

This went on for 14 years until Fritz died. Suddenly, George no longer acted like the same dog. He slept more, withdrew from social activities and lost interest in his food.

At that point, a visit to the vet was in order. "In such cases, I always begin by looking for a physical cause," said Dr. Raymond Van Lienden, DVM, a veterinarian at The Animal Clinic of Clifton, Va. "I conduct a full examination, do the blood work, run x-rays and analyze the dog's complete health history to see what may be wrong." He added that for dogs like George, no physical malady might show up in the barrage of medical tests. "It's then that we have to look at other possible causes, including grief and depression."

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