In a dog with a shunt, a lot of unprocessed ammonia may be eliminated through the kidneys, and too much ammonia in the urine can combine with minerals and precipitate out, forming stones. A special lab test also had very abnormal results that indicated a liver shunt. As luck would have it, the Washington State University Veterinary Hospital is currently conducting a research program on liver shunts. They accepted Velvet into the program, where they did even more special tests, and confirmed that she had a liver shunt. They successfully performed the difficult surgery to repair a shunt.
Velvet is back home and doing great.
If a liver shunt is not detected early enough, the liver sort of adjusts to the abnormality, and by the time symptoms appear, it can be too late to repair the shunt. The shunt gets progressively worse, eventually leading to debilitation and death. So it was really lucky that Velvet had that bladder infection, which lead to the stones, which lead to the lab work, and the early discovery of her liver shunt. There's a bright side to everything, as my mother used to say.