What tests has the vet performed? What is the vet looking for? What does the vet say that the problem is, based on tests performed? What does the vet say about the blood in her stool? When was the last time she went to the vet? Did the complete refusal to use the litterpan start before or after you shut her in the bathroom? Isn't it possible that either the toddler is bothering her (perfectly normal toddler activity, with supervision and intervention to protect the cat from unwelcome attention it's okay), or that she's reacting to the new baby's arrival? What are you using to clean the soiled places? have you recently changed her routine, her litter, her litterpan location?

She's 15 years old, so some physical things are bound to have changed and she may be quite uncomfortable. It could be a simple fix, like changing to a flat pan that's easier to get into and out of.

Whew. Lot of questions! If it helps at all, I have a cat who's but 11 who has begun to poo in one particular spot nearly every day. She's clear of any physiological problems except some stiffening of the old joints. I tried various things to make her littering easier but still find the poo a little too often. She was always fastidious, too. If that's the only problem I have with her I consider myself lucky. She's a sweet, gentle, daft cat but that pooing drives me batty. You're not alone. There are also medications (clomipramine, amitryptylline) to help kitty while you work out the problem. I had another cat on clomipramine for the same issue. In under three months I was able to wean her off the med. She hasn't poo'd inappropriately since. A little calm retraining works nicely if the cat's not upset. However, it's up to the vet to decide if she needs drug therapy.