So, Mom and I talked again. I told her what Sealgair suggested about thrombosis, and I began Googling. I came across a few sites for
Feline Hypertrophic Cardiomyopathy and read out loud for Mom. She interrupted me to say that Daniel had most of those symptoms, including pulmonary edema and pleural effusion. I learned that feline hypertrophic cardiomyopathy could be linked with thrombosis, although Daniel has no signs of saddle thrombus. We're trying to find out if either thrombosis or hypertrophic cardiomyopathy could cause such severe anemia that the red blood cell count would drop down to ten (yes, ten -- without obvious blood loss). Mom will bring this up with the vet, so we shall see (Daniel is now buried in the backyard, so a necropsy isn't an option).
However, there is better news. Mom went to ARF today, and went into the main cat room. She looked at an orange tabby kitten, who was too feisty and energetic for what she wanted. Then, an older orange tabby walked calmly up to her and sat down at her feet. She talked to him, asked "Are you a good kitty? May I pick you up?" He let her hold him and peacefully snuggled in her arms. She turned him onto his back, which is how she tests a cat to see how docile it is. The cat was perfectly content and even purring. She learned that he was five years old. His name was Toby. His previous owner became too sick to care for him, and he'd been at the shelter for two months. Mom was really considering adopting him, since of course older cats need love too, and most people want kittens. I told her to go for it, and she laughed and said she was going to ask my opinion. So, it's a high possibility that Toby will be my parents' new cat. Future bulletins, of course.