Blood drops where my cat has been.

My cat has had issues with crystals in his bladder before. He had to have a LOT of granulate stones flushed out about 2 years ago, but he's been mostly fine since. 

Until last week. 

I started noticing little drops of blood in places he was hanging out. The first few days it was happening, I'd actually left a lot of my make-up out on the bathroom counter and I thought what I was seeing was make-up he'd walked in and tracked. 

Then I noticed it on a piece of paper on the desk he'd been sitting on, and I brought him straight to the vet. 

They did a sonogram of his bladder and they said it was swollen but no crystals or stones could be seen and none were detected in the urine sample. They said they only found microscopic blood in the sample and that he had a bladder infection (which seems odd to me because his body temp was actually low when they checked it, and it just seems to me it would be higher instead of lower if he was having an infection). They gave him a shot of antibiotics and told me to be back in 2 weeks, which puts me bringing him back this Monday. 

But I am still finding blood places he likes to hang out. I am not seeing it in his litter box, but I assume that's just because it's not showing up well on the litter. I haven't found any injuries on him, so I can only assume it is coming from his urinary or digestive tract. 

Is my vet doing things right? Do I need to rush him back immediately? Has anyone ever dealt with this before? Is there anything else I should say or ask or point out when I bring him back? 

Any info is much appreciated. 

We do try to see that he gets plenty of water. He gets a fresh bowl at least once a day with ice and filtered water just the way he seems to like it. He's been drinking slightly less, but is still drinking and seems to be using the litter box normally, though he doesn't often stray far from it lately, which also raises some concern.

Could it be coming from his anus?  Is it possible he's constipated and straining to produce stools?  That can cause some minor bleeding, although I'd think you'd be able to see it ON his stool in the litter box (but maybe not if he's thoughtful enough to bury them )

It's also possible he's bleeding from somewhere else...his mouth possibly?  What exactly are you seeing?  Droplets, smears?  Bright red? 

I suggest that you roll your cat over after he pees and take a peak at his penis, to see if there is a blood drop still hanging on.  At least that might help verify the source of the blood. 

You say your cat is already under vet care (antibiotic) and is going back for a recheck on Monday.  So, assuming he's able to pee and fully void the bladder, drinking water and consuming fluid through wet food (high animal protein, no grain, low carb), then know that it takes time for the bladder to heal from whatever irritated it in the first place (this time sounds like bacteria).  The presence of blood is often the nature of an irritated bladder.  Unless he blocks (which requires an immediate visit to the vet) then I'd give him time and continue what your are doing. 

I have a cat with a long history of bladder issues that includes bright red blood in the box, to blood droplets around the house, followed by perfectly clear urine.  When he's having problems with his bladder, I put out an additional litter box in a different part of the house.  It gives him someplace different to go to the bathroom, often closer to wear he hangs out, and it seems to reduce his stress a bit - it's private from the other boxes and cats.  I also put out an extra bowl of water in a different part of the house to remind him to drink. 

I'm sure your vet will want to do another urinalysis.  Sometimes stones do not show up in a sonogram.  My cat had three ultrasounds done in a period of a couple months and his stones only showed up in the second US.  Are you tracking the pH of his urine?  That is a pretty easy at-home test (with strips) to see if the diet is keeping him in the correct pH range. 

Diet, of course, is important, but it's not a guaranteed cure.  My cat's brother has eaten the same food, bite for bite for 16 years, and he's never even thought about having a bladder issue.  I now feed a home cooked diet to make sure they get quality ingredients and no carbs.  Would it have helped the one if I had done this all along?  Can't say, sometimes it's just the cat. 

So keep watch that he is in fact able to void his urine and isn't showing too much stress.  A bladder with blood can be painful to the cat, occasionally I've given my cat a dose of Buprenex (from the vet) to help him not be stressed by pain.  That may be something you could ask your vet about. 

Keep the litter box clean so you can track his pee volume.  If my cat shows trouble peeing or his pee frequency increases (his current normal is about 30 times a day), I'll clean the boxes more frequently and put his pee sand in a different holding bag from the rest of the cats so I can see if the volume is normal. 

There's probably more I can say, but I'll stop for now.  This is never easy and always scary.  I hope he clears up soon!