(Dog has been to emergency clincic already) question about bloody diarrhea and UTI

[chkths]

My dog had a UTI about 2 weeks ago and was put on Clavamox (sp?) which did well.  Two days ago she started having bloody diarrhea/soft stool, but was eating drinking and being normal.  I took her to the emergency clinic since it was the weekend.  They suspect she has colitis or unknown origin.  They gave metronidizol, pepcid ac, and a bland diet.
The night I brought her back from the emergency clinic, I think she peed in the house and had a little blood in it.  If this is the UTI recurring, can these two be related or could it mean it is not colitis and UTI, but something more serious?  Or is this a UTI and colitis that coincidentaly are happening at the same time?

Thanks!

[Aleda M Cheng, D.V.M., C.V.A]

If there is still blood in the urine it means that the Urinary tract infection did not clear because of one of the following: the antibiotic was not given long enough, or the antibiotic was the incorrect one,  or that your dog has crystals or stones in her bladder.

When this occurs a culture and sensitivity should be performed on urine removed from the bladder via a cystocentesis when the dog has not been on antibiotics for at least 48 hours or so.  

The colitis is probably unrelated and coincidental to the urinary tract infection, but could be secondary to the Clavamox.  Clavamox can cause diarrhea, but usually not bloody diarrhea.  Colitis is relatively common in dogs and usually highly treatable.

If your dog has anemia, or thrombocytopenia, it can cause increased bleeding from the bladder and rectum, (and also nose bleeds).  This can be checked by CBC blood test.

[chkths]

There were some crystals when the urinalysis was done for the first UTI.