In addition to ansewers & comments above:
BooBear just had a littel blood in her poos too. My vet is a very no-nonsense, pragmatic doc (not undereacting but not overreactign to things).
She said not to worry, "just a touch of puppy colitis...", gave us a minute amount of a liquid med called Metronidazole that I use a teeeny dropper with. The metered amount, at .03ml is so little that I just swirled it in nutracal and th Poo-problem cleared up in ONE day :-)
That being said -- my situation might be tad bit different -- I had just had Boo in the ER/ICU for what ended up being very bad naseau & gas, not a blockage. Little girl swallowed a gel cap. Not the insides, just the outside gelatin casing. So she had the test for Pravo, etc. Xrays, Ultrasound then later barium (sp?) contrast. She is fine but I nearly lost my mind last week.
Anyway -- we had 5 different levels of poo-consistency from hard to the runs w/the barium stuff and doc indicated that as poo-poo moves thru baby's little tract the end production will often be looser thant the beginning poop. "...The last drabs w/blood was not surprising and as long as it was not profuse, the meds woudl clear it up".... And they did.
__________________  my little Boo Bear 
.........Rita |