Last week my dog was having having extremely runny BM. He was waking us up two times a night to let him out and he was producing a lot of poop, though in the day he produced little poop and more mucus. We went to the vet after three days and they did not find any parasities. They did prescibe Metronidazole and told us to feed him rice and cottage cheese instead of his normal food for a week. We have been doing this since Monday and now he doesn't poop at all! He went a little on Tuesday, but that is it! He is eating and is energetic. Any ideas?

First, fecals are only 80% effective at finding parasites unless they are using a centrifuge. Then only if they had a fresh sample, spun it at the correct speed, let it sit and the sample actually had any eggs in it. Oh and depending on who read the fecal could give a negative reading. Typically (not always), mucus in the poop is intestinal parasites. (

Because many of the parasites are zoonotic it is important to do strategic deworming. One way is to keep your dog on heartworm prevention monthly.

Metronidazole does not list constipation as a side effect, but your dog may be an odd case. I would call your vet just in case. Did they put you on FortiFlora? It is a prescription digestive enzyme by Purina. Or yogurt? This helps the gut get back the good bacteria that the antibiotic killed.

You are much better off staying in touch with your local vet in cases like this.

My dog does take take his heartworm pill monthly. The vet did not say anything about yogart, but maybe this is why she recommed cottage cheese. I was a little worried about a bowel obstruction, as he has not pooped in a couple of days, so was worried that this would warrant a visit to the 24hr vet (and this means $$$, as I know from rushing my pets off in the middle of the night and having it turn out that it was not needed. In anycase, I will call my vet tomorrow.

Yogurt has live bacteria. Cottage Cheese does not, but it is a bland diet to rest the gut. The purpose is to help the intestinal tract; Since antibiotic kills good and bad bacteria.
I don't think that a rush to ER vet is necessary, but most definitely a call in the am is warranted.
Good job on the heartworm!