I have a small breed litter of pups at 6 days old. One pup was born a lot smaller than her litter mates. She was only 88g while the others in the litter were between 121g and 140g.
She initially suckled on mum very shortly after birth, but then became weak. I bottle fed her for the first two days and gave her some nutridrops on the bottle teat at each feed. I stimulated her to wee and poo at each feed with no problem. By day three she was strong enough to suckle from mum and mum seemed to be cleaning her. She has now got to 99g and was doing fine.
Late tonight I have noticed her tummy has become swollen. She is still feeding and is active. I've tried to stimulate her to poo without success although she did pass urine. She doesn't seem to be in any discomfort but I'm obviously worried about her.
I'm going to take her to the vet tomorrow but does anyone have any advice in the meantime that might help.

After a lot of stimulating I've finally got her to empty her bowels. Hopefully if I can stimulate her at feed times through the night she will be ok. Fingers crossed her stomach will have gone down somewhat by morning.

I must have missed this earlier.

Hopefully the distension will go down now her bowels are functioning, was the dam wormed daily through the last 3 weeks of her pregnancy?

The pups stomach already looks better I'm relieved to say.
Yes the dam was wormed from day 40 with panacur. It was her first litter and she delivered on day 58. My other bitch of the same breed always delivered on day 62, so I don't know if the shorter gestation would make a difference to the panacur working. The other pups are all fine though it was just this little one with the problem.
I'm thinking the dam maybe just wasn't stimulating this pup enough for her to empty her bowels. I had seen the dam cleaning all the pups and thought she was doing her job properly. I've taken over stimulating the little one again until I know she can go on her own and am keeping a check on her litter mates too just in case.
I've never had a pup this small before so I was a little panicky last night. She was doing really well after her initial slow start, so I was a little upset to see her stomach like that after 6 days of her getting so much stronger. Fingers crossed all will be well from now on.