I want to add rice to my soup, but all I have is sushi rice... would that be okay?!

I have used Basmati rice, brown rice and Chinese white rice, long grain and parboiled rice in various soups and all have come out well and tasted delicious. I've never used sushi rice, but don't see why it won't work.

The key to cooking rice in soups, is to put only a small portion so when it boils and swells, it won't make the soup real thick.

Alternately, I've cooked the rice separately and just added it to the soup before eating. So yummy!
Bon appetite!!!

I don't see that you'd have any problem doing that. It will thicken the soup quite a bit, but I suspect that's what you're looking to do. I wouldn't add very much of it. As other responders mentioned, you can always cook it separately and then add it, if you're not looking to thicken the soup.

sushi rice tends to be of a mushi/sticky/soft texture after it cooks. You can surely use it, but just keep a watch on the soup, you don't want mushy rice in your soup.

Well i would cook it first. but do you want to add rice when you all ready have potatoes in it. that's a lot of starch.