Perhaps his feet were very cold and frightened him.

SG

I was wondering if maybe he was shocked by the cold wet on his side/legs? Or thought something had kicked him?

I hadn't even thought about him being cold. This past winter, we had about 2 feet of snow on the ground for a few weeks, and he was out playing in it all the time, and he would wrestle with his brother in it and lay down in it, and he never screamed like that before. I thought maybe he had twisted his ankle (or doggie equivelent to an ankle) or something. Don't get me wrong, I am glad he is not hurt, but the reason I even considered dramatics is that he is a notorious whiner. Tired? Whine. Hungry? Whine. Bored? Whine. Want attention? Whine. Want to go out to potty, or just play? Whine. That's why I wondered about him being an exagerator (spelling?).

Perhaps he dislocated something, and when it went back into place, he was fine?

My sisters grandmothers dog will exagerate injury. Well, she won't exagerate, she fakes it. If she's being ignored, or hasn't had a lot of attention she starts to drag her leg, and then will refuse to walk. They've taken her to the vet many times thinking something is wrong, but nothing is. Now they suspect that before they owned her, she may have had an injury and realised how much attention she got when it happened.

Though if he's never been hurt, I can't see him faking an injury. My dog is whiney like yours, and she will scream if something startles her or scares her, so maybe he just scared himself when he slipped?? My cat did that once too, I thought I broke her leg! she was on my lap on my computer chair, and I pushed her off cause I was getting up, and her leg was caught under the arm of the chair and she howled, so I jumped, and then she took off yowling and howling, and of course being a whiney girl, I started crying and dug her out from under the table, still yowling, checked her out, and then she was fine. So maybe it was nothing major, but enough to make him hurt.

Dogs don't know to fake pain silly. He was hurting, it was probably no different than if you hit your funny bone or bang your head. It hurts for a bit and you get over it.

If you have de-icer or salt on your sidewalk, that can really hurt their feet, not just from the sharpness of the crystals but it actually causes a chemical burn. Sometimes dogs scream when they are frightened or startled- he might have been so surprised by falling that he just had a minor panic attack.

Dogs DO fake injuries!
There was a stray dog in Ecuador that had mastered begging. He would walk up to strangers playing 3-legged lame, and look very pitiful. We of course being vet students immediately gave him treats and then did a full orthopedic exam. Couldn't find anything wrong. Gave him a lot more treats, and he followed us down the road quite a bit- walking COMPLETELY normally. We came up to another group of Gringos, and he pulled up a DIFFERENT leg and hobbled over to them- he even threw in a little whining for good measure! We busted out laughing that the dog had figured out how to get the best handouts. Dogs DO fake injuries at times, especially when they are rewarded handsomely for doing so!

Obviously onyxdaily's dog was not begging and something did bother him briefly, but I just had to share that story!

I think your dog likely had a sharp/jagged piece of ice between his pads. By the time you had finished your examination, it had melted.

Thank you all for the responses. And I also want to make sure everyone knows that by asking about him faking or exagerating pain, I was not trying to minimize his incident. I truly did wonder if dogs had the know how to use faking / exagerating to get attention. The reality of it is, though, when he started screaming, I, too, was almost screaming, I was so scared and actually getting ready to scoop him up and take him to the animal ER. Him weighing 95 pounds, it probably would not have been pretty, but I would have gotten him out to the car if it killed me. One thing I've wondered about after reading an earlier post saying that if he hadn't been injured before, he wouldn't know to fake an injury. He hasn't had an injury, but he has experienced pain. When he had badly infected hot spots on his head and neck, it was quite painful when the vet was trying to clean the areas, and he cried during the treatment. At that time, Jasper got lots of attention and treats and hugs and praise for being brave from us. So maybe he remembers that attention?
You know, I could probably keep wondering what it was, and actually never know, but I know that I never want to hear that scream again.
And Meghane, thank you for the information about the de-icer and salt causing burns. I didn't use any salt this winter because I was worried they would try and eat it, but now with the possibility of the burns, I will be careful about using it even after they get out of their "i'm a puppy and I want to eat everything i see" stage.

A friends dogs were playing and they T boned. The one dog that was run into did nothing, three days later it was limping a bit and the friend took her baby to the vet only to find a shattered shoulder. I hope your dog is okay, that it was in that much pain causes me to pause, I would ask the vet to check him out in case. I mean you dont want anything like a bone break to knit wrong. As far as pain goes, some dogs are more sensitive than others, my mastiff mix did not let out one peep when he ripped his ligaments or broke his toe.

Onyx, I had something similar happen two days ago in the middle of the night. I took my dog to the emergency vet at 4am and then to his own vet at 8am. I told them he would start screaming when he moved his neck when he was laying down. However, when he was standing up he didn't seem to be in any pain from his neck. They couldn't find anything and decided it must be gas. All bloodwork and four abdominal and back x-rays came back fine.

It happened again as soon as I brought him home, but he would start yelping instead of screaming. It would only happen when he was laying on his side and would raise his neck to get up. It was worse if he'd been laying down longer. I called the vet back and got pain meds. The vet hadn't x-rayed his neck, but concluded it might be a pulled muscle.

Anyway, I learned to always ask for pain meds up front just in case you need them. I got Tramadol, which worked really well. I didn't think to ask for an anti-inflammatory, but I probably should have.

I've also found that I have to be a really strong advocate for my dog at the vet's because he is real good at acting normal. As with cars, the problem rarely manifests itself when you want it to. With my dog, a slightly lower head position , a lower tail, and a slower walk can mean something's up.

I hope your dog continues to do well. In answer to your question, I don't think dogs would fake a scream, but I have seen one that faked a limp after his hurt leg healed.