What causes my dog's bulging vein on his side to appear sometimes?

Are you talking about the veins on the side of his legs? Those appear normal for his breed and its nothing to worry about. The line on his left side along his ribs is harder to tell what is going on there. There's not a vein, per se, that would be there to be prominent normally. Does the skin appear normal in this line? Is he acting normally? If he's acting ok, make an appointment to get it checked out but its not an emergency. Thank you for asking Petco Pet Education Center, formerly Petcoach!

On thinner areas of the dog such as the lower back leg, you can see the veins and it's not a problem. That being said, you can see inflammation of the superficial veins in dogs caused by an infection or formation of a clot. Without seeing Rey in person, I can't say for certain if this is ok or not. Even though she doesn't seem irritated by it, a vet visit just to make sure everything is ok would be best. I hope this helps!

It is prominent, but not necessarily abnormal as long as he’s otherwise acting normal. If he is favoring the leg at all, or there are any masses on the leg, or any swelling noted, take him to your vet. But if he is otherwise fine there is no cause for concern. Thanks for asking Petco Pet Education Center, formerly Petcoach!

Yes, dogs have arteries and veins that can become more visible when they are excited (higher blood pressure) or during heat cycle. The veins that you have highlighted are carrying blood from the mammary glands and can be more prominent while in Precious is in heat. These are not a cause for concern. :-)

It depends where the blood vessel is located. Whether the vessel you are seeing is in or on the surface of the eye can really help determine if this should be cause for concern. There can be normal blood vessels that are on the white part (sclera) of the eye ball itself. However, any evidence of a blood vessel inside the eyeball is not normal. Bulging vessels can occur if a dog has high blood pressure or something blocking flow of the blood through the vessel. It may be best to have your veterinarian examine Diesel's eye to ensure that this is not a sign of a disease affecting his entire body, such as high blood pressure.

She is very young, there is a good chance that it will go away on it's own eventually but it is impossible to know for sure, and even if it doesn't go away, it's not likely to cause any medical problems.

If Scarlet is squinting or if her eye has discharge I'd recommend seeing a veterinarian. The blood vessels in the eye can become larger when dogs are excited or when they have eye infection or inflammation. If just the one blood vessel is affected and she doesn't seem uncomfortable you probably don't need to intervene unless the redness gets worse.