Can a dogs testicles grow back?

No. I would get the lumps checked out as they may be a tumor of some sort.

Thanks,
 
And I didn't think so.  I'm wondreing if she bit him there for some reason.

No, testicles will not grow back.  What you are most likely seeing is glands...perfectly normal.  I know someone else can elaborate on this more....but don't worry over it.
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As the recent adopter of my first male dog, I can tell you this concerned me greatly at first!  It would come and go, sometimes more than once per day - but our dog had been neutered only 2 days before we got him. So here I go to the vet and find out that he is just excited!!  As long as it's really the base of the penis and not back where his testicles used to be......  and it never lasts more than a few minutes with Sammy before it goes down.  It may come back, or not.  I've noticed it MUCH less now that we are several months post-neuter, but now it's still a few times a week. 
 
If it has been there SINCE you saw it a few days ago, then I might be concerned.  Or if the dog pays it a lot of attention.  Sometimes it's worth a few bucks to go to the vet, even if they laugh at you as they take your money []
 
Oh, and btw, I noticed you're new around here - so welcome!  And let us know if this helps you out.  Also, we'd really LOVE to see pictures of your dog!!! 

That is the Bulbis Glandis a normal part of the male canine's anatomy. This is the part clasped by the bitch from inside and then it swells causing the infamous "tie". It will swell in moments of excitement such as walks or belly rubs or any handling the dog particularly likes...or sometimes for no reason at all. I wouldn't worry about it unless the actual swelling is in the scrotum proper.

Gina is absolutely right.

The first time this happened to Rupert I was so worried! It was about a week after he was neutered and I thought there was some sort of infection or something had burst inside. It was right when we woke up in the morning. I called the vet... turns out it was just, uh, "morning wood." [sm=blush.gif]

ORIGINAL: janobonano

The first time this happened to Rupert I was so worried! It was about a week after he was neutered and I thought there was some sort of infection or something had burst inside. It was right when we woke up in the morning. I called the vet... turns out it was just, uh, "morning wood." [sm=blush.gif]

LOL  I love the way you put that!

This happens to Hercules occasionally.  The first time I saw it, I brought him to the vet and thought that they might have "missed", but the assured me this was normal.

Thanks too all, but these lumps havn't gone away.

Well, if it's been a few days and they really haven't gone away then I would probably try the vet next.........  I have no idea what it could be, but it doesn't seem normal.  Sammy's go down in minutes usually.  I would call the vet..... in the meantime, perhaps you could get pictures?  It might be that we are talking about two completely different things and everyone is misunderstanding everyone else.  Hard to dx online. 
 
Good luck!

ORIGINAL: janobonano

The first time this happened to Rupert I was so worried! It was about a week after he was neutered and I thought there was some sort of infection or something had burst inside. It was right when we woke up in the morning. I called the vet... turns out it was just, uh, "morning wood." [sm=blush.gif]

 
And yes this was my reaction as well!!  And of course I felt stupid because I totally overreacted, but hey []

Well...you are probably looking quite often which is either him on his back or you looking under him while standing? Either one probably elicits some excitement from placed in a submissive position or receiving attention, and this could be triggering the issue. I think you might consider backing off completely a day and see then.. Do be aware that the bulbis glandis is PART of the penis and is always there....even in an 8 week old puppy you can see it quite readily many times thruout the day.
 
Watch for STRANGE or copious discharge from the end of the penis...as in NOT yellowish green which is quite normal. Make sure the "red lipstick" portion of the penis can return FULLY to the sheath. In true cases of persistent erection breeders will apply ice to the testicles...since your dog has no testicles you can try applying ice to the bulbis but be sure to wrap it first in something to avoid ice burn. You can also take your dogs temp and make sure it is normal...not above 102 say. You do this with a traditional or digital thermometer and vaseline rectally.
 
Personally I think it is just residual testosterone coupled with a lot of attention being applied to the area. But I agree a vet trip might make you breathe easier.

Thanks,
 
I may call the vet.  I have no way to take pictures.