This is on a 5 month old mixed breed pup, about 8-10 lb. He has a firm bump on his naval area that has been present since birth. The vet who examined him at 9 weeks didn't think it needed surgery as it would not reduce. In his opinion it is an isolated fat pad. A different vet who examined him at 10 or 11 weeks old wants to do surgery on it "because he could rip it open, so it could be life threatening".

I would really appreciate your opinion Betty. Anyone else?

Well, we all know you aren't really doing anybody any favors when you make a diagnosis w/o an exam.....but, I think your pup probably had a little naval infection as a baby pup, perhaps his mother clipped the umbilical cord a little short, or his whelping area was filthy--and now he has an "outy" instead of an "Inny" for a belly button.
If it is not soft, and there is no "hole" behind it, it can probably be ignored. If it gets bigger, softer, then it could possibly entrap a loop of bowel,(umbilical hernia) then probably I'd fix it.
Also, it looks a little red around it -- did you clip it for the photo, or is that how it is? Is this area ever wet? Does it weep, or is it dry?

It was clipped just before the photo. The area has never been wet or weepy, always dry.

I'd just keep an eye on it. My guess is that it is not going to be a problem.

Thank you very much Betty.

Despite my advice the owners of this pup went ahead and had surgery on him. This is what they found.

What does it look like to you?

YIKES! A State Board question! I don't remember too much of this.
So, thru the belly button when pup is in the womb travels the urachus, a tube which carries urine, and the umbilical artery and vein, all that=umbilical cord.
So, the stringy thing could either go to the bladder, making it the remnant of the urachus(it used to carry urine out of pup into mom,allantoic fluid, the fluid in the "foot-sac" when you see something giving birth) or toward the liver,because it used to go there to carry nutrients to pup's liver from mom or visa versa.

In any case all this "stuff" is supposed to shrink down when the cord is severed. Some of these structures become things like the broad ligament of the uterus in the pup. But if cord becomes infected , or there's just bad luck, cord doesn't shrink and you get what you see. In calves, (colts too I saw one once) urine can come out of the belly button, a bad deal, called "patent urachus", causes infections, why I asked if it was wet. In that deal the tube has remained open from bladder thru belly button. Also in calves these navel things going to the liver can form a liver abcess.
Was that the right answer? Hope that's not a loop of bowel they are cutting off!
Did that once in a calf, it died!!!!

Betty

Sorry to bring back State Board questions flash-backs.

The surgeon only said "tissue". The pup is still alive, as far as I know, so it probably wasn't intestine.

Thanks for the anatomy lesson.

Sorry that I went on and on. What I should have said simply is that it looked like a remnant of the umbilical cord that either went to the liver or the bladder. One sentence.
I bet the pup does fine. Some of those things can have internal abcesses, so it was probably a good idea to take a look.