Two other thoughts come in my

Two other thoughts come in my mind besides the prostate as mentioned by Eric. Occasionally you can see the hypogastric lymph node outlined in this region. It bears the same echogenic resemblance as what you demonstrate here on your video. The other possibility, although I think it much less likely, is a uterus masculinus. This is a vestigial remnant of Mullerian duct that can develop into a prostatic cyst later on in life. To me this is very low onthe list but I add it here as I have never seen one this early in a pets life so I’m not sure what it would really look like. I would expect ity  to look differently but then again I just see them at the later on cystic stage.