They don't look like parasitic worms to me. It is more likely that these are just fibers - hair, fabric which has gotten into the urethrea and were washed out when he peed. The movement was probably due to the small currents in the toilet bowl. Have him collect his urine in a clear glass container for a few days and look for more of them.
If more come out your Dr can order a stain and culture of the sediment.
Does he have any problems with urinating, frequent urination, pain or burning when he urinates? Does he have poor immunity? How old is he?
I looked at some websites and it seems that worms can be seen in urine but it is very rare and didn't see any images or more information about this. Pinworms could crawl up the urethera but these don't look like Enterobius vermicularis.