Hey there. Sorry your b'friend is having this pain. Urinary problems are no fun for any of us. It could be a UTI (urinary tract infection) or possibly a kidney-stone. Has he been experiencing this for a while, or did it just start (sudden onset)? When you say the pain is in his lower abdomen, is it more towards his back (flank)? Is the pain in his genitals a shooting pain (like lightning bolts) that radiates to the base of his testicles?
If he's been experiencing it consistently over a period of time, then signs point to UTI.
If this suddenly happened, then I'd lean in the kidney-stone directing.
Whatever the case, and if it's neither of the above, if it's urinary system related, he needs to get himself, at the very least, to his PCP (primary care physician). His PCP should be able to give him a good idea of what it is, or refer him to a good urologist.
If the pain gets worse... get him to the ER.
(*I'm not an expert... I've just had more UTI's than I can count, and more kidney-stones in the last 19 years than you could possibly imagine)