AMoonHawk saidYou are probed and poked in places depending on your response to their questions:
When was the last time you had sex?
Do you have anal sex?
Do you use IV drugs?
They will check our dick for dripping and your pubes for crabs and your skin for scabies.
It doesn't hurt, it's no big deal, just do it.
If it is a woman checking you then you might feel a little embarrassed, but don't be .. they see hundreds of dicks and asses a week, yours won't be the first.
Sometimes they don't ask if you have anal sex, so you have to let them know you are gay and you bottom. And if you have oral sex you have to tell them that too if they don't ask. You might be embarrassed, but don't be, they have heard it all a thousand times before and they are not judgmental.
If you use condoms you should have no worries.
Stuff you might need to worry about are crabs, scabies, herpes ... there are no protections for these.
Not judgmental? HAHAHAHA. You should try the Austin Travis County Health and Human Services. Most judgmental STD clinic female nurses in the world. My god. They specialize in guilt and scare tactics.
They only swab your butt if you have anal sex as a bottom without condoms or have admitted to "dipping," ie it went in but you didn't fuck without condoms. The swab tests for rectal gonorrhea, NOT chlamydia. They cannot check for rectal chlamydia, so that's a major reason not to have unprotected anal sex even if a guy says he is disease free--clinics don't test for it--they only treat genital and oral chlamydia.
I've never had a urethral swab--just the pee in the cup. You should only pee the inital part to barely go over 1cm of the cup and pee the rest into the toilet. The more you pee, the more it dilutes the bacteria and could make your test go bad--and most bacteria is in the intial part of the urethra rather than further into the bladder...unless it's the first time you've ever had an STD check and have advanced chlamydia/gonorrhea or something, which I'm sure you would have symptoms for by now (early chlamydia, no symptoms though, at least in my case when I had it).
They will feel your balls and squeeze your urethra to see if juice cums out. You will also have to tell them all the sordid details of what body part went where how many times in the past few months. Blood is taken at the place I go to in order to check for syph and HIV, but your results aren't accurate if you have had unprotected sex within the past 6 weeks-3 months, so don't use it as a free pass to go have unprotected sex with other "negative" guys, because they could be positive and not show up positive on an HIV test for months, and men are sluts and will lie or just not know they have it and be overly confident in their status.
Finally, to reiterate above, they have no way of detecting chlamydia in the rectum, so unless you are having symptoms or have been contacted by partners you had unprotected sex with, you could have rectal chlamydia if you have had unprotected anal sex and be walking around with it until you one day top and develop genital chlamydia or throat dick and get oral chlamydia. They only treat the latter two.