Hi
Welcome to the MedHelp forum!
The only way you can get urine from the anus is through a fistula between urethra and anus and this can be serious. The other possibility is that you have a urine leak that trickles down to the anus and you feel it is coming from there. The leaking could be due to urine getting trapped by a tumor, a hydrocele, a hernia, cancer of testicle, varicoceles or enlarged prostate. The leaking could also be due to weak bladder wall muscle---this gives a sensation of incomplete emptying of bladder. Inertstitial cystitis of bladder or narrowing of urethra could also cause leaking.
You need a comprehensive investigation taking all these points in consideration. Please discuss this with your doctor and get yourself investigated accordingly. Please let me know if there is any thing else and do keep me posted. Take care!