Can a uti go undetected in a urinalysis in a man if the bacteria is in the urethra?

Possibly, yes: With a midstream urine specimen, infection in the urethra might night not show elevated white blood cells or bacteria on urinalysis; the initial flow could flush them from the urethra. However, UTI is rarely limited to the urethra. The main causes of localized urethral infections are STDs: gonorrhea, chlamydia, or nongonoccal urethritis (NGU). Discuss with doctor, especially if at risk for STD.