Possible causes of sudden painful urination: i. . Acute urethritis or cystitis, this can appear sudden painful urination, mostly accompanied by urinary urgency, urinary frequency or incomplete urination, etc. Serious patients may even be accompanied by the symptoms of flesh-eye hematuria, it is recommended to carry out routine urine examination to further confirm the presence of infection. Second, stones in the urinary system can cause sudden painful urination, accompanied by symptoms such as lumbago and abdominal pain, which may be accompanied by bifurcation of urination or symptoms of flesh-eye hematuria. If stones are acutely obstructed in the urethra, serious patients may even have symptoms of inability to urinate, and need to undergo ultrasound examination of the urinary system and urethroscopy to further clarify the presence of stones. Third, sexually transmitted diseases, such as gonorrhea, non-gonococcal urethritis, through unclean sexual contact, patients suddenly appear painful symptoms when urinating, to be highly suspicious of sexually transmitted diseases, need to conduct gonococcal culture, mycoplasma, chlamydia culture and other tests to further clarify.