What is the problem when the semen has a very bad smell?

Patient's question:

I would like to ask the doctor why the semen I eject every time after having sex with my girlfriend has a very unpleasant odor? What is the problem? I thought semen is supposed to be colorless and odorless?

Doctor's answer:

Hello
According to the normal semen standards stipulated by the World Health Organization, whether semen is normal can be analyzed from the following aspects:
(1) Semen volume: Normal ≥ 2ml. Exceeding 7ml is considered excessive, not only reducing sperm density but also making it easy to flow out of the vagina, thereby decreasing total sperm count, commonly seen in seminal vesiculitis; less than 2ml is considered semen volume too low, but usually below 1ml is considered too low. At this time, the contact area between semen and the female reproductive tract is small, or due to viscosity, it is not conducive to sperm entering the cervix of the female, leading to infertility, commonly seen in severe accessory gland inflammation, low testosterone levels, ejaculation duct obstruction, retrograde ejaculation, etc.
(2) Color: Normal is grayish-white or slightly yellowish. Milky white or yellowish-green suggests inflammation in the reproductive tract or accessory glands; pink, red, or red blood cells observed under a microscope indicate bloody semen, commonly seen in accessory gland or posterior urethra inflammation, occasionally seen in tuberculosis or tumors.
(3) Acidity/alkalinity: The normal pH value of semen is 7.2 to 7.8. Less than 7.2 is seen in ejaculation duct obstruction or urine contamination; greater than 7.8 is seen in seminal vesicle inflammation or outdated samples.
(4) Liquefaction time: After normal semen is emitted, under the action of seminal vesicle coagulase, it becomes gelatinous, and within 15 to 30 minutes, under the action of prostatic liquefying enzyme, it becomes liquid, this is semen liquefaction. If the semen does not liquefy within 30 minutes after emission, it is considered abnormal.
(5) Viscosity: By touching a glass rod to liquefied semen and gently lifting it, semen threads can be formed. Normally, the length of these threads is less than 2cm.