The reasons why dogs have yellow pus in their urethral opening:

1. When a male dog is in heat, there will be a mixture of semen and prostatic fluid in the urethral opening. Symptoms of yellow purulent discharge will appear.

2. If it is a male dog, it may also be caused by prostatitis or urinary tract infection.

3. If it is a female dog, it may be caused by uterine, vaginal or urinary tract infection.

4. If it is a female dog, it may also have some abnormal pathological problems such as pyometra or uterine effusion.

Solutions to yellow pus in the dog's urethra:

1. If it is caused by normal estrus, the owner can use some to clean the dog's genitals and keep them Genital cleanliness.

2. If it is caused by a urinary tract infection, it is recommended to flush the external genitalia with medicine containing metronidazole and take an appropriate amount of anti-inflammatory medicine.

3. If it is caused by uterine or vaginal infection, it is recommended to flush the external vagina with saline and feed appropriate antibacterial and anti-inflammatory drugs.

4. If it is caused by pyometra, etc., it is recommended to perform surgical treatment immediately.