Your doctor is likely to start with a physical exam to check for enlarged lymph nodes in your groin and an enlarged testicle on the affected side. Your doctor may also do a rectal examination to check for prostate enlargement or tenderness.
After that, your doctor may recommend:
STI screening. A narrow swab is inserted into the end of your penis to obtain a sample of discharge from your urethra. The sample is checked in the laboratory for gonorrhea and chlamydia.
Urine test. A sample of your urine is analyzed for abnormalities in appearance, concentration or content.
Ultrasound. This imaging test may be used to rule out testicular torsion. Ultrasound with color Doppler can determine if the blood flow to your testicles is lower than normal — indicating torsion — or higher than normal, which helps confirm the diagnosis of orchitis.
Nuclear scan of the testicles. A radioactive tracer is inserted into your bloodstream. The scanner then maps blood flow to your testicles, which can indicate torsion or orchitis.