Imaging the kidneys can be considered. In cases of infection and other kidney disease, they can be enlarged and lead to discomfort. This can be evaluated with a kidney ultrasound.
Blood in the semen can be due to an infection. Prostate disease can also lead to this. I would suggest a transrectal ultrasound to image the prostate for any possible causes.
Finally, regarding the discomfort on urination - you can consider further testing for infection. Specifically, looking for STDs and other causes for urethritis. A cystoscopy can be considered to evaluate for anatomical abnormalities - such as a urethral stricture or polyp.
These options can be discussed with your personal physician.
Followup with your personal physician is essential.
This answer is not intended as and does not substitute for medical advice - the information presented is for patient education only. Please see your personal physician for further evaluation of your individual case.
Kevin, M.D.
kevinmd_