What is Prostatitis?
The prostate gland in men, located between the rectum and the bladder (where urine is stored), may become inflamed (swelling, irritation, and pain).
This gland surrounds the neck of the bladder and the urethra (a tube that voids urine from the bladder via penis). Inflammation or Prostatitis tends to choke the urethra and obstruct the flow of semen and urine. Prostatitis can be acute (sudden) or chronic (over time).

Symptoms
Acute:
Frequent urination
A feeling of having to push the urine out
Decreased urinary stream (amount of urine)
Inability to completely empty the bladder
Fever, Chills, Lower back pain, Painful ejaculation
Pain or burning during urination (dysuria)
Frequent urination at night (nocturia)
Pain in the lower abdomen, testicles
Pain with bowel movement
Blood in the Urine or semen

Cause
Infection:
Bacteria such as escherichia coli, pseudomonas, proteus, Chlamydia, Gonorrhea, and many others can cause inflammation of the prostate.
Bacteria may cause both acute and the chronic forms.
Nonbacterial cause:
A narrowing or stricture of the urethra can cause the urine to back up (reflux) and cause Prostatitis.
Prostate Cancer or enlargement can block the neck of the bladder, causing urine to leak around and result in Prostatitis.