What Causes Prostatitis?

Prostatitis is the inflammation of the prostate gland, which is located next to the bladder. It is usually due to an infection, but other prostatitis causes are sometimes recorded.

This inflammation can be microscopic and not very noticeable or macroscopic, and easy to diagnose. In some cases, it can visualize as edema and swelling in ultrasound imaging. But, in other cases, the only way to see prostatic inflammation is through a prostate biopsy.

In this article, we discuss each prostatitis symptom, explore their causes and how the disease progresses.

Prostatitis Symptoms

Prostatitis symptoms are often similar to those found in an enlarged prostate-for example, a reduction in urine flow and others that suggest a prostate problem.

Painful urination is also common, especially when there’s a recurrent urinary tract infection. They are similar to those found in urinary tract infections. However, other patients are diagnosed by chance and have no symptoms at all.

The classification of prostatitis has had some changes through the years. It currently breaks down into 4 types. They are (1):

  • Acute bacterial prostatitis

  • Chronic bacterial prostatitis

  • Chronic prostatitis and pelvic pain syndrome

  • Asymptomatic inflammatory prostatitis

Acute Prostatitis

We call this acute bacterial prostatitis because a bacterial agent causes it. These agents reach the prostate through one of four pathways (2):

Urinary reflux

The prostate is a gland with intraprostatic ducts that connects to the urethra. If you have a backward flow of urine, it can reach the prostate and fill the intraprostatic ducts. The urine is sterile before leaving the body, but it is no sterile anymore once in the urethra. Thus, it brings bacteria to the prostate. They cause an infection and begin an inflammatory process.

Ascending urethral infection

The urethra hosts many bacteria, and its lining is designed for the challenge. However, there are urethral infections with pathogen bacteria, too. Causes of urethritis include Chlamydia, gonorrhea, and other sexually transmitted diseases. When these agents infect the urethra, they can proceed with an ascending invasion of the urinary tract. The prostate is in the way and gets infected, causing prostatitis.

Infection spread from the rectum

Digital rectal examination is appropriate to evaluate the prostate because the rectum is right next to the gland. This proximity also works against the prostate because there are many bacteria in the rectum. They can spread from the rectum to the prostate using two main pathways. One of them is a lymphomatous spread through the lymph. The other is direct migration through direct proximity. These causes are only considered when there’s no further explanation for prostatitis. They can be more common in immunocompromised individuals.

Direct hematogenous infection

The blood should be sterile and utterly free from pathogens. However, it is sometimes invaded by bacteria that travel along with red blood cells in the blood vessels. When this happens, bacteria can reach almost every organ in the body, including the prostate. It is possible to suspect hematogenous spread in individual patients. However, it is not the most common cause of prostatitis.

Sexual intercourse is one of the more common causes of prostatitis in younger men. Hospitalized men and those who underwent recent surgery may also get this problem if they had prolonged catheterization. It can also happen after prostate surgery or instrumentation near the prostate. A urinary infection is another possible cause, but not the most widespread because they are not as common in men as they are in women (1,2).

Chronic Bacterial Prostatitis

Similar events to acute bacterial prostatitis can trigger this type of prostatitis. It is a bacterial agent that reaches the prostate and causes inflammation. The infection source may also come from urinary reflux, an ascending urethral infection, or bacterial spread.

However, these patients have something very particular that we can highlight. The most common pathogens, in this case, are uropathogens. In other words, these patients are usually infected by bacteria that cause urinary infections.

There is some evidence that Chlamydia could be implicated sometimes, but it is not yet clear. So, sexual transmission is not very common, and these patients may have repeated urinary infections.

After studying possible causes and risk factors, these are particularly relevant:

Intraprostatic ductal reflux

As noted above, the prostate gland has many ducts. They are located in the peripheral zone of the prostate, and their drainage is poor. Reflux is more common as we age, and the prostate enlarges with obstructed draining ducts. In people with voiding problems, intraprostatic reflux is more common and leads to chronic infection.

Bacteria ascend through the urethral canal with refluxing urine. Then they stay in the prostate and form aggregates. If the patient has prostate calculi, they become a nidus of infections and contribute to prostatitis. Actually, prostate stones or calculi are a sign of intraprostatic ductal reflux. They contain substances found in the urine, which can sometimes be sterile and not cause inflammation. However, it only takes some bacteria to create a living culture in the prostate and trigger inflammation (3).

Instrumental manipulation of the lower urinary tract

Another common cause of chronic prostatitis is manipulating the urethra. A typical example would be prolonged catheterization, but it can also be prolonged use of a condom catheter.

When patients undergo transurethral surgery, they have some risk of prostatitis after surgery. The risk increases in men with infected urine or known urinary tract infections.

Another procedure that causes infection is a prostate biopsy. This leads to chronic inflammation of the prostate, usually due to a specific type of Escherichia coli. We call this ESBL E. coli.

Secretory dysfunction of the prostate

Another possibility has an alteration in prostatic secretions. The prostatic fluid has an antibacterial effect that protects the prostate. In patients with chronic prostatitis, the prostatic antibacterial factor reduces, and other components alter. This is probably one of the reasons why inflammation prevails for a long time. The pH becomes alkaline and makes it even harder to treat chronic prostatitis because antibiotics can’t reach the gland under these circumstances (4).

Other risk factors that increase your chance of chronic prostatitis include:

  • Phimosis, because it links with more bacteria in the urethra

  • Urethral infections such as acute epididymitis

  • Unprotected anal intercourse

Chronic Non-bacterial Prostatitis (Chronic pelvic pain syndrome (CP/CPPS)

Prostatitis is a very complex topic to cover sometimes, especially in chronic diseases. In some cases, there is no explanation for the symptoms, and treatment is not satisfactory. That is what happens in chronic pelvic pain syndrome.

This a catch-all category that covers pretty much everything that is not explained by acute or chronic bacterial prostatitis. Thus, talking about causes is going very deep into multiple and very complex etiologies. 

These patients only meet three criteria (5):

  • Symptoms related to the prostate or located above the thig and below the umbilicus

  • No clear explanation for the symptoms of the patient

  • No treatment cures or has satisfactory results for the symptoms

Still, some authors proposed some mechanisms that may explain Chronic pelvic pain syndrome (CPPS). The causes are still unknown, but they apparently link with a dysfunction in the immune system as a result of endocrine changes triggered by neurologic or psychological factors.

Chronic pelvic pain syndrome is so complex that inflammation is not necessarily a part of the process. The number of white blood cells in the prostatic fluid does not predict which patient has more severe symptoms. Histologic evaluation of the prostate only finds inflammation in one-third of the patients. Thus, the cause of CPPS is sometimes outside of the prostate or still unknown by science. Other cases can be traced back to the prostate, especially when inflammation is present. 

Inflammatory CPPS

In inflammatory CPPS, the leading cause is cytokine signaling. Cytokines are substances that potentiate inflammation in different parts of the body. In Chronic pelvic pain syndrome, the main cytokines at play include interleukins, interferons, tissue necrosis factors, and others. An imbalance of these substances causes pelvic inflammation and triggers pain, which is not always traced back to the prostate.

Conditions linked to CPPS

There is some genetic predisposition, and autoimmune problems are apparently linked to CPPS. Another factor at play is testosterone. Men with lower testosterone levels have a higher risk of CPPS. Similarly, other authors have found an increase in pain sensitivity after overstimulation of nerves by growth factors. Psychological stress contributes to flare-ups in these patients, reduces pain threshold, and contributes to cytokine imbalances. However, these findings cannot be pointed out as direct causes. They probably interact with each other in very complex ways triggering inflammation and pain (6).

The organisms that typically cause CPPS include Chlamydia trachomatis, Mycoplasma hominis and other types of mycoplasma, Neisseria gonorrhoeae, anaerobic bacteria, and gram-positive bacteria. Actually, many chronic nonbacterial prostatitis cases are caused by gram-positive bacteria dismissed by laboratories because they are tagged as normal flora. However, in CPPS, there’s a failure in defense mechanisms, and they become harmful hitchhikers (5).

Unlike acute and chronic bacterial prostatitis, in Chronic pelvic pain syndrome, we can find nonbacterial prostatitis organisms such as protozoans, fungi, and viruses. The most common viruses that infect the prostate in CPPS include herpes virus, papillomavirus, and cytomegalovirus.

Asymptomatic Prostatitis

Asymptomatic prostatitis can be found by chance in healthy individuals. They do not usually display urinary symptoms. If they do, they are often attributed to BPH and other prostate-related conditions.

However, one fact about prostatitis is that it raises our blood PSA levels. This is one of the reasons why patients are diagnosed with asymptomatic prostatitis. It is an otherwise healthy prostate that happens to undergo an inflammatory process.

Thus, it is not possible to know how much time has it been like that and whether it is acute or chronic inflammation. In some cases, inflammation improves after antibiotic therapy. In other cases, it is independent of antibiotics and improves with anti-inflammatories. That’s why it won’t be possible to point out a single cause. Moreover, we can’t reproduce asymptomatic cases in clinical trials. This makes them even more difficult to study.

However, it is postulated that the causes of asymptomatic prostatitis are pretty much the same as the ones listed above.

This can be a case of asymptomatic acute prostatitis. If that’s the case, the most common causes include (1,2):

  • Urinary reflux

  • Ascending urethral infection

  • Microbial spread from the rectum

  • Microbial spread via blood infection

If we’re talking about the chronic infection of the prostate, other possible causes are:

  • A secretory dysfunction of the prostate

  • Intraprostatic reflux

  • Instrumental manipulation of the urethra

Asymptomatic cases are more likely due to chronic prostatitis. It can also be acute prostatitis that turned into a chronic condition. Or it could be simply an imbalance in cytokine production that works similar to CPPS but is not as severe.

Either way, exploring the cause of asymptomatic prostatitis does not contribute much to the patient’s clinical assessment. This type of prostatitis does not require treatment. Thus, it is not necessary to know what causes asymptomatic prostatitis to treat the condition (1,2).

This approach may change in the future as clinical evidence shows the real dangers of asymptomatic prostatitis. Even if you don’t have symptoms, prolonged inflammation in the prostate may contribute to prostate cancer development. It may also contribute to future sexual dysfunction by impairing the mechanism of erection.

It may sometimes contribute to erectile dysfunction. Studies also suggest a correlation between lower urinary tract symptoms when patients have benign prostatic hyperplasia or another cause of enlarged prostate (7).

All of this data may contribute to future developments on the exact causes and risk factors of asymptomatic prostatitis as a foundational step to prevent its consequences.


Prostatitis causes are sometimes easy or quite difficult to trace. They depend on the type of prostatitis, and the most common cause is a bacterial infection. However, it is essential to know the origins of prostate infection to prevent and treat prostatitis.

In acute prostatitis, causes include urine reflux into the prostate ducts, urinary catheter placement, and bacterial spread. In chronic prostatitis, intraprostatic reflux also plays a significant role. However, these patients often have a change in prostate secretion. Their prostate fluid does not have a typical antibacterial substance. That’s why the infection remains for a very long period without a complete resolution.

Besides acute and chronic bacterial prostatitis, there’s also nonbacterial prostatitis. It is also known as chronic pelvic pain syndrome. In this case, different causes form together in one single place. It is very difficult to treat because there are many theories about its causes without a clear answer. Some studies mention that it is due to immune dysfunction.

Others argue that it has a nervous, neurologic, or even psychologic link. Others mention that it is related to low levels of testosterone. This syndrome is likely an interplay of different risk factors that increase pain sensitivity and trigger inflammation in this area.

Common symptoms in prostatitis are similar to those found in benign prostatic hyperplasia. They include urinary retention, frequent urination, and sometimes a burning pain when urinating. They depend on whether or not there’s an associated urinary tract infection.

However, we also need to mention asymptomatic prostatitis. In these cases, there is inflammation in the prostate, but the patient has no symptoms. Doctors diagnose the condition by chance, usually after a high PSA reading. This condition is not easy to reproduce in a study, and therefore patients usually don’t receive treatment.


  1. Khan, F. U., Ihsan, A. U., Khan, H. U., Jana, R., Wazir, J., Khongorzul, P., … & Zhou, X. (2017). Comprehensive overview of prostatitis. Biomedicine & Pharmacotherapy, 94, 1064-1076.
  2. Brede, C. M., & Shoskes, D. A. (2011). The etiology and management of acute prostatitis. Nature Reviews Urology, 8(4), 207.
  3. Wyndaele, J. J. (2002). Complications of intermittent catheterization: their prevention and treatment. Spinal cord, 40(10), 536-541.
  4. Cui, D., Han, G., Shang, Y., Mu, L., Long, Q., & Du, Y. (2015). The effect of chronic prostatitis on zinc concentration of prostatic fluid and seminal plasma: a systematic review and meta-analysis. Current medical research and opinion, 31(9), 1763-1769.
  5. Pontari, M. A., & Ruggieri, M. R. (2008). Mechanisms in prostatitis/chronic pelvic pain syndrome. The Journal of urology, 179(5), S61-S67.
  6. Krsmanovic, A., Tripp, D. A., Nickel, J. C., Shoskes, D. A., Pontari, M., Litwin, M. S., & McNaughton-Collins, M. F. (2014). Psychosocial mechanisms of the pain and quality of life relationship for chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS). Canadian Urological Association Journal, 8(11-12), 403.
  7. Urkmez, A., Yuksel, O. H., Uruc, F., Akan, S., Yildirim, C., Sahin, A., & Verit, A. (2016). The effect of asymptomatic histological prostatitis on sexual function and lower urinary tract symptoms. Archivos espanoles de urologia, 69(4), 185-191.

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