Acute Bacterial Prostatitis and Prostatic Abscess

Introduction

Acute prostatitis presents as an acute urinary tract infection in men. It is much less common than chronic prostatitis but is easier to identify because of its more uniform clinical presentation. Chronic prostatitis, which now has several classifications, is poorly understood partly because of its uncertain etiology and lack of clearly distinguishing clinical features.

Acute prostatitis is usually associated with predisposing risk factors, including bladder outlet obstruction secondary to benign prostatic hyperplasia (BPH) or an immunosuppressed state. This review focuses on acute bacterial prostatitis (ABP).

History of the Procedure

In 1978-1979, symptoms due to acute and chronic prostatitis accounted for 25% of outpatient urinary conditions. In 1985, according to Nickel, acute and chronic prostatitis accounted for more office visits than BPH or prostate cancer. Most of these visits were for chronic prostatitis. In the early 1990s, the diagnosis of prostatitis resulted in slightly more than 2 million office visits per year.

Problem

Pathologically, prostatitis is defined as an increased number of inflammatory cells within the prostate gland. The inflammatory process may be infectious or inflammatory in origin. The most common histologic pattern is a lymphocytic infiltrate in the stroma immediately adjacent to the prostatic acini.Prostatitis occurs in distinct forms that have separate causes, clinical features, and outcomes. Four clinical entities have been described: ABP, chronic bacterial prostatitis, nonbacterial or abacterial prostatitis, and prostatodynia.

The National Institutes of Health (NIH) classification and definition of the categories of prostatitis are as follows:

• Category I – ABP, ie, acute infection of the prostate
• Category II – Chronic bacterial prostatitis, ie, recurrent urinary tract infection and/or chronic infection of the prostate
• Category III – Chronic abacterial prostatitis/chronic pelvic pain syndrome, ie, discomfort or pain in the pelvic region for at least 3 months with variable voiding and sexual symptoms and/or no demonstrable infection (By definition, the syndrome becomes chronic after 3 mo.)
• Category IIIA – Inflammatory chronic pelvic pain syndrome, ie, white blood cells in semen and/or expressed prostatic secretions and/or third midstream bladder specimen
• Category IIIB – Noninflammatory chronic pelvic pain syndrome, ie, no white blood cells in semen and/or expressed prostatic secretions
• Category IV – Asymptomatic inflammatory prostatitis, ie, evidence of inflammation in biopsy samples, semen and/or expressed prostatic secretions, and no symptoms

Frequency

In 1998, a statewide survey in Wisconsin estimated the incidence of acute prostatitis at 6%. The prevalence rate is 8%, although the rate varies from 6-44%, depending on the study. Prostatitis is the most common urologic diagnosis in males younger than 50 years. It is the third most common diagnosis in men older than 50 years, after BPH and prostate cancer.

The international prevalence rate is similar to that in the United States. Of 600 men diagnosed with prostatitis, 5% had bacterial prostatitis, 64% had nonbacterial prostatitis, and 31% had pelvic-perineal pain syndrome or prostatodynia.

Etiology

Most infections (82%) involve only a single bacterial organism. Occasionally, 2 or 3 strains of bacteria may be involved. The organisms primarily responsible for ABP are also those responsible for most urinary tract infections. The most common causal organisms for ABP are gram-negative members of the Enterobacteriaceae family. They include Escherichia coli, Proteus mirabilis, Klebsiella species, Enterobacter species, Pseudomonas aeruginosa, and Serratia species. Of these, E coli is involved most often and has been shown to increase biofilm formation.

Obligate anaerobic bacteria and gram-positive bacteria other than enterococci rarely cause ABP. Enterococci account for 5-10% of documented prostate infections. Staphylococcus aureus infection due to prolonged catheterization may occur in the hospital. Other occasional causes include Neisseria gonorrhea, Mycobacterium tuberculosis, Salmonella species, Clostridium species, and parasitic or mycotic organisms. N gonorrhea should be suspected in sexually active men younger than 35 years.

If recurrent urinary tract infections are confirmed, patients need to be evaluated for structural abnormality.

Pathophysiology

Several theories exist regarding the pathogenesis of ABP.

• Intraprostatic urinary reflux: This theory is the most widely accepted. Infected urine refluxes into the ejaculatory and prostatic ducts that empty into the posterior urethra. Because of the anatomy of the prostate gland, ducts that drain glands in the large peripheral zone are positioned more horizontally than other prostatic ducts and, thus, facilitate the reflux of urine into the prostate. Consequently, most infections occur in the peripheral zone.
• Ascending urethral infection: In younger men, ascending urethral infection may occur following sexual intercourse. Meatal inoculation may occur during unprotected anal intercourse, instrumentation, and prolonged catheterization.
• Direct invasion or lymphogenous spread from the rectum
• Direct hematogenous infection
• The following are risk factors for ABP (all allow bacterial colonization):
  • Intraprostatic ductal reflux
  • Phimosis and redundant foreskin
  • Specific blood groups
  • Unprotected anal intercourse
  • Urinary tract infections  
  • Acute epididymitis
  • Indwelling Foley catheter and condom catheter
  • Transurethral surgery
  • Altered prostatic secretions

Clinical

ABP usually presents as an acute illness with moderate to severe fever, chills, low back and perineal pain, urinary frequency and urgency, nocturia, dysuria, and generalized malaise. Arthralgia and myalgia may accompany these symptoms. ABP also may result in acute urinary retention due to varying degrees of bladder outlet obstruction. The diagnosis of ABP is based primarily on clinical findings, in association with positive results on urinalysis and urine culture.

Rectal palpation usually reveals an enlarged, exquisitely tender, swollen prostate gland, which is firm, warm, and, occasionally, irregular to the touch. Care must be taken to avoid vigorous prostatic massage in a patient with suspected ABP to prevent bacteremia and sepsis.

Sexual dysfunction is described as a symptom of chronic prostatitis and chronic pelvic pain syndrome. Pain associated with ejaculation (which translates to impaired overall quality of life) contributes to or causes erectile dysfunction.

Indications

Prostatic abscess is a potential indication for surgery. Prostatic abscess is an uncommon but well-described complication of ABP. Medical management is often not successful.Transrectal or perineal aspiration of the abscess is preferred and is often effective, especially if symptoms do not improve after 1 week of medical therapy. Transurethral resection of the prostate and drainage of the cavity is another approach. However, this approach is less desirable because of the potential hematogenic spread of bacteria.

Relevant Anatomy

The prostate is an extraperitoneal organ that encircles the neck of the bladder and urethra and weighs approximately 20 g in a healthy man. The adult prostate is divided into 4 distinct zones or regions: the periurethral, central, transitional, and peripheral. Carcinoma arises more often in the peripheral zone. However, the distribution of prostatic inflammation among the various zones is not clear.

Histologically, the prostate gland is composed of tubuloalveolar glands. The glandular spaces are lined by epithelium, which is composed of 2 layers of cells, a basal layer of low cuboidal epithelium covered by a layer of columnar mucus-secreting cells. The glands have a distinct basement membrane and are separated by a fibromuscular stroma.

Contraindications

Prostate biopsy is contraindicated in patients with suspected ABP because of the potential complication of seeding the bacterial infection in adjacent organs. Furthermore, prostate biopsy is extremely painful without a prostatic nerve block. Current practice is to anesthetize the area prior to core biopsy sampling. Biopsy in the face of ABP may result in gram-negative sepsis.

Because of the potential for systemic infection and bacteremia, urethral instrumentation should be avoided in patients with ABP, especially if the patient is unstable or is already showing signs of sepsis, although placement of a small drainage catheter is safe in experienced hands. Pretreatment with appropriate antibiotics is mandatory.

Transurethral or perineal surgical approaches in the treatment of a prostatic abscess should be undertaken with caution and currently are not advised unless other drainage techniques have failed. Perineal incision can cause impotence due to nerve injury, and transurethral resection can elicit hematogenous spread of bacteria, leading to sepsis.

Workup

Lab Studies

• Prostatic secretions contain large numbers of leukocytes and fat-laden macrophages.
• Urinalysis, which shows leukocytes, and a positive result on urine culture are essential for diagnosis. The urine specimen should include premassage and postmassage of the prostate. This test is known as the 2-glass test. If the patient is febrile or exhibits signs of ABP, massage should not be performed.
• Urethral swab culture and postmassage urine culture and microscopic examination may be an alternative standard protocol to simplify the evaluation of prostatitislike syndrome in the clinical practice.
• Occasionally, blood culture results may be positive.
• Serum prostate-specific antigen (PSA) levels are also increased but should not be used as a screening test for prostatitis. In the setting of ABP, PSA has little to no clinical value. If the PSA level is obtained and elevated, the study should be repeated 30-60 days after adequate treatment. Recent studies showed that a 2- to 4-week treatment with antibiotics decreased the PSA levels in approximately half of patients with PSA levels in the gray zone who did not have prostatitis symptoms.
• Urodynamics: Because prostatitis may cause irritative and obstructive voiding symptoms that mimic other primary causes of those symptoms, the use of urodynamics helps to avoid misdiagnosis of prostatitis.

Imaging Studies

Imaging studies, including a CT scan of the pelvis or transrectal ultrasonography, should be reserved for cases in which laboratory analysis findings are equivocal or when no improvement is observed following medical therapy. Ruling out complications of prostatitis (eg, prostatic abscess) is a strong indication to proceed to imaging studies. Transrectal ultrasonography can be very useful in diagnosing and draining prostatic abscesses.

Diagnostic Procedures

Prostate biopsy is contraindicated in suspected ABP because of the potential complication of seeding the bacterial infection in adjacent organs. Furthermore, prostate biopsy is extremely painful without a prostatic nerve block. Current practice is to anesthetize the area prior to core biopsy sampling to make the procedure comfortable. Biopsy in the face of ABP may result in gram-negative sepsis.

Histologic Findings

A stromal leukocytic infiltrate may be accompanied by increased prostatic secretion or leukocytic infiltration within gland spaces. When complicated by abscess formation, focal or larger areas of the prostate become necrotic.

Treatment

Medical therapy

The intense inflammation in ABP makes the prostate gland highly responsive to antibiotics, which otherwise penetrate poorly into the prostate. Hospitalization is required for patients in whom acute urinary retention develops and in those who require intravenous antimicrobial therapy.

The choice of antibiotic is based on results of the initial culture and sensitivity. However, initial therapy should be directed at gram-negative enteric bacteria. Useful agents include fluoroquinolones, trimethoprim-sulfamethoxazole, and ampicillin with gentamicin. Antipyretics, analgesics, stool softeners, bed rest, and increased fluid intake provide supportive therapy. A Foley catheter can be inserted gently for drainage if severe obstruction is suspected. A punch suprapubic tube can be used if a catheter cannot be passed easily or is not tolerated by the patient. The catheter can be removed 24-36 hours later.

If the initial clinical response to therapy is satisfactory and the pathogen is susceptible to the chosen antibiotic, treatment is continued orally for 30 days to prevent sequelae such as chronic bacterial prostatitis and prostatic abscess formation.

For intravenous therapy, use trimethoprim-sulfamethoxazole (Bactrim), 8-10 mg/kg/d (based on the trimethoprim component) in 2-4 intravenous doses bid, tid, or qid until the culture and sensitivity results are known. An alternate regimen is gentamicin with ampicillin 3-5 mg/kg/d IV (gentamicin dose divided tid and 2 g ampicillin divided qid). After the patient is afebrile for 24 hours, an appropriate oral agent can be substituted for an additional 30 days.

For oral therapy, use trimethoprim-sulfamethoxazole (Bactrim), 160 mg of trimethoprim and 800 mg of sulfamethoxazole, PO bid for 30 days. Use levofloxacin (Levaquin) 500 mg PO bid; ciprofloxacin, 500 mg PO bid; norfloxacin, 400 mg PO bid; ofloxacin, 400 mg PO bid; or enoxacin, 400 mg PO bid for 30 days when clinical response is favorable.

Alpha-blocker therapy should also be considered. Because the bladder neck and prostate are rich in a receptors, alpha blockade may improve outflow obstruction and diminish intraprostatic urinary reflux (terazosin 5 mg/d PO for 4-52 wk).¹Tamsulosin (Flomax) and alfuzosin (UroXatral) are acceptable alternatives.

Because of the limitation of alpha-blockers, clinical trials are ongoing using combination of alpha-blockers and 5-alpha-reductase inhibitors.

Surgical therapy

A prostatic abscess can be surgically drained with either transrectal or perineal aspiration or transurethral resection. Because of the potential for systemic infection and bacteremia, urethral instrumentation should be avoided in patients with ABP, especially if the patient is unstable or already showing signs of sepsis. In patients with sepsis, transurethral resection may be life-saving and should be considered if they are not responding to conservative therapy.

In patients with acute urinary retention, a Foley catheter may be attempted first as tolerated by the patient. However, it may cause extreme discomfort. In some cases, the transurethral catheter may obstruct drainage of an acutely inflamed prostate and cause bacteremia or prostatic abscess. If the catheter is not easy to pass, a suprapubic punch cystostomy is indicated.

Complications

Prostatic abscess is an uncommon but well-described complication of ABP. Although very rare, it usually occurs in patients who are immunocompromised, patients who have diabetes, patients with urethral instrumentation or prolonged indwelling urethral catheters, or patients on maintenance dialysis. Coliform bacteria, especially E coli, cause more than 70% of prostatic abscesses. A prostatic abscess should be suspected when worsening clinical symptoms follow an initial favorable response to treatment of ABP or a fluctuant mass is developing in the prostate gland. The presence of the abscess is confirmed with transrectal ultrasonography.

Once an abscess is diagnosed, anaerobic antimicrobial therapy should be added to the treatment regimen. Clindamycin intravenously at 600-900 mg q8h or orally at 150-450 mg q8h is a good choice. However, medical management is often unsuccessful. Transrectal or perineal aspiration of the abscess is preferred and is often effective, especially if symptoms do not improve after 1 week of medical therapy. Transurethral resection of the prostate and drainage of the cavity is another approach. Recurrent abscesses are rare. The abscess should be allowed to drain and should be monitored closely if a spontaneous rupture occurs into the urethra.

Other potential sequelae of ABP include progression to chronic prostatitis, septicemia, pyelonephritis, and epididymitis.

Outcome and Prognosis

If the initial response to medical therapy is favorable, the patient’s prognosis is very good. Decreased fertility has been reported, but only in cases of massive bacterial inoculation. Decreased sperm viability, including impaired motility and agglutination, was reported in samples that contained more than 10⁶ colony-forming units (CFU)/mL.

Future and Controversies

Despite the fact that prostatitis syndromes are common disease processes in urology, little is known about chronic prostatitis and the factors associated with the condition. Several important questions need to be answered, including the following:

• Is prostatitis associated with prostate cancer?
• What are the natural history and the epidemiology of prostatitis?
• What is the best way to elucidate the exact etiology, diagnosis, and management of prostatitis?

The first question is important considering the recent efforts to find the most accurate and most expedient method of diagnosing and treating prostate cancer. Prostatitis is more common in younger men, whereas BPH and prostate cancer are more common in men older than 50 years. An important research question is whether prostatitis in younger men leads to the development of BPH or prostate cancer later. Although one study reported that nearly 50% of prostate specimens resected for prostate cancer showed evidence of prostatitis, no causal association has been demonstrated.

The exact public health burden of prostatitis should also be addressed. Most urologists agree about the ever-growing need for both community-based cross-sectional and longitudinal epidemiological prostatitis studies. Active research and a more aggressive effort are needed to generate hypotheses regarding the etiology of prostatitis.

Formulating risk factors associated with prostatitis is important. For example, the incidence of prostatitis among men with a history of a prostatic biopsy requires investigation. With increased screening for prostate cancer, more men are undergoing biopsy based on elevated serum PSA levels. These biopsies may trigger an inflammatory response in the prostate, leading to prostatitis, or, alternatively, a biopsy may be a source of transmission of organisms into the prostate gland.

These examples outline potential research directions in the field of prostatitis. Results of these and other studies could promote an increased awareness of the disease and increase the knowledge about prostatitis. This research should improve diagnosis and treatment, promote an appropriate allocation of resources to the management of the disease, and reduce the incidence and public health burden of prostatitis.