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Acute Bacterial Prostatitis and Prostatic Abscess

Last Updated: July 8, 2004
Synonyms and related keywords: ABP, acute prostatitis, prostatitis, prostate disease, bladder outlet obstruction secondary to benign prostatic hyperplasia, chronic bacterial prostatitis, nonbacterial prostatitis, abacterial prostatitis, prostatodynia, urinary tract infection in men, Escherichia coli, Proteus mirabilis, Klebsiella species, Enterobacter species, Pseudomonas aeruginosa, Serratia species

  AUTHOR INFORMATION  

Author: Michael Piesman, MD, Staff Physician, Department of Internal Medicine, Madigan Army Medical Center

Coauthor(s): Raymond A Costabile, MD, Jay Y Gillenwater Professor of Urology, University of Virginia Health System

Michael Piesman, MD, is a member of the following medical societies: American Medical Association

Editor(s): Edmund Sabanegh, MD, Chair, Assistant Professor, Department of Urology, Wilford Hall United States Air Force Medical Center; Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, Pharmacy, eMedicine; Laurence Klotz, MD, Professor, Department of Surgery, University of Toronto School of Medicine, Canada; J Stuart Wolf, Jr, MD, Director of Michigan Center for Minimally Invasive Urology, Associate Professor, Department of Urology, University of Michigan Medical Center; and Stephen W Leslie, MD, FACS, Founder and Medical Director, Lorain Kidney Stone Research Center, Clinical Assistant Professor, Department of Urology, Medical College of Ohio
  INTRODUCTION  

Acute prostatitis presents as an acute urinary tract infection in adult males. 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 a poorly understood disease entity due in part to its uncertain etiology and lack of clearly distinguishing clinical features.

Acute prostatitis usually is 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 prostatitis (ie, acute, chronic) accounted for 25% of outpatient urinary conditions. In 1985, according to Nickel, more office visits were for acute and chronic prostatitis than for 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: Prostatitis is an inflammation of the prostate gland. It may be infectious or inflammatory in origin. 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 mo) with variable voiding and sexual symptoms and/or no demonstrable infection

  • 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, 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% (Meares, 1998). The prevalence rate is 8%, although the rate varies from 6-44%, depending on the study (Meares, 1998).

The international prevalence rate is similar to that of 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 also are those responsible for most urinary tract infections. The most common causal organisms for ABP include the following: Escherichia coli, Proteus mirabilis, Klebsiella species, Enterobacter species, Pseudomonas aeruginosa, and Serratia species. Of these, E coli is involved most often.

Obligate anaerobic bacteria and gram-positive bacteria, other than enterococci, rarely cause ABP. Staphylococcus aureus infection may occur in the hospital due to prolonged catheterization. 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.

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. Due to 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

Clinical: ABP usually presents as an acute illness with moderate-to-high 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 avoid bacteremia and sepsis.
  INDICATIONS  

Prostatic abscess is a potential indication for surgery. Prostatic abscess is an infrequent but well-described complication of ABP. Medical management often is not successful. Transrectal or perineal aspiration of the abscess is preferred and often is 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 germs.

  RELEVANT ANATOMY AND CONTRAINDICATIONS  

Relevant Anatomy: The prostate is a retroperitoneal organ encircling 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: Performing a 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 and may cause gram-negative sepsis.

Due to the potential for systemic infection and bacteremia, urethral instrumentation should be avoided in ABP, especially if the patient is unstable or is already showing signs of sepsis.

Transurethral or perineal surgical approaches to treat 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 (Barozzi, 1998).


  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.
  • Occasionally, blood culture results may be positive.
  • Increased serum prostate-specific antigen (PSA) levels also are found but should not be used as a screening test for prostatitis.

Imaging Studies:

  • Imaging studies, including a CT scan of the pelvis or prostate ultrasonography, should be reserved for those cases where laboratory analysis is 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.

Diagnostic Procedures:

  • Performing a 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 and may cause 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 IV 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 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.

Surgical therapy: Surgical drainage of a prostatic abscess can be accomplished by either transrectal or perineal aspiration or transurethral resection. Because of the potential for systemic infection and bacteremia, urethral instrumentation should be avoided in ABP, especially if the patient is unstable or already showing signs of sepsis.

For 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 the development of a prostatic abscess. If easily passing the catheter is not possible, a suprapubic punch cystostomy is indicated.

Follow-up care: For excellent patient education resources, visit eMedicine's Prostate Health Center. Also, see eMedicine's patient education articles Understanding the Male Anatomy and Prostate Infections.

  COMPLICATIONS  

Prostatic abscess is an infrequent but well described complication of ABP. Although very rare, it most often 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 by transrectal ultrasound.

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 often is not successful. Transrectal or perineal aspiration of the abscess is preferred and often is 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 are progression to chronic prostatitis, septicemia, pyelonephritis, and epididymitis.

  OUTCOME AND PROGNOSIS  

If the initial response to medical therapy is favorable, then patient prognosis is very good. Decreased fertility has been reported, but only in cases of massive bacterial inoculation. A report of decreased sperm viability, including impaired motility and agglutination, was observed in samples containing 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 occur more commonly 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 evidence of prostatitis was found in nearly 50% of prostate specimens resected for prostate cancer, no causal association has been demonstrated (Meares, 1991).

The exact public health burden of prostatitis also should 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 on the basis of elevated serum PSA levels. These biopsies may trigger an inflammatory response in the prostate, leading to the development of 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.

  PICTURES  

Caption: Picture 1. Leukocytic infiltration of stroma and glandular lumina during acute bacterial prostatitis (ABP).
Click to see larger picture
Picture Type: Photo
  BIBLIOGRAPHY  

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