A 56-year-old man has experienced seven distinct incidents of cystitis over the previous 13 months. Each incident was characterized by mild dysuria, along with some frequency and urgency. Each was diagnosed as cystitis by detection of Gram negative bacilli in his urine, with urine counts ranging from 103 to 105 bacterial cells/mL. No efforts were made to identify the causative agents in the first two incidents, but in the other five, the lab managed to isolate the same strain of Proteus mirabilis from a urine specimen. A brief course of antibiotic treatment appeared to be effective in each incident, as the noticeable symptoms always subsided quickly. Nevertheless, the man is tired of these repeated incidents and goes to see if there is anything else his physician can do for him. A detailed history is taken, in which he indicates that he has sometimes experienced mild lower back pain during the past year or so, even though he had no prior history of this complaint. He may also be experiencing occasional perineal discomfort based on the signs and symptoms that he describes, but he cannot recall any other unusual problems. The man has no urinary symptoms at present, and the physical examination is entirely unremarkable. His vital signs are normal. There is no evidence of costovertebral angle tenderness and his prostate feels reasonably normal in size and consistency on palpation by digital rectal examination.

Question 4.1: What is your preliminary diagnosis?

Although it is now seen only infrequently in the U.S., chronic prostatitis should always be considered in men with a history of recurrent bacteriuria and/or cystitis (especially in middle-aged men). The fact that the last five incidents were caused by the same strain of Proteus mirabilis suggests either relapse of a continuing infection or some constant source of this bacterium that facilitates periodic re-infection of the bladder and the resulting cystitis. A chronically infected prostate is one of the likely sources of infection in these situations. Nepholithiasis and anatomic abnormalities of the renal tract must also be considered.

Question 4.2: How can you confirm your diagnosis?

To diagnose a suspected case of chronic prostatitis, you should take first-void, midstream, and postmassage urine specimens, as well as a specimen of prostatic expressate. All of these should be quantitatively cultured and evaluated for numbers of leukocytes.

Test Results

Gram stains of the urine specimens indicate the presence of Gram negative bacilli and numerous leukocytes (pyuria). The bacterial counts for all of the specimens are positive. The numbers of bacteria and leukocytes are significantly higher in the prostatic secretion and postmassage urine samples than in the first-catch and midstream urine samples. The laboratory is able to isolate a Gram-negative bacillus from each of the samples, and all of the isolates are identified as Proteus mirabilis. Additional tests indicate that it is the same strain that was detected in the previous five incidents of cystitits.

Question 4.3: Do the lab results support your diagnosis?

The lab results are consistent with a diagnosis of chronic prostatitis. Higher bacterial and leukocyte counts in the postmassage urine and prostatic secretion specimens are an excellent indicator of this disease. The finding of a bacterium known to frequently cause UTIs in both the urine and prostatic secretions helps to confirm the diagnosis. Most cases of chronic prostatitis do not produce many obvious symptoms, and the prostate usually feels normal on palpation. Perineal pain and/or obstructive symptoms appear in some patients, but the most reliable indicator appears to be pyuria. As noted earlier, a pattern of relapsing infection is also very suggestive.

Question 4.4: How should this condition be treated?

Antibiotic treatment promptly relieves the symptoms associated with acute exacerbations but is less effective in eradicating the focus of chronic infection in the prostate. The relative ineffectiveness of antimicrobial agents for long-term cure results in part from the poor penetration of the prostate by most of these drugs; the low pH that prevails in this organ precludes the passage of most agents. Fluoroquinolones such as ciprofloxacin and ofloxacin have been considerably more successful than other antimicrobial drugs, but they typically must be given for at least 12 weeks to be effective. Patients with frequent episodes of acute cystitis in whom attempts at curative therapy fail can be managed with prolonged courses of antibiotics (usually a sulfonamide, trimethoprim, or nitrofurantoin), with a view toward suppressing symptoms and keeping the bladder urine sterile. Total prostatectomy obviously results in the cure of chronic prostatitis but is associated with considerable morbidity. Transurethral prostatectomy is safer, but it cures only one-third of patients.

Question 4.5: How can Proteus be identified in the lab?

Proteus is a gram-negative rod and one of the Enterobacteriaciae. To summarize, the genera of Enterobacteriaciae exhibit fermentative metabolism, utilize glucose, produce catalase, do not produce oxidase, and reduce nitrates to nitrites. On blood agar, Proteus may have a characteristic "swarming" growth pattern. It will be oxidase negative. It will appear as growth of white colonies on MacConkey agar. It will be positive for H2S production. If it is indole positive, it is P vulgaris; P mirabilis is indole negative.

Question 4.6: What is the differential diagnosis for this man's condition? (What if the culture had been negative?)

Chronic nonbacterial prostatitis is more common than bacterial prostatitis. The cause is unknown. Symptoms simulate those of chronic bacterial prostatitis; WBCs and oval fat bodies are usually increased in prostatic secretions. However, a history of UTI is rare. Lower-tract localization cultures of urethral, bladder, and prostatic secretions are required for diagnosis to rule out a bacterial pathogen.

Hot sitz baths, anticholinergic drugs, and periodic prostatic massage (especially for congestive prostatitis) provide some symptomatic relief. Antibiotics do not relieve symptoms, but NSAIDs may be helpful.

Prostatodynia is a noninfectious, noninflammatory condition of younger men. The symptoms mimic those of prostatitis. Usually, no signs of infection or inflammation are present on examination of the urine or prostatic secretions. Treatment is empiric and supportive.