Urinary Tract Infection (UTI) in Males Workup

Updated: Sep 19, 2017
  • Author: John L Brusch, MD, FACP; Chief Editor: Michael Stuart Bronze, MD  more...
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Workup

Approach Considerations

The workup of urinary tract infections (UTIs) is dependent on the suspected diagnosis; however, routine studies include urine studies, such as urinalysis, Gram staining, and urine culture. The threshold for establishing true UTI includes finding 2-5 or more white blood cells (WBCs) or 15 bacteria per high-power field (HPF) in a centrifuged urine sediment.

As with females, a positive nitrite test is poorly sensitive but highly specific for UTI, and false-positives are uncommon.

Proteinuria is commonly observed in UTIs, but the proteinuria is usually low-grade. More than 2g of protein per 24 hours suggests glomerular disease.

The older patient who appears toxic, has diabetes, or is immunocompromised may be at risk for emphysematous pyelonephritis; radiographic studies (eg, kidney, ureters, bladder [KUB]) may be necessary to exclude this possibility.

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Urine Studies

Urine specimens may be obtained by suprapubic aspiration, catheterization, or midstream clean catch. Most males can perform a midstream clean catch reasonably well, with a reliability approaching that of suprapubic aspiration. Uncircumcised men must retract the prepuce and cleanse the glans before obtaining a specimen. If the patient is unable to cooperate, a catheterized specimen or suprapubic aspiration is necessary.

Bacteriuria without pyuria suggests contamination or colonization. Pyuria without bacteriuria suggests nongonococcal urethritis (NGU), genitourinary tuberculosis, stone disease, or malignancy.

If a Gram stain of an uncentrifuged clean-catch midstream urine sample reveals the presence of 1 bacterium per oil-immersion field, this represents 10,000 bacteria/mL of urine. A specimen (5mL) that has been centrifuged for 5 minutes at 2000 revolutions per minute (rpm) and examined under high power after Gram staining allows for the identification of bacteria in lower numbers. In general, Gram staining has a sensitivity of 90% and a specificity of 88%.

Urine culture remains the criterion standard for the diagnosis of UTI. Collected urine should be immediately sent for culture; if not, it should be refrigerated at 4°C. Two culture techniques (dip slide, agar) are used widely and are accurate.

The exact number of bacteria in a urine culture that is needed to define UTI in a man is a bit controversial; generally, positive results are seen if there are more than 1000 colony-forming units (CFU)/mL of urine, much lower than the threshold for women. [6] However, most authors would accept a value of more than 10,000 CFU/mL. Some advocate the treatment of any pathogens growing in a patient with symptoms of UTI.

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Imaging Studies

Imaging and urologic intervention should be considered in the following patients:

  • Patients with a history of kidney stones, especially struvite stones, are candidates for urosepsis.
  • Patients with diabetes are susceptible to emphysematous pyelonephritis, and they may require immediate nephrectomy; persons with diabetes may also develop obstruction from necrotic renal papillae that are sloughed into the collecting system and obstruct the ureter.
  • Patients with polycystic kidneys are prone to abscess formation
  • Patients with tuberculosis are prone to developing ureteral strictures, fungus balls, and stones

Imaging in the emergency department is typically not necessary unless concomitant obstructive uropathy is suspected, as this is an emergent condition that requires prompt intervention. Modalities for this include ultrasonography, contrasted computed tomography (CT) scanning, or helical CT scanning of the urinary system (currently preferred by most experts).

Plain film imaging

Plain films may localize stone densities, but identification within the urinary tract cannot be confirmed. Uric acid and some struvite stones are radiolucent. Plain films provide no information about the renal parenchyma or function.

Ultrasonography

Measurement of the postvoid residual by bladder scan or ultrasonography should be performed on every patient admitted to the hospital for UTI. Its use may minimize the need for Foley catheter insertion.

Renal ultrasonography is a noninvasive study that requires no contrast and provides useful information about the renal parenchyma. This imaging modality can be performed at the bedside in a hemodynamically unstable patient, and it can help to detect hydronephrosis, pyonephrosis, and perirenal abscess. However, the quality of the study depends on the skill of the examiner; the study may be of little benefit in patients who are obese. Ureteral dilatation secondary to UTIs may mimic obstruction.

Transrectal ultrasonography is the study of choice to demonstrate a prostate abscess; [7] a CT or magnetic resonance imaging (MRI) scan may also be useful. Virtually all men older than 60 years have some prostatic calculi (see the CT scan below); however, no correlation exists between chronic prostatitis and the presence or absence of prostatic calculi.

Prostatic calcifications in a male with a urinary Prostatic calcifications in a male with a urinary tract infection.

Scrotal ultrasonography with Doppler interrogation and radionuclide scans can be helpful in equivocal cases to differentiate the causes of acute scrotum, including epididymitis, torsion of the spermatic chord, and torsion of a testicular appendage. Torsion of the spermatic cord must be assumed until proven otherwise, because necrosis can develop in less than 3 hours. Consultation with a urologist is mandatory in all but the most clear-cut cases of torsion, because the standard is to try to intervene in less than 3 hours.

CT scanning

Noncontrast helical CT scanning is the preferred diagnostic test for obstructive nephrolithiasis. CT scanning with contrast is the imaging study of choice, offering excellent information about the renal parenchyma and the collecting system. It is also a functional study when the excretory phase is included, which demonstrates the site and degree of obstruction very well.

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Histologic Findings

In acute bacterial prostatitis, inflammation is observed in part or all of the gland. This is characterized by marked infiltration with neutrophils and diffuse edema. Microabscesses may be present, and these may coalesce into larger collections.

The histology of chronic bacterial prostatitis is that of focal, nonacute inflammation; however, this finding is not diagnostic, because it may be observed in men without bacterial infection. Because chronic bacterial prostatitis may be a focal disease, needle biopsies may be unreliable. Occasionally, biopsies reveal a granulomatous prostatitis of unknown cause.

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Pyuria Workup

The most accurate method to measure pyuria is counting leukocytes in unspun fresh urine using a hemocytometer chamber; more than 10 WBCs/mL is considered abnormal. Examination for pyuria is a sensitive (80-95%), but nonspecific (50-76%), method of diagnosing UTI. WBC counts determined from a wet mount of centrifuged urine are not reliable measures of pyuria. An uncontaminated specimen is suggested by a lack of squamous epithelial cells.

White cell casts in urine specimens may be observed in conditions other than infection, and they may not be observed in all cases of pyelonephritis. If the patient has evidence of acute infection and white cell casts are present, the infection likely represents pyelonephritis. A spun sample (5mL at 2000rpm for 5min) is best used for evaluation of cellular casts.

The presence of leukocyte esterase on a dipstick test is a rapid screening for pyuria; it is 57-96% sensitive and 94-98% specific for identifying pyuria.

The nitrite test is a rapid screening test for bacteriuria; false-negative test results are seen in low-grade bacteriuria, but false-positive results are rare. A positive nitrite test has 27% sensitivity and 94% specificity for UTI when the cutoff is 100,000 CFU/mL.

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Prostatitis Workup

In acute bacterial prostatitis, most patients have pyuria and bacteruria, allowing the infecting organism to be isolated by midstream urine collection. Blood cultures, a complete blood count (CBC), and a basic metabolic panel should be obtained.

In chronic bacterial prostatitis, bacteria and leukocytes may or may not be observed in prostate-specific secretions (ie, expressed prostatic secretions [EPS] or a third midstream bladder specimen [VB3] postprostatic massage). More than 15 leukocytes/HPF is abnormal.

4-Glass test

Although the 4-glass test is the standard for the diagnosis of chronic prostatitis, it is used infrequently.

The 4-glass test was described by Meares and Stamey in 1968 to accurately localize bacteria (ie, urethra vs prostate). [3] One should obtain simultaneous cultures of: (1) urethral urine,(ie, first voided bladder specimen [VB1]); (2) midstream urine (ie, second midstream bladder specimen [VB2]); (3) EPS; and (4) VB3.

The tests should be performed when the patient does not have significant bacteruria, and the specimens must be quantitatively cultured immediately after collection.

If bacteruria is present, ampicillin, cephalexin, or nitrofurantoin should be given for 2-3 days to sterilize the urine; these agents are not effective against chronic bacterial prostatitis. If the number of bacteria in EPS ejaculate or VB3 exceeds that in VB1 or VB2 by at least 10-fold, the infection is prostatic in origin.

Premassage/postmassage test

A simpler procedure for the diagnosis of chronic prostatitis was suggested by Nickel. [8] In the premassage and postmassage test, urine is obtained before and after prostate massage. These specimens are sent for culture and sediment microscopy. If bacteria and leukocytosis in the postmassage specimen exceed those in the premassage specimen, category II prostatitis is suggested. Leukocytosis alone indicates category IIIA, whereas no bacteria or leukocytosis indicates category IIIB.

Postvoid residual urine volume measurement

Measurement of the postvoid residual urine volume may be helpful in the older patient for whom prostatism is suspected. Although this measurement is traditionally performed via catheterization, some institutions are now using ultrasonography for this measurement. [9] If the postvoid residual urine volume is elevated, then a urinary catheter must be placed and urologic consultation obtained.

Urodynamic studies

Chronic prostatitis may result in an element of bladder neck obstruction, which may be demonstrated by urodynamic studies and may be corrected with transurethral surgery. [1]

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Epididymitis and Orchitis Workup

In epididymitis, a microscopic examination of the urethral secretions is helpful only in cases with very mild symptoms, when torsion is not a consideration. Leukocytes and bacteria on a Gram stain would suggest epididymitis (unless the patient previously had a vasectomy).

Torsion of the spermatic cord and torsion of a testicular appendage would be the main differential diagnosis considerations. Spermatic cord torsion is normally diagnosed using ultrasonography, which is very sensitive and specific, or with surgical exploration. The latter does not alter the outcome of epididymitis if the testicle is inadvertently explored to pursue torsion.

Of patients with orchitis resulting from tuberculosis, 70% have other genitourinary or pulmonary symptoms of this disease. Testing urine for acid-fast bacilli (AFB), testing using purified-protein derivative (PPD), and performing chest radiography are helpful.

Testicular cancer is the most common malignancy in males aged 15-35 years. Although it usually presents as a painless intraparenchymal mass, 10% of cases present after minor trauma. For this reason, any patient felt to have a lesion within the parenchyma of the testicle should be referred for immediate urologic evaluation.

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Cystitis Workup

Microscopic hematuria is found in approximately 50% of cystitis cases; when microscopic hematuria is found without symptoms or pyuria, it should prompt a search for malignancy. Other conditions that should be considered include calculi, vasculitis, renal tuberculosis, and glomerulonephritis. In a developing country, hematuria is suggestive of schistosomiasis, which can be associated with salmonellosis and squamous cell malignancies of the bladder.

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Urethritis Workup

In younger men, differentiation of UTI from urethritis may necessitate a urethral smear and culture or urinary antigen testing for chlamydia and N gonorrhoeae.

For urethritis, a urethral swab obtained 1 hour after the last micturition is 95% sensitive and 99% specific for gonorrhea. Inflammatory cells without intracellular gram-negative diplococci suggest nongonococcal urethritis (NGU).

A small swab should be carefully inserted approximately 1 inch into the male urethra and rotated about its axis 5 times. The swab then should be withdrawn and immediately streaked onto either chocolate agar or Thayer-Martin/New York City media. The same swab then should be rolled onto a slide, which should then be heat-fixed and stained (ie, Gram stain). Importantly, roll the specimen on only a very limited part of the slide; this will make the microscopic search easier. The same swab then may be sent for chlamydia testing, although many public health facilities do not have the funds to test males for this disease.

Chocolate agar is heated blood agar; the heating causes the red blood cells (RBCs) to lyse, releasing their intracellular contents, thereby enhancing the recovery of fastidious organisms such as N gonorrhea. This media is perfectly suited for culturing the male urethra, which is normally sterile. Thayer-Martin and New York City agars have antibiotics (including vancomycin) incorporated into them, thereby limiting the growth of competing bacteria that may overgrow the gonococcus.

These media are perfect for culturing the female cervix, the pharynx, or the anus. They also can be used for the male urethra, although the vancomycin may actually inhibit the growth of the gonococcus, creating a false-negative culture result. All neisserial growths must be confirmed as gonorrhea with a quadFERM test (a 2h carbohydrate degradation method for detecting Neisseria species); gonorrhea will only change the color in the glucose well.

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