Urinalysis is one of the most important and useful urologic tests available, yet all too often, the necessary details are neglected and significant information is overlooked or misinterpreted. Reasons for inadequate urinalyses include (1) improper collection, (2) failure to examine the specimen immediately, (3) incomplete examination (eg, most laboratories do not perform a microscopic analysis unless it is specifically requested by the provider), (4) inexperience of the examiner, and (5) inadequate appreciation of the significance of the findings.
The necessity of routine urinalysis as a screen in asymptomatic individuals, those admitted to hospitals, or those undergoing elective surgery continues to be debated. Numerous studies indicate that in these situations, urinalysis is not routinely necessary (Godbole and Johnstone, 2004). However, patients presenting with urinary tract symptoms or signs should undergo urinalysis. Studies also indicate that, if macroscopic urinalysis (dip-strip) is normal, microscopic analysis is not necessary. If the patient has signs or symptoms suggestive of urologic disease, or the dip-strip is positive for protein, heme, leukocyte esterase, or nitrite, a complete urinalysis, including microscopic examination of the sediment, should be carried out (Simerville et al, 2005).
It is best to examine urine that has been properly obtained in the office. First-voided morning specimens are helpful for qualitative protein testing in patients with possible orthostatic proteinuria and for specific-gravity assessment as a presumptive test of renal function in patients with minimal renal disease due to diabetes mellitus or sickle cell anemia or in those with suspected diabetes insipidus. Evaluation of sequential morning specimens may be required to obviate the variability often encountered. Urine specimens that are obtained immediately after the patient has eaten or that have been left standing for a few hours become alkaline and thus may contain lysed red cells, disintegrated casts, or rapidly multiplying bacteria; therefore, a freshly voided specimen obtained a few hours after the patient has eaten and examined within 1 hour of voiding is most reliable. The patient's state of hydration may alter the concentration of urinary constituents. Timed urine collections may be required for definitive assessment of renal function or proteinuria.
Proper collection of the specimen is particularly important when patients have hematuria or proteinuria or are being evaluated for urinary tract infection. Examination of a urine specimen collected sequentially during voiding in several containers may help to identify the site of origin of hematuria or urinary tract infection. To gather consistent and meaningful urinalysis data, urine must be collected by a uniform method in the physician's office or laboratory. The specimen should be obtained before a genital or rectal examination in order to prevent contamination from the introitus or expressed prostatic secretions. Urine obtained from a condom, chronic catheter, or intestinal conduit drainage bag is not a proper specimen for urinalysis.
It is usually simple to collect a clean-voided midstream urine sample from men. Routine instructions may be printed on a sheet given to the patient or placed on the lavatory wall. The procedure should include (1) retraction of the foreskin (a common source of contamination of the specimen) and cleansing of the meatus with benzalkonium chloride or hexachlorophene, (2) passing the first part of the stream (15–30 mL) without collection, and (3) collecting the next or midstream portion (approximately 50–100 mL) in a sterile specimen container, which is capped immediately afterward. A portion of the specimen is prepared immediately for both macroscopic and microscopic examination, and the rest is saved in the sterile container for subsequent culture if this proves necessary.
With this midstream clean-catch method, the likelihood that the specimen will be contaminated by meatal or urethral secretions is markedly decreased, although not completely eliminated. In adult males, it is rarely necessary to collect urine by catheterization unless urinary retention is present.
The best method for collecting a clean-voided midstream specimen from a woman is as follows: (1) the patient is placed on the examining table in the lithotomy position; (2) the vulva and urethral meatus are cleansed with benzalkonium chloride or hexachlorophene; (3) the labia are separated; and (4) the patient is instructed to initiate voiding into a container held close to the vulva. After she has passed the first 10–20 mL of urine, the next 50–100 mL is collected in a sterile container that is immediately capped. Because this technique requires considerable effort, it is acceptable to have the patient provide an initial specimen in a nonsterile container in the office lavatory. If results of urinalysis are normal, no further study is indicated; if abnormal, a urine specimen must be obtained by the more exacting technique. In either case, the specimen should be prepared for immediate examination.
If a satisfactory specimen cannot be obtained by the method described earlier, one should not hesitate to obtain a specimen by catheterization to eliminate nonvaginal sources of abnormal urinary constituents.
Urine for analysis, other than bacterial cultures, can be obtained from males or females by covering the cleansed urethral meatus with a plastic bag; a urine specimen for culture may require catheterization or suprapubic needle aspiration. In girls, catheterization with a small catheter attached to a centrifuge tube is appropriate, but boys should not be routinely catheterized. It is often preferable in either sex to proceed with suprapubic needle aspiration. This is easier if the patient has been previously hydrated, so that the bladder is full. Suprapubic needle aspiration is performed as follows. (1) Cleanse the suprapubic area by sponging with alcohol. (2) With a small amount of local anesthetic, raise an intradermal wheal on the midline 1–2 cm above the pubis (the bladder lies just above the pubis in young children). (3) Attach a 10-mL syringe to a 22-gauge needle. Insert the needle perpendicularly through the abdominal wheal into the bladder wall, maintaining gentle suction with the syringe so that urine will be aspirated as soon as the bladder is entered.
Macroscopic examination of urine often provides a clue when diagnosis is difficult.
Urine is often colored owing to drugs: phenazopyridine (Pyridium) will turn the urine orange; rifampin will turn it yellow-orange; nitrofurantoin will turn it brown; and l-dopa, α-methyldopa, and metronidazole will turn it reddish-brown. Red urine does not always signify hematuria. A red discoloration unassociated with intact erythrocytes in the urine can result from betacyanin excretion after beet ingestion, phenolphthalein in laxatives, ingestion of vegetable dyes, concentrated urate excretion, myoglobinuria due to significant muscle trauma, or hemoglobinuria following hemolysis. In addition, Serratia marcescens bacteria can cause the “red diaper” syndrome. However, whenever red urine is seen, hematuria must be ruled out by microscopic analysis. Cloudy urine is commonly thought to represent pyuria, but more often the cloudiness is due to large amounts of amorphous phosphates, which disappear with the addition of acid, or urates, which dissolve with the use of alkali. The odor of urine is rarely clinically significant.
The specific gravity of urine (normal, 1.003–1.030) is often important for diagnostic purposes: that of patients with significant intracranial trauma may be low owing to a lack of antidiuretic hormone (vasopressin); that of patients with primary diabetes insipidus is <1.010 even after overnight dehydration; that of patients with extensive acute renal tubular damage is consistently 1.010 (similar to the specific gravity of plasma); and a low specific gravity can be an early sign of renal damage from conditions such as sickle cell anemia. Urine specific gravity is the simplest time-honored test for evaluating hydration in postoperative patients. The specific gravity of urine may affect the results of other urine tests: in dilute urine, a pregnancy test may be falsely negative; in concentrated urine, protein may be falsely positive on dip-strips yet unconfirmed on quantitative tests. The specific gravity of urine may be falsely elevated by the presence of glucose, protein, artificial plasma expanders, or intravenous contrast agents.
Studies of specific-gravity reagent strips (method based on ionic alteration of a polyelectrolyte solution) have shown the method to be rapid, reliable, and unaffected by elevated amounts of glucose or contrast medium; however, alkaline pH may falsely lower the result (0.005 per pH unit >7.0). In the routine office setting, these strips are as reliable as either the hydrometer or refractometer methods.
Chemically impregnated reagent strips are accurate and have simplified routine urinalysis greatly. However, they must be monitored routinely by appropriate standardized quality-control reagents. The dip-strips are reliable only when not outdated and when used with room temperature urine.
The pH of urine is important in a few specific clinical situations. Patients with uric acid stones rarely have a urinary pH >6.5 (uric acid is soluble in alkaline urine). Patients with calcium stones, nephrocalcinosis, or both may have renal tubular acidosis and will be unable to acidify urine pH <6.0. With urinary tract infections caused by urea-splitting organisms (most commonly Proteus species), the urinary pH tends to be >7.0. It should be reemphasized that urine obtained within 2 hours of a large meal or left standing at room temperature for several hours tends to be alkaline. The indicator paper in most dip-strips is quite accurate; however, confirmation by a pH meter is occasionally required.
Dip-strips containing bromphenol blue can be used to determine the presence of >10 mg/dL protein in urine, but persistent proteinuria detected in this manner requires quantitative protein testing for confirmation. The dip-strip measures primarily albumin and is not sensitive to Bence-Jones proteins (immunoglobulins). Concentrated urine may give a false-positive result, as will urine containing numerous white blood cells (leukocytes) or vaginal secretions replete with epithelial cells. Orthostatic proteinuria can be demonstrated by detecting elevated protein levels in a urine specimen obtained after the patient has been in the upright position for several hours, whereas normal levels are found before ambulation. Prolonged fever and excessive physical exertion are also common causes of transient proteinuria.
Persistently elevated protein levels in the urine (>150 mg/24 h) may indicate significant disease. Therefore, specific quantitative protein tests, electrophoretic studies of the urine, or both may be required to determine the specific type of protein that is present.
The glucose oxidase–peroxidase tests used in dip-strips are quite accurate and specific for urinary glucose. False-positive results may be obtained when patients have ingested large doses of aspirin, ascorbic acid, or cephalosporins. An occasional patient has a blood glucose level below 180 mg/dL and yet has significant glucosuria; this indicates a low renal threshold of glucose excretion. However, most patients with a positive reading have diabetes mellitus.
The dip-strip test for hemoglobin is not specific for erythrocytes and should be used only to screen for hematuria, with microscopic analysis of the urinary sediment used for confirmation. Free hemoglobin or myoglobin in the urine may give a positive reading; ascorbic acid in the urine can inhibit the dip-strip reaction and give a false-negative result. Note that dilute urine (<1.008) will lyse erythrocytes and thus provide a positive dip-strip reading for hemoglobin but no visible erythrocytes on microscopic analysis.
Test strips to determine the number of bacteria (nitrite) or leukocytes (leukocyte esterase) as predictors of bacteriuria are as accurate as microscopic sediment analysis in studies using quantitative urine cultures as the standard. The nitrite reductase test depends on the conversion of nitrate to nitrite. Many of the bacteria responsible for urinary tract infections, particularly enterobacteria, are capable of reducing nitrate to nitrite and, therefore, detectable by this test. When the nitrite test is positive, it suggests the presence of >100,000 organisms per milliliter; however, several factors can lead to false-negative results. The nitrite test is positive only for coagulase-splitting bacteria, and thus, when used alone it is only 40–60% accurate. Urine must be in the bladder for a sufficient time before sampling for the reduction of nitrate to occur (>4 hours); therefore, this test is most likely to be positive when first-voided morning urine is tested. A false-negative test will also result if the bacteria present do not contain nitrate reductase or if dietary nitrate is absent. A false-negative nitrite study may occur in a patient taking vitamin C. The leukocyte esterase test is a widely used chemical test that depends on the presence of esterase in granulocytic leukocytes. The leukocyte esterase test is an indication of pyuria and will remain positive even after the leukocytes have degenerated. The test accurately identifies patients with 10–12 leukocytes per high-power field in a centrifuged specimen. Although this test is a good indicator of pyuria, it does not detect bacteriuria. Therefore, it is often combined with the nitrite test to detect both bacteriuria and inflammation to maximize the chances of predicting urinary tract infection. Used together, the two tests are as predictive as the microscopic analysis but not as accurate as a urine culture. A false-negative leukocyte esterase study can be caused by glucosuria, or by phenazopyridine hydrochloride (Pyridium), nitrofurantoin, vitamin C, or rifampin in the urine.
To be most accurate, the microscopic sediment examination should be done personally by an experienced physician or technician. Early-morning urine is the best specimen if it can be examined within a few minutes of collection. In most cases, the sediment can be prepared as follows: (1) centrifuge a 10-mL specimen at 2000 rpm for 5 minutes; (2) decant the supernatant; (3) resuspend the sediment in the remaining 1 mL of urine by tapping the tube gently against a countertop; and (4) place one drop of the mixture on a microscope slide, cover with a coverslip, and examine first under a low-power (10×) lens and then under a high-power (40×) lens. For maximal contrast of the elements in the sediment, the microscope diaphragm should be nearly closed to prevent overillumination. Significant elements (particularly bacteria) are more easily seen if the slide is stained with methylene blue, but staining is not essential. Figure 5–1 shows typical findings in the urinary sediment.
Microscopic examination of urine sediment. (Redrawn after Todd–Sanford–Davidson.)
The significance of bacteria in the urinary sediment is discussed in Section “Bacteriuria.”
Just as the presence of bacteria in the sediment is not an absolute indication of infection, neither is the finding of pyuria. In the sediment from clean-voided midstream specimens from men and those obtained by suprapubic aspiration or catheterization in women, a finding of more than five leukocytes per high-power field is generally considered abnormal (pyuria). If the patient has symptoms of a urinary tract infection as well as pyuria and bacteriuria, one is justified in making a diagnosis of infection and initiating empiric therapy. However, in female patients with symptoms of urinary tract infection, 60% of those with pyuria will have no bacterial growth from bladder urine obtained by catheterization or suprapubic aspiration emphasizing the need for confirmation by bacterial cultures.
Renal tuberculosis can cause “sterile” acid pyuria and should be considered in any patient with persistent pyuria and negative results on routine bacterial cultures. Specific fluorescent staining of the urinary sediment for acid-fast bacteria can be diagnostic; however, results will be positive from the sediment of spot specimens in only approximately 50% of patients with renal tuberculosis, whereas they are positive in the sediment of 24-hour specimens in 70–80% of such cases. Mycobacterium smegmatis, a commensal organism, may be present in the urine (particularly in uncircumcised men) and can give false-positive results on acid-fast stains.
Urolithiasis can also cause pyuria. In patients with persistent pyuria, the physician should consider obtaining at least a plain x-ray of the abdomen and possibly a CT urogram to determine whether urolithiasis is present. Similarly, a retained foreign body such as a self-induced bladder object or a forgotten internal ureteral stent can cause pyuria. A plain x-ray (KUB film) of the abdomen should reveal the offender.
The presence of even a few erythrocytes in the urine (hematuria) is abnormal and requires further investigation. Although gross hematuria is more alarming to the patient, microscopic hematuria is no less significant. Infrequent causes of hematuria include strenuous exercise (long-distance running), vaginal bleeding, and inflammation of organs near or directly adjoining the urinary tract, for example, diverticulitis or appendicitis. Hematuria associated with cystitis or urethritis generally clears after treatment. Persistent hematuria in an otherwise asymptomatic patient of either sex and any age signifies disease and is an indication for further testing. Studies indicated that approximately 20% of patients with hematuria will eventually be diagnosed with bladder cancer (Messing and Vaillancourt, 1990).
In patients with microscopic hematuria, a three-container method for collection of urine can provide information on the site of origin of erythrocytes. (1) Give the patient three containers, labeled 1, 2, and 3 (or initial, mid, and final). (2) Instruct the patient to urinate and to collect the initial portion of the urine stream (10–15 mL) in the first container, the middle portion (30–40 mL) in the second, and the final portion (5–10 mL) in the third. (3) Using methods described previously, centrifuge the three specimens individually, prepare slides of the urinary sediment (with or without staining), and examine the slides microscopically. If erythrocytes predominate in the initial portion of the specimen, they are usually from the anterior urethra; those in the final portion are generally from the bladder neck or posterior urethra; and the presence of equal numbers of erythrocytes in all three containers usually indicates a source above the bladder neck (bladder, ureters, or kidneys). It is important to collect the urine before physical examination (particularly before rectal examination in men) to avoid misleading results.
The three-container test may not be necessary in patients with gross hematuria, since the patients (men in particular) can usually tell the physician which portion of the stream contains the darkest urine (ie, the most erythrocytes). A specific dysmorphic erythrocyte configuration that can be detected with phase-contrast microscopy or by particle analyzer study of the urinary sediment and is highly indicative of active glomerular disease (Figure 5–2) can be useful. This dysmorphism is thought to be a result of extreme changes in osmolality and the high concentration of urinary chemical constituents affecting erythrocytes during passage through the kidney tubules. An automated system, iQ200, has been shown to be highly accurate for detecting, enumerating, and sizing erythrocytes in urine (Wah et al, 2005).
Left: Dysmorphic erythrocytes in urine (arrows), viewed under light microscopy (magnification ×400). Right: Dysmorphic erythrocytes in urine (identical field), viewed under phase-contrast microscopy. (Reproduced, with permission, from Stamey TA, Kindrachuk RW: Urinary Sediment and Urinalysis: A Practical Guide for the Health Science Professional. WB Saunders, Philadelphia, PA, 1985.)
Squamous epithelial cells in the urinary sediment indicate contamination of the specimen from the distal urethra in males and from the introitus in females; no other significance should be placed on them. It is not uncommon to find transitional epithelial cells in the normal urinary sediment; however, if they are present in large numbers or clumps and are abnormal histologically (including large nuclei, multiple nucleoli, and an increased ratio of nucleus to cytoplasm), they are indicative of a malignant process affecting the urothelium (Figure 5–3).
Papanicolaou-stained bladder cytology specimens. A: Normal cells (left) and malignant cells (right). B: High-power view of malignant cells. C: Papillary cluster of malignant cells. (Courtesy of Larry Kluskens, MD, Cytopathology Laboratory, University of Iowa.)
Casts are formed in the distal tubules and collecting ducts, for the most part, are not seen in normal urinary sediment; therefore, they commonly signify intrinsic renal disease.
Although leukocyte casts have been considered suggestive of pyelonephritis, they are not an absolute indicator and should not be used as the sole criterion for diagnosis. Leukocyte casts must be distinguished from epithelial cell casts, because the latter have little significance when present in small numbers. The distinction can be made easily if a small amount of acetic acid is added under the coverslip to enhance nuclear detail. (Note that casts tend to congregate near the edges of the coverslip.) Epithelial cell or leukocyte casts in large numbers signify underlying intrinsic renal disease requiring further diagnostic workup. In renal transplant recipients, an increase in the number of epithelial cells or casts from the renal tubules may be an early indication of acute graft rejection.
Erythrocyte casts are pathognomonic of underlying glomerulitis or vasculitis. Hyaline casts probably represent a mixture of mucus and globulin congealed in the tubules; in small numbers, they are not significant. Hyaline casts are commonly seen in urine specimens taken after exercise and in concentrated or highly acidic urine specimens. Casts are rarely seen in alkaline urine and are therefore not usually present in urine specimens that have been left standing or in specimens from patients unable to acidify.
Granular casts most commonly represent disintegrated epithelial cells, leukocytes, or protein; they usually indicate intrinsic renal tubular disease.
The finding of crystals in urine can be helpful in some instances, but the mere presence of crystals does not indicate disease. Crystals form in normal urine below room temperature. Cystine, leucine, tyrosine, cholesterol, bilirubin, hematoidin, and sulfonamide crystals are abnormal findings of varying importance. Several types of crystals that may be found on microscopic examination of urinary sediment are shown in Figure 5–1.
The use of protease inhibitors for treatment of human immunodeficiency virus (HIV) has resulted in urolithiasis due to indinavir crystal formation in urine. The characteristic crystals are flat, rectangular plates, often in a fan or starburst pattern. The presence of trichomonads or yeast cells in the stained or unstained smear of sediment from a properly obtained urine specimen establishes a diagnosis and the need for treatment.
Artifacts present in the urine sediment can be difficult to differentiate from real abnormalities. Dirt and small pieces of vegetable fiber or hair are frequently found, but the most common artifacts are starch granules from examination gloves.
A presumptive diagnosis of bacterial infection may be made on the basis of results of microscopic examination of the urinary sediment. If several bacteria per high-power field are found in a urine specimen obtained by suprapubic aspiration or catheterization in a woman or in a properly obtained clean-voided midstream specimen from a man, a provisional diagnosis of bacterial infection can be made and empiric treatment started. The findings should be confirmed by bacterial culture. Finding several bacteria per high-power field in a voided specimen from a woman is of little significance. Methods using flow cytometry-based urine analysis (UF-50) can detect bacteria with nearly 80% accuracy.
The presumptive diagnosis of bacterial infection based on microscopic examination of the urinary sediment should be confirmed by culture.
Indications and interpretation
Cultures can be used to estimate the number of bacteria in the urine (quantitative cultures), to identify the exact organism present, and to predict which drugs will be effective in treating the infection. Cultures are particularly important in patients with recurrent or persistent infections, renal insufficiency, or drug allergies.
The number of bacteria present in the urine (colony count) is influenced by the method used to collect the urine specimen, the patient's hydration status, and whether the patient has been taking antimicrobial drugs. The concept that urinary tract infection is present only when the urine specimen contains 105 or more bacteria per milliliter is not an absolute rule; a lower count does not exclude the possibility of an infection, particularly in a symptomatic patient. Cultures with growth of multiple organisms usually signify contamination. The presence of a few organisms in a specimen with a low specific gravity is more significant than the same finding in a specimen with a high specific gravity, because the former is more dilute.
Identifying the drugs to which the bacteria are sensitive may or may not be necessary. Escherichia coli, which causes 85% of “routine” urinary tract infections, is known to be sensitive to numerous oral antimicrobial drugs. However, in patients with septicemia, renal insufficiency, diabetes mellitus, or suspected enterococcal, Proteus, or Pseudomonas infections, it is important to determine the antibiotic sensitivity of the organism and the drug concentration necessary for efficacious treatment. Monitoring antibiotic levels in blood and urine during treatment may be indicated, especially in severely ill patients and those receiving highly toxic drugs. These measurements can be done by most hospital laboratories.
Rapid tests for bacteriuria
In general, seriously ill or hospitalized patients with urinary tract infections should have cultures processed by an accredited bacteriology laboratory. However, for “routine” infections encountered in office practice, there are many satisfactory, cost-effective testing methods.
Rapid methods to screen for bacteria include growth-independent systems and growth-dependent systems. Several growth-dependent systems are available. One measures the turbidity of urine incubated in a broth medium for several hours. Positive results can be determined in as short a time period as 4 hours; however, 12 hours of growth is required before a test sample can be regarded as negative. A single non–growth-dependent screening test uses the leukocyte esterase test and the nitrite test. If both tests are positive, the specificity increases to 98–99.5%, which indicates probable urinary tract infection (Young and Soper, 2001).
Reliable culture methods involve use of small strips or glass slides coated with eosin–methylene blue agar on one side and nutrient agar on the other. The strips or slides are dipped in the urine specimen and then incubated for 24 hours. Although these methods are easy to use, their disadvantages are that (1) not all bacteria will grow under these conditions and (2) the accuracy of colony counts is debatable.
Perhaps, preferable for the physician's office (but still subject to some of the same limitations) is use of a divided plastic culture plate with blood agar on one side and deoxycholate agar on the other. A known amount of urine is inoculated onto the agar on each side of the plate, and colony counts are determined at 24–48 hours. The numbers of bacteria in 1 mL of the original urine specimen can be determined by multiplying the number of colonies by the volume (in milliliters) and dilution (if any) of the inoculum. If antibiotic sensitivity testing is also desired, an additional culture plate can be inoculated and small antibiotic-impregnated disks placed on the agar. Zones of growth inhibition seen around the disks at 12–24 hours indicate sensitivity.
Cultures for tuberculosis
A microscopic examination (fluorescent stain) that shows acid-fast bacilli can give a presumptive diagnosis of urinary tuberculosis. The rapidity of recovering mycobacteria in culture depends somewhat on the patient's bacillary load. Thus, if the smear is highly positive (3–4+), cultures would become positive in 1–2 weeks. At that time, a DNA culture probe can be done for tuberculosis. It should be noted that the probe cannot distinguish between tuberculosis and patients treated with bacillus Calmette-Guérin (BCG); if the patient had not received BCG treatment, then Mycobacterium tuberculosis infection is likely. The total time from receipt of the specimen to presumptive diagnosis is typically about 2 weeks. Susceptibility tests, if positive for tuberculosis, would require another week.
Many other tests of urine can be helpful in determining the presence of urologic disease.
The evaluation of voided or bladder wash (barbotage) urine for bladder urothelial cancer cells has been quite successful for high-grade tumors and carcinoma in situ with sensitivity ranging from 38% to 51% and specificity between 81% and 100% (Konety, 2006; Mowatt, 2010). Lower grade tumors less commonly shed abnormal cells and cytology is relatively insensitive in this setting. Urinary cytology is fairly interpreter dependent and detection of cancer can be improved by collection of fresh urine samples that are not given in the early morning, barbotage samples, and collection of multiple samples (at least three consecutive specimens). Cystoscopy remains the standard diagnostic test for initial diagnosis and surveillance of bladder cancer.
Bladder tumor antigen test
The bladder tumor antigen test (BTA; Bard Diagnostic Sciences, Inc, Redmond, WA, and Polymedco, Inc, Cortland Manor, NY) is an assay for the detection of bladder tumor antigen (human complement factor H related protein) in the urine. The BTA-TRAK test is quantitative assay and the BTA-STAT test is its qualitative, point of care counterpart. Both are more sensitive than cytology (especially for low-grade cancers) but less specific. The greatest utility of these tests is in surveillance of patients already diagnosed with bladder cancer, although they are Food and Drug Administration (FDA) approved for diagnostic use. The BTA test is unreliable in patients with active infection and those that have received intravesical therapy.
Nuclear matrix protein 22
The nuclear matrix protein 22 test (NMP22; Matritech, Inc, Newton, MA) is an immunoassay. Normal subjects will have low levels of NMP22 in the urine, whereas patients with active transitional cell carcinoma may have high levels of urinary NMP22 (Grossman et al, 2005). Like BTA testing, other urologic conditions can increase NMP22 levels in the absence of bladder cancer (Boman et al, 2002). Compared with cytology, NMP22 is more sensitive for detecting low-grade tumors but is equivalent in the detection of high-grade cancers. It is FDA approved for the diagnosis of bladder cancer (most effective in high-risk populations) and surveillance for known bladder cancer. NMP22 is unable to accurately detect recurrent disease in patients with urinary diversion.
The ImmunoCyt test (Diagnocure, Quebec City, Canada) is an immunocytochemical test using fluorescent labeled antibodies to three markers found on exfoliated malignant urothelial cells: 19A211 a high-molecular-weight carcinoembryonic antigen and mucins LDQ10 and M344. It is done in conjunction with cytology to improve sensitivity in detection of low-grade urothelial tumor recurrence.
UroVysion Florescence in situ hybridization (FISH)
The UroVysion FISH test (Abbott Laboratories, Abbott Park, IL) detects increased copy numbers of chromosomes 3, 7, 17, and deletions at 9p21. Using a panel of abnormalities, it is useful in the diagnosis of bladder cancer (especially in patients with hematuria) and for surveillance in patients with known cancer. Like other bladder tumor markers, it can improve upon the sensitivity of urine cytology. Unlike other tests, UroVysion FISH can be used in monitoring patients who have undergone intravesical chemotherapy (Mengual et al, 2007) Additionally, barbotage should be avoided because of an increase in false-positive readings and only voided urine samples should be sent for analysis.
The characteristics of these bladder cancer tests and others are compared in Table 5–1 (Konety, 2006; Konety and Getzenberg, 2001; Mowatt, 2010).
Table 5–1. Comparison of Different Urine Tests for Bladder Transitional Cell Carcinoma. |Favorite Table|Download (.pdf)
Table 5–1. Comparison of Different Urine Tests for Bladder Transitional Cell Carcinoma.
Recent studies have identified a novel biomarker, prostate cancer antigen 3 (PCA3), that is measured in voided urine sediment after prostate massage. PCA3 is a noncoding messenger RNA (mRNA) overexpressed in prostate cancer cells by 60–100-fold, and its use is currently experimental. At this time, it appears to be useful in helping to decide if men with a negative first biopsy and high suspicion of prostate cancer should undergo repeat biopsy (Remzi et al, 2010). The role of PCA3 as a population-based screening test and its ability to predict prostate cancer in men with an elevated prostate-specific antigen (PSA) is currently under investigation.
Tests for abnormalities in adrenal hormone secretion are important in the workup of patients with suspected adrenal tumors. Pheochromocytoma and neuroblastoma can be detected by measuring the excretion of vanillylmandelic acid. However, serum and urinary levels of metanephrine, epinephrine, and norepinephrine are more sensitive indicators, particularly in cases of pheochromocytoma. Although high levels of aldosterone in urine usually indicate an aldosterone-secreting tumor, drug interference may cause false-positive or false-negative results. Other adrenocortical tumors may be detected by their production of elevated levels of urinary 17-ketosteroids.
Studies of Stone Constituents
Patients with recurrent urolithiasis may have an underlying abnormality of excretion of calcium, uric acid, oxalate, magnesium, or citrate. Samples of 24-hour urine collections can be tested to determine abnormally high levels of each. A few patients may have elevated cystine levels in urine. The nitroprusside test, a simple qualitative screening test for cystine, may indicate the need for quantifying cystine levels in timed urine collections. Whenever a stone is recovered, a formal stone analysis is recommended.
In patients with suspected fistulas of the urinary tract and bowel (eg, cancer of the colon, diverticulitis, and regional ileitis), discoloration of the urine after ingestion of a poorly absorbed dye such as phenol red will confirm the diagnosis. In an equally satisfactory test for fistulas, the patient is instructed to ingest gelatin capsules filled with granulated charcoal and to submit a urine sample several days later. Examination of the centrifuged urinary sediment will reveal the typical black granules if a fistula is present. In patients with suspected vesicovaginal fistulas, intravesical instillation of methylene blue or indigo carmine dye with resultant blue staining of a vaginal tampon can assist in diagnosis.