Examination of specimens of urine, blood, and genitourinary secretions or exudates commonly directs the subsequent urologic workup and frequently establishes a diagnosis. Since approximately 20% of patients who visit a primary physician's office have a urologic problem, it is important for the physician to have a broad knowledge of the laboratory methods available to test appropriate specimens. Judicious use of such tests permits rapid, accurate, and cost-effective determination of the probable diagnosis and directs the management of patients with urologic disease.
*Originally written by Karl J. Kreder Jr, MD, & Richard D. Williams, MD.
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 ...