Urinalysis in the diagnosis of urinary tract infections

Urinary tract infection is the commonest human bacterial infection. Bacteriuria alone does not appear to produce progressive renal damage or hypertension. However, it can produce considerable morbidity. Urinalysis is a simple, relatively sensitive, and reliable way of diagnosing urinary tract infection. It is not clear that routine screening should be performed in all patients, but pregnant females, patients with known anatomic abnormalities, and patients with recent genitourinary instrumentation should be screened. The major determinant of therapeutic success in patients with urinary tract infections is the anatomic site of infection. Superficial mucosal infection of the bladder is well treated with a single dose of an appropriate antibiotic, whereas deep tissue infection of the kidney or prostate should be treated with a prolonged and intensive course of therapy. Urinalysis is an insensitive tool in the localization of infection. However, the presence of white cell casts on the examination of the urinary sediment is pathognomonic of upper tract infection and would lead one to pursue an aggressive course of therapy. Examination of the concentrating ability is of limited help in this regard because of the wide range of overlap of concentrating ability in patients with upper and lower tract infections. In selected instances, urinalysis is of help in guiding therapy of urinary tract infections. This is particularly true of the patients with acute urethral syndrome where therapy is guided by the presence or absence of pyuria. Urinalysis, a simple front-line test, is of paramount importance in the evaluation and management of the patient with urinary tract infection.