a. Urinary tract infections (UTI) are caused by the presence of pathogenic microorganisms in the urinary tract.

In most urinary tract infections, bacteria enter through the urethra and ascend to the bladder. Once established within the bladder, the bacteria are able to ascend through the ureters to the kidneys. Contamination of the urinary tract can occur in the following ways:

(1) Reflux of urine from the bladder, into the urethra, and back up into the bladder.

(2) Reflux of urine from the bladder into the ureters.

(3) Fecal contamination of the urinary meatus.

(4) Introduction of instruments for examination or catheterization.

b. Urinary tract infections may occur in the urethra (urethritis), the urinary bladder (cystitis), the prostate gland (prostatitis), and the kidney (pyelonephritis).

(1) Cystitis is more common in females because the female urethra is short and in close anatomical proximity to the vagina and rectum. The male urethra is longer, and the prostatic secretions have an antibacterial property that discourages passage of bacteria.

(2) Urethritis may be associated with cystitis, may occur as a result of trauma from a catheter or cystoscope, or may be sexually transmitted. If urethral discharge is present, with or without other symptoms, a urethral smear should be sent to the laboratory for analysis along with the standard urine culture.

(3) Pyelonephritis is an infection of the kidney’s renal pelvis, tubules, or interstitial tissue. It may occur as an acute or chronic condition. Pyelonephritis can result in renal insufficiency, which may lead to renal failure.

(4) Prostatitis is inflammation of the male prostate gland. Inflammation of the prostate commonly occurs without the presence of infection. However, bacterial invasion of the prostate may occur as a result of bacteria descending from the kidney or bacteria ascending from the urethra.

c. Certain factors predispose the urinary tract to infection:

(1) Urinary stasis.

(2) Obstructions to urine flow such as strictures or stones.

(3) Systemic infection, which may enter the kidney through the blood or lymph.

(4) The presence of other renal disease.