Urinary tract infections

Drug Store News, Dec 11, 1989

Urinary Tract Infections

Dec. 11, 1989, lesson 679-401-89-12

Goal

To provide practicing pharmacists with current knowledge of the terminology, etiology, clinical presentation, medical diagnosis and drug therapies of urinary tract infections.

Objectives

1. Identify proper definitions for the following: urinary tract, urinary tract infection, (UTI) significant bacteriuria, cystitis, prostatitis, urethritis, pyelonephritis, acute urethral syndrome, pyuria, dysuria, complicated UTI, recurrent UTI, relapse UTI, reinfection, asymptomatic bacteriuria, frequency and urgency. 2. Recognize defense mechanisms which prevent UTI. 3. Recommend proper treatment for the UTI listed in objectives 1. 4. Recognize correct single dose, conventional and prophylactic drug therapies.

Urinary tract infections (UTI) are the most frequent form of urologic pathology observed in the ambulatory patient and hospitalized setting. UTI, next to infections of the upper respiratory tract, are the most commonly diagnosed infections. This is clearly an area where pharmacists can continue to provide significant contributions to therapeutic monitoring, rational antibiotic prescribing and patient compliance and education.

Terminology

This article will commence with certain definitions which are key to an understanding of UTI drug therapy. The urinary tract (UT) is the urethra, prostate gland (in males), urinary bladder, ureters and the kidneys. A UTI is a microbial invasion of tissues of the tract extending from the renal cortex (outer layer) to urethral meatus (opening). Significant bacteriuria provides for the diagnosis of UTI and refers to the finding of 105 bacteria (or greater) per ml of urine obtained by a midstream, clean-catch.

Asymptomatic bacteriuria is when 105 (or more) bacteria per ml of urine are present. Acute urethral syndrome or symptomatic abacteriuria is seen in patients who do not have significant bacteriuria but who have UTI symptoms (frequency, urgency dysuria).

Cystitis is inflammation of the urinary bladder. Prostatitis is inflammation of the prostate gland. Urethritis is inflammation of the urethra. Pyelonephritis is an upper UTI inflammation of the kidney and its pelvis (the funnel-shaped upper part of the ureter). Pyuria is the presence of pus cells in the urine.

Dysuria is painful or difficult urination. Frequency is the number of times the patient urinates. Urgency is when the patient feels the need to urinate. A complicated UTI is from a congenital abnormality or distortion of the urinary tract. Recurrent UTI is the recurrence of an infection in a given patient which is either a relapse or reinfection. Relapse UTI is a recurrent UTI which is an invasion by the same specific serotype of bacteria present in the previous infection. Reinfection is a recurrent UTI which is the result of a completely different bacteria or same bacteria but of a different serotype.

Incidence

UTI predominate in women and girls. The female is more susceptible to UTI due to the short urethra which is a short distance for bacteria travel into the bladder. The incidence rate for UTI in school girls is approximately 1.2 percent, by age 18 it is 5 percent. The childbearing age appears to have an even greater UTI incidence. The pyelonephritis of pregnancy and "honeymoon cystitis" account for this increase. The actual increase in female UTI is estimated at 1 to 2 percent per decade of life. Ten percent of women will have UTI by age 70.

UTI are uncommon in men except in the first year of life after age 50. This is probably due to a long urethra and a prostatic fluid which has antibacterial properties. During the first year of life congenital urologic anatomical abnormalities predispose to UTI. After age 50 enlargement (hypertrophy) of the prostate, kidney stones and urologic manipulation produce an increased incidence: 50-69 years, 0.6 percent; 60-69 years, 1.5 percent; and greater than 70 years, 3.6 percent.

Pathogenesis

Bacteria can invade the UT by 3 routes: the ascending (bacteria ascend the urethra into the bladder), hematogenous (bacteria enters through the bloodstream) and the lymphatic.

The most common is the ascending route. The bacterial source is a fecal reservoir of enteric bacteria. This has been confirmed by a high correlation between etiologic bacteria in the urine and those cultured from a rectal swab. The female urethra is usually colonized with these enteric bacteria and the bacteria can easily ascend into the bladder and then pass into the kidneys via the ureters.

This bacterial ascent can be due to sexual intercourse. The bacteria located on the perineum and vaginal vestibule can be mechanically transferred by the male to the female urethra. "Urethral milking," an intensified peristaltic activity of the female urethra during intercourse, transports bacteria into the bladder. Any mechanical trauma such as the insertion of a cystoscope or urinary catheter can also directly induce bacteria.

The second method previously mentioned in which bacteria invade the UT is the hematogenous spread of organisms. This descending route appears to occur very rarely in humans. A possible example could be an infected renal abscess where organisms spread from the blood.