Porth's Essentials of Pathophysiology, 4e

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Disorders of the Bladder and Lower Urinary Tract

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may relieve signs and symptoms, and this approach is used as an adjunct to antimicrobial treatment. Recurrent lower UTIs are those that recur after treat- ment. They are due either to bacterial persistence or reinfection. 38 Bacterial persistence usually is curable by removal of the infectious source (e.g., urinary cath- eter or infected bladder stones). Reinfection is man- aged principally through education regarding pathogen transmission and prevention measures. Cranberry juice or blueberry juice has been suggested as a preventive measure for persons with frequent UTIs. Studies sug- gest that these juices reduce bacterial adherence to the epithelial lining of the urinary tract. 42 Because of their mechanism of action, these juices are used more appro- priately in prevention rather than treatment of an estab- lished UTI. Chronic UTIs are more difficult to treat. Because they often are associated with obstructive uropathy or reflux flow of urine, diagnostic tests usually are per- formed to detect such abnormalities. When possible, the condition causing the reflux flow or obstruction is corrected. Most persons with recurrent UTIs are treated with antimicrobial agents for longer periods of time in doses sufficient to maintain high urine lev- els of the drug, and they are examined for obstruction or other causes of infection. Men in particular should be investigated for obstructive disorders or a prostatic focus of infection. Infections in Special Populations Urinary tract infections affect persons of all ages. In infants, they occur more often in boys than in girls. After the first year of life UTIs occur more often in girls. Urinary tract infections are more common in women than men, specifically between 16 and 35 years of age, at which time women are 40 times more likely to develop a UTI than age-matched men. 35 This is because of the shorter length of the female urethra and because the vaginal vestibule can be easily contaminated with fecal flora. In men, the longer length of the urethra and the antibacterial properties of the prostatic fluid provide some protection from ascending UTIs until approxi- mately 60 years of age. 43 After this age, prostatic hyper- plasia becomes more common, and with it may come obstruction and increased risk for UTI (see Chapter 39). UrinaryTract Infections in Non-pregnant Women Approximately half of all adult women have at least one UTI during their lifetime. 37 The anterior urethra usually is colonized with bacteria; urethral massage or sexual intercourse can force these bacteria back into the bladder. Using a diaphragm and spermicide enhances the susceptibility to infection. 35,37 A nonpharmacologic approach to the treatment of frequent UTIs associated with sexual intercourse is to increase fluid intake before intercourse and to void soon after intercourse. This pro- cedure uses the washout phenomenon to remove bacte- ria from the bladder.

 UrinaryTract Infections in Pregnant Women

Pregnant women are at increased risk for UTIs. Normal changes in the functioning of the urinary tract that occur during pregnancy predispose pregnant women to UTIs. 44–46 These changes involve the collecting system of the kidneys and include dilation of the renal calyces, pel- ves, and ureters that begins during the first trimester and becomes most pronounced during the third trimester. Dilation of the upper urinary system is accompanied by a reduction in the peristaltic activity of the ureters that is thought to result from the muscle-relaxing effects of progesterone-like hormones and mechanical obstruction from the enlarging uterus. In addition to the changes in the kidneys and ureters, the bladder becomes displaced from its pelvic position to a more abdominal position, producing further changes in ureteral position. The complications of asymptomatic UTIs during preg- nancy include persistent bacteriuria, acute and chronic pyelonephritis, and preterm delivery of infants with low birth weight. Evidence suggests that few women become bacteriuric during pregnancy. Rather, it appears that symptomatic UTIs during pregnancy reflect preexist- ing asymptomatic bacteriuria and that changes occur- ring during pregnancy simply permit the prior urinary colonization to progress to symptomatic infection and invasion of the kidneys. Because bacteriuria may occur as an asymptomatic condition in pregnant women, it is recommended that a urine culture be obtained at the time of their first prenatal visit. 45,46 A repeat culture should be obtained during the third trimester. Women with bacteriuria should be followed closely, and infec- tions should be properly treated to prevent complica- tions. The choice of antimicrobial agent should address the common infecting organisms and should be safe for both the mother and fetus.  UrinaryTract Infections in Children Acute urinary tract infection is considered to be the most common serious bacterial infection in childhood, affecting as many as 8% of girls and 2% of boys dur- ing the first 7 to 8 years of life. 47,48 In girls, the average age at first diagnosis is 5 years or younger, with peaks during infancy and toilet training. 49 In boys, most UTIs occur during the first year of life and are more common in uncircumcised than in circumcised boys. 49 Vesicoureteral reflux (VUR), a common childhood disorder, is believed to predispose to UTI, with both VUR and UTI being associated with renal scarring and per- manent kidney damage. Most UTIs that lead to scarring and diminished kidney growth occur in children younger than 4 years, especially infants younger than 1 year of age. 49 The incidence of renal scarring is greatest in chil- dren with gross VUR or obstruction, in children with recurrent UTIs, and in those with a delay in treatment. Childhood UTIs usually are ascending, with inoc- ulation of feces from the urethra and periurethral