Recurrent lower urinary tract infections (UTIs) are a frequent problem in young women; 10% to 20% experience an episode of cystitis during adolescence. A short urethra that is in close proximity to vaginal and rectal flora predisposes women to these infections. Additional risk factors include sexual intercourse or diaphragm use in the previous 48 hours, not urinating after intercourse, and a history of UTIs. Escherichia coli is responsible for 75% to 90% of infections, Staphylococcus saprophyticus accounts for approximately 10%, and the remaining infections are caused by a variety of gram-negative organisms.
The patient described in the vignette has experienced four separate episodes of cystitis linked temporally to sexual activity. Single-dose, postcoital antibiotic prophylaxis (eg, nitrofurantoin 50 to 100 mg, trimethoprim-sulfamethoxazole 40 mg/200 mg, or cephalexin 250 mg) can reduce the risk of infection recurrence. The patient also should be advised to take the medication within 2 hours of intercourse and to urinate promptly after intercourse. Although daily antibiotic prophylaxis is effective in preventing cystitis, it usually is more costly and less convenient than postcoital therapy, and it may lead to the development of antibiotic-resistant organisms. Because postpubertal females who have uncomplicated cystitis associated with sexual intercourse rarely have urinary tract abnormalities, radiographic imaging or cystoscopy is not necessary.
Neinstein LS. Genitourinary tract infections. In: Adolescent Health
Care. A Practical Guide. 3rd ed. Baltimore, Md: Williams & Wilkins;
Stapleton A, Latham RH, Johnson C, Stamm WE. Postcoital antimicrobial
prophylaxis for recurrent urinary tract infection. A randomized,
double-blind, placebo-controlled trial. JAMA. 1990;264:703-706