A 23-year-old woman is being evaluated for recurrent episodes of urinary tract infection. She has had 5 episodes of cystitis and an episode of pyelonephritis over the past year. The symptoms tend to occur a few days following sexual intercourse. The patient has no other medical problems and takes no medications. Her temperature is 36.7 C (98 F), blood pressure is 110/70 mm Hg, respirations are 16/min, and pulse is 65/min. Abdominal and genitourinary examinations are normal. Which of the following is the most likely predisposing factor for pyelonephritis in this patient?

Question

A 23-year-old woman is being evaluated for recurrent episodes of urinary tract infection.  She has had 5 episodes of cystitis and an episode of pyelonephritis over the past year.  The symptoms tend to occur a few days following sexual intercourse.  The patient has no other medical problems and takes no medications.  Her temperature is 36.7 C (98 F), blood pressure is 110/70 mm Hg, respirations are 16/min, and pulse is 65/min.  Abdominal and genitourinary examinations are normal.  Which of the following is the most likely predisposing factor for pyelonephritis in this patient?

Quizplus · Accepted Answer

The bacteria that usually cause urinary tract infections (UTIs) such as cystitis (bladder infection) and pyelonephritis (kidney infection) typically originate from fecal flora and include gram-negative rods (eg, Escherichia coli, Klebsiella, Proteus) and Enterococcus. In women, sexual intercourse facilitates bacterial ascent up the relatively short urethra and into the bladder, which has several antibacterial defenses, including: When these mechanisms are disrupted or overcome due to bacterial virulence factors (eg, fimbriae to facilitate attachment, capsule to resist phagocytosis), cystitis occurs. The normal vesicoureteral junction does not allow retrograde flow of urine. If there is an anatomic abnormality of this area or an increase in bladder pressure, some urine returns to the ureter, carrying any pathogens present in the bladder (vesicoureteral reflux). Frequent bladder infections, such as in this patient, may weaken the vesicoureteral junction and facilitate reflux. Without vesicoureteral reflux, the ascent of pathogens to the kidneys is very unlikely, and pyelonephritis does not occur. (Choice A) Frequent voiding may be a symptom of UTI but does not cause the infection. In fact, frequent urination may prevent UTIs by washing pathogens away. Frequency of sexual intercourse is an important risk factor for recurrent UTIs. (Choice B) Hematogenous bacterial spread is a possible cause of acute pyelonephritis. This mechanism is most significant in hospitalized, elderly, debilitated patients with multiple potential infectious sources or significantly weakened immune defenses. This patient is young and generally healthy with no signs of systemic infection or immunosuppression, making hematogenous spread very unlikely. (Choices C and D) Normal urethral flora microorganisms (lactobacilli, nonpathogenic staphylococci and streptococci) do not multiply readily in urine and generally do not cause infection. Suppression of this endogenous flora can occur in pregnancy, with antibiotic use, or during a systemic illness and may facilitate distal urethral colonization by pathogenic gram-negative rods. This may play an important role in the development of lower UTIs but generally is not sufficient to cause pyelonephritis. Educational objective: Suppression of endogenous flora, colonization of the distal urethra by pathogenic gram-negative rods, and attachment of these pathogens to the bladder mucosa are the stages of pathogenesis in lower urinary tract infections. Anatomic or functional vesicoureteral reflux is almost always necessary for the development of acute pyelonephritis.

A 23-Year-Old Woman Is Being Evaluated for Recurrent Episodes of Urinary