Aetiology

Urinary tract infection (UTI) results from pathogenic organisms gaining access to the urinary tract and not being effectively eliminated. The bacteria ascend the urethra and generally have an intestinal origin; therefore, Escherichia coli causes most UTIs in men and women.[5][12][13][14]

Men, however, more frequently have UTI that is classified as complicated and associated with a varied group of causative organisms. Other gram-negative bacteria that cause UTI in men include Klebsiella, Proteus, and Providencia.[3][6][12][13][14] Gram-positive infections also occur in complicated UTI patients. A 5-year study involving male veterans demonstrated that 40% of community-acquired infections and 55% of inpatient infections resulted from organisms such as Enterococcus and Staphylococcus.[15] When UTI develops in patients in hospitals or long-term care facilities or as the result of indwelling catheters, Pseudomonas, Candida, and resistant organisms must be considered.[16][17]

Pathophysiology

UTI develops when the balance between host defence mechanisms and the virulence of the invading organism is distorted.[18] For example, men with immunodeficiency from HIV infection more often acquire UTI.[3][19] Another important defence mechanism is urine flow. Disruption of this defence often contributes to the development of UTI in men and results in a classification of complicated UTI. In general, complicated UTI occurs as a result of structural or functional abnormalities of the urinary tract that impair urine flow, such as:[1]

  • Prostate disorders

  • Calculi within the collecting system or the kidney

  • External drainage devices or internal devices such as stents

  • Urinary diversion surgeries

  • Vesicoureteral reflux

  • Neurogenic bladder disorders, including diabetes mellitus.

Available studies in men frequently identify impaired urine flow due to prostate hyperplasia, urinary calculi, or urethral stricture as a factor related to UTI.[16][20][21][22] Also, reviewing the epidemiology of UTI in men corroborates the hypothesis that altered urine flow is significant to the pathophysiology.

With ageing, the incidence of problems causing complicated UTI increases, and this corresponds to the increased incidence of UTI in older men. Structural or functional abnormalities of the urinary tract occur more frequently in older men.[13] The incidence of UTI in men is highest among those residing in long-term care facilities.[9]

Other risk factors include a history of anal intercourse, which is associated with urological symptoms and infection in both men and women.[23] In one study, UTI was more common amongst men who have sex with men, compared to men who have sex with women alone.[24]

Vaginal intercourse also may result in UTI if the vagina is colonised by pathogenic organisms.[19]

In summary, factors contributing to UTI development in men include alteration of the host defences, with altered urine flow contributing significantly.

Classification

Healthcare-associated versus community-acquired

Healthcare-associated (nosocomial) UTI implies acquisition of the pathogenic organism from within a healthcare facility, whereas community-acquired infection occurs without exposure to such a facility.

Complicated

Complicated UTI implies the presence of other factors that hinder the efficacy of therapy, such as:[1][2][3]

  • Structural or functional abnormalities of the urinary tract

  • Immunodeficiency (e.g., HIV infection)

  • Indwelling catheter

  • Infection due to resistant organisms.

UTIs in men are often complicated.

Recurrent

Recurrent UTI results from either persistence of an infection that is inadequately treated or the acquisition of a new infection.

Asymptomatic bacteriuria

Patients with ≥10⁵ CFU/mL in culture from a single specimen, but without dysuria, frequency, urgency, or suprapubic or costovertebral angle (CVA) pain, are classified as having asymptomatic bacteriuria.[4]

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