Genitourinary System Diseases

Viral Urinary Tract Infections

Viruses most commonly cause urinary tract infections in immunocompromised individuals.

Viruses occur in urine in healthy individuals and are rarely a cause for concern. While bacteria are the most prevalent causative agents of urinary tract infections (UTI), viral infections do occur, particularly in the ureter and bladder. Individuals receiving organ or stem cell transplantation who are immunocompromised as a result are the most susceptible to viral UTIs. Hemorrhagic cystitis, causing a painful inflamed bladder and blood in the urine, is the most common type of viral UTI.

Viruses responsible for urinary infections include adenovirus, BK virus, cytomegalovirus, and JC virus. Diagnosis of viral causative agents of UTIs is difficult. The viruses that can cause a UTI are not uncommon in healthy individuals, and shedding of viral particles in the urine occurs and is not diagnostic of an active local infection. Likewise, patients may have antibodies to the virus from previous subclinical infections, precluding the use of many immunological diagnostic techniques. Most of the UTI viruses can be cultured, though the time required to culture them is too long for practical clinical purposes.

With some precaution, the polymerase chain reaction (PCR) can provide a rapid and definitive diagnosis. Viruses have rapidly evolving genomes, necessitating that the primers used during PCR must be chosen carefully and regularly updated. Since PCR can detect even trace quantities of the target genetic sequence, a positive PCR result does not necessarily correspond to an active infection. Using PCR techniques that provide a quantitative assessment of the genetic load in a sample may allow differentiation of an active infection from stray viral shedding into the urine. The antiviral cidofovir is the first-line treatment for adenovirus, BK virus, and cytomegalovirus urinary tract infections.