Funguria is common in hospitalized patients, and is generally benign. Invasive infection of the kidney is unusual, and is difficult to treat. The vast majority of fungal infections of the kidney and bladder result from Candida albicans and other Candida species. A variety of other fungi can rarely involve the kidney as a result of disseminated infection. These include:
- Aspergillus species
- Fusarium species
- Trichosporon species
- Mucorales (eg, Rhizopus, Mucor species)
- Dematiaceous molds
- Cryptococcus neoformans
- Dimorphic fungi (eg, Histoplasma capsulatum, Coccidioides species, Blastomyces dermatitidis, Paracoccidioides brasiliensis, Sporothrix schenckii, and Penicillium marneffei)
A review of Candida infections of the bladder and kidney will be presented here. Issues related to fungal peritonitis in patients treated with continuous peritoneal dialysis are presented separately. (See "Fungal peritonitis in continuous peritoneal dialysis".)
Mice or rabbits infected intravenously with fungi clear these organisms quickly from their bloodstream. Despite this ability, fungal multiplication is commonly found within the kidney, the only organ in which this appears to occur . Whether fungi preferentially localize in the kidney or are cleared from other organs more efficiently by host defense mechanisms is not understood.
In these animal models, the two key steps in the pathogenesis of fungal renal infection are the attachment of fungi to endothelial surfaces and penetration into tissue. Within five minutes of injection, yeast forms are found in the capillary beds of the kidneys. Since this elicits an inflammatory response, yeasts survive only if they penetrate the capillary walls and invade the interstitium. Invasion is expedited by attachment to the capillary walls via adherence mechanisms . Penetration through the capillary walls is facilitated by the formation of pseudohyphal or hyphal forms .