Candida is a genus of yeast, a type of fungus, that naturally resides on the skin and mucosal surfaces of the human body, including the gastrointestinal and genitourinary tracts. The presence of Candida in a urine sample, known as candiduria, is a common finding, particularly in hospital settings. Its detection can range from simple contamination of the sample to a severe systemic infection. Understanding the context of this yeast’s presence is important for determining the significance and the need for medical intervention.
Defining the Presence of Candida in Urine
The detection of Candida in a urine culture requires careful interpretation to distinguish between three possibilities: contamination, colonization, or true infection. Contamination occurs when yeast from the genital area or skin enters the specimen during collection, often resolved by repeating the collection with proper technique.
Colonization is a frequent finding where the yeast is present and multiplying within the urinary tract, often the bladder, but is not causing symptoms or actively invading the tissue. Most patients with candiduria fall into this asymptomatic category, where the overgrowth results from local factors.
A true Candidal Urinary Tract Infection (UTI) occurs when the Candida invades the lining of the urinary tract. This leads to symptoms such as painful urination, frequent urge to urinate, or suprapubic pain. This active infection, known as candidal cystitis (bladder) or pyelonephritis (kidneys), requires a different management approach than colonization.
Factors That Increase Candiduria Risk
Candiduria is strongly associated with underlying medical conditions and interventions that disrupt the body’s normal microbial balance and defenses. The most frequent contributing factor, especially in hospitalized patients, is the use of an indwelling urinary catheter. The catheter provides a surface for the Candida to adhere to and form a protective biofilm, shielding it from the immune system and antifungal agents.
Primary Risk Factors
- Poorly controlled diabetes mellitus, as high glucose levels and impaired immune function create a favorable environment for fungal growth.
- Recent or prolonged use of broad-spectrum antibiotics, which eliminate competing bacteria in the genitourinary tract.
- Immunocompromised status due to conditions like AIDS, cancer, or the use of immunosuppressive medications.
- Advanced age.
- Prolonged stays in intensive care units.
- Previous urological surgery or structural abnormalities within the urinary tract.
Diagnostic Testing and Interpretation
The initial step in evaluating the presence of Candida involves a standard urinalysis and urine culture. The urinalysis may reveal the presence of yeast cells and white blood cells, a finding known as pyuria, which suggests inflammation. Pyuria is not specific to Candida infection and can occur with colonization or other types of infection.
The definitive detection and identification of the yeast rely on culturing the urine sample, which includes growing the organism on specific laboratory media. The result is reported as Colony Forming Units per milliliter of urine (CFU/mL), which is a measure of the fungal burden. The interpretation of the CFU count for Candida is less straightforward than for bacteria and is not a reliable predictor of true infection.
In adults, a finding of \(10^{3}\) to \(10^{5}\) CFU/mL confirms candiduria, but the number alone cannot differentiate between colonization and infection. The diagnosis of a true candidal UTI relies more heavily on the presence of specific symptoms, like fever or flank pain, in conjunction with the positive culture. If the initial sample shows yeast, repeating the culture with a properly collected specimen is necessary to rule out simple contamination.
Managing and Treating Candidal Infections
The management of candiduria is primarily determined by whether the patient is experiencing symptoms and is based on the critical decision of treating colonization versus treating infection. For the majority of cases, which are asymptomatic colonization, antifungal treatment is typically not necessary. Instead, the focus is on removing or correcting the underlying predisposing factors that allowed the yeast to grow.
If an indwelling urinary catheter is present, the most effective intervention is its removal or replacement, which can resolve the candiduria in up to 50% of asymptomatic patients without any medication. Other corrective measures include achieving better control of blood sugar in diabetic patients and discontinuing any unnecessary antibiotic therapy.
For true symptomatic candidal UTIs, such as cystitis or pyelonephritis, antifungal medication is required. Fluconazole is generally the agent of choice because it achieves high concentrations in the urine and is available in an oral form. The recommended treatment for uncomplicated candidal cystitis is typically oral fluconazole at a dose of 200 mg daily for two weeks. Higher doses, such as 200 to 400 mg daily, may be used for more severe upper tract infections like pyelonephritis. In cases involving fluconazole-resistant species, such as Candida glabrata, alternative treatments like amphotericin B or flucytosine may be considered.