What is the diagnosis and treatment for an elderly, possibly diabetic or immunocompromised, patient with a urinary tract infection (UTI) showing yeast hyphae, white blood cells, epithelial cells, casts, hyalin casts, and calcium oxalate crystals, but no bacterial growth on culture?

Fungal Urinary Tract Infection (Candiduria)

Diagnosis

This urinalysis pattern—yeast hyphae with white blood cells, epithelial cells, casts (including hyalin casts), calcium oxalate crystals, and no bacterial growth—indicates a fungal urinary tract infection (candiduria), most likely caused by Candida species. 1, 2

Key Diagnostic Features Supporting Fungal UTI:

• Yeast hyphae presence is the critical finding that distinguishes fungal from bacterial infection and represents active fungal colonization or infection 3
• White blood cells (pyuria) indicate an inflammatory response to the fungal pathogen 3
• Negative bacterial culture with symptomatic presentation points toward non-bacterial etiology 2
• Epithelial cells and casts suggest upper urinary tract involvement and tissue response to infection 3
• Calcium oxalate crystals are incidental findings unrelated to the infection itself 3

Critical Risk Factor Assessment:

Before initiating treatment, identify if the patient has:

• Diabetes mellitus (major risk factor for candiduria) 2, 4
• Indwelling urinary catheter (most common risk factor) 2, 4
• Recent broad-spectrum antibiotic use 2, 4
• Immunosuppression (corticosteroids, chemotherapy, transplant) 4, 5
• Urinary obstruction or urological abnormalities 2, 4

Treatment Decision Algorithm

Step 1: Determine if Treatment is Indicated

Treatment is ONLY indicated if the patient has symptomatic infection. 2, 4

Treat if ANY of the following are present:

• Recent-onset dysuria, frequency, or urgency 6, 7
• Fever, systemic signs, or hemodynamic instability 7, 8
• Neutropenia 2
• Planned urologic procedure 2
• Flank pain or costoverteboral angle tenderness (suggesting pyelonephritis) 2

Do NOT treat if:

• Patient is asymptomatic (asymptomatic candiduria) 2, 4
• Only agitation or delirium without urinary symptoms (assess alternative causes first) 8

Step 2: First-Line Antifungal Treatment

Fluconazole is the treatment of choice for symptomatic fungal UTI because it achieves high urinary concentrations. 1, 2

Recommended fluconazole regimen:

• Oral fluconazole 200-400 mg daily for 7-14 days 1, 2
• Single-dose therapy is insufficient for UTI (unlike vaginal candidiasis) 2
• Fluconazole is effective against most Candida species including C. albicans, C. parapsilosis, and C. tropicalis 1

Step 3: Alternative Treatment Options

If fluconazole cannot be used (resistance, allergy, or treatment failure):

• Amphotericin B deoxycholate is the alternative agent 2
• Bladder irrigation with amphotericin B for localized cystitis 4
• Single intravenous dose of amphotericin B may be considered 4

Important caveat: Echinocandins and other azoles do NOT achieve adequate urinary concentrations and should be avoided for isolated urinary tract candidiasis 2

Step 4: Address Underlying Risk Factors

The majority of candiduria cases resolve when underlying risk factors are corrected: 4

• Remove or change indwelling urinary catheter if present 2, 4
• Discontinue unnecessary broad-spectrum antibiotics 2, 4
• Optimize diabetes control if applicable 2, 4
• Relieve urinary obstruction if identified 2, 4

Special Considerations for Elderly or Immunocompromised Patients

Renal Function Assessment:

• Calculate creatinine clearance before prescribing any antifungal, as renal function declines approximately 40% by age 70 7
• Fluconazole dosing may require adjustment in severe renal impairment 7

Warning Signs Requiring Aggressive Treatment:

• Disseminated candidemia (positive blood cultures) requires systemic antifungal therapy beyond urinary-focused treatment 5
• Fungus-ball formation causing ureteric obstruction may require endourological intervention 5
• Pyelonephritis or prostatitis requires longer treatment duration (14-21 days) 2

Critical Pitfalls to Avoid

• Do not treat asymptomatic candiduria in non-neutropenic, non-surgical patients—this only promotes antifungal resistance without improving outcomes 2, 4
• Do not rely on colony count to determine treatment need; intensity of fungal growth does not correlate with clinical significance 4
• Do not use echinocandins for isolated urinary candidiasis as they achieve inadequate urine levels 2
• Do not assume Candida krusei susceptibility—this species is inherently resistant to fluconazole and requires alternative therapy 1

Monitoring and Follow-Up

• Assess clinical response within 48-72 hours of initiating antifungal therapy 6
• Repeat urine culture after treatment completion to document mycological clearance 2
• Obtain fungal culture with susceptibility testing if initial treatment fails to guide alternative therapy 1, 2