Urine KOH Preparation is NOT a Standard Procedure for Diagnosing Urinary Yeast Infections in Children
KOH (potassium hydroxide) preparation is a diagnostic technique used for identifying fungal elements in skin, nail, or vaginal specimens—not urine specimens—and is not part of standard urinary tract infection evaluation in children. 1
Why KOH Prep is Not Used for Urine
KOH preparation is specifically designed for vaginal discharge specimens to diagnose vulvovaginal candidiasis, where a sample is diluted in 10% KOH solution and examined microscopically for yeast or pseudohyphae 1
For suspected urinary yeast infections in children, standard urine culture is the appropriate diagnostic test, not KOH preparation 2, 3
Correct Diagnostic Approach for Suspected Urinary Yeast Infection
Specimen Collection in a 2-Year-Old
Obtain urine by urethral catheterization or suprapubic aspiration for culture in non-toilet-trained children, as these methods minimize contamination 1, 4
Discard the first few milliliters obtained by catheter and collect only subsequent urine in the sterile vessel to avoid urethral flora contamination 1
Never use bag collection for culture due to extremely high false-positive rates (70% specificity, resulting in 85% false-positive rate) 1, 5
Laboratory Testing
Request standard urine culture with fungal culture if Candida infection is suspected, particularly in high-risk neonates or children with indwelling catheters 2, 3
Urinalysis should be performed first to look for pyuria (≥10 WBCs) and bacteriuria, though fungal elements may occasionally be noted on microscopy 1
Candida species in urine are most commonly associated with instrumentation (catheters) or systemic candidemia in high-risk newborns requiring intensive care 2
When to Suspect Urinary Candidiasis
Candidal urinary tract infections are rare in otherwise healthy children and are typically seen in neonates requiring intensive care, children with indwelling catheters, or those with recent urinary tract instrumentation 2, 3
Renal candidiasis may present with "fungus balls" visible on ultrasound or renal parenchymal infiltration, and is frequently associated with candidemia warranting systemic antifungal therapy 2
Critical Pitfalls to Avoid
Do not attempt KOH preparation on urine specimens—this is not a validated or useful diagnostic technique for urinary infections 1
Do not confuse vaginal candidiasis (where KOH prep is appropriate) with urinary candidiasis (where urine culture is required) 1, 2
Do not delay obtaining proper urine culture if yeast infection is suspected, as Candida UTI in high-risk infants may be associated with systemic infection requiring amphotericin B therapy 2