Urinalysis with +3 Squamous Epithelial Cells: Interpretation and Management
Primary Interpretation
A urinalysis showing +3 squamous epithelial cells indicates specimen contamination from the distal urethra, bladder trigone, or cervicovaginal region (in women), and the specimen should be recollected using proper technique—preferably via catheterization—if clinical suspicion for urinary tract infection or other pathology remains high. 1, 2
Understanding the Clinical Significance
Origin of Squamous Cells
- Squamous epithelial cells normally line the distal third of the urethra and the trigone area of the bladder, as well as the cervicovaginal region in women 1
- Their presence in urine typically reflects contamination during collection rather than true urinary tract pathology 1, 2
Contamination Indicators
- When +3 squamous cells appear alongside >10 WBCs or mixed bacterial flora, this strongly suggests specimen contamination rather than true infection 3, 1, 2
- The presence of squamous cells reduces the diagnostic accuracy of urinalysis markers for predicting positive urine cultures, with areas under the curve dropping significantly for pyuria, bacteriuria, and leukocyte esterase 4
- Squamous cells are present in 94-96% of urine samples from women, yet only 21% of midstream clean-catch samples with squamous cells show actual bacterial contamination 5
Collection Method Impact
Contamination Rates by Technique
- Clean-catch specimens: 27% contamination rate 1, 2
- Bag collection specimens: 65-68% contamination rate 1
- Catheterized specimens: 4.7% contamination rate 1, 2
Improving Collection Quality
- Proper perineal cleansing before collection reduces contamination rates from 23.9% to 7.8% 1, 2
- Catheterization provides specimens with 95% sensitivity and 99% specificity 3, 1, 2
Management Algorithm
Step 1: Assess Clinical Context
- Determine if clinical suspicion for UTI or other urinary pathology is high based on symptoms (dysuria, frequency, urgency, fever, flank pain) 3
- Consider patient demographics: children <1 year with fever, females 1-2 years with fever without source are at higher risk for UTI 3
Step 2: Decision Point
- If clinical suspicion is LOW: No further action needed; the squamous cells represent normal contamination 1, 2
- If clinical suspicion is HIGH: Recollect specimen using improved technique 3, 1, 2
Step 3: Recollection Strategy
- First attempt: Repeat clean-catch with proper perineal cleansing instructions 1, 2
- If repeat shows persistent contamination or patient is ill-appearing: Proceed directly to catheterization 3, 1, 2
- For septic-appearing children, catheterization or suprapubic aspiration should be the initial method of choice 3
Step 4: Do Not Treat Based on Contaminated Specimen
- Do not initiate antibiotic therapy for presumed UTI based on urinalysis showing squamous cells and bacteria without proper specimen recollection 2
- A positive culture from a bag specimen with high squamous cells has an 85% false-positive rate when UTI prevalence is 5% 3
Important Caveats
When to Consider Alternative Diagnoses
- While rare (0.3% of cases), atypical squamous cells in urine may indicate underlying malignancy including squamous cell carcinoma of the bladder, urothelial carcinoma with squamous differentiation, or cervical carcinoma 6, 7
- If squamous cells appear atypical (large hyperchromatic nuclei, high nuclear-to-cytoplasmic ratio, abnormal shapes, densely orangeophilic cytoplasm), cytology should be reported using the Bethesda System and may warrant cystoscopic or gynecologic evaluation 3, 1, 7
- In patients with hematuria and squamous cells, particularly those with neurogenic bladder, cystoscopic evaluation may be warranted 1