# Clean catch: an Olympic sport?

Andrew Bland, MD, FACP, FAAP · October 28, 2026

Squamous cells, mucus and mixed flora are collection clues. Read them with the collection method and clinical syndrome. The microscopy drawings are teaching schematics, not diagnostic photomicrographs.

## Many squamous epithelial cells

Large, flat cells from distal urethral or external genital surfaces can flag carryover during collection. They reduce confidence in interpreting a UA, but do not reliably establish culture contamination alone. Use the laboratory’s reporting units and reference range; there is no universal yes/no cutoff.

## Mucus threads

Small amounts can occur normally. Abundant mucus may accompany genital secretions or urinary inflammation. Together with many squamous cells, mixed organisms and a difficult collection it adds context; mucus alone diagnoses neither contamination nor UTI.

## Mixed bacterial forms or mixed growth

A mixture can suggest external flora, especially after pad, bag or skin contact. True polymicrobial infection can occur in selected settings, particularly with instrumentation or catheters; interpret the clinical setting and culture report.

## White cells and leukocyte esterase

These indicate inflammatory cells in the sample, not necessarily bacterial infection in the bladder. Genital carryover and asymptomatic bacteriuria can also produce an abnormal UA. Neither pyuria nor bacteria alone establishes symptomatic UTI.

## Renal tubular epithelial cells

Do not put every epithelial cell in the contamination bucket. Renal tubular epithelial cells, especially with granular casts, support a tubular injury process; they are different from large squamous cells.

## The Olympic challenge

“Clean catch is an Olympic sport” is a memorable way to describe the task: position safely, reach, separate skin folds, clean, aim, collect midstream and keep the cup away from the body—all while needing to urinate. Arthritis, limited mobility, body habitus, visual difficulty, urgency and cognitive impairment can make that coordination unrealistic. Ask what the patient can actually do, give clear instructions, provide a suitable setup and offer assistance. A difficult collection is a practical care problem, not a patient failure.

## The dunker problem

“Dunkers” is Dr Bland’s informal teaching term for collection in which the penile tip touches the cup or dips into already collected urine, allowing external cells and flora into the specimen. Urgency, dribbling, obstructive symptoms or difficulty positioning the cup may contribute; BPH does not make this inevitable. Keep a gap between skin and container. Midstream collection does not require stopping and restarting the flow: begin into the toilet, move the cup into the stream, then remove it and finish into the toilet.

## Coach the collection

Wash hands and prepare the supplied container. Follow local cleansing instructions; separate the labia or retract the foreskin as appropriate. Avoid touching the inside of the cup or lid. Collect the middle portion without contacting the skin, cap it and return it promptly; use the laboratory’s storage instructions if transport is delayed.

## A reason to test comes first

First decide whether urine testing will answer a clinical question. If a specimen is needed and collection quality is poor, repeat with coached or assisted midstream collection; consider a trained clinician’s in-and-out catheter specimen when a reliable sample is clinically necessary and clean catch is not feasible. Catheterization is not a routine response to incidental pyuria or bacteriuria. A contaminated-looking specimen can coexist with true infection, and suspected sepsis requires prompt assessment and treatment while the source is evaluated.

## Sources

- [Mohr et al., 2016: squamous cells are not a reliable standalone contamination test](https://pubmed.ncbi.nlm.nih.gov/26782662/)
- [Maher et al., 2020: squamous cells reduce UA diagnostic accuracy](https://pubmed.ncbi.nlm.nih.gov/31843330/)
- [MedlinePlus: mucus in urine](https://medlineplus.gov/lab-tests/mucus-in-urine/)
- [NHS: adult midstream urine collection without stopping flow](https://www.gloshospitals.nhs.uk/your-visit/patient-information-leaflets/collection-of-mid-stream-sample-of-urine-mssu-for-adults/)
- [IDSA: asymptomatic bacteriuria, delirium and testing decisions](https://www.idsociety.org/practice-guideline/asymptomatic-bacteriuria/)