Which urine collection method is least likely to yield contamination with squamous cells?

Which urine collection method is least likely to yield contamination with squamous cells?

• A. Catheterization
• B. Manual expression
• C. Free catch
• D. Cystocentesis

Answer: (D)

Squamous cells come from the surfaces of the genital tract and the distal urethra, so a urine sample is most reliable when it avoids contact with those surfaces. Cystocentesis draws urine directly from the bladder through the abdominal wall, bypassing the urethra and external genitalia entirely. Because the urine doesn’t pass over mucosal surfaces or genital skin during collection, there’s minimal opportunity for squamous cells to contaminate the sample. In comparison, free catch urine travels past the urethral opening and external tissues, which readily shed squamous cells into the sample. Manual expression can push urine through the urethra and surrounding tissues, increasing contact with mucosa and skin. Catheterization, while more controlled, still involves passing a catheter through the urethral tract, which can introduce some squamous cells from that mucosal surface. Therefore, the method that yields the cleanest sample with the least squamous cell contamination is cystocentesis, though it carries its own risks such as potential bladder puncture or infection in some patients.

Squamous cells come from the surfaces of the genital tract and the distal urethra, so a urine sample is most reliable when it avoids contact with those surfaces. Cystocentesis draws urine directly from the bladder through the abdominal wall, bypassing the urethra and external genitalia entirely. Because the urine doesn’t pass over mucosal surfaces or genital skin during collection, there’s minimal opportunity for squamous cells to contaminate the sample.

In comparison, free catch urine travels past the urethral opening and external tissues, which readily shed squamous cells into the sample. Manual expression can push urine through the urethra and surrounding tissues, increasing contact with mucosa and skin. Catheterization, while more controlled, still involves passing a catheter through the urethral tract, which can introduce some squamous cells from that mucosal surface.

Therefore, the method that yields the cleanest sample with the least squamous cell contamination is cystocentesis, though it carries its own risks such as potential bladder puncture or infection in some patients.