Suprapubic aspiration and urinary catheterisation: Viva

Branch 1: The urine collection methods and their contamination rates

The candidate should state that the non-toilet-trained child needs a low-contamination specimen for the culture, and that the two indicated methods are the suprapubic aspiration and the urethral catheterisation. A strong candidate gives the contamination rates: the suprapubic aspiration under 1 percent, the urethral catheterisation approximately 1 to 10 percent, the clean catch approximately 25 to 30 percent, and the bag or pad up to 50 to 85 percent. The candidate should explain that any organism grown from a suprapubic aspirate is a true pathogen because the bladder urine is sterile, and that the catheter specimen uses the threshold of the single organism at greater than 10 000 to 50 000 colony forming units per millilitre. ^[5]

If the examiner presses on the bag specimen, the candidate should state that the bag and the pad are for the screen dipstick only and must never be used to diagnose a urinary tract infection. A negative screen lowers the probability enough to defer the invasive collection, but a positive screen must be confirmed by the catheterisation or the aspiration before the antibiotic. The American Academy of Pediatrics guideline requires the catheterisation or the aspiration before any antimicrobial in the febrile infant two to twenty-four months with the suspected infection. ^[1]