A single-centre, patient- and assessor-blinded randomised trial compared 4.7Fr with 6Fr ureteric stents after intracorporeal lithotripsy, which is a question every endourologist decides by habit rather than evidence.
Stone-free rates were the same. IPSS scores at three weeks were comparable, with a mean difference of 0.7 and a confidence interval crossing zero. But the Ureteral Stent Symptom Questionnaire, which is the instrument actually designed for this, favoured the smaller stent: 73 against 80, a mean difference of 7 points with an interval from 13 to 1.5.
The trade is early dislodgement. Grade 3 complications, mostly stent migration, occurred in 8.8% of the 4.7Fr group against 3.2% of the 6Fr group — a relative risk of 2.6 whose interval runs from 0.5 to 13 and therefore does not establish a real difference. Eighty-four per cent of patients had no complication at all.
So the practical version: the smaller stent is more comfortable by a measure built to detect exactly that, and the dislodgement signal is worth mentioning at consent rather than worth avoiding the stent for. This was registered in India, which makes the population directly relevant.
- Prefer 4.7Fr after intracorporeal lithotripsy where stent comfort is the concern.
- Use the USSQ, not the IPSS, if you measure stent symptoms — IPSS showed nothing here.
- Warn about migration and set a clear route back if the patient thinks the stent has moved.
- The dislodgement difference did not reach significance; do not present it as established.
The statistics, in plain English
Two instruments disagreed and the disagreement is the lesson. The IPSS found nothing — mean difference 0.7, interval crossing zero — because it was designed for prostatic symptoms, not stent symptoms. The USSQ found a 7-point difference with an interval from 13 to 1.5 that stays clear of zero. Using an instrument suited to the question is often what separates a positive trial from a negative one. On harm, a relative risk of 2.6 sounds alarming, but the interval from 0.5 to 13 includes 1.0 and is enormously wide, which is what happens when you compare 8.8% against 3.2% in a single-centre trial: too few events to say anything firm.
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