Stone composition changes management more than almost anything else in the follow-up clinic, and it is the investigation most often skipped. A uric acid stone is dissolvable and alkalinisation is the treatment. A cystine stone means a lifelong metabolic problem in a young patient. An infection stone means the urea-splitting organism must be eradicated or the stone recurs. Calcium oxalate means something different again.
So make retrieval the default. Give the patient a filter or a sieve if they are passing the stone; send fragments from every procedure rather than only the large ones; and set a clinic review at which the composition is the first thing read.
The common failure is not the laboratory. It is that the stone reaches the lab and the result is never looked at, because nobody scheduled the visit at which it would matter.
- Send fragments for composition analysis from every stone procedure, not only large stones.
- Give a sieve to patients managed expectantly, with written instructions.
- Book the follow-up around when the composition result will be available.
- Repeat the 24-hour urine metabolic work-up for recurrent, young or bilateral stone formers.
- Record the composition where the next clinician will find it; recurrence is years later.
Why it matters
The single test that determines prevention is the one most often lost between theatre and clinic.
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