Urinary stone disease is very common, with an estimated
prevalence among the general population of 2% to 3%
and an estimated lifetime risk of 1 in 8 for white males
[1] and 5% to 6% for white females [2], with men forming
stones three times as often as women. Urinary stones
often recur and the lifetime recurrence rate is approximately
50% [3]. The interval between recurrences is
variable, with approximately 10% within 1 year, 35% within
5 years and 50% within 10 years [2]. The increased incidence
of urinary stones in the industrialized world is
associated with improved standards of living (mainly
owing to the high dietary intake of proteins and minerals)
and there is also an association with ethnicity and region
of residence [4]. All urinary tract stones, and ureteric
stones in particular, have a significant impact on patients’
quality of life. They are a common cause of emergency
hospital admission due to severe pain with over 15,000
hospital admissions in England annually [5] using over
21,500 bed days. The pain leads to a requirement for analgesia,
time off work and, often, repeated hospital admissions
for therapeutic interventions.
A clinical guideline on the management of ureteric
stones by the European Association of Urology and the
American Urological Association [6] estimates that 68%
of stones ≤5 mm and 47% of stones 5 to 10 mm in size
can be expected to pass spontaneously and concluded
that the majority of these stones pass within 4 to 6 weeks
of presentation. Stones in the distal ureter pass more
readily than stones located more proximally. The majority
of the studies included in the guideline meta-analysis
assessed stones in the distal (lower) ureter only. Consequently,
patients with favourable features and with
smaller stones in the lower ureter are traditionally
treated expectantly. Those who fail standard supportive
care (which involves analgesia, anti-emetics if nauseated,
and intravenous fluids if there is associated vomiting), or
who subsequently develop complications, undergo active
treatment, such as extracorporeal shock wave lithotripsy,
ureteric stenting, ureteroscopy with stone retrieval or
in-situ lithotripsy, or percutaneous nephrostomy insertion.
However, such interventions are expensive, require urological
expertise and carry a risk of complications. For instance,
extracorporeal shock wave lithotripsy is associated