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STONE
DISEASE
Computed
tomography-determined stone-free rates for ureteroscopy of upper-tract
stones
Macejko A, Okotie OT, Zhao LC, Liu J, Perry K, Nadler RB
Department of Urology, Northwestern University Feinberg School of Medicine, Chicago,
Illinois, USA
J Endourol. 2009; 23: 379-82
- Background
and Purpose: Most series on ureteroscopy for urolithiasis
use postoperative plain radiography of the kidneys, ureters, and bladder
(KUB) or intravenous urography (IVU) to determine outcomes. These imaging
modalities, however, are not very sensitive and may overestimate stone-free
rates (SFRs). The aim of our study was to assess SFRs after ureteroscopy
for urolithiasis using CT follow-up.
- Patients
and Methods: A total of 92 patients underwent 113 ureteroscopic
procedures for either renal or ureteral stones. Success of
ureteroscopy was then determined
by the absence of any stone fragments (stone-free). Stone-clearance rates
(SCRs) were also calculated for ≤ 2 mm and ≤ 4 mm residual
stone fragments.
- Results: Each renal unit contained a mean of 1.87 stones with a
mean stone diameter of 8 ± 6 mm. The overall SFR was 50.4%. SFRs were significantly
higher for ureteral stones (80%) than renal stones (34.8%) (P = 0.0001). Renal
units with multiple stones were less likely to be stone free than those with
single stones (P = 0.011). No difference in SFRs was found between lower pole
and non-lower-pole stones.
- Conclusions: Overall SFRs by CT were lower than SFRs reported by
radiography of the KUB or IVU criteria. Further studies to
identify the clinical
significance and natural history of residual stone fragments on CT
scan after ureteroscopy
are needed.
- Editorial Comment
The study spanned a seven-year period - such that the average number of patients
treated was 1 per month. It is feasible that a center with a higher volume
of ureteroscopic procedures might have different stone-free results. Indeed,
though the authors attribute the lower stone-free rate to the sensitivity
of CT scan detecting “tiny” stones, 16% of patients in this study
had residual stones > 4 mm in size. In addition, technology has evolved
and improved over the study period - indeed the ureteroscopes utilized in
this study lacked exaggerated active deflection and are no longer available
on the market. This characteristic of the scopes might have affected stone
free rates. The authors state that larger fragments were basket extracted
while stones < 2 mm in size were left to pass. The authors do not describe
what visual cues they utilized to determine stone size - for example were
all fragments larger than the safety wire diameter basket extracted?
The authors did not standardize the time of post-operative imaging. Indeed
some patients were imaged on day 1 (too early for clinical relevance) and some
were imaged after 16 months (residual or recurrence of stones)? CT scan imaging
at a predetermined time point (ex. 1 month) would have added clarity to the
findings.
Twenty-six percent of patients were pre-stented. While this may facilitate
ureteroscopy by ureteral dilation, it may also lead to edema, clot and/or debris
that prevent an adequate visualization of the entire collecting system.
Dr. Manoj Monga
Professor, Department of Urology
University of Minnesota
Edina, Minnesota, USA
E-mail: endourol@yahoo.com
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