Brain E. et al., 2021: Natural History of Post-treatment Kidney Stone Fragments: A Systematic Review and Meta-Analysis.
Brain E, Geraghty RM, Lovegrove CE, Yang B, Somani BK.
Newcastle Medical School, Newcastle-upon-Tyne, England.
Department of Urology, Freeman Hospital, Newcastle-upon-Tyne, England.
Translational and Clinical Research Institute, Faculty of Medical Sciences, Newcastle University, International Centre for Life, Newcastle upon Tyne, England.
Department of Urology, Churchill Hospital, Oxford, England.
Nuffield Department of Surgery, Oxford University, Oxford, England.
Department of Urology, University Hospital Southampton, Southampton, England.
Purpose: To assess the literature around post-treatment asymptomatic residual stone fragments, and to perform a meta-analysis. The main outcomes were intervention rate and disease progression.
Materials and methods: We searched Ovid Medline, Embase, Cochrane library and Clinicaltrials.gov using search terms: "asymptomatic", "nephrolithiasis", "ESWL", "PCNL", "URS" and "intervention". Inclusion criteria were all studies with residual renal fragments following treatment (shockwave lithotripsy, ureteroscopy or percutaneous nephrolithotomy). Analysis performed using 'metafor' in R and bias using Newcastle-Ottawa scale.
Results: From 273 articles, 18 papers (2096 patients) had details of intervention rate for residual fragments. Aggregate intervention rates for ≤4mm fragments rose from 19% (20 months) to 22% (50 months), whilst >4mm fragments rose from 22% to 47%. Aggregate disease progression rates for ≤4mm rose from 25% to 47% and >4mm rose from 26% to 88%. However, there was substantial difference in definition of "disease progression." Meta-analysis comparing >4mm against ≤4mm fragments: Intervention rate for >4mm (vs ≤4mm): OR=1.50 (95% CI: 0.70-2.30), p<0.001, I2=67.6%, tau2=0.48, Cochran's Q=11.4 (p=0.02) and Egger's regression: z=3.11, p=0.002. Disease progression rate for >4mm: OR=0.06 (95% CI: -0.98-1.10), p=0.91, I2=53.0%, tau2=0.57, Cochran's Q=7.11 (p=0.07) and Egger's regression: z=-0.75, p=0.45. Bias analysis demonstrated a moderate risk.
Conclusions: Larger post-treatment residual fragments are significantly more likely to require further intervention especially in the long-term. Smaller fragments, although less likely to require further intervention, still carry that risk. Notably, there is no significant difference in disease progression between fragment sizes. Patients with residual fragments should be appropriately counselled and informed decision making regarding further management should be done.
J Urol. 2021 Apr 27:101097JU0000000000001836. doi: 10.1097/JU.0000000000001836. Online ahead of print. PMID: 33904756
One of the fundamental questions regarding modern non-invasive and low-invasive stone removal is the course of residual fragments. This issue is of great importance because SWL, URS/RIRS and PCNL all can end up with residual fragments in the kidney. The authors of this article accordingly have carried out a systematic review and meta-analysis with the aim of increasing our knowledge of this problem.
Altogether there were 273 articles examined, but only 18, including 2069 patients, had sufficient information. SWL =8, URS=3, PCNL=6 and URS+PCNL=1. One important conclusion was that turning stones into dust resulted in a significant difference.
Spontaneous passage of residuals was higher when fragments were ≤4 mm than when they were > 4 mm. The same conclusion was made for need of intervention. One finding was that larger fragments were less likely to pass spontaneously. This is an expected outcome, but whether the intervention really was necessary is an open question. The intervention after 4 years increased from 22% for 4 mm stones. It is difficult to know if the intervention was driven by symptoms or carried out only as a cosmetic need? More interesting is information on disease progress which after 3 years was 47% for 4 mm stones.
The table below summarizes events over time;
It is noteworthy that stone progress comes early and subsequently obviously stabilizes.
The bottom-line conclusions from this review were as follow:
Re-intervention increases with time and large fragments have a higher likelihood of requiring intervention.
The term “clinically insignificant fragments” should not be used. This basic conclusion, however, has been the truth since decades!
Residual fragments left in the kidney should be as small as possible.
The metabolic care of patients with residual fragment is mentioned in the text, but no data are available most certainly as a consequence of urologists’ lack of interest in such measures.