What is the definition of stone dust and how does it compare with clinically insignificant residual fragments? A comprehensive review.

PURPOSE: During endoscopic stone surgery, Holmium:YAG (Ho:YAG) and Thulium Fiber Laser (TFL) technologies allow to pulverize urinary stones into fine particles, ie DUST. Yet, currently there is no consensus on the exact definition of DUST. This review aimed to define stone DUST and Clinically Insignificant Residual Fragments (CIRF). METHODS: Embase, MEDLINE (PubMed) and Cochrane databases were searched for both in vitro and in vivo articles relating to DUST and CIRF definitions, in November 2023, using keyword combinations: "dust", "stones", "urinary calculi", "urolithiasis", "residual fragments", "dusting", "fragments", "lasers" and "clinical insignificant residual fragments". RESULTS: DUST relates to the fine pulverization of urinary stones, defined in vitro as particles spontaneously floating with a sedimentation duration ≥ 2 sec and suited for aspiration through a 3.6Fr-working channel (WC) of a flexible ureteroscope (FURS). Generally, an upper size limit of 250 µm seems to agree with the definition of DUST. Ho:YAG with and without "Moses Technology", TFL and the recent pulsed-Thulium:YAG (pTm:YAG) can produce DUST, but no perioperative technology can currently measure DUST size. The TFL and pTm:YAG achieve better dusting compared to Ho:YAG. CIRF relates to residual fragments (RF) that are not associated with imminent stone-related events: loin pain, acute renal colic, medical or interventional retreatment. CIRF size definition has decreased from older studies based on Shock Wave Lithotripsy (SWL) (≤ 4 mm) to more recent studies based on FURS (≤ 2 mm) and Percutaneous Nephrolithotomy(PCNL) (≤ 4 mm). RF ≤ 2 mm are associated with lower stone recurrence, regrowth and clinical events rates. While CIRF should be evaluated postoperatively using Non-Contrast Computed Tomography(NCCT), there is no consensus on the best diagnostic modality to assess the presence and quantity of DUST. CONCLUSION: DUST and CIRF refer to independent entities. DUST is defined in vitro by a stone particle size criteria of 250 µm, translating clinically as particles able to be fully aspirated through a 3.6Fr-WC without blockage. CIRF relates to ≤ 2 RF on postoperative NCCT.

Interassay Variability and Clinical Implications of Five Different Prostate-specific Antigen Assays.

Background and objective: Prostate-specific antigen (PSA) remains a critical marker for prostate cancer (PCa) detection and monitoring. Recognising historical variability in PSA assays and the evolution of assay technology and calibration, this study aims to reassess interassay variability using the latest generation of five assays in a contemporary cohort of men undergoing prostate biopsy. Methods: Five different commercially available PSA assays were tested in a blood sample of 76 men before undergoing a prostate biopsy. Total PSA (tPSA) and free-to-total PSA ratio (%fPSA) were compared across assays, using Roche (Basel, Switzerland) as the benchmark, and correlated with biopsy outcome to analyse the impact on PCa diagnosis. The statistical analysis included Passing-Bablok regression and Bland-Altman plots, with a p value threshold of <0.05 for significance. Key findings and limitations: Among the 76 men, 28 (36.8%) were diagnosed with significant PCa (defined as International Society of Urological Pathology grade ≥2). A high correlation was observed between tPSA and %fPSA values among the different PSA assays tested (r2 ≥ 0.9). The Passing-Bablok analysis showed that tPSA results varied substantially among the assays, with slopes ranging between 0.78 and 1.04. Compared with the tPSA of Roche, tPSA values were on average 20.7% lower by Beckman (Oststeinbeck, Germany), 15.2% lower by Abbott (Chicago, IL, USA), 6.1% lower by Diasorin (Saluggia, Italy), and 9.6% higher by Brahms (Hennigsdorf, Germany; p < 0.001 for all). The %fPSA values by Abbott and Brahms were higher at 15.7% and 10.6%, respectively (p < 0.001), while the Beckman and Diasorin values had minimal differences of -0.3% and 2.3%, respectively (p > 0.05). The variability across assays would have resulted in discrepancies in both the sensitivity and the specificity for tPSA and %fPSA by at least 14%, depending on the cut-offs applied. Conclusions and clinical implications: Despite the use of the latest PSA assays, relevant variability of tPSA and %fPSA results can be observed among different assays. There is an urgent need for standardised calibration methods and greater awareness among practitioners concerning interassay variability. Clinicians should acknowledge that clinically relevant thresholds may depend on the specific PSA assay and that ideally the same assay is applied over time for better clinical decision-making. Patient summary: Prostate-specific antigen (PSA) is a critical marker for prostate cancer (PCa) detection and monitoring. However, significant variations were observed in the results of the latest PSA assays. Thus, standardised calibration methods and greater awareness among practitioners concerning interassay variability are needed.

Fluid dynamics within renal cavities during endoscopic stone surgery: does the position of the flexible ureteroscope and ureteral access sheath affect the outflow rate?

PURPOSE: To evaluate the impact of ureteroscope position within renal cavities as well as different locations of the tip of the ureteral access sheath (UAS) on fluid dynamics during retrograde intrarenal surgery (RIRS). MATERIALS AND METHODS: A prospective observational clinical study was performed. Measurements with a flexible ureteroscope placed in the upper, middle and lower calyces were obtained with the tip of the UAS placed either 2 cm below the pyelo-ureteric junction (PUJ), or at the level of the iliac crest. RESULTS: 74 patients were included. The outflow rates from the middle and upper calyxes were statistically significantly higher compared to the lower calyx, both with the UAS close to the pyelo-ureteric junction and at the iliac crest. When the UAS was withdrawn and positioned at the level of the iliac crest, a significant decrease in outflow rates from the upper (40.1 ± 4.3 ml/min vs 35.8 ± 4.1 ml/min) and middle calyces (40.6 ± 4.0 ml/min vs 36.8 ± 4.6 ml/min) and an increase in the outflow from the lower calyx (28.5 ± 3.3 ml/min vs 33.7 ± 5.7 ml/min) were noted. CONCLUSIONS: Our study showed that higher fluid outflow rates are observed from upper and middle calyces compared to lower calyx. This was true when the UAS was positioned 2 cm below the PUJ and at the iliac crest. Significant worsening of fluid dynamics from upper and middle calyces was observed when the UAS was placed distally at the level of the iliac crest. While the difference was statistically significant, the absolute change was not significant. In contrast, for lower calyces, a statistically significant improvement was documented.

Radiation exposure of patients during endourological procedures.

PURPOSE: Considering the existing gaps in the literature regarding patient radiation dose (RD) and its associated risks, a systematic review of the literature on RD was conducted, focusing on percutaneous nephrolithotomy (PCNL), extracorporeal shock wave lithotripsy (SWL), and ureteroscopy (URS). METHODS: Two authors conducted a literature search on PubMed, Web of Science, and Google Scholar to identify studies on RD during endourological procedures. Two thousand two hundred sixty-six articles were screened. Sixty-five publications met the inclusion criteria using the PRISMA standards. RESULTS: RD was generally highest for PCNL, reaching levels up to 33 mSv, 28,700 mGycm2, and 430.8 mGy. This was followed by SWL, with RD reaching up to 7.32 mSv, 13,082 mGycm2, and 142 mGy. URS demonstrated lower RD, reaching up to 6.07 mSv, 8920 mGycm2, and 46.99 mGy. Surgeon experience and case load were inversely associated with RD. Strategies such as optimizing fluoroscopy settings, implementing ultrasound (US), and following the ALARA (As Low As Reasonably Achievable) principle minimized RD. CONCLUSIONS: This is the first systematic review analyzing RD, which was generally highest during PCNL, followed by SWL and URS. There is no specific RD limit for these procedures. Implementation of strategies such as optimizing fluoroscopy settings, utilizing US, and adhering to the ALARA principle proved effective in reducing RD. However, further research is needed to explore the factors influencing RD, assess their impact on patient outcomes, and establish procedure-specific reference levels for RD.