The paper related to the 2025 meeting presents an updated overview of the most recent evidence regarding the pathogenesis and management of kidney stones. The abstract of the paper summarizes and outlines all the topics covered in the review. In this short supplementary text, we highlight some noteworthy developments in the medical and endoscopic treatment of urinary stones. In particular, the meeting emphasized the importance of emerging medical therapies that supplement the traditional use of citrates, as well as the introduction of new devices for the retrograde endoscopic treatment of renal stones.
Phytates
Phytate (myo-inositol hexakisphosphate, InsP₆) is a naturally occurring polyphosphorylated carbohydrate found in seeds, legumes, nuts, and whole grains. In vitro studies have demonstrated that both InsP₆ and its lower phosphorylated derivatives (InsPs) exert a potent inhibitory effect on the nucleation, growth, and aggregation of calcium salts, particularly calcium oxalate and calcium phosphate crystals. Epidemiological evidence from a large-scale, prospective cohort study involving 96,245 women over eight years has revealed that higher dietary phytate intake is significantly associated with a reduced risk of developing symptomatic kidney stones. Furthermore, experimental data indicate a synergistic interaction between phytate and magnesium, which enhances the inhibitory effect on crystal formation.
Theobromine
Theobromine, a naturally occurring dimethylxanthine abundant in cocoa beans, has demonstrated effective inhibition of uric acid crystallization. Due to its structural similarity to uric acid, theobromine can incorporate into forming crystals, modifying their morphology by producing longer and thinner structures with reduced growth kinetics. Unlike calcium-containing stones, pharmacological options to prevent uric acid crystallization remain limited. Upon ingestion, theobromine is metabolized and excreted in the urine primarily as 7-methylxanthine (36%), unchanged theobromine (21%), 3-methylxanthine (21%), and 3,7-dimethyluric acid (1.3%), all of which remain potent inhibitors of uric acid crystallization. The co-administration of urinary alkalinizing agents, such as potassium citrate, alongside theobromine has been proposed as a therapeutic strategy to optimize uric acid solubility. This combination enables lower citrate dosages, reducing the risk of excessive alkalinization and subsequent sodium urate precipitation. Additionally, minimizing citrate dosage decreases the risk of hyperkalemia, particularly in patients with impaired renal function or cardiovascular comorbidities.
Methionine
Specific measures for the prevention of struvite stones include complete surgical removal of the entire stone burden, short- or long-term antibiotic therapy, urinary acidification to a pH below 6.2, and a urine volume of at least 2 litres per 24 hours. It has been confirmed that L-methionine effectively lowers urinary pH and the relative supersaturation of struvite under physiological conditions.
Optimizing Citrate Supplementation
In addition to the introduction of new pharmacological therapies, technological tools have been developed to optimize treatment and enhance patient adherence. Key challenges in the management of urolithiasis include maintaining proper hydration, tracking patient adherence to specific diets, and prophylactic medications. Citrate supplementation plays a well-established role in preventing recurrence and managing residual stone fragments; however, its effectiveness may be reduced by poor adherence due to irregular medication intake. Daily measurement of urinary pH using portable electronic devices such as the Lit-Control® pH Meter 2.0 is crucial for improving adherence and therapeutic efficacy. Regular urine pH monitoring allows for proper citrate dosage adjustment, preventing treatment failure due to insufficient medication intake or, conversely, the risk of uncontrolled urinary pH elevation (≥7.5) caused by over-alkalinization. Sustained elevations in urinary pH may increase the risk of calcium phosphate stone formation. In parallel, patients can use a digital tool like the myLit-Control® App, which connects to the portable Lit-Control® pH Meter via Bluetooth to monitor urinary pH values alongside medication intake.
New Lasers for Lithotripsy
Also, in the endoscopic treatment of urinary calculi, several innovations have been introduced, driven by technological advances in endoscopy and lithotripsy equipment.
At similar laser settings (pulse energy, pulse rate, and average power), the Thulium Fibre Laser (TFL) demonstrates higher stone ablation rates and produces smaller stone fragments than the standard Ho:YAG laser. It is highly effective in disintegrating all major urinary stone types into particles smaller than 500 µm (dusting). High Power (HP) Ho:YAG systems represent an improvement over standard Ho:YAG units, offering a wider range of settings, including energy as low as 0.2 J and frequencies up to 100 Hz. The higher frequencies on high-power holmium devices facilitate faster dusting, smaller fragments and a 50% reduction in lasing time compared to standard machines. Pulse modulation technologies available in some HP units (Moses Technology®, Vapour Tunnel, and Virtual Basket®) enable reduced retropulsion, improved dusting efficiency, and enhanced distance fragmentation. HP Ho:YAG lasers can also deliver higher peak-power than TFL, providing not only excellent pulverization but also efficient fragmentation, which may be advantageous in specific clinical scenarios.
Flexible and Navigable Suction UAS (FANS-UAS)
The use of newer lasers for lithotripsy can increase the risk of generating high temperatures and high pressures within the renal cavities, which may lead to thermal injury or septic complications. Monitoring these parameters is essential to mitigate such risks and enhance procedural safety. Temperature control can be achieved through efficient irrigation and the use of appropriate laser settings. Conversely, the potential effects of excessive irrigation must be mitigated by ensuring effective outflow of irrigation fluids, either through a ureteral access sheath or the endoscope itself.
Ureteral Access Sheath (UAS) enables repeated scope access and improves irrigation outflow, contributing to procedural safety and efficacy. The latest advancements are the flexi-bendable UAS equipped with suction capabilities—Flexible and Navigable Suction UAS (FANS-UAS)—which combine mechanical flexibility with continuous irrigation management and stone clearance mechanisms. These flexi-bendable sheaths feature a soft, passively bendable distal tip that can follow the ureteroscope's movement into difficult-to-reach areas, significantly improving navigation and clinical access in complex renal anatomies. FANS-UAS incorporate a vacuum-assisted side port, allowing active removal of stone dust, blood clots, and irrigation fluid during lithotripsy. This functionality enhances stone visualization and procedural control, improving fragmentation accuracy and shortening operative times. FANS-UAS have demonstrated the ability to maintain intrarenal pressure below 20–30 cm H₂O and to significantly outperform traditional sheaths in achieving stone-free status, as well as reduce the risk of infectious complications, including postoperative fever and sepsis.
Direct in Scope Suction (DISS)
An alternative or complementary approach is suction through the scope. Direct in Scope Suction (DISS) has been developed to control intrarenal pressure and remove residual stone fragments and can be combined with the use of FANS-UAS.
Large, randomized, multicenter studies are now needed to standardize the results and draw definitive conclusions regarding the benefit of these procedures. The true practical impact on the medium- and long-term success rates of the procedure remains to be fully elucidated.
Slim Ureteroscopes
An additional novelty is the miniaturization of flexible ureteroscopes, aimed at increasing both the safety and cost-effectiveness of flexible ureteroscopy. A 6.3 Fr flexible ureteroscope has recently been launched on the market that allows flexible ureteroscopy to be performed without pre-placed double-J stenting (thus avoiding an additional procedure) and without the insertion of ureteral access sheaths (thus reducing the risk of ureteral injury). If the scope is used through a ureteral access sheath, a slim 9 Fr sheath can be used, maintaining more space for fluid infusion and fragment evacuation. Consequently, this helps prevent temperature rise during laser lithotripsy, relieve renal pressure, and improve the stone-clearance rate.
Written by:
- Alberto Trinchieri, CDC Ambrosiana, Cesano B, Milano, Italy
- Bernat Isern, Renal Lithiasis and Pathological Calcification Group (LiRCaP), Research Institute of Health Sciences (IUNICS), University of the Balearic Islands & Health Research Institute of the Balearic Islands (IdISBa), Spain