The AUA Meeting in Chicago was an outstanding showcase of endourology; numerous authors and institutions worldwide were represented across multiple poster, podium, and plenary sessions. This review highlights novel areas pertinent to our current and future daily practice in kidney stone disease, from dietary and medical prevention to surgical techniques and technology.

Disparities in kidney stone disease exist; access to healthy foods is a significant limitation for patients with recurrent stone disease and low socioeconomic status. Sui and colleagues from University of California San Francisco correlated median income data to 24-hour urine parameters from the ReSKU (Registry for Stones of the Kidneys and Ureter) database (MP21-13). They demonstrated the lowest income quintile had the highest urinary sodium, while the highest income quintile had the lowest urinary sodium. We need to do more than emphasize a low-sodium diet to our vulnerable patients. Better counseling regarding less processed foods, and programs to improve access to less processed foods, are crucial to improving recurrence rates in this at-risk population.

A recent study in The New England Journal of Medicine questioned the benefit of thiazide diuretics on recurrent stone formation. Hollingsworth and colleagues used a unique database link between Medicare claims and Litholink 24-hour urine results to evaluate the benefit of preventive pharmacologic therapy (PPT) for stone disease (MP10-09). In 14,000 patients, the most common urinary abnormality was hypocitraturia (54%), and of the 30% prescribed PPT, alkali monotherapy was the most common (67%). They showed that for patients who are adherent to PPT there was a 13% risk reduction in a symptomatic stone event, compared to patients who were not adherent to PPT (20% risk increase).

Pulse modulation highlights a significant advancement in laser technology over the past decade, but the benefits during ureteroscopy are not entirely clear. The EDGE consortium presented their multi-institutional, randomized, blinded trial of MOSES 2.0 vs standard short-pulse mode during laser lithotripsy (LBA01-15). With 143 patients and stone sizes 8-20 mm, they found no significant difference in operative time or CT-based stone-free rates. They did demonstrate a significant reduction in surgeon fatigue based on the NASA Task Load Index survey, as well as significantly less retropulsion.

Thulium-fiber laser lithotripsy has grown in popularity over recent years due to improvements in dusting efficiency. However, optimal laser settings based on stone composition have not been determined. Johnson et al presented their in vitro work looking at 7 different stone compositions, and the dusting efficiency of 13 different thulium-fiber laser settings (LBA01-16). Figure 1 summarizes their findings. They did note significant charring in approximately 40% of cases, most notably in uric acid, cystine, and brushite stones.

Figure 1. LBA01-16. Optimal laser settings for thulium-fiber laser based on stone composition. CaPhos Apatite indicates carbonate apatite; COD, calcium oxalate dihydrate; COM, calcium oxalate monohydrate.

Intrarenal pressure during ureteroscopy continues to be a pertinent topic as we learn more about infections and postoperative pain. Croghan and colleagues reported in vivo intrarenal pressures during ureteroscopy using a COMET II pressure-sensing guidewire placed retrograde into the renal pelvis (PD28-9). They captured pressures during ureteroscopy with and without an access sheath, and with gravity, manual pump, and pressure bag irrigation at both 100 and 150 mm Hg. They demonstrated that ureteral access sheaths (UASs) significantly reduce intrarenal pressures, and higher fluid pressure and manual pump irrigation significantly increase intrarenal pressures. Most notably, in their series of 120 cases 5 patients who were readmitted with postoperative fevers concerning for urosepsis all had higher mean intrarenal pressures compared to patients who were afebrile (Figure 2).

Figure 2. PD28-9. Mean intrarenal pressures (IRPs) and preoperative urine cultures of flexible ureteroscopy (FURS) patients admitted postoperatively with fever vs afebrile controls.

Prior studies from the CROES database demonstrated that UASs reduce the risk of infectious complications, although this has yet to be replicated in another series. Becker and colleagues used the MUSIC ROCKS (Michigan Urological Surgery Improvement Collaborative Reducing Operative Complications from Kidney Stones) collaborative to analyze infection outcomes after over 6,100 ureteroscopy procedures comparing procedures with a UAS to those without (PD45-11). They found no significant difference in 30-day emergency department visits (3.0% vs 3.1%, P = .8) or hospitalizations related to infections (2.3% vs 2.6%, P = .5). On multivariable analysis, UAS use was not associated with infection related hospitalizations.

One significant limitation with many of the UAS studies is they do not capture the type of irrigation, how the irrigation was used, and the effect on pressure. Chew and colleagues presented the first in-human series of a novel single-use ureteroscope with a built-in pressure sensor (PD28-7). They demonstrated that tight ureters, subjectively determined by the surgeon, tend to have higher intrarenal pressures. Pre-stented patients and the use of an UAS showed lower intrarenal pressures. We do not know quite how to interpret these data; this technology holds promise to determine the association between UAS, irrigation, infections, and other possible outcomes.

Burst wave lithotripsy is a novel technology that delivers short bursts of ultrasound in a handheld probe to break and move stones. Chew and colleagues presented the first in-human multi-institutional clinical trial of burst wave lithotripsy in 44 patients with a mean stone size and density of 6 mm and 850 HU, respectively (LBA01-14). Stone location was variable, with 39% in the lower pole, 41% in the distal ureter or ureterovesical junction, and no proximal or mid ureter stones. They had no significant adverse events, an overall CT-based stone-free rate of 49%, but a distal ureter/ureterovesical junction stone-free rate of 89%, and a residual fragment ≤4 mm (ie, the classic clinically insignificant residual fragment) rate of 70%. Notably, 50% of patients received no sedation or analgesia, and 36% only had minor analgesia. The overall retreatment rate was 7% at 90 days. It will be exciting to see this technology incorporated into daily clinical practice.

The annual AUA meeting demonstrated the advancement of endourology, from medical management to surgical technology. As the prevalence of kidney stone disease climbs, our colleagues consistently uncover opportunities to improve kidney stone care. Clearly, we are up to the challenge to combat this burdensome disease.

Disclosures: Consultant for Boston Scientific and Cook Medical.