(UroToday.com) The 2022 WCET annual meeting included a clinical stones session involving work by Rohit Bhatt and colleagues evaluating a new gel technology for lithotripsy. One of the current challenges with laser lithotripsy of renal stone burden is the inability to completely remove all stone fragments. While larger fragments are either re-treated with the laser or removed with a basket, smaller fragments are often left behind in hopes of them being spontaneously passed. However, sometimes these fragments can cause a sequela of complications including a nidus for infection or recurrence of stone formation. UroGen Pharma invented a novel gel, Hydrogel®, that can aid with this complication. Rohit presented work that he and colleagues conducted in regard to evaluating the benefits and efficacy of this gel to aid in stone removal during laser lithotripsy. The researchers hypothesized that this gel could entrap the smaller fragments typically left behind and thereby aid in complete stone removal. The novel utility of the gel is that it is a reverse thermal gel that stays semisolid at body temperature and can surround stone burden but transforms to liquid outside the body at room temperature.
In this experiment, two pigs were studied, and each animal served as its own control. One of the pig’s kidneys was used on the experimental side treated with Hydrogel and the other kidney was untreated. Calcium oxalate stones were implanted prior to the procedure via an open pyelotomy into the animals’ upper calyx. In the experimental kidney, 5cc of Hydrogel was infused into the calyx bearing the calcium oxalate stones and an access sheath was placed. A thulium laser was used to perform lithotripsy and dust the stones, and a ureteroscopic brush was introduced thereafter in order to remove any fragments trapped in the Hydrogel.
The presenter included the figure below which demonstrates the procedural steps involved in the setup:
At the conclusion of the experiment, the researchers found that 98.9% and 99.7% of stone burden was removed from the two experimental kidneys treated with Hydrogel. In the control, untreated, kidneys, 85.5% and 98.8% of the stone burden was removed. Peak temperatures were also recorded in the kidneys for all experiments, and peak temperatures were 35ºC and 55ºC in the two control kidneys. It was noted that temperatures above 44ºC, which is the threshold for urothelial injury, occurred for a total of 0 times in one control kidney and 4 times in the other control kidney. In the two experimental kidneys treated with Hydrogel, peak temperatures reached 36ºC in one kidney and unmeasured in the other kidney. Temperatures above 44ºC occurred 0 times in the measured kidney.
Rohit Bhatt included a table indicating all the results found from the four kidneys:
Rohit Bhatt concluded his presentation with the following statement:
- The use of Hydrogel to augment thulium laser ureteroscopic stone removal resulted in >99% clearance of stone fragments/dust from both kidneys while also having a possible insulating effect from intracalyceal temperature spikes.
Presented by: Rohit Bhatt, MD, Department of Urology – University of California, Irvine
Written by: Allen Rojhani, BS - MD Candidate at the Drexel University College of Medicine and 2022-2023 LIFT Research Fellow at the University of California, Irvine Department of Urology during the 39th World Congress of Endo urology and Uro-Technology (WCET), Oct 1 - 4, 2022, San Diego, California.