Laser for stone treatment

ACHAIKI IATRIKI | 2021; 40(2):84–86


Angelis Peteinaris1, Panagiotis Kallidonis1, Evangelos Liatsikos1-4

1Department of Urology, University Hospital of Rion, Patras, Greece
2Medical School, University of Patras, Patras, Greece
3Institute for Urology and Reproductive Health, Sechenov University, Moscow, Russia
4Medical University of Vienna, Vienna, Austria

Received: 28 Feb 2021; Accepted: 21 Apr 2021

Corresponding author: Evangelos Liatsikos, Medical School, University of Patras, Patras, GR-26500, Greece, Tel.: +30 2610999385, E-mail:

Key words: Laser, lithotripsy, endourology


Laser lithotripsy is used worldwide and is an increasingly evolving field based on novel and continuous research. It has been almost 35 years since laser was established as an option for urinary stone treatment, and as most technological advancements, laser technology has not ceased to develop. It is currently used for the treatment of urolithiasis of every part of the urinary tract and is one of the most attractive specializing fields for urologists.

Lasers for the management of renal stones are used during two endoscopic procedures. The first one is flexible ureteroscopy /retrograde intrarenal surgery (RIRS) and the second is percutaneous nephrolithotomy (PCNL).

RIRS is the treatment of choice for renal stones with a maximal diameter smaller than 2cm. The patient must be placed into lithotomy position under general anesthesia. With the use of a flexible ureteroscope, the surgeon approaches the stone and a laser fiber is inserted through the working channel of the instrument to fragmentize the stone. The surgeon has the ability to investigate through this flexible instrument the renal pelvis and calyxes for stones and to address any stone in the pelvicalyceal system. Usually, after this type of surgery, a double-j stent is inserted for a few days. The double-j stent provides safety for the removal of fragments and the possible post-surgical edema of the ureter [1].

PCNL is the treatment of choice for renal stones with a maximal diameter larger than 2cm. This technique can be used even for the fragmentation of staghorn stones. These stones occupy more than one branch of the renal collecting system. For this type of surgery, the patient must be placed into prone position under general anesthesia. A percutaneous access to the pelvicalyceal system is established under fluoroscopic and/or ultrasound guidance. A rigid or flexible endoscope (nephroscope) is inserted through the tract and the renal pelvis and calyxes are investigated for stones. A laser is used for stone fragmentation by inserting a laser fiber though the working channel of the nephroscope. Larger stones and a more direct access to the pelvicalyceal system allows for faster stone management with the use of the laser and the removal of large fragments with a grasper or basket. Thus, large renal stones could be more efficiently managed. Compared to RIRS, PCNL has a higher stone free-rate. In addition, PCNL has a longer hospital stay. The operation time and the complication rate are similar between these two types of surgery [2]. After the surgery, a renal drainage with or without a double-j stent is inserted for several days. The indications, contraindications and possible complications of both kind of surgery are presented in Table 1.


Pulsed lasers, such as the holmium:yttrium–aluminum–garnet (Ho:YAG) are mainly used for lithotripsy. The main reason is that they deliver their energy in pulses, which is more efficient and safer during stone lithotripsy [3]. Ho:YAG lithotripters allow the surgeon to control three parameters: pulse energy, pulse length and pulse frequency. During a short pulse, the energy is delivered during a short period of time (~ 300 μs). In long-pulse mode, the energy is distributed over approximately 600μs or more [4].

The Moses effect is designed for a high-power 120- W Ho:YAG lithotripter. This lithotripsy mode releases a modulated laser pulse. The first pulse creates space between the stone and the fiber tip dividing the water, and the second pulse can hit the stone without obstruction. This can increase efficiency and lower retropulsion [5]. The burst laser lithotripsy is a mode of the Ho:YAG lithotripter. Three rapidly successive pulses constitute a burst. The pulses have increasing lengths and decreasing energy. The novel new mode increases significantly the ablation [6]. Pulsed thulium laser has recently been used in lithotripsy. It appears fast, does not produce much heat and produces less retropulsion than the Ho:YAG lithotripsy [7].

Laser Fibers

The lithotripter is important, but the laser fiber plays also an important role in the lithotripsy procedure. In urology the use of small-diameter fibers is preferred. Larger fibers may decrease the flexibility of surgical instruments and the irrigation fluid’s flow through the scope. In addition, they create larger stone fragments and produce more retropulsion. It is also known that thulium lithotripters are compatible with smaller diameter laser fibers, than the fibers used with the Ho:YAG lasers. This fact is an advantage of the thulium laser lithotripsy [8].

There are single-use or reusable fibers. Regardless of the fiber type, the fibers can be damaged during the surgery. It has been proved that higher pulse energy, shorter pulse length and harder stones can create more damage to the fiber. Because of these degradation factors, laser fibers are “renewed” before or during surgery. This means that the plastic fiber coating and the glassy fiber part are cut by special instruments [9].

Laser settings-techniques

It is known that higher pulse energy combined with shorter pulse length are ideal for breaking large stones into smaller. These settings are usually used for kidney and bladder stones that could have a large caliber percutaneous approach. In ureteroscopy the “dusting” technique is preferred [10]. Dusting settings consist of low pulse energy (0.2–0.5 J), higher frequency, and longer pulse length. This may increase the ablation time of stone material, but it reduces extraction-associated complications, as dust is naturally eliminated and reduces operation time as no extraction procedures are needed [11]. In addition, there are two different settings that are used for the non-contact lithotripsy technique. This is usually used in an enclosed and small space (e.g. calix) and the aim is to break stones to smaller fragments that will spontaneously pass. The first one is the “pop-corn” technique. Its settings consist of high pulse energy (≈ 1.5 J), high frequency (20-40 Hz) and long-pulse mode in order to break a stone to clinically insignificant fragments. The second technique is the “popdusting”. It is using lower pulse energy (0.5 J) than the pop-corn technique in order to create smaller fragments while partially protecting the fiber tip.

In conclusion, the kind of the lithotripter, the size of the fiber or the settings are important, but the most vital part for this procedure is the experience and the ability of the surgeon to use all these advantages in a wise and efficient way [12].

Conflict of interest disclosure

None to declare.

Declaration of funding sources

None to declare.


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